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+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * linux/mm/filemap.c
+ *
+ * Copyright (C) 1994-1999 Linus Torvalds
+ */
+
+/*
+ * This file handles the generic file mmap semantics used by
+ * most "normal" filesystems (but you don't /have/ to use this:
+ * the NFS filesystem used to do this differently, for example)
+ */
+#include <linux/export.h>
+#include <linux/compiler.h>
+#include <linux/dax.h>
+#include <linux/fs.h>
+#include <linux/sched/signal.h>
+#include <linux/uaccess.h>
+#include <linux/capability.h>
+#include <linux/kernel_stat.h>
+#include <linux/gfp.h>
+#include <linux/mm.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
+#include <linux/mman.h>
+#include <linux/pagemap.h>
+#include <linux/file.h>
+#include <linux/uio.h>
+#include <linux/error-injection.h>
+#include <linux/hash.h>
+#include <linux/writeback.h>
+#include <linux/backing-dev.h>
+#include <linux/pagevec.h>
+#include <linux/security.h>
+#include <linux/cpuset.h>
+#include <linux/hugetlb.h>
+#include <linux/memcontrol.h>
+#include <linux/shmem_fs.h>
+#include <linux/rmap.h>
+#include <linux/delayacct.h>
+#include <linux/psi.h>
+#include <linux/ramfs.h>
+#include <linux/page_idle.h>
+#include <linux/migrate.h>
+#include <asm/pgalloc.h>
+#include <asm/tlbflush.h>
+#include "internal.h"
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/filemap.h>
+
+/*
+ * FIXME: remove all knowledge of the buffer layer from the core VM
+ */
+#include <linux/buffer_head.h> /* for try_to_free_buffers */
+
+#include <asm/mman.h>
+
+/*
+ * Shared mappings implemented 30.11.1994. It's not fully working yet,
+ * though.
+ *
+ * Shared mappings now work. 15.8.1995 Bruno.
+ *
+ * finished 'unifying' the page and buffer cache and SMP-threaded the
+ * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
+ *
+ * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
+ */
+
+/*
+ * Lock ordering:
+ *
+ * ->i_mmap_rwsem (truncate_pagecache)
+ * ->private_lock (__free_pte->block_dirty_folio)
+ * ->swap_lock (exclusive_swap_page, others)
+ * ->i_pages lock
+ *
+ * ->i_rwsem
+ * ->invalidate_lock (acquired by fs in truncate path)
+ * ->i_mmap_rwsem (truncate->unmap_mapping_range)
+ *
+ * ->mmap_lock
+ * ->i_mmap_rwsem
+ * ->page_table_lock or pte_lock (various, mainly in memory.c)
+ * ->i_pages lock (arch-dependent flush_dcache_mmap_lock)
+ *
+ * ->mmap_lock
+ * ->invalidate_lock (filemap_fault)
+ * ->lock_page (filemap_fault, access_process_vm)
+ *
+ * ->i_rwsem (generic_perform_write)
+ * ->mmap_lock (fault_in_readable->do_page_fault)
+ *
+ * bdi->wb.list_lock
+ * sb_lock (fs/fs-writeback.c)
+ * ->i_pages lock (__sync_single_inode)
+ *
+ * ->i_mmap_rwsem
+ * ->anon_vma.lock (vma_adjust)
+ *
+ * ->anon_vma.lock
+ * ->page_table_lock or pte_lock (anon_vma_prepare and various)
+ *
+ * ->page_table_lock or pte_lock
+ * ->swap_lock (try_to_unmap_one)
+ * ->private_lock (try_to_unmap_one)
+ * ->i_pages lock (try_to_unmap_one)
+ * ->lruvec->lru_lock (follow_page->mark_page_accessed)
+ * ->lruvec->lru_lock (check_pte_range->isolate_lru_page)
+ * ->private_lock (page_remove_rmap->set_page_dirty)
+ * ->i_pages lock (page_remove_rmap->set_page_dirty)
+ * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
+ * ->inode->i_lock (page_remove_rmap->set_page_dirty)
+ * ->memcg->move_lock (page_remove_rmap->lock_page_memcg)
+ * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
+ * ->inode->i_lock (zap_pte_range->set_page_dirty)
+ * ->private_lock (zap_pte_range->block_dirty_folio)
+ *
+ * ->i_mmap_rwsem
+ * ->tasklist_lock (memory_failure, collect_procs_ao)
+ */
+
+static void page_cache_delete(struct address_space *mapping,
+ struct folio *folio, void *shadow)
+{
+ XA_STATE(xas, &mapping->i_pages, folio->index);
+ long nr = 1;
+
+ mapping_set_update(&xas, mapping);
+
+ /* hugetlb pages are represented by a single entry in the xarray */
+ if (!folio_test_hugetlb(folio)) {
+ xas_set_order(&xas, folio->index, folio_order(folio));
+ nr = folio_nr_pages(folio);
+ }
+
+ VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
+
+ xas_store(&xas, shadow);
+ xas_init_marks(&xas);
+
+ folio->mapping = NULL;
+ /* Leave page->index set: truncation lookup relies upon it */
+ mapping->nrpages -= nr;
+}
+
+static void filemap_unaccount_folio(struct address_space *mapping,
+ struct folio *folio)
+{
+ long nr;
+
+ VM_BUG_ON_FOLIO(folio_mapped(folio), folio);
+ if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(folio_mapped(folio))) {
+ pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n",
+ current->comm, folio_pfn(folio));
+ dump_page(&folio->page, "still mapped when deleted");
+ dump_stack();
+ add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
+
+ if (mapping_exiting(mapping) && !folio_test_large(folio)) {
+ int mapcount = page_mapcount(&folio->page);
+
+ if (folio_ref_count(folio) >= mapcount + 2) {
+ /*
+ * All vmas have already been torn down, so it's
+ * a good bet that actually the page is unmapped
+ * and we'd rather not leak it: if we're wrong,
+ * another bad page check should catch it later.
+ */
+ page_mapcount_reset(&folio->page);
+ folio_ref_sub(folio, mapcount);
+ }
+ }
+ }
+
+ /* hugetlb folios do not participate in page cache accounting. */
+ if (folio_test_hugetlb(folio))
+ return;
+
+ nr = folio_nr_pages(folio);
+
+ __lruvec_stat_mod_folio(folio, NR_FILE_PAGES, -nr);
+ if (folio_test_swapbacked(folio)) {
+ __lruvec_stat_mod_folio(folio, NR_SHMEM, -nr);
+ if (folio_test_pmd_mappable(folio))
+ __lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, -nr);
+ } else if (folio_test_pmd_mappable(folio)) {
+ __lruvec_stat_mod_folio(folio, NR_FILE_THPS, -nr);
+ filemap_nr_thps_dec(mapping);
+ }
+
+ /*
+ * At this point folio must be either written or cleaned by
+ * truncate. Dirty folio here signals a bug and loss of
+ * unwritten data - on ordinary filesystems.
+ *
+ * But it's harmless on in-memory filesystems like tmpfs; and can
+ * occur when a driver which did get_user_pages() sets page dirty
+ * before putting it, while the inode is being finally evicted.
+ *
+ * Below fixes dirty accounting after removing the folio entirely
+ * but leaves the dirty flag set: it has no effect for truncated
+ * folio and anyway will be cleared before returning folio to
+ * buddy allocator.
+ */
+ if (WARN_ON_ONCE(folio_test_dirty(folio) &&
+ mapping_can_writeback(mapping)))
+ folio_account_cleaned(folio, inode_to_wb(mapping->host));
+}
+
+/*
+ * Delete a page from the page cache and free it. Caller has to make
+ * sure the page is locked and that nobody else uses it - or that usage
+ * is safe. The caller must hold the i_pages lock.
+ */
+void __filemap_remove_folio(struct folio *folio, void *shadow)
+{
+ struct address_space *mapping = folio->mapping;
+
+ trace_mm_filemap_delete_from_page_cache(folio);
+ filemap_unaccount_folio(mapping, folio);
+ page_cache_delete(mapping, folio, shadow);
+}
+
+void filemap_free_folio(struct address_space *mapping, struct folio *folio)
+{
+ void (*free_folio)(struct folio *);
+ int refs = 1;
+
+ free_folio = mapping->a_ops->free_folio;
+ if (free_folio)
+ free_folio(folio);
+
+ if (folio_test_large(folio) && !folio_test_hugetlb(folio))
+ refs = folio_nr_pages(folio);
+ folio_put_refs(folio, refs);
+}
+
+/**
+ * filemap_remove_folio - Remove folio from page cache.
+ * @folio: The folio.
+ *
+ * This must be called only on folios that are locked and have been
+ * verified to be in the page cache. It will never put the folio into
+ * the free list because the caller has a reference on the page.
+ */
+void filemap_remove_folio(struct folio *folio)
+{
+ struct address_space *mapping = folio->mapping;
+
+ BUG_ON(!folio_test_locked(folio));
+ spin_lock(&mapping->host->i_lock);
+ xa_lock_irq(&mapping->i_pages);
+ __filemap_remove_folio(folio, NULL);
+ xa_unlock_irq(&mapping->i_pages);
+ if (mapping_shrinkable(mapping))
+ inode_add_lru(mapping->host);
+ spin_unlock(&mapping->host->i_lock);
+
+ filemap_free_folio(mapping, folio);
+}
+
+/*
+ * page_cache_delete_batch - delete several folios from page cache
+ * @mapping: the mapping to which folios belong
+ * @fbatch: batch of folios to delete
+ *
+ * The function walks over mapping->i_pages and removes folios passed in
+ * @fbatch from the mapping. The function expects @fbatch to be sorted
+ * by page index and is optimised for it to be dense.
+ * It tolerates holes in @fbatch (mapping entries at those indices are not
+ * modified).
+ *
+ * The function expects the i_pages lock to be held.
+ */
+static void page_cache_delete_batch(struct address_space *mapping,
+ struct folio_batch *fbatch)
+{
+ XA_STATE(xas, &mapping->i_pages, fbatch->folios[0]->index);
+ long total_pages = 0;
+ int i = 0;
+ struct folio *folio;
+
+ mapping_set_update(&xas, mapping);
+ xas_for_each(&xas, folio, ULONG_MAX) {
+ if (i >= folio_batch_count(fbatch))
+ break;
+
+ /* A swap/dax/shadow entry got inserted? Skip it. */
+ if (xa_is_value(folio))
+ continue;
+ /*
+ * A page got inserted in our range? Skip it. We have our
+ * pages locked so they are protected from being removed.
+ * If we see a page whose index is higher than ours, it
+ * means our page has been removed, which shouldn't be
+ * possible because we're holding the PageLock.
+ */
+ if (folio != fbatch->folios[i]) {
+ VM_BUG_ON_FOLIO(folio->index >
+ fbatch->folios[i]->index, folio);
+ continue;
+ }
+
+ WARN_ON_ONCE(!folio_test_locked(folio));
+
+ folio->mapping = NULL;
+ /* Leave folio->index set: truncation lookup relies on it */
+
+ i++;
+ xas_store(&xas, NULL);
+ total_pages += folio_nr_pages(folio);
+ }
+ mapping->nrpages -= total_pages;
+}
+
+void delete_from_page_cache_batch(struct address_space *mapping,
+ struct folio_batch *fbatch)
+{
+ int i;
+
+ if (!folio_batch_count(fbatch))
+ return;
+
+ spin_lock(&mapping->host->i_lock);
+ xa_lock_irq(&mapping->i_pages);
+ for (i = 0; i < folio_batch_count(fbatch); i++) {
+ struct folio *folio = fbatch->folios[i];
+
+ trace_mm_filemap_delete_from_page_cache(folio);
+ filemap_unaccount_folio(mapping, folio);
+ }
+ page_cache_delete_batch(mapping, fbatch);
+ xa_unlock_irq(&mapping->i_pages);
+ if (mapping_shrinkable(mapping))
+ inode_add_lru(mapping->host);
+ spin_unlock(&mapping->host->i_lock);
+
+ for (i = 0; i < folio_batch_count(fbatch); i++)
+ filemap_free_folio(mapping, fbatch->folios[i]);
+}
+
+int filemap_check_errors(struct address_space *mapping)
+{
+ int ret = 0;
+ /* Check for outstanding write errors */
+ if (test_bit(AS_ENOSPC, &mapping->flags) &&
+ test_and_clear_bit(AS_ENOSPC, &mapping->flags))
+ ret = -ENOSPC;
+ if (test_bit(AS_EIO, &mapping->flags) &&
+ test_and_clear_bit(AS_EIO, &mapping->flags))
+ ret = -EIO;
+ return ret;
+}
+EXPORT_SYMBOL(filemap_check_errors);
+
+static int filemap_check_and_keep_errors(struct address_space *mapping)
+{
+ /* Check for outstanding write errors */
+ if (test_bit(AS_EIO, &mapping->flags))
+ return -EIO;
+ if (test_bit(AS_ENOSPC, &mapping->flags))
+ return -ENOSPC;
+ return 0;
+}
+
+/**
+ * filemap_fdatawrite_wbc - start writeback on mapping dirty pages in range
+ * @mapping: address space structure to write
+ * @wbc: the writeback_control controlling the writeout
+ *
+ * Call writepages on the mapping using the provided wbc to control the
+ * writeout.
+ *
+ * Return: %0 on success, negative error code otherwise.
+ */
+int filemap_fdatawrite_wbc(struct address_space *mapping,
+ struct writeback_control *wbc)
+{
+ int ret;
+
+ if (!mapping_can_writeback(mapping) ||
+ !mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
+ return 0;
+
+ wbc_attach_fdatawrite_inode(wbc, mapping->host);
+ ret = do_writepages(mapping, wbc);
+ wbc_detach_inode(wbc);
+ return ret;
+}
+EXPORT_SYMBOL(filemap_fdatawrite_wbc);
+
+/**
+ * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
+ * @mapping: address space structure to write
+ * @start: offset in bytes where the range starts
+ * @end: offset in bytes where the range ends (inclusive)
+ * @sync_mode: enable synchronous operation
+ *
+ * Start writeback against all of a mapping's dirty pages that lie
+ * within the byte offsets <start, end> inclusive.
+ *
+ * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
+ * opposed to a regular memory cleansing writeback. The difference between
+ * these two operations is that if a dirty page/buffer is encountered, it must
+ * be waited upon, and not just skipped over.
+ *
+ * Return: %0 on success, negative error code otherwise.
+ */
+int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
+ loff_t end, int sync_mode)
+{
+ struct writeback_control wbc = {
+ .sync_mode = sync_mode,
+ .nr_to_write = LONG_MAX,
+ .range_start = start,
+ .range_end = end,
+ };
+
+ return filemap_fdatawrite_wbc(mapping, &wbc);
+}
+
+static inline int __filemap_fdatawrite(struct address_space *mapping,
+ int sync_mode)
+{
+ return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
+}
+
+int filemap_fdatawrite(struct address_space *mapping)
+{
+ return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
+}
+EXPORT_SYMBOL(filemap_fdatawrite);
+
+int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
+ loff_t end)
+{
+ return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
+}
+EXPORT_SYMBOL(filemap_fdatawrite_range);
+
+/**
+ * filemap_flush - mostly a non-blocking flush
+ * @mapping: target address_space
+ *
+ * This is a mostly non-blocking flush. Not suitable for data-integrity
+ * purposes - I/O may not be started against all dirty pages.
+ *
+ * Return: %0 on success, negative error code otherwise.
+ */
+int filemap_flush(struct address_space *mapping)
+{
+ return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
+}
+EXPORT_SYMBOL(filemap_flush);
+
+/**
+ * filemap_range_has_page - check if a page exists in range.
+ * @mapping: address space within which to check
+ * @start_byte: offset in bytes where the range starts
+ * @end_byte: offset in bytes where the range ends (inclusive)
+ *
+ * Find at least one page in the range supplied, usually used to check if
+ * direct writing in this range will trigger a writeback.
+ *
+ * Return: %true if at least one page exists in the specified range,
+ * %false otherwise.
+ */
+bool filemap_range_has_page(struct address_space *mapping,
+ loff_t start_byte, loff_t end_byte)
+{
+ struct page *page;
+ XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT);
+ pgoff_t max = end_byte >> PAGE_SHIFT;
+
+ if (end_byte < start_byte)
+ return false;
+
+ rcu_read_lock();
+ for (;;) {
+ page = xas_find(&xas, max);
+ if (xas_retry(&xas, page))
+ continue;
+ /* Shadow entries don't count */
+ if (xa_is_value(page))
+ continue;
+ /*
+ * We don't need to try to pin this page; we're about to
+ * release the RCU lock anyway. It is enough to know that
+ * there was a page here recently.
+ */
+ break;
+ }
+ rcu_read_unlock();
+
+ return page != NULL;
+}
+EXPORT_SYMBOL(filemap_range_has_page);
+
+static void __filemap_fdatawait_range(struct address_space *mapping,
+ loff_t start_byte, loff_t end_byte)
+{
+ pgoff_t index = start_byte >> PAGE_SHIFT;
+ pgoff_t end = end_byte >> PAGE_SHIFT;
+ struct pagevec pvec;
+ int nr_pages;
+
+ if (end_byte < start_byte)
+ return;
+
+ pagevec_init(&pvec);
+ while (index <= end) {
+ unsigned i;
+
+ nr_pages = pagevec_lookup_range_tag(&pvec, mapping, &index,
+ end, PAGECACHE_TAG_WRITEBACK);
+ if (!nr_pages)
+ break;
+
+ for (i = 0; i < nr_pages; i++) {
+ struct page *page = pvec.pages[i];
+
+ wait_on_page_writeback(page);
+ ClearPageError(page);
+ }
+ pagevec_release(&pvec);
+ cond_resched();
+ }
+}
+
+/**
+ * filemap_fdatawait_range - wait for writeback to complete
+ * @mapping: address space structure to wait for
+ * @start_byte: offset in bytes where the range starts
+ * @end_byte: offset in bytes where the range ends (inclusive)
+ *
+ * Walk the list of under-writeback pages of the given address space
+ * in the given range and wait for all of them. Check error status of
+ * the address space and return it.
+ *
+ * Since the error status of the address space is cleared by this function,
+ * callers are responsible for checking the return value and handling and/or
+ * reporting the error.
+ *
+ * Return: error status of the address space.
+ */
+int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
+ loff_t end_byte)
+{
+ __filemap_fdatawait_range(mapping, start_byte, end_byte);
+ return filemap_check_errors(mapping);
+}
+EXPORT_SYMBOL(filemap_fdatawait_range);
+
+/**
+ * filemap_fdatawait_range_keep_errors - wait for writeback to complete
+ * @mapping: address space structure to wait for
+ * @start_byte: offset in bytes where the range starts
+ * @end_byte: offset in bytes where the range ends (inclusive)
+ *
+ * Walk the list of under-writeback pages of the given address space in the
+ * given range and wait for all of them. Unlike filemap_fdatawait_range(),
+ * this function does not clear error status of the address space.
+ *
+ * Use this function if callers don't handle errors themselves. Expected
+ * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
+ * fsfreeze(8)
+ */
+int filemap_fdatawait_range_keep_errors(struct address_space *mapping,
+ loff_t start_byte, loff_t end_byte)
+{
+ __filemap_fdatawait_range(mapping, start_byte, end_byte);
+ return filemap_check_and_keep_errors(mapping);
+}
+EXPORT_SYMBOL(filemap_fdatawait_range_keep_errors);
+
+/**
+ * file_fdatawait_range - wait for writeback to complete
+ * @file: file pointing to address space structure to wait for
+ * @start_byte: offset in bytes where the range starts
+ * @end_byte: offset in bytes where the range ends (inclusive)
+ *
+ * Walk the list of under-writeback pages of the address space that file
+ * refers to, in the given range and wait for all of them. Check error
+ * status of the address space vs. the file->f_wb_err cursor and return it.
+ *
+ * Since the error status of the file is advanced by this function,
+ * callers are responsible for checking the return value and handling and/or
+ * reporting the error.
+ *
+ * Return: error status of the address space vs. the file->f_wb_err cursor.
+ */
+int file_fdatawait_range(struct file *file, loff_t start_byte, loff_t end_byte)
+{
+ struct address_space *mapping = file->f_mapping;
+
+ __filemap_fdatawait_range(mapping, start_byte, end_byte);
+ return file_check_and_advance_wb_err(file);
+}
+EXPORT_SYMBOL(file_fdatawait_range);
+
+/**
+ * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
+ * @mapping: address space structure to wait for
+ *
+ * Walk the list of under-writeback pages of the given address space
+ * and wait for all of them. Unlike filemap_fdatawait(), this function
+ * does not clear error status of the address space.
+ *
+ * Use this function if callers don't handle errors themselves. Expected
+ * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
+ * fsfreeze(8)
+ *
+ * Return: error status of the address space.
+ */
+int filemap_fdatawait_keep_errors(struct address_space *mapping)
+{
+ __filemap_fdatawait_range(mapping, 0, LLONG_MAX);
+ return filemap_check_and_keep_errors(mapping);
+}
+EXPORT_SYMBOL(filemap_fdatawait_keep_errors);
+
+/* Returns true if writeback might be needed or already in progress. */
+static bool mapping_needs_writeback(struct address_space *mapping)
+{
+ return mapping->nrpages;
+}
+
+bool filemap_range_has_writeback(struct address_space *mapping,
+ loff_t start_byte, loff_t end_byte)
+{
+ XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT);
+ pgoff_t max = end_byte >> PAGE_SHIFT;
+ struct folio *folio;
+
+ if (end_byte < start_byte)
+ return false;
+
+ rcu_read_lock();
+ xas_for_each(&xas, folio, max) {
+ if (xas_retry(&xas, folio))
+ continue;
+ if (xa_is_value(folio))
+ continue;
+ if (folio_test_dirty(folio) || folio_test_locked(folio) ||
+ folio_test_writeback(folio))
+ break;
+ }
+ rcu_read_unlock();
+ return folio != NULL;
+}
+EXPORT_SYMBOL_GPL(filemap_range_has_writeback);
+
+/**
+ * filemap_write_and_wait_range - write out & wait on a file range
+ * @mapping: the address_space for the pages
+ * @lstart: offset in bytes where the range starts
+ * @lend: offset in bytes where the range ends (inclusive)
+ *
+ * Write out and wait upon file offsets lstart->lend, inclusive.
+ *
+ * Note that @lend is inclusive (describes the last byte to be written) so
+ * that this function can be used to write to the very end-of-file (end = -1).
+ *
+ * Return: error status of the address space.
+ */
+int filemap_write_and_wait_range(struct address_space *mapping,
+ loff_t lstart, loff_t lend)
+{
+ int err = 0, err2;
+
+ if (mapping_needs_writeback(mapping)) {
+ err = __filemap_fdatawrite_range(mapping, lstart, lend,
+ WB_SYNC_ALL);
+ /*
+ * Even if the above returned error, the pages may be
+ * written partially (e.g. -ENOSPC), so we wait for it.
+ * But the -EIO is special case, it may indicate the worst
+ * thing (e.g. bug) happened, so we avoid waiting for it.
+ */
+ if (err != -EIO)
+ __filemap_fdatawait_range(mapping, lstart, lend);
+ }
+ err2 = filemap_check_errors(mapping);
+ if (!err)
+ err = err2;
+ return err;
+}
+EXPORT_SYMBOL(filemap_write_and_wait_range);
+
+void __filemap_set_wb_err(struct address_space *mapping, int err)
+{
+ errseq_t eseq = errseq_set(&mapping->wb_err, err);
+
+ trace_filemap_set_wb_err(mapping, eseq);
+}
+EXPORT_SYMBOL(__filemap_set_wb_err);
+
+/**
+ * file_check_and_advance_wb_err - report wb error (if any) that was previously
+ * and advance wb_err to current one
+ * @file: struct file on which the error is being reported
+ *
+ * When userland calls fsync (or something like nfsd does the equivalent), we
+ * want to report any writeback errors that occurred since the last fsync (or
+ * since the file was opened if there haven't been any).
+ *
+ * Grab the wb_err from the mapping. If it matches what we have in the file,
+ * then just quickly return 0. The file is all caught up.
+ *
+ * If it doesn't match, then take the mapping value, set the "seen" flag in
+ * it and try to swap it into place. If it works, or another task beat us
+ * to it with the new value, then update the f_wb_err and return the error
+ * portion. The error at this point must be reported via proper channels
+ * (a'la fsync, or NFS COMMIT operation, etc.).
+ *
+ * While we handle mapping->wb_err with atomic operations, the f_wb_err
+ * value is protected by the f_lock since we must ensure that it reflects
+ * the latest value swapped in for this file descriptor.
+ *
+ * Return: %0 on success, negative error code otherwise.
+ */
+int file_check_and_advance_wb_err(struct file *file)
+{
+ int err = 0;
+ errseq_t old = READ_ONCE(file->f_wb_err);
+ struct address_space *mapping = file->f_mapping;
+
+ /* Locklessly handle the common case where nothing has changed */
+ if (errseq_check(&mapping->wb_err, old)) {
+ /* Something changed, must use slow path */
+ spin_lock(&file->f_lock);
+ old = file->f_wb_err;
+ err = errseq_check_and_advance(&mapping->wb_err,
+ &file->f_wb_err);
+ trace_file_check_and_advance_wb_err(file, old);
+ spin_unlock(&file->f_lock);
+ }
+
+ /*
+ * We're mostly using this function as a drop in replacement for
+ * filemap_check_errors. Clear AS_EIO/AS_ENOSPC to emulate the effect
+ * that the legacy code would have had on these flags.
+ */
+ clear_bit(AS_EIO, &mapping->flags);
+ clear_bit(AS_ENOSPC, &mapping->flags);
+ return err;
+}
+EXPORT_SYMBOL(file_check_and_advance_wb_err);
+
+/**
+ * file_write_and_wait_range - write out & wait on a file range
+ * @file: file pointing to address_space with pages
+ * @lstart: offset in bytes where the range starts
+ * @lend: offset in bytes where the range ends (inclusive)
+ *
+ * Write out and wait upon file offsets lstart->lend, inclusive.
+ *
+ * Note that @lend is inclusive (describes the last byte to be written) so
+ * that this function can be used to write to the very end-of-file (end = -1).
+ *
+ * After writing out and waiting on the data, we check and advance the
+ * f_wb_err cursor to the latest value, and return any errors detected there.
+ *
+ * Return: %0 on success, negative error code otherwise.
+ */
+int file_write_and_wait_range(struct file *file, loff_t lstart, loff_t lend)
+{
+ int err = 0, err2;
+ struct address_space *mapping = file->f_mapping;
+
+ if (mapping_needs_writeback(mapping)) {
+ err = __filemap_fdatawrite_range(mapping, lstart, lend,
+ WB_SYNC_ALL);
+ /* See comment of filemap_write_and_wait() */
+ if (err != -EIO)
+ __filemap_fdatawait_range(mapping, lstart, lend);
+ }
+ err2 = file_check_and_advance_wb_err(file);
+ if (!err)
+ err = err2;
+ return err;
+}
+EXPORT_SYMBOL(file_write_and_wait_range);
+
+/**
+ * replace_page_cache_page - replace a pagecache page with a new one
+ * @old: page to be replaced
+ * @new: page to replace with
+ *
+ * This function replaces a page in the pagecache with a new one. On
+ * success it acquires the pagecache reference for the new page and
+ * drops it for the old page. Both the old and new pages must be
+ * locked. This function does not add the new page to the LRU, the
+ * caller must do that.
+ *
+ * The remove + add is atomic. This function cannot fail.
+ */
+void replace_page_cache_page(struct page *old, struct page *new)
+{
+ struct folio *fold = page_folio(old);
+ struct folio *fnew = page_folio(new);
+ struct address_space *mapping = old->mapping;
+ void (*free_folio)(struct folio *) = mapping->a_ops->free_folio;
+ pgoff_t offset = old->index;
+ XA_STATE(xas, &mapping->i_pages, offset);
+
+ VM_BUG_ON_PAGE(!PageLocked(old), old);
+ VM_BUG_ON_PAGE(!PageLocked(new), new);
+ VM_BUG_ON_PAGE(new->mapping, new);
+
+ get_page(new);
+ new->mapping = mapping;
+ new->index = offset;
+
+ mem_cgroup_migrate(fold, fnew);
+
+ xas_lock_irq(&xas);
+ xas_store(&xas, new);
+
+ old->mapping = NULL;
+ /* hugetlb pages do not participate in page cache accounting. */
+ if (!PageHuge(old))
+ __dec_lruvec_page_state(old, NR_FILE_PAGES);
+ if (!PageHuge(new))
+ __inc_lruvec_page_state(new, NR_FILE_PAGES);
+ if (PageSwapBacked(old))
+ __dec_lruvec_page_state(old, NR_SHMEM);
+ if (PageSwapBacked(new))
+ __inc_lruvec_page_state(new, NR_SHMEM);
+ xas_unlock_irq(&xas);
+ if (free_folio)
+ free_folio(fold);
+ folio_put(fold);
+}
+EXPORT_SYMBOL_GPL(replace_page_cache_page);
+
+noinline int __filemap_add_folio(struct address_space *mapping,
+ struct folio *folio, pgoff_t index, gfp_t gfp, void **shadowp)
+{
+ XA_STATE(xas, &mapping->i_pages, index);
+ int huge = folio_test_hugetlb(folio);
+ bool charged = false;
+ long nr = 1;
+
+ VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
+ VM_BUG_ON_FOLIO(folio_test_swapbacked(folio), folio);
+ mapping_set_update(&xas, mapping);
+
+ if (!huge) {
+ int error = mem_cgroup_charge(folio, NULL, gfp);
+ VM_BUG_ON_FOLIO(index & (folio_nr_pages(folio) - 1), folio);
+ if (error)
+ return error;
+ charged = true;
+ xas_set_order(&xas, index, folio_order(folio));
+ nr = folio_nr_pages(folio);
+ }
+
+ gfp &= GFP_RECLAIM_MASK;
+ folio_ref_add(folio, nr);
+ folio->mapping = mapping;
+ folio->index = xas.xa_index;
+
+ do {
+ unsigned int order = xa_get_order(xas.xa, xas.xa_index);
+ void *entry, *old = NULL;
+
+ if (order > folio_order(folio))
+ xas_split_alloc(&xas, xa_load(xas.xa, xas.xa_index),
+ order, gfp);
+ xas_lock_irq(&xas);
+ xas_for_each_conflict(&xas, entry) {
+ old = entry;
+ if (!xa_is_value(entry)) {
+ xas_set_err(&xas, -EEXIST);
+ goto unlock;
+ }
+ }
+
+ if (old) {
+ if (shadowp)
+ *shadowp = old;
+ /* entry may have been split before we acquired lock */
+ order = xa_get_order(xas.xa, xas.xa_index);
+ if (order > folio_order(folio)) {
+ /* How to handle large swap entries? */
+ BUG_ON(shmem_mapping(mapping));
+ xas_split(&xas, old, order);
+ xas_reset(&xas);
+ }
+ }
+
+ xas_store(&xas, folio);
+ if (xas_error(&xas))
+ goto unlock;
+
+ mapping->nrpages += nr;
+
+ /* hugetlb pages do not participate in page cache accounting */
+ if (!huge) {
+ __lruvec_stat_mod_folio(folio, NR_FILE_PAGES, nr);
+ if (folio_test_pmd_mappable(folio))
+ __lruvec_stat_mod_folio(folio,
+ NR_FILE_THPS, nr);
+ }
+unlock:
+ xas_unlock_irq(&xas);
+ } while (xas_nomem(&xas, gfp));
+
+ if (xas_error(&xas))
+ goto error;
+
+ trace_mm_filemap_add_to_page_cache(folio);
+ return 0;
+error:
+ if (charged)
+ mem_cgroup_uncharge(folio);
+ folio->mapping = NULL;
+ /* Leave page->index set: truncation relies upon it */
+ folio_put_refs(folio, nr);
+ return xas_error(&xas);
+}
+ALLOW_ERROR_INJECTION(__filemap_add_folio, ERRNO);
+
+int filemap_add_folio(struct address_space *mapping, struct folio *folio,
+ pgoff_t index, gfp_t gfp)
+{
+ void *shadow = NULL;
+ int ret;
+
+ __folio_set_locked(folio);
+ ret = __filemap_add_folio(mapping, folio, index, gfp, &shadow);
+ if (unlikely(ret))
+ __folio_clear_locked(folio);
+ else {
+ /*
+ * The folio might have been evicted from cache only
+ * recently, in which case it should be activated like
+ * any other repeatedly accessed folio.
+ * The exception is folios getting rewritten; evicting other
+ * data from the working set, only to cache data that will
+ * get overwritten with something else, is a waste of memory.
+ */
+ WARN_ON_ONCE(folio_test_active(folio));
+ if (!(gfp & __GFP_WRITE) && shadow)
+ workingset_refault(folio, shadow);
+ folio_add_lru(folio);
+ }
+ return ret;
+}
+EXPORT_SYMBOL_GPL(filemap_add_folio);
+
+#ifdef CONFIG_NUMA
+struct folio *filemap_alloc_folio(gfp_t gfp, unsigned int order)
+{
+ int n;
+ struct folio *folio;
+
+ if (cpuset_do_page_mem_spread()) {
+ unsigned int cpuset_mems_cookie;
+ do {
+ cpuset_mems_cookie = read_mems_allowed_begin();
+ n = cpuset_mem_spread_node();
+ folio = __folio_alloc_node(gfp, order, n);
+ } while (!folio && read_mems_allowed_retry(cpuset_mems_cookie));
+
+ return folio;
+ }
+ return folio_alloc(gfp, order);
+}
+EXPORT_SYMBOL(filemap_alloc_folio);
+#endif
+
+/*
+ * filemap_invalidate_lock_two - lock invalidate_lock for two mappings
+ *
+ * Lock exclusively invalidate_lock of any passed mapping that is not NULL.
+ *
+ * @mapping1: the first mapping to lock
+ * @mapping2: the second mapping to lock
+ */
+void filemap_invalidate_lock_two(struct address_space *mapping1,
+ struct address_space *mapping2)
+{
+ if (mapping1 > mapping2)
+ swap(mapping1, mapping2);
+ if (mapping1)
+ down_write(&mapping1->invalidate_lock);
+ if (mapping2 && mapping1 != mapping2)
+ down_write_nested(&mapping2->invalidate_lock, 1);
+}
+EXPORT_SYMBOL(filemap_invalidate_lock_two);
+
+/*
+ * filemap_invalidate_unlock_two - unlock invalidate_lock for two mappings
+ *
+ * Unlock exclusive invalidate_lock of any passed mapping that is not NULL.
+ *
+ * @mapping1: the first mapping to unlock
+ * @mapping2: the second mapping to unlock
+ */
+void filemap_invalidate_unlock_two(struct address_space *mapping1,
+ struct address_space *mapping2)
+{
+ if (mapping1)
+ up_write(&mapping1->invalidate_lock);
+ if (mapping2 && mapping1 != mapping2)
+ up_write(&mapping2->invalidate_lock);
+}
+EXPORT_SYMBOL(filemap_invalidate_unlock_two);
+
+/*
+ * In order to wait for pages to become available there must be
+ * waitqueues associated with pages. By using a hash table of
+ * waitqueues where the bucket discipline is to maintain all
+ * waiters on the same queue and wake all when any of the pages
+ * become available, and for the woken contexts to check to be
+ * sure the appropriate page became available, this saves space
+ * at a cost of "thundering herd" phenomena during rare hash
+ * collisions.
+ */
+#define PAGE_WAIT_TABLE_BITS 8
+#define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
+static wait_queue_head_t folio_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned;
+
+static wait_queue_head_t *folio_waitqueue(struct folio *folio)
+{
+ return &folio_wait_table[hash_ptr(folio, PAGE_WAIT_TABLE_BITS)];
+}
+
+void __init pagecache_init(void)
+{
+ int i;
+
+ for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++)
+ init_waitqueue_head(&folio_wait_table[i]);
+
+ page_writeback_init();
+}
+
+/*
+ * The page wait code treats the "wait->flags" somewhat unusually, because
+ * we have multiple different kinds of waits, not just the usual "exclusive"
+ * one.
+ *
+ * We have:
+ *
+ * (a) no special bits set:
+ *
+ * We're just waiting for the bit to be released, and when a waker
+ * calls the wakeup function, we set WQ_FLAG_WOKEN and wake it up,
+ * and remove it from the wait queue.
+ *
+ * Simple and straightforward.
+ *
+ * (b) WQ_FLAG_EXCLUSIVE:
+ *
+ * The waiter is waiting to get the lock, and only one waiter should
+ * be woken up to avoid any thundering herd behavior. We'll set the
+ * WQ_FLAG_WOKEN bit, wake it up, and remove it from the wait queue.
+ *
+ * This is the traditional exclusive wait.
+ *
+ * (c) WQ_FLAG_EXCLUSIVE | WQ_FLAG_CUSTOM:
+ *
+ * The waiter is waiting to get the bit, and additionally wants the
+ * lock to be transferred to it for fair lock behavior. If the lock
+ * cannot be taken, we stop walking the wait queue without waking
+ * the waiter.
+ *
+ * This is the "fair lock handoff" case, and in addition to setting
+ * WQ_FLAG_WOKEN, we set WQ_FLAG_DONE to let the waiter easily see
+ * that it now has the lock.
+ */
+static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *arg)
+{
+ unsigned int flags;
+ struct wait_page_key *key = arg;
+ struct wait_page_queue *wait_page
+ = container_of(wait, struct wait_page_queue, wait);
+
+ if (!wake_page_match(wait_page, key))
+ return 0;
+
+ /*
+ * If it's a lock handoff wait, we get the bit for it, and
+ * stop walking (and do not wake it up) if we can't.
+ */
+ flags = wait->flags;
+ if (flags & WQ_FLAG_EXCLUSIVE) {
+ if (test_bit(key->bit_nr, &key->folio->flags))
+ return -1;
+ if (flags & WQ_FLAG_CUSTOM) {
+ if (test_and_set_bit(key->bit_nr, &key->folio->flags))
+ return -1;
+ flags |= WQ_FLAG_DONE;
+ }
+ }
+
+ /*
+ * We are holding the wait-queue lock, but the waiter that
+ * is waiting for this will be checking the flags without
+ * any locking.
+ *
+ * So update the flags atomically, and wake up the waiter
+ * afterwards to avoid any races. This store-release pairs
+ * with the load-acquire in folio_wait_bit_common().
+ */
+ smp_store_release(&wait->flags, flags | WQ_FLAG_WOKEN);
+ wake_up_state(wait->private, mode);
+
+ /*
+ * Ok, we have successfully done what we're waiting for,
+ * and we can unconditionally remove the wait entry.
+ *
+ * Note that this pairs with the "finish_wait()" in the
+ * waiter, and has to be the absolute last thing we do.
+ * After this list_del_init(&wait->entry) the wait entry
+ * might be de-allocated and the process might even have
+ * exited.
+ */
+ list_del_init_careful(&wait->entry);
+ return (flags & WQ_FLAG_EXCLUSIVE) != 0;
+}
+
+static void folio_wake_bit(struct folio *folio, int bit_nr)
+{
+ wait_queue_head_t *q = folio_waitqueue(folio);
+ struct wait_page_key key;
+ unsigned long flags;
+ wait_queue_entry_t bookmark;
+
+ key.folio = folio;
+ key.bit_nr = bit_nr;
+ key.page_match = 0;
+
+ bookmark.flags = 0;
+ bookmark.private = NULL;
+ bookmark.func = NULL;
+ INIT_LIST_HEAD(&bookmark.entry);
+
+ spin_lock_irqsave(&q->lock, flags);
+ __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);
+
+ while (bookmark.flags & WQ_FLAG_BOOKMARK) {
+ /*
+ * Take a breather from holding the lock,
+ * allow pages that finish wake up asynchronously
+ * to acquire the lock and remove themselves
+ * from wait queue
+ */
+ spin_unlock_irqrestore(&q->lock, flags);
+ cpu_relax();
+ spin_lock_irqsave(&q->lock, flags);
+ __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);
+ }
+
+ /*
+ * It's possible to miss clearing waiters here, when we woke our page
+ * waiters, but the hashed waitqueue has waiters for other pages on it.
+ * That's okay, it's a rare case. The next waker will clear it.
+ *
+ * Note that, depending on the page pool (buddy, hugetlb, ZONE_DEVICE,
+ * other), the flag may be cleared in the course of freeing the page;
+ * but that is not required for correctness.
+ */
+ if (!waitqueue_active(q) || !key.page_match)
+ folio_clear_waiters(folio);
+
+ spin_unlock_irqrestore(&q->lock, flags);
+}
+
+static void folio_wake(struct folio *folio, int bit)
+{
+ if (!folio_test_waiters(folio))
+ return;
+ folio_wake_bit(folio, bit);
+}
+
+/*
+ * A choice of three behaviors for folio_wait_bit_common():
+ */
+enum behavior {
+ EXCLUSIVE, /* Hold ref to page and take the bit when woken, like
+ * __folio_lock() waiting on then setting PG_locked.
+ */
+ SHARED, /* Hold ref to page and check the bit when woken, like
+ * folio_wait_writeback() waiting on PG_writeback.
+ */
+ DROP, /* Drop ref to page before wait, no check when woken,
+ * like folio_put_wait_locked() on PG_locked.
+ */
+};
+
+/*
+ * Attempt to check (or get) the folio flag, and mark us done
+ * if successful.
+ */
+static inline bool folio_trylock_flag(struct folio *folio, int bit_nr,
+ struct wait_queue_entry *wait)
+{
+ if (wait->flags & WQ_FLAG_EXCLUSIVE) {
+ if (test_and_set_bit(bit_nr, &folio->flags))
+ return false;
+ } else if (test_bit(bit_nr, &folio->flags))
+ return false;
+
+ wait->flags |= WQ_FLAG_WOKEN | WQ_FLAG_DONE;
+ return true;
+}
+
+/* How many times do we accept lock stealing from under a waiter? */
+int sysctl_page_lock_unfairness = 5;
+
+static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
+ int state, enum behavior behavior)
+{
+ wait_queue_head_t *q = folio_waitqueue(folio);
+ int unfairness = sysctl_page_lock_unfairness;
+ struct wait_page_queue wait_page;
+ wait_queue_entry_t *wait = &wait_page.wait;
+ bool thrashing = false;
+ unsigned long pflags;
+ bool in_thrashing;
+
+ if (bit_nr == PG_locked &&
+ !folio_test_uptodate(folio) && folio_test_workingset(folio)) {
+ delayacct_thrashing_start(&in_thrashing);
+ psi_memstall_enter(&pflags);
+ thrashing = true;
+ }
+
+ init_wait(wait);
+ wait->func = wake_page_function;
+ wait_page.folio = folio;
+ wait_page.bit_nr = bit_nr;
+
+repeat:
+ wait->flags = 0;
+ if (behavior == EXCLUSIVE) {
+ wait->flags = WQ_FLAG_EXCLUSIVE;
+ if (--unfairness < 0)
+ wait->flags |= WQ_FLAG_CUSTOM;
+ }
+
+ /*
+ * Do one last check whether we can get the
+ * page bit synchronously.
+ *
+ * Do the folio_set_waiters() marking before that
+ * to let any waker we _just_ missed know they
+ * need to wake us up (otherwise they'll never
+ * even go to the slow case that looks at the
+ * page queue), and add ourselves to the wait
+ * queue if we need to sleep.
+ *
+ * This part needs to be done under the queue
+ * lock to avoid races.
+ */
+ spin_lock_irq(&q->lock);
+ folio_set_waiters(folio);
+ if (!folio_trylock_flag(folio, bit_nr, wait))
+ __add_wait_queue_entry_tail(q, wait);
+ spin_unlock_irq(&q->lock);
+
+ /*
+ * From now on, all the logic will be based on
+ * the WQ_FLAG_WOKEN and WQ_FLAG_DONE flag, to
+ * see whether the page bit testing has already
+ * been done by the wake function.
+ *
+ * We can drop our reference to the folio.
+ */
+ if (behavior == DROP)
+ folio_put(folio);
+
+ /*
+ * Note that until the "finish_wait()", or until
+ * we see the WQ_FLAG_WOKEN flag, we need to
+ * be very careful with the 'wait->flags', because
+ * we may race with a waker that sets them.
+ */
+ for (;;) {
+ unsigned int flags;
+
+ set_current_state(state);
+
+ /* Loop until we've been woken or interrupted */
+ flags = smp_load_acquire(&wait->flags);
+ if (!(flags & WQ_FLAG_WOKEN)) {
+ if (signal_pending_state(state, current))
+ break;
+
+ io_schedule();
+ continue;
+ }
+
+ /* If we were non-exclusive, we're done */
+ if (behavior != EXCLUSIVE)
+ break;
+
+ /* If the waker got the lock for us, we're done */
+ if (flags & WQ_FLAG_DONE)
+ break;
+
+ /*
+ * Otherwise, if we're getting the lock, we need to
+ * try to get it ourselves.
+ *
+ * And if that fails, we'll have to retry this all.
+ */
+ if (unlikely(test_and_set_bit(bit_nr, folio_flags(folio, 0))))
+ goto repeat;
+
+ wait->flags |= WQ_FLAG_DONE;
+ break;
+ }
+
+ /*
+ * If a signal happened, this 'finish_wait()' may remove the last
+ * waiter from the wait-queues, but the folio waiters bit will remain
+ * set. That's ok. The next wakeup will take care of it, and trying
+ * to do it here would be difficult and prone to races.
+ */
+ finish_wait(q, wait);
+
+ if (thrashing) {
+ delayacct_thrashing_end(&in_thrashing);
+ psi_memstall_leave(&pflags);
+ }
+
+ /*
+ * NOTE! The wait->flags weren't stable until we've done the
+ * 'finish_wait()', and we could have exited the loop above due
+ * to a signal, and had a wakeup event happen after the signal
+ * test but before the 'finish_wait()'.
+ *
+ * So only after the finish_wait() can we reliably determine
+ * if we got woken up or not, so we can now figure out the final
+ * return value based on that state without races.
+ *
+ * Also note that WQ_FLAG_WOKEN is sufficient for a non-exclusive
+ * waiter, but an exclusive one requires WQ_FLAG_DONE.
+ */
+ if (behavior == EXCLUSIVE)
+ return wait->flags & WQ_FLAG_DONE ? 0 : -EINTR;
+
+ return wait->flags & WQ_FLAG_WOKEN ? 0 : -EINTR;
+}
+
+#ifdef CONFIG_MIGRATION
+/**
+ * migration_entry_wait_on_locked - Wait for a migration entry to be removed
+ * @entry: migration swap entry.
+ * @ptep: mapped pte pointer. Will return with the ptep unmapped. Only required
+ * for pte entries, pass NULL for pmd entries.
+ * @ptl: already locked ptl. This function will drop the lock.
+ *
+ * Wait for a migration entry referencing the given page to be removed. This is
+ * equivalent to put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE) except
+ * this can be called without taking a reference on the page. Instead this
+ * should be called while holding the ptl for the migration entry referencing
+ * the page.
+ *
+ * Returns after unmapping and unlocking the pte/ptl with pte_unmap_unlock().
+ *
+ * This follows the same logic as folio_wait_bit_common() so see the comments
+ * there.
+ */
+void migration_entry_wait_on_locked(swp_entry_t entry, pte_t *ptep,
+ spinlock_t *ptl)
+{
+ struct wait_page_queue wait_page;
+ wait_queue_entry_t *wait = &wait_page.wait;
+ bool thrashing = false;
+ unsigned long pflags;
+ bool in_thrashing;
+ wait_queue_head_t *q;
+ struct folio *folio = page_folio(pfn_swap_entry_to_page(entry));
+
+ q = folio_waitqueue(folio);
+ if (!folio_test_uptodate(folio) && folio_test_workingset(folio)) {
+ delayacct_thrashing_start(&in_thrashing);
+ psi_memstall_enter(&pflags);
+ thrashing = true;
+ }
+
+ init_wait(wait);
+ wait->func = wake_page_function;
+ wait_page.folio = folio;
+ wait_page.bit_nr = PG_locked;
+ wait->flags = 0;
+
+ spin_lock_irq(&q->lock);
+ folio_set_waiters(folio);
+ if (!folio_trylock_flag(folio, PG_locked, wait))
+ __add_wait_queue_entry_tail(q, wait);
+ spin_unlock_irq(&q->lock);
+
+ /*
+ * If a migration entry exists for the page the migration path must hold
+ * a valid reference to the page, and it must take the ptl to remove the
+ * migration entry. So the page is valid until the ptl is dropped.
+ */
+ if (ptep)
+ pte_unmap_unlock(ptep, ptl);
+ else
+ spin_unlock(ptl);
+
+ for (;;) {
+ unsigned int flags;
+
+ set_current_state(TASK_UNINTERRUPTIBLE);
+
+ /* Loop until we've been woken or interrupted */
+ flags = smp_load_acquire(&wait->flags);
+ if (!(flags & WQ_FLAG_WOKEN)) {
+ if (signal_pending_state(TASK_UNINTERRUPTIBLE, current))
+ break;
+
+ io_schedule();
+ continue;
+ }
+ break;
+ }
+
+ finish_wait(q, wait);
+
+ if (thrashing) {
+ delayacct_thrashing_end(&in_thrashing);
+ psi_memstall_leave(&pflags);
+ }
+}
+#endif
+
+void folio_wait_bit(struct folio *folio, int bit_nr)
+{
+ folio_wait_bit_common(folio, bit_nr, TASK_UNINTERRUPTIBLE, SHARED);
+}
+EXPORT_SYMBOL(folio_wait_bit);
+
+int folio_wait_bit_killable(struct folio *folio, int bit_nr)
+{
+ return folio_wait_bit_common(folio, bit_nr, TASK_KILLABLE, SHARED);
+}
+EXPORT_SYMBOL(folio_wait_bit_killable);
+
+/**
+ * folio_put_wait_locked - Drop a reference and wait for it to be unlocked
+ * @folio: The folio to wait for.
+ * @state: The sleep state (TASK_KILLABLE, TASK_UNINTERRUPTIBLE, etc).
+ *
+ * The caller should hold a reference on @folio. They expect the page to
+ * become unlocked relatively soon, but do not wish to hold up migration
+ * (for example) by holding the reference while waiting for the folio to
+ * come unlocked. After this function returns, the caller should not
+ * dereference @folio.
+ *
+ * Return: 0 if the folio was unlocked or -EINTR if interrupted by a signal.
+ */
+static int folio_put_wait_locked(struct folio *folio, int state)
+{
+ return folio_wait_bit_common(folio, PG_locked, state, DROP);
+}
+
+/**
+ * folio_add_wait_queue - Add an arbitrary waiter to a folio's wait queue
+ * @folio: Folio defining the wait queue of interest
+ * @waiter: Waiter to add to the queue
+ *
+ * Add an arbitrary @waiter to the wait queue for the nominated @folio.
+ */
+void folio_add_wait_queue(struct folio *folio, wait_queue_entry_t *waiter)
+{
+ wait_queue_head_t *q = folio_waitqueue(folio);
+ unsigned long flags;
+
+ spin_lock_irqsave(&q->lock, flags);
+ __add_wait_queue_entry_tail(q, waiter);
+ folio_set_waiters(folio);
+ spin_unlock_irqrestore(&q->lock, flags);
+}
+EXPORT_SYMBOL_GPL(folio_add_wait_queue);
+
+#ifndef clear_bit_unlock_is_negative_byte
+
+/*
+ * PG_waiters is the high bit in the same byte as PG_lock.
+ *
+ * On x86 (and on many other architectures), we can clear PG_lock and
+ * test the sign bit at the same time. But if the architecture does
+ * not support that special operation, we just do this all by hand
+ * instead.
+ *
+ * The read of PG_waiters has to be after (or concurrently with) PG_locked
+ * being cleared, but a memory barrier should be unnecessary since it is
+ * in the same byte as PG_locked.
+ */
+static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem)
+{
+ clear_bit_unlock(nr, mem);
+ /* smp_mb__after_atomic(); */
+ return test_bit(PG_waiters, mem);
+}
+
+#endif
+
+/**
+ * folio_unlock - Unlock a locked folio.
+ * @folio: The folio.
+ *
+ * Unlocks the folio and wakes up any thread sleeping on the page lock.
+ *
+ * Context: May be called from interrupt or process context. May not be
+ * called from NMI context.
+ */
+void folio_unlock(struct folio *folio)
+{
+ /* Bit 7 allows x86 to check the byte's sign bit */
+ BUILD_BUG_ON(PG_waiters != 7);
+ BUILD_BUG_ON(PG_locked > 7);
+ VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
+ if (clear_bit_unlock_is_negative_byte(PG_locked, folio_flags(folio, 0)))
+ folio_wake_bit(folio, PG_locked);
+}
+EXPORT_SYMBOL(folio_unlock);
+
+/**
+ * folio_end_private_2 - Clear PG_private_2 and wake any waiters.
+ * @folio: The folio.
+ *
+ * Clear the PG_private_2 bit on a folio and wake up any sleepers waiting for
+ * it. The folio reference held for PG_private_2 being set is released.
+ *
+ * This is, for example, used when a netfs folio is being written to a local
+ * disk cache, thereby allowing writes to the cache for the same folio to be
+ * serialised.
+ */
+void folio_end_private_2(struct folio *folio)
+{
+ VM_BUG_ON_FOLIO(!folio_test_private_2(folio), folio);
+ clear_bit_unlock(PG_private_2, folio_flags(folio, 0));
+ folio_wake_bit(folio, PG_private_2);
+ folio_put(folio);
+}
+EXPORT_SYMBOL(folio_end_private_2);
+
+/**
+ * folio_wait_private_2 - Wait for PG_private_2 to be cleared on a folio.
+ * @folio: The folio to wait on.
+ *
+ * Wait for PG_private_2 (aka PG_fscache) to be cleared on a folio.
+ */
+void folio_wait_private_2(struct folio *folio)
+{
+ while (folio_test_private_2(folio))
+ folio_wait_bit(folio, PG_private_2);
+}
+EXPORT_SYMBOL(folio_wait_private_2);
+
+/**
+ * folio_wait_private_2_killable - Wait for PG_private_2 to be cleared on a folio.
+ * @folio: The folio to wait on.
+ *
+ * Wait for PG_private_2 (aka PG_fscache) to be cleared on a folio or until a
+ * fatal signal is received by the calling task.
+ *
+ * Return:
+ * - 0 if successful.
+ * - -EINTR if a fatal signal was encountered.
+ */
+int folio_wait_private_2_killable(struct folio *folio)
+{
+ int ret = 0;
+
+ while (folio_test_private_2(folio)) {
+ ret = folio_wait_bit_killable(folio, PG_private_2);
+ if (ret < 0)
+ break;
+ }
+
+ return ret;
+}
+EXPORT_SYMBOL(folio_wait_private_2_killable);
+
+/**
+ * folio_end_writeback - End writeback against a folio.
+ * @folio: The folio.
+ */
+void folio_end_writeback(struct folio *folio)
+{
+ /*
+ * folio_test_clear_reclaim() could be used here but it is an
+ * atomic operation and overkill in this particular case. Failing
+ * to shuffle a folio marked for immediate reclaim is too mild
+ * a gain to justify taking an atomic operation penalty at the
+ * end of every folio writeback.
+ */
+ if (folio_test_reclaim(folio)) {
+ folio_clear_reclaim(folio);
+ folio_rotate_reclaimable(folio);
+ }
+
+ /*
+ * Writeback does not hold a folio reference of its own, relying
+ * on truncation to wait for the clearing of PG_writeback.
+ * But here we must make sure that the folio is not freed and
+ * reused before the folio_wake().
+ */
+ folio_get(folio);
+ if (!__folio_end_writeback(folio))
+ BUG();
+
+ smp_mb__after_atomic();
+ folio_wake(folio, PG_writeback);
+ acct_reclaim_writeback(folio);
+ folio_put(folio);
+}
+EXPORT_SYMBOL(folio_end_writeback);
+
+/*
+ * After completing I/O on a page, call this routine to update the page
+ * flags appropriately
+ */
+void page_endio(struct page *page, bool is_write, int err)
+{
+ struct folio *folio = page_folio(page);
+
+ if (!is_write) {
+ if (!err) {
+ folio_mark_uptodate(folio);
+ } else {
+ folio_clear_uptodate(folio);
+ folio_set_error(folio);
+ }
+ folio_unlock(folio);
+ } else {
+ if (err) {
+ struct address_space *mapping;
+
+ folio_set_error(folio);
+ mapping = folio_mapping(folio);
+ if (mapping)
+ mapping_set_error(mapping, err);
+ }
+ folio_end_writeback(folio);
+ }
+}
+EXPORT_SYMBOL_GPL(page_endio);
+
+/**
+ * __folio_lock - Get a lock on the folio, assuming we need to sleep to get it.
+ * @folio: The folio to lock
+ */
+void __folio_lock(struct folio *folio)
+{
+ folio_wait_bit_common(folio, PG_locked, TASK_UNINTERRUPTIBLE,
+ EXCLUSIVE);
+}
+EXPORT_SYMBOL(__folio_lock);
+
+int __folio_lock_killable(struct folio *folio)
+{
+ return folio_wait_bit_common(folio, PG_locked, TASK_KILLABLE,
+ EXCLUSIVE);
+}
+EXPORT_SYMBOL_GPL(__folio_lock_killable);
+
+static int __folio_lock_async(struct folio *folio, struct wait_page_queue *wait)
+{
+ struct wait_queue_head *q = folio_waitqueue(folio);
+ int ret = 0;
+
+ wait->folio = folio;
+ wait->bit_nr = PG_locked;
+
+ spin_lock_irq(&q->lock);
+ __add_wait_queue_entry_tail(q, &wait->wait);
+ folio_set_waiters(folio);
+ ret = !folio_trylock(folio);
+ /*
+ * If we were successful now, we know we're still on the
+ * waitqueue as we're still under the lock. This means it's
+ * safe to remove and return success, we know the callback
+ * isn't going to trigger.
+ */
+ if (!ret)
+ __remove_wait_queue(q, &wait->wait);
+ else
+ ret = -EIOCBQUEUED;
+ spin_unlock_irq(&q->lock);
+ return ret;
+}
+
+/*
+ * Return values:
+ * true - folio is locked; mmap_lock is still held.
+ * false - folio is not locked.
+ * mmap_lock has been released (mmap_read_unlock(), unless flags had both
+ * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
+ * which case mmap_lock is still held.
+ *
+ * If neither ALLOW_RETRY nor KILLABLE are set, will always return true
+ * with the folio locked and the mmap_lock unperturbed.
+ */
+bool __folio_lock_or_retry(struct folio *folio, struct mm_struct *mm,
+ unsigned int flags)
+{
+ if (fault_flag_allow_retry_first(flags)) {
+ /*
+ * CAUTION! In this case, mmap_lock is not released
+ * even though return 0.
+ */
+ if (flags & FAULT_FLAG_RETRY_NOWAIT)
+ return false;
+
+ mmap_read_unlock(mm);
+ if (flags & FAULT_FLAG_KILLABLE)
+ folio_wait_locked_killable(folio);
+ else
+ folio_wait_locked(folio);
+ return false;
+ }
+ if (flags & FAULT_FLAG_KILLABLE) {
+ bool ret;
+
+ ret = __folio_lock_killable(folio);
+ if (ret) {
+ mmap_read_unlock(mm);
+ return false;
+ }
+ } else {
+ __folio_lock(folio);
+ }
+
+ return true;
+}
+
+/**
+ * page_cache_next_miss() - Find the next gap in the page cache.
+ * @mapping: Mapping.
+ * @index: Index.
+ * @max_scan: Maximum range to search.
+ *
+ * Search the range [index, min(index + max_scan - 1, ULONG_MAX)] for the
+ * gap with the lowest index.
+ *
+ * This function may be called under the rcu_read_lock. However, this will
+ * not atomically search a snapshot of the cache at a single point in time.
+ * For example, if a gap is created at index 5, then subsequently a gap is
+ * created at index 10, page_cache_next_miss covering both indices may
+ * return 10 if called under the rcu_read_lock.
+ *
+ * Return: The index of the gap if found, otherwise an index outside the
+ * range specified (in which case 'return - index >= max_scan' will be true).
+ * In the rare case of index wrap-around, 0 will be returned.
+ */
+pgoff_t page_cache_next_miss(struct address_space *mapping,
+ pgoff_t index, unsigned long max_scan)
+{
+ XA_STATE(xas, &mapping->i_pages, index);
+
+ while (max_scan--) {
+ void *entry = xas_next(&xas);
+ if (!entry || xa_is_value(entry))
+ break;
+ if (xas.xa_index == 0)
+ break;
+ }
+
+ return xas.xa_index;
+}
+EXPORT_SYMBOL(page_cache_next_miss);
+
+/**
+ * page_cache_prev_miss() - Find the previous gap in the page cache.
+ * @mapping: Mapping.
+ * @index: Index.
+ * @max_scan: Maximum range to search.
+ *
+ * Search the range [max(index - max_scan + 1, 0), index] for the
+ * gap with the highest index.
+ *
+ * This function may be called under the rcu_read_lock. However, this will
+ * not atomically search a snapshot of the cache at a single point in time.
+ * For example, if a gap is created at index 10, then subsequently a gap is
+ * created at index 5, page_cache_prev_miss() covering both indices may
+ * return 5 if called under the rcu_read_lock.
+ *
+ * Return: The index of the gap if found, otherwise an index outside the
+ * range specified (in which case 'index - return >= max_scan' will be true).
+ * In the rare case of wrap-around, ULONG_MAX will be returned.
+ */
+pgoff_t page_cache_prev_miss(struct address_space *mapping,
+ pgoff_t index, unsigned long max_scan)
+{
+ XA_STATE(xas, &mapping->i_pages, index);
+
+ while (max_scan--) {
+ void *entry = xas_prev(&xas);
+ if (!entry || xa_is_value(entry))
+ break;
+ if (xas.xa_index == ULONG_MAX)
+ break;
+ }
+
+ return xas.xa_index;
+}
+EXPORT_SYMBOL(page_cache_prev_miss);
+
+/*
+ * Lockless page cache protocol:
+ * On the lookup side:
+ * 1. Load the folio from i_pages
+ * 2. Increment the refcount if it's not zero
+ * 3. If the folio is not found by xas_reload(), put the refcount and retry
+ *
+ * On the removal side:
+ * A. Freeze the page (by zeroing the refcount if nobody else has a reference)
+ * B. Remove the page from i_pages
+ * C. Return the page to the page allocator
+ *
+ * This means that any page may have its reference count temporarily
+ * increased by a speculative page cache (or fast GUP) lookup as it can
+ * be allocated by another user before the RCU grace period expires.
+ * Because the refcount temporarily acquired here may end up being the
+ * last refcount on the page, any page allocation must be freeable by
+ * folio_put().
+ */
+
+/*
+ * mapping_get_entry - Get a page cache entry.
+ * @mapping: the address_space to search
+ * @index: The page cache index.
+ *
+ * Looks up the page cache entry at @mapping & @index. If it is a folio,
+ * it is returned with an increased refcount. If it is a shadow entry
+ * of a previously evicted folio, or a swap entry from shmem/tmpfs,
+ * it is returned without further action.
+ *
+ * Return: The folio, swap or shadow entry, %NULL if nothing is found.
+ */
+static void *mapping_get_entry(struct address_space *mapping, pgoff_t index)
+{
+ XA_STATE(xas, &mapping->i_pages, index);
+ struct folio *folio;
+
+ rcu_read_lock();
+repeat:
+ xas_reset(&xas);
+ folio = xas_load(&xas);
+ if (xas_retry(&xas, folio))
+ goto repeat;
+ /*
+ * A shadow entry of a recently evicted page, or a swap entry from
+ * shmem/tmpfs. Return it without attempting to raise page count.
+ */
+ if (!folio || xa_is_value(folio))
+ goto out;
+
+ if (!folio_try_get_rcu(folio))
+ goto repeat;
+
+ if (unlikely(folio != xas_reload(&xas))) {
+ folio_put(folio);
+ goto repeat;
+ }
+out:
+ rcu_read_unlock();
+
+ return folio;
+}
+
+/**
+ * __filemap_get_folio - Find and get a reference to a folio.
+ * @mapping: The address_space to search.
+ * @index: The page index.
+ * @fgp_flags: %FGP flags modify how the folio is returned.
+ * @gfp: Memory allocation flags to use if %FGP_CREAT is specified.
+ *
+ * Looks up the page cache entry at @mapping & @index.
+ *
+ * @fgp_flags can be zero or more of these flags:
+ *
+ * * %FGP_ACCESSED - The folio will be marked accessed.
+ * * %FGP_LOCK - The folio is returned locked.
+ * * %FGP_ENTRY - If there is a shadow / swap / DAX entry, return it
+ * instead of allocating a new folio to replace it.
+ * * %FGP_CREAT - If no page is present then a new page is allocated using
+ * @gfp and added to the page cache and the VM's LRU list.
+ * The page is returned locked and with an increased refcount.
+ * * %FGP_FOR_MMAP - The caller wants to do its own locking dance if the
+ * page is already in cache. If the page was allocated, unlock it before
+ * returning so the caller can do the same dance.
+ * * %FGP_WRITE - The page will be written to by the caller.
+ * * %FGP_NOFS - __GFP_FS will get cleared in gfp.
+ * * %FGP_NOWAIT - Don't get blocked by page lock.
+ * * %FGP_STABLE - Wait for the folio to be stable (finished writeback)
+ *
+ * If %FGP_LOCK or %FGP_CREAT are specified then the function may sleep even
+ * if the %GFP flags specified for %FGP_CREAT are atomic.
+ *
+ * If there is a page cache page, it is returned with an increased refcount.
+ *
+ * Return: The found folio or %NULL otherwise.
+ */
+struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
+ int fgp_flags, gfp_t gfp)
+{
+ struct folio *folio;
+
+repeat:
+ folio = mapping_get_entry(mapping, index);
+ if (xa_is_value(folio)) {
+ if (fgp_flags & FGP_ENTRY)
+ return folio;
+ folio = NULL;
+ }
+ if (!folio)
+ goto no_page;
+
+ if (fgp_flags & FGP_LOCK) {
+ if (fgp_flags & FGP_NOWAIT) {
+ if (!folio_trylock(folio)) {
+ folio_put(folio);
+ return NULL;
+ }
+ } else {
+ folio_lock(folio);
+ }
+
+ /* Has the page been truncated? */
+ if (unlikely(folio->mapping != mapping)) {
+ folio_unlock(folio);
+ folio_put(folio);
+ goto repeat;
+ }
+ VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio);
+ }
+
+ if (fgp_flags & FGP_ACCESSED)
+ folio_mark_accessed(folio);
+ else if (fgp_flags & FGP_WRITE) {
+ /* Clear idle flag for buffer write */
+ if (folio_test_idle(folio))
+ folio_clear_idle(folio);
+ }
+
+ if (fgp_flags & FGP_STABLE)
+ folio_wait_stable(folio);
+no_page:
+ if (!folio && (fgp_flags & FGP_CREAT)) {
+ int err;
+ if ((fgp_flags & FGP_WRITE) && mapping_can_writeback(mapping))
+ gfp |= __GFP_WRITE;
+ if (fgp_flags & FGP_NOFS)
+ gfp &= ~__GFP_FS;
+ if (fgp_flags & FGP_NOWAIT) {
+ gfp &= ~GFP_KERNEL;
+ gfp |= GFP_NOWAIT | __GFP_NOWARN;
+ }
+
+ folio = filemap_alloc_folio(gfp, 0);
+ if (!folio)
+ return NULL;
+
+ if (WARN_ON_ONCE(!(fgp_flags & (FGP_LOCK | FGP_FOR_MMAP))))
+ fgp_flags |= FGP_LOCK;
+
+ /* Init accessed so avoid atomic mark_page_accessed later */
+ if (fgp_flags & FGP_ACCESSED)
+ __folio_set_referenced(folio);
+
+ err = filemap_add_folio(mapping, folio, index, gfp);
+ if (unlikely(err)) {
+ folio_put(folio);
+ folio = NULL;
+ if (err == -EEXIST)
+ goto repeat;
+ }
+
+ /*
+ * filemap_add_folio locks the page, and for mmap
+ * we expect an unlocked page.
+ */
+ if (folio && (fgp_flags & FGP_FOR_MMAP))
+ folio_unlock(folio);
+ }
+
+ return folio;
+}
+EXPORT_SYMBOL(__filemap_get_folio);
+
+static inline struct folio *find_get_entry(struct xa_state *xas, pgoff_t max,
+ xa_mark_t mark)
+{
+ struct folio *folio;
+
+retry:
+ if (mark == XA_PRESENT)
+ folio = xas_find(xas, max);
+ else
+ folio = xas_find_marked(xas, max, mark);
+
+ if (xas_retry(xas, folio))
+ goto retry;
+ /*
+ * A shadow entry of a recently evicted page, a swap
+ * entry from shmem/tmpfs or a DAX entry. Return it
+ * without attempting to raise page count.
+ */
+ if (!folio || xa_is_value(folio))
+ return folio;
+
+ if (!folio_try_get_rcu(folio))
+ goto reset;
+
+ if (unlikely(folio != xas_reload(xas))) {
+ folio_put(folio);
+ goto reset;
+ }
+
+ return folio;
+reset:
+ xas_reset(xas);
+ goto retry;
+}
+
+/**
+ * find_get_entries - gang pagecache lookup
+ * @mapping: The address_space to search
+ * @start: The starting page cache index
+ * @end: The final page index (inclusive).
+ * @fbatch: Where the resulting entries are placed.
+ * @indices: The cache indices corresponding to the entries in @entries
+ *
+ * find_get_entries() will search for and return a batch of entries in
+ * the mapping. The entries are placed in @fbatch. find_get_entries()
+ * takes a reference on any actual folios it returns.
+ *
+ * The entries have ascending indexes. The indices may not be consecutive
+ * due to not-present entries or large folios.
+ *
+ * Any shadow entries of evicted folios, or swap entries from
+ * shmem/tmpfs, are included in the returned array.
+ *
+ * Return: The number of entries which were found.
+ */
+unsigned find_get_entries(struct address_space *mapping, pgoff_t start,
+ pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices)
+{
+ XA_STATE(xas, &mapping->i_pages, start);
+ struct folio *folio;
+
+ rcu_read_lock();
+ while ((folio = find_get_entry(&xas, end, XA_PRESENT)) != NULL) {
+ indices[fbatch->nr] = xas.xa_index;
+ if (!folio_batch_add(fbatch, folio))
+ break;
+ }
+ rcu_read_unlock();
+
+ return folio_batch_count(fbatch);
+}
+
+/**
+ * find_lock_entries - Find a batch of pagecache entries.
+ * @mapping: The address_space to search.
+ * @start: The starting page cache index.
+ * @end: The final page index (inclusive).
+ * @fbatch: Where the resulting entries are placed.
+ * @indices: The cache indices of the entries in @fbatch.
+ *
+ * find_lock_entries() will return a batch of entries from @mapping.
+ * Swap, shadow and DAX entries are included. Folios are returned
+ * locked and with an incremented refcount. Folios which are locked
+ * by somebody else or under writeback are skipped. Folios which are
+ * partially outside the range are not returned.
+ *
+ * The entries have ascending indexes. The indices may not be consecutive
+ * due to not-present entries, large folios, folios which could not be
+ * locked or folios under writeback.
+ *
+ * Return: The number of entries which were found.
+ */
+unsigned find_lock_entries(struct address_space *mapping, pgoff_t start,
+ pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices)
+{
+ XA_STATE(xas, &mapping->i_pages, start);
+ struct folio *folio;
+
+ rcu_read_lock();
+ while ((folio = find_get_entry(&xas, end, XA_PRESENT))) {
+ if (!xa_is_value(folio)) {
+ if (folio->index < start)
+ goto put;
+ if (folio->index + folio_nr_pages(folio) - 1 > end)
+ goto put;
+ if (!folio_trylock(folio))
+ goto put;
+ if (folio->mapping != mapping ||
+ folio_test_writeback(folio))
+ goto unlock;
+ VM_BUG_ON_FOLIO(!folio_contains(folio, xas.xa_index),
+ folio);
+ }
+ indices[fbatch->nr] = xas.xa_index;
+ if (!folio_batch_add(fbatch, folio))
+ break;
+ continue;
+unlock:
+ folio_unlock(folio);
+put:
+ folio_put(folio);
+ }
+ rcu_read_unlock();
+
+ return folio_batch_count(fbatch);
+}
+
+/**
+ * filemap_get_folios - Get a batch of folios
+ * @mapping: The address_space to search
+ * @start: The starting page index
+ * @end: The final page index (inclusive)
+ * @fbatch: The batch to fill.
+ *
+ * Search for and return a batch of folios in the mapping starting at
+ * index @start and up to index @end (inclusive). The folios are returned
+ * in @fbatch with an elevated reference count.
+ *
+ * The first folio may start before @start; if it does, it will contain
+ * @start. The final folio may extend beyond @end; if it does, it will
+ * contain @end. The folios have ascending indices. There may be gaps
+ * between the folios if there are indices which have no folio in the
+ * page cache. If folios are added to or removed from the page cache
+ * while this is running, they may or may not be found by this call.
+ *
+ * Return: The number of folios which were found.
+ * We also update @start to index the next folio for the traversal.
+ */
+unsigned filemap_get_folios(struct address_space *mapping, pgoff_t *start,
+ pgoff_t end, struct folio_batch *fbatch)
+{
+ XA_STATE(xas, &mapping->i_pages, *start);
+ struct folio *folio;
+
+ rcu_read_lock();
+ while ((folio = find_get_entry(&xas, end, XA_PRESENT)) != NULL) {
+ /* Skip over shadow, swap and DAX entries */
+ if (xa_is_value(folio))
+ continue;
+ if (!folio_batch_add(fbatch, folio)) {
+ unsigned long nr = folio_nr_pages(folio);
+
+ if (folio_test_hugetlb(folio))
+ nr = 1;
+ *start = folio->index + nr;
+ goto out;
+ }
+ }
+
+ /*
+ * We come here when there is no page beyond @end. We take care to not
+ * overflow the index @start as it confuses some of the callers. This
+ * breaks the iteration when there is a page at index -1 but that is
+ * already broken anyway.
+ */
+ if (end == (pgoff_t)-1)
+ *start = (pgoff_t)-1;
+ else
+ *start = end + 1;
+out:
+ rcu_read_unlock();
+
+ return folio_batch_count(fbatch);
+}
+EXPORT_SYMBOL(filemap_get_folios);
+
+static inline
+bool folio_more_pages(struct folio *folio, pgoff_t index, pgoff_t max)
+{
+ if (!folio_test_large(folio) || folio_test_hugetlb(folio))
+ return false;
+ if (index >= max)
+ return false;
+ return index < folio->index + folio_nr_pages(folio) - 1;
+}
+
+/**
+ * filemap_get_folios_contig - Get a batch of contiguous folios
+ * @mapping: The address_space to search
+ * @start: The starting page index
+ * @end: The final page index (inclusive)
+ * @fbatch: The batch to fill
+ *
+ * filemap_get_folios_contig() works exactly like filemap_get_folios(),
+ * except the returned folios are guaranteed to be contiguous. This may
+ * not return all contiguous folios if the batch gets filled up.
+ *
+ * Return: The number of folios found.
+ * Also update @start to be positioned for traversal of the next folio.
+ */
+
+unsigned filemap_get_folios_contig(struct address_space *mapping,
+ pgoff_t *start, pgoff_t end, struct folio_batch *fbatch)
+{
+ XA_STATE(xas, &mapping->i_pages, *start);
+ unsigned long nr;
+ struct folio *folio;
+
+ rcu_read_lock();
+
+ for (folio = xas_load(&xas); folio && xas.xa_index <= end;
+ folio = xas_next(&xas)) {
+ if (xas_retry(&xas, folio))
+ continue;
+ /*
+ * If the entry has been swapped out, we can stop looking.
+ * No current caller is looking for DAX entries.
+ */
+ if (xa_is_value(folio))
+ goto update_start;
+
+ if (!folio_try_get_rcu(folio))
+ goto retry;
+
+ if (unlikely(folio != xas_reload(&xas)))
+ goto put_folio;
+
+ if (!folio_batch_add(fbatch, folio)) {
+ nr = folio_nr_pages(folio);
+
+ if (folio_test_hugetlb(folio))
+ nr = 1;
+ *start = folio->index + nr;
+ goto out;
+ }
+ continue;
+put_folio:
+ folio_put(folio);
+
+retry:
+ xas_reset(&xas);
+ }
+
+update_start:
+ nr = folio_batch_count(fbatch);
+
+ if (nr) {
+ folio = fbatch->folios[nr - 1];
+ if (folio_test_hugetlb(folio))
+ *start = folio->index + 1;
+ else
+ *start = folio->index + folio_nr_pages(folio);
+ }
+out:
+ rcu_read_unlock();
+ return folio_batch_count(fbatch);
+}
+EXPORT_SYMBOL(filemap_get_folios_contig);
+
+/**
+ * filemap_get_folios_tag - Get a batch of folios matching @tag
+ * @mapping: The address_space to search
+ * @start: The starting page index
+ * @end: The final page index (inclusive)
+ * @tag: The tag index
+ * @fbatch: The batch to fill
+ *
+ * Same as filemap_get_folios(), but only returning folios tagged with @tag.
+ *
+ * Return: The number of folios found.
+ * Also update @start to index the next folio for traversal.
+ */
+unsigned filemap_get_folios_tag(struct address_space *mapping, pgoff_t *start,
+ pgoff_t end, xa_mark_t tag, struct folio_batch *fbatch)
+{
+ XA_STATE(xas, &mapping->i_pages, *start);
+ struct folio *folio;
+
+ rcu_read_lock();
+ while ((folio = find_get_entry(&xas, end, tag)) != NULL) {
+ /*
+ * Shadow entries should never be tagged, but this iteration
+ * is lockless so there is a window for page reclaim to evict
+ * a page we saw tagged. Skip over it.
+ */
+ if (xa_is_value(folio))
+ continue;
+ if (!folio_batch_add(fbatch, folio)) {
+ unsigned long nr = folio_nr_pages(folio);
+
+ if (folio_test_hugetlb(folio))
+ nr = 1;
+ *start = folio->index + nr;
+ goto out;
+ }
+ }
+ /*
+ * We come here when there is no page beyond @end. We take care to not
+ * overflow the index @start as it confuses some of the callers. This
+ * breaks the iteration when there is a page at index -1 but that is
+ * already broke anyway.
+ */
+ if (end == (pgoff_t)-1)
+ *start = (pgoff_t)-1;
+ else
+ *start = end + 1;
+out:
+ rcu_read_unlock();
+
+ return folio_batch_count(fbatch);
+}
+EXPORT_SYMBOL(filemap_get_folios_tag);
+
+/**
+ * find_get_pages_range_tag - Find and return head pages matching @tag.
+ * @mapping: the address_space to search
+ * @index: the starting page index
+ * @end: The final page index (inclusive)
+ * @tag: the tag index
+ * @nr_pages: the maximum number of pages
+ * @pages: where the resulting pages are placed
+ *
+ * Like find_get_pages_range(), except we only return head pages which are
+ * tagged with @tag. @index is updated to the index immediately after the
+ * last page we return, ready for the next iteration.
+ *
+ * Return: the number of pages which were found.
+ */
+unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index,
+ pgoff_t end, xa_mark_t tag, unsigned int nr_pages,
+ struct page **pages)
+{
+ XA_STATE(xas, &mapping->i_pages, *index);
+ struct folio *folio;
+ unsigned ret = 0;
+
+ if (unlikely(!nr_pages))
+ return 0;
+
+ rcu_read_lock();
+ while ((folio = find_get_entry(&xas, end, tag))) {
+ /*
+ * Shadow entries should never be tagged, but this iteration
+ * is lockless so there is a window for page reclaim to evict
+ * a page we saw tagged. Skip over it.
+ */
+ if (xa_is_value(folio))
+ continue;
+
+ pages[ret] = &folio->page;
+ if (++ret == nr_pages) {
+ *index = folio->index + folio_nr_pages(folio);
+ goto out;
+ }
+ }
+
+ /*
+ * We come here when we got to @end. We take care to not overflow the
+ * index @index as it confuses some of the callers. This breaks the
+ * iteration when there is a page at index -1 but that is already
+ * broken anyway.
+ */
+ if (end == (pgoff_t)-1)
+ *index = (pgoff_t)-1;
+ else
+ *index = end + 1;
+out:
+ rcu_read_unlock();
+
+ return ret;
+}
+EXPORT_SYMBOL(find_get_pages_range_tag);
+
+/*
+ * CD/DVDs are error prone. When a medium error occurs, the driver may fail
+ * a _large_ part of the i/o request. Imagine the worst scenario:
+ *
+ * ---R__________________________________________B__________
+ * ^ reading here ^ bad block(assume 4k)
+ *
+ * read(R) => miss => readahead(R...B) => media error => frustrating retries
+ * => failing the whole request => read(R) => read(R+1) =>
+ * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
+ * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
+ * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
+ *
+ * It is going insane. Fix it by quickly scaling down the readahead size.
+ */
+static void shrink_readahead_size_eio(struct file_ra_state *ra)
+{
+ ra->ra_pages /= 4;
+}
+
+/*
+ * filemap_get_read_batch - Get a batch of folios for read
+ *
+ * Get a batch of folios which represent a contiguous range of bytes in
+ * the file. No exceptional entries will be returned. If @index is in
+ * the middle of a folio, the entire folio will be returned. The last
+ * folio in the batch may have the readahead flag set or the uptodate flag
+ * clear so that the caller can take the appropriate action.
+ */
+static void filemap_get_read_batch(struct address_space *mapping,
+ pgoff_t index, pgoff_t max, struct folio_batch *fbatch)
+{
+ XA_STATE(xas, &mapping->i_pages, index);
+ struct folio *folio;
+
+ rcu_read_lock();
+ for (folio = xas_load(&xas); folio; folio = xas_next(&xas)) {
+ if (xas_retry(&xas, folio))
+ continue;
+ if (xas.xa_index > max || xa_is_value(folio))
+ break;
+ if (xa_is_sibling(folio))
+ break;
+ if (!folio_try_get_rcu(folio))
+ goto retry;
+
+ if (unlikely(folio != xas_reload(&xas)))
+ goto put_folio;
+
+ if (!folio_batch_add(fbatch, folio))
+ break;
+ if (!folio_test_uptodate(folio))
+ break;
+ if (folio_test_readahead(folio))
+ break;
+ xas_advance(&xas, folio->index + folio_nr_pages(folio) - 1);
+ continue;
+put_folio:
+ folio_put(folio);
+retry:
+ xas_reset(&xas);
+ }
+ rcu_read_unlock();
+}
+
+static int filemap_read_folio(struct file *file, filler_t filler,
+ struct folio *folio)
+{
+ bool workingset = folio_test_workingset(folio);
+ unsigned long pflags;
+ int error;
+
+ /*
+ * A previous I/O error may have been due to temporary failures,
+ * eg. multipath errors. PG_error will be set again if read_folio
+ * fails.
+ */
+ folio_clear_error(folio);
+
+ /* Start the actual read. The read will unlock the page. */
+ if (unlikely(workingset))
+ psi_memstall_enter(&pflags);
+ error = filler(file, folio);
+ if (unlikely(workingset))
+ psi_memstall_leave(&pflags);
+ if (error)
+ return error;
+
+ error = folio_wait_locked_killable(folio);
+ if (error)
+ return error;
+ if (folio_test_uptodate(folio))
+ return 0;
+ if (file)
+ shrink_readahead_size_eio(&file->f_ra);
+ return -EIO;
+}
+
+static bool filemap_range_uptodate(struct address_space *mapping,
+ loff_t pos, struct iov_iter *iter, struct folio *folio)
+{
+ int count;
+
+ if (folio_test_uptodate(folio))
+ return true;
+ /* pipes can't handle partially uptodate pages */
+ if (iov_iter_is_pipe(iter))
+ return false;
+ if (!mapping->a_ops->is_partially_uptodate)
+ return false;
+ if (mapping->host->i_blkbits >= folio_shift(folio))
+ return false;
+
+ count = iter->count;
+ if (folio_pos(folio) > pos) {
+ count -= folio_pos(folio) - pos;
+ pos = 0;
+ } else {
+ pos -= folio_pos(folio);
+ }
+
+ return mapping->a_ops->is_partially_uptodate(folio, pos, count);
+}
+
+static int filemap_update_page(struct kiocb *iocb,
+ struct address_space *mapping, struct iov_iter *iter,
+ struct folio *folio)
+{
+ int error;
+
+ if (iocb->ki_flags & IOCB_NOWAIT) {
+ if (!filemap_invalidate_trylock_shared(mapping))
+ return -EAGAIN;
+ } else {
+ filemap_invalidate_lock_shared(mapping);
+ }
+
+ if (!folio_trylock(folio)) {
+ error = -EAGAIN;
+ if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO))
+ goto unlock_mapping;
+ if (!(iocb->ki_flags & IOCB_WAITQ)) {
+ filemap_invalidate_unlock_shared(mapping);
+ /*
+ * This is where we usually end up waiting for a
+ * previously submitted readahead to finish.
+ */
+ folio_put_wait_locked(folio, TASK_KILLABLE);
+ return AOP_TRUNCATED_PAGE;
+ }
+ error = __folio_lock_async(folio, iocb->ki_waitq);
+ if (error)
+ goto unlock_mapping;
+ }
+
+ error = AOP_TRUNCATED_PAGE;
+ if (!folio->mapping)
+ goto unlock;
+
+ error = 0;
+ if (filemap_range_uptodate(mapping, iocb->ki_pos, iter, folio))
+ goto unlock;
+
+ error = -EAGAIN;
+ if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ))
+ goto unlock;
+
+ error = filemap_read_folio(iocb->ki_filp, mapping->a_ops->read_folio,
+ folio);
+ goto unlock_mapping;
+unlock:
+ folio_unlock(folio);
+unlock_mapping:
+ filemap_invalidate_unlock_shared(mapping);
+ if (error == AOP_TRUNCATED_PAGE)
+ folio_put(folio);
+ return error;
+}
+
+static int filemap_create_folio(struct file *file,
+ struct address_space *mapping, pgoff_t index,
+ struct folio_batch *fbatch)
+{
+ struct folio *folio;
+ int error;
+
+ folio = filemap_alloc_folio(mapping_gfp_mask(mapping), 0);
+ if (!folio)
+ return -ENOMEM;
+
+ /*
+ * Protect against truncate / hole punch. Grabbing invalidate_lock
+ * here assures we cannot instantiate and bring uptodate new
+ * pagecache folios after evicting page cache during truncate
+ * and before actually freeing blocks. Note that we could
+ * release invalidate_lock after inserting the folio into
+ * the page cache as the locked folio would then be enough to
+ * synchronize with hole punching. But there are code paths
+ * such as filemap_update_page() filling in partially uptodate
+ * pages or ->readahead() that need to hold invalidate_lock
+ * while mapping blocks for IO so let's hold the lock here as
+ * well to keep locking rules simple.
+ */
+ filemap_invalidate_lock_shared(mapping);
+ error = filemap_add_folio(mapping, folio, index,
+ mapping_gfp_constraint(mapping, GFP_KERNEL));
+ if (error == -EEXIST)
+ error = AOP_TRUNCATED_PAGE;
+ if (error)
+ goto error;
+
+ error = filemap_read_folio(file, mapping->a_ops->read_folio, folio);
+ if (error)
+ goto error;
+
+ filemap_invalidate_unlock_shared(mapping);
+ folio_batch_add(fbatch, folio);
+ return 0;
+error:
+ filemap_invalidate_unlock_shared(mapping);
+ folio_put(folio);
+ return error;
+}
+
+static int filemap_readahead(struct kiocb *iocb, struct file *file,
+ struct address_space *mapping, struct folio *folio,
+ pgoff_t last_index)
+{
+ DEFINE_READAHEAD(ractl, file, &file->f_ra, mapping, folio->index);
+
+ if (iocb->ki_flags & IOCB_NOIO)
+ return -EAGAIN;
+ page_cache_async_ra(&ractl, folio, last_index - folio->index);
+ return 0;
+}
+
+static int filemap_get_pages(struct kiocb *iocb, struct iov_iter *iter,
+ struct folio_batch *fbatch)
+{
+ struct file *filp = iocb->ki_filp;
+ struct address_space *mapping = filp->f_mapping;
+ struct file_ra_state *ra = &filp->f_ra;
+ pgoff_t index = iocb->ki_pos >> PAGE_SHIFT;
+ pgoff_t last_index;
+ struct folio *folio;
+ int err = 0;
+
+ /* "last_index" is the index of the page beyond the end of the read */
+ last_index = DIV_ROUND_UP(iocb->ki_pos + iter->count, PAGE_SIZE);
+retry:
+ if (fatal_signal_pending(current))
+ return -EINTR;
+
+ filemap_get_read_batch(mapping, index, last_index - 1, fbatch);
+ if (!folio_batch_count(fbatch)) {
+ if (iocb->ki_flags & IOCB_NOIO)
+ return -EAGAIN;
+ page_cache_sync_readahead(mapping, ra, filp, index,
+ last_index - index);
+ filemap_get_read_batch(mapping, index, last_index - 1, fbatch);
+ }
+ if (!folio_batch_count(fbatch)) {
+ if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ))
+ return -EAGAIN;
+ err = filemap_create_folio(filp, mapping,
+ iocb->ki_pos >> PAGE_SHIFT, fbatch);
+ if (err == AOP_TRUNCATED_PAGE)
+ goto retry;
+ return err;
+ }
+
+ folio = fbatch->folios[folio_batch_count(fbatch) - 1];
+ if (folio_test_readahead(folio)) {
+ err = filemap_readahead(iocb, filp, mapping, folio, last_index);
+ if (err)
+ goto err;
+ }
+ if (!folio_test_uptodate(folio)) {
+ if ((iocb->ki_flags & IOCB_WAITQ) &&
+ folio_batch_count(fbatch) > 1)
+ iocb->ki_flags |= IOCB_NOWAIT;
+ err = filemap_update_page(iocb, mapping, iter, folio);
+ if (err)
+ goto err;
+ }
+
+ return 0;
+err:
+ if (err < 0)
+ folio_put(folio);
+ if (likely(--fbatch->nr))
+ return 0;
+ if (err == AOP_TRUNCATED_PAGE)
+ goto retry;
+ return err;
+}
+
+static inline bool pos_same_folio(loff_t pos1, loff_t pos2, struct folio *folio)
+{
+ unsigned int shift = folio_shift(folio);
+
+ return (pos1 >> shift == pos2 >> shift);
+}
+
+/**
+ * filemap_read - Read data from the page cache.
+ * @iocb: The iocb to read.
+ * @iter: Destination for the data.
+ * @already_read: Number of bytes already read by the caller.
+ *
+ * Copies data from the page cache. If the data is not currently present,
+ * uses the readahead and read_folio address_space operations to fetch it.
+ *
+ * Return: Total number of bytes copied, including those already read by
+ * the caller. If an error happens before any bytes are copied, returns
+ * a negative error number.
+ */
+ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter,
+ ssize_t already_read)
+{
+ struct file *filp = iocb->ki_filp;
+ struct file_ra_state *ra = &filp->f_ra;
+ struct address_space *mapping = filp->f_mapping;
+ struct inode *inode = mapping->host;
+ struct folio_batch fbatch;
+ int i, error = 0;
+ bool writably_mapped;
+ loff_t isize, end_offset;
+
+ if (unlikely(iocb->ki_pos >= inode->i_sb->s_maxbytes))
+ return 0;
+ if (unlikely(!iov_iter_count(iter)))
+ return 0;
+
+ iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
+ folio_batch_init(&fbatch);
+
+ do {
+ cond_resched();
+
+ /*
+ * If we've already successfully copied some data, then we
+ * can no longer safely return -EIOCBQUEUED. Hence mark
+ * an async read NOWAIT at that point.
+ */
+ if ((iocb->ki_flags & IOCB_WAITQ) && already_read)
+ iocb->ki_flags |= IOCB_NOWAIT;
+
+ if (unlikely(iocb->ki_pos >= i_size_read(inode)))
+ break;
+
+ error = filemap_get_pages(iocb, iter, &fbatch);
+ if (error < 0)
+ break;
+
+ /*
+ * i_size must be checked after we know the pages are Uptodate.
+ *
+ * Checking i_size after the check allows us to calculate
+ * the correct value for "nr", which means the zero-filled
+ * part of the page is not copied back to userspace (unless
+ * another truncate extends the file - this is desired though).
+ */
+ isize = i_size_read(inode);
+ if (unlikely(iocb->ki_pos >= isize))
+ goto put_folios;
+ end_offset = min_t(loff_t, isize, iocb->ki_pos + iter->count);
+
+ /*
+ * Pairs with a barrier in
+ * block_write_end()->mark_buffer_dirty() or other page
+ * dirtying routines like iomap_write_end() to ensure
+ * changes to page contents are visible before we see
+ * increased inode size.
+ */
+ smp_rmb();
+
+ /*
+ * Once we start copying data, we don't want to be touching any
+ * cachelines that might be contended:
+ */
+ writably_mapped = mapping_writably_mapped(mapping);
+
+ /*
+ * When a read accesses the same folio several times, only
+ * mark it as accessed the first time.
+ */
+ if (!pos_same_folio(iocb->ki_pos, ra->prev_pos - 1,
+ fbatch.folios[0]))
+ folio_mark_accessed(fbatch.folios[0]);
+
+ for (i = 0; i < folio_batch_count(&fbatch); i++) {
+ struct folio *folio = fbatch.folios[i];
+ size_t fsize = folio_size(folio);
+ size_t offset = iocb->ki_pos & (fsize - 1);
+ size_t bytes = min_t(loff_t, end_offset - iocb->ki_pos,
+ fsize - offset);
+ size_t copied;
+
+ if (end_offset < folio_pos(folio))
+ break;
+ if (i > 0)
+ folio_mark_accessed(folio);
+ /*
+ * If users can be writing to this folio using arbitrary
+ * virtual addresses, take care of potential aliasing
+ * before reading the folio on the kernel side.
+ */
+ if (writably_mapped)
+ flush_dcache_folio(folio);
+
+ copied = copy_folio_to_iter(folio, offset, bytes, iter);
+
+ already_read += copied;
+ iocb->ki_pos += copied;
+ ra->prev_pos = iocb->ki_pos;
+
+ if (copied < bytes) {
+ error = -EFAULT;
+ break;
+ }
+ }
+put_folios:
+ for (i = 0; i < folio_batch_count(&fbatch); i++)
+ folio_put(fbatch.folios[i]);
+ folio_batch_init(&fbatch);
+ } while (iov_iter_count(iter) && iocb->ki_pos < isize && !error);
+
+ file_accessed(filp);
+
+ return already_read ? already_read : error;
+}
+EXPORT_SYMBOL_GPL(filemap_read);
+
+/**
+ * generic_file_read_iter - generic filesystem read routine
+ * @iocb: kernel I/O control block
+ * @iter: destination for the data read
+ *
+ * This is the "read_iter()" routine for all filesystems
+ * that can use the page cache directly.
+ *
+ * The IOCB_NOWAIT flag in iocb->ki_flags indicates that -EAGAIN shall
+ * be returned when no data can be read without waiting for I/O requests
+ * to complete; it doesn't prevent readahead.
+ *
+ * The IOCB_NOIO flag in iocb->ki_flags indicates that no new I/O
+ * requests shall be made for the read or for readahead. When no data
+ * can be read, -EAGAIN shall be returned. When readahead would be
+ * triggered, a partial, possibly empty read shall be returned.
+ *
+ * Return:
+ * * number of bytes copied, even for partial reads
+ * * negative error code (or 0 if IOCB_NOIO) if nothing was read
+ */
+ssize_t
+generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
+{
+ size_t count = iov_iter_count(iter);
+ ssize_t retval = 0;
+
+ if (!count)
+ return 0; /* skip atime */
+
+ if (iocb->ki_flags & IOCB_DIRECT) {
+ struct file *file = iocb->ki_filp;
+ struct address_space *mapping = file->f_mapping;
+ struct inode *inode = mapping->host;
+
+ if (iocb->ki_flags & IOCB_NOWAIT) {
+ if (filemap_range_needs_writeback(mapping, iocb->ki_pos,
+ iocb->ki_pos + count - 1))
+ return -EAGAIN;
+ } else {
+ retval = filemap_write_and_wait_range(mapping,
+ iocb->ki_pos,
+ iocb->ki_pos + count - 1);
+ if (retval < 0)
+ return retval;
+ }
+
+ file_accessed(file);
+
+ retval = mapping->a_ops->direct_IO(iocb, iter);
+ if (retval >= 0) {
+ iocb->ki_pos += retval;
+ count -= retval;
+ }
+ if (retval != -EIOCBQUEUED)
+ iov_iter_revert(iter, count - iov_iter_count(iter));
+
+ /*
+ * Btrfs can have a short DIO read if we encounter
+ * compressed extents, so if there was an error, or if
+ * we've already read everything we wanted to, or if
+ * there was a short read because we hit EOF, go ahead
+ * and return. Otherwise fallthrough to buffered io for
+ * the rest of the read. Buffered reads will not work for
+ * DAX files, so don't bother trying.
+ */
+ if (retval < 0 || !count || IS_DAX(inode))
+ return retval;
+ if (iocb->ki_pos >= i_size_read(inode))
+ return retval;
+ }
+
+ return filemap_read(iocb, iter, retval);
+}
+EXPORT_SYMBOL(generic_file_read_iter);
+
+static inline loff_t folio_seek_hole_data(struct xa_state *xas,
+ struct address_space *mapping, struct folio *folio,
+ loff_t start, loff_t end, bool seek_data)
+{
+ const struct address_space_operations *ops = mapping->a_ops;
+ size_t offset, bsz = i_blocksize(mapping->host);
+
+ if (xa_is_value(folio) || folio_test_uptodate(folio))
+ return seek_data ? start : end;
+ if (!ops->is_partially_uptodate)
+ return seek_data ? end : start;
+
+ xas_pause(xas);
+ rcu_read_unlock();
+ folio_lock(folio);
+ if (unlikely(folio->mapping != mapping))
+ goto unlock;
+
+ offset = offset_in_folio(folio, start) & ~(bsz - 1);
+
+ do {
+ if (ops->is_partially_uptodate(folio, offset, bsz) ==
+ seek_data)
+ break;
+ start = (start + bsz) & ~(bsz - 1);
+ offset += bsz;
+ } while (offset < folio_size(folio));
+unlock:
+ folio_unlock(folio);
+ rcu_read_lock();
+ return start;
+}
+
+static inline size_t seek_folio_size(struct xa_state *xas, struct folio *folio)
+{
+ if (xa_is_value(folio))
+ return PAGE_SIZE << xa_get_order(xas->xa, xas->xa_index);
+ return folio_size(folio);
+}
+
+/**
+ * mapping_seek_hole_data - Seek for SEEK_DATA / SEEK_HOLE in the page cache.
+ * @mapping: Address space to search.
+ * @start: First byte to consider.
+ * @end: Limit of search (exclusive).
+ * @whence: Either SEEK_HOLE or SEEK_DATA.
+ *
+ * If the page cache knows which blocks contain holes and which blocks
+ * contain data, your filesystem can use this function to implement
+ * SEEK_HOLE and SEEK_DATA. This is useful for filesystems which are
+ * entirely memory-based such as tmpfs, and filesystems which support
+ * unwritten extents.
+ *
+ * Return: The requested offset on success, or -ENXIO if @whence specifies
+ * SEEK_DATA and there is no data after @start. There is an implicit hole
+ * after @end - 1, so SEEK_HOLE returns @end if all the bytes between @start
+ * and @end contain data.
+ */
+loff_t mapping_seek_hole_data(struct address_space *mapping, loff_t start,
+ loff_t end, int whence)
+{
+ XA_STATE(xas, &mapping->i_pages, start >> PAGE_SHIFT);
+ pgoff_t max = (end - 1) >> PAGE_SHIFT;
+ bool seek_data = (whence == SEEK_DATA);
+ struct folio *folio;
+
+ if (end <= start)
+ return -ENXIO;
+
+ rcu_read_lock();
+ while ((folio = find_get_entry(&xas, max, XA_PRESENT))) {
+ loff_t pos = (u64)xas.xa_index << PAGE_SHIFT;
+ size_t seek_size;
+
+ if (start < pos) {
+ if (!seek_data)
+ goto unlock;
+ start = pos;
+ }
+
+ seek_size = seek_folio_size(&xas, folio);
+ pos = round_up((u64)pos + 1, seek_size);
+ start = folio_seek_hole_data(&xas, mapping, folio, start, pos,
+ seek_data);
+ if (start < pos)
+ goto unlock;
+ if (start >= end)
+ break;
+ if (seek_size > PAGE_SIZE)
+ xas_set(&xas, pos >> PAGE_SHIFT);
+ if (!xa_is_value(folio))
+ folio_put(folio);
+ }
+ if (seek_data)
+ start = -ENXIO;
+unlock:
+ rcu_read_unlock();
+ if (folio && !xa_is_value(folio))
+ folio_put(folio);
+ if (start > end)
+ return end;
+ return start;
+}
+
+#ifdef CONFIG_MMU
+#define MMAP_LOTSAMISS (100)
+/*
+ * lock_folio_maybe_drop_mmap - lock the page, possibly dropping the mmap_lock
+ * @vmf - the vm_fault for this fault.
+ * @folio - the folio to lock.
+ * @fpin - the pointer to the file we may pin (or is already pinned).
+ *
+ * This works similar to lock_folio_or_retry in that it can drop the
+ * mmap_lock. It differs in that it actually returns the folio locked
+ * if it returns 1 and 0 if it couldn't lock the folio. If we did have
+ * to drop the mmap_lock then fpin will point to the pinned file and
+ * needs to be fput()'ed at a later point.
+ */
+static int lock_folio_maybe_drop_mmap(struct vm_fault *vmf, struct folio *folio,
+ struct file **fpin)
+{
+ if (folio_trylock(folio))
+ return 1;
+
+ /*
+ * NOTE! This will make us return with VM_FAULT_RETRY, but with
+ * the mmap_lock still held. That's how FAULT_FLAG_RETRY_NOWAIT
+ * is supposed to work. We have way too many special cases..
+ */
+ if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
+ return 0;
+
+ *fpin = maybe_unlock_mmap_for_io(vmf, *fpin);
+ if (vmf->flags & FAULT_FLAG_KILLABLE) {
+ if (__folio_lock_killable(folio)) {
+ /*
+ * We didn't have the right flags to drop the mmap_lock,
+ * but all fault_handlers only check for fatal signals
+ * if we return VM_FAULT_RETRY, so we need to drop the
+ * mmap_lock here and return 0 if we don't have a fpin.
+ */
+ if (*fpin == NULL)
+ mmap_read_unlock(vmf->vma->vm_mm);
+ return 0;
+ }
+ } else
+ __folio_lock(folio);
+
+ return 1;
+}
+
+/*
+ * Synchronous readahead happens when we don't even find a page in the page
+ * cache at all. We don't want to perform IO under the mmap sem, so if we have
+ * to drop the mmap sem we return the file that was pinned in order for us to do
+ * that. If we didn't pin a file then we return NULL. The file that is
+ * returned needs to be fput()'ed when we're done with it.
+ */
+static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
+{
+ struct file *file = vmf->vma->vm_file;
+ struct file_ra_state *ra = &file->f_ra;
+ struct address_space *mapping = file->f_mapping;
+ DEFINE_READAHEAD(ractl, file, ra, mapping, vmf->pgoff);
+ struct file *fpin = NULL;
+ unsigned long vm_flags = vmf->vma->vm_flags;
+ unsigned int mmap_miss;
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+ /* Use the readahead code, even if readahead is disabled */
+ if (vm_flags & VM_HUGEPAGE) {
+ fpin = maybe_unlock_mmap_for_io(vmf, fpin);
+ ractl._index &= ~((unsigned long)HPAGE_PMD_NR - 1);
+ ra->size = HPAGE_PMD_NR;
+ /*
+ * Fetch two PMD folios, so we get the chance to actually
+ * readahead, unless we've been told not to.
+ */
+ if (!(vm_flags & VM_RAND_READ))
+ ra->size *= 2;
+ ra->async_size = HPAGE_PMD_NR;
+ page_cache_ra_order(&ractl, ra, HPAGE_PMD_ORDER);
+ return fpin;
+ }
+#endif
+
+ /* If we don't want any read-ahead, don't bother */
+ if (vm_flags & VM_RAND_READ)
+ return fpin;
+ if (!ra->ra_pages)
+ return fpin;
+
+ if (vm_flags & VM_SEQ_READ) {
+ fpin = maybe_unlock_mmap_for_io(vmf, fpin);
+ page_cache_sync_ra(&ractl, ra->ra_pages);
+ return fpin;
+ }
+
+ /* Avoid banging the cache line if not needed */
+ mmap_miss = READ_ONCE(ra->mmap_miss);
+ if (mmap_miss < MMAP_LOTSAMISS * 10)
+ WRITE_ONCE(ra->mmap_miss, ++mmap_miss);
+
+ /*
+ * Do we miss much more than hit in this file? If so,
+ * stop bothering with read-ahead. It will only hurt.
+ */
+ if (mmap_miss > MMAP_LOTSAMISS)
+ return fpin;
+
+ /*
+ * mmap read-around
+ */
+ fpin = maybe_unlock_mmap_for_io(vmf, fpin);
+ ra->start = max_t(long, 0, vmf->pgoff - ra->ra_pages / 2);
+ ra->size = ra->ra_pages;
+ ra->async_size = ra->ra_pages / 4;
+ ractl._index = ra->start;
+ page_cache_ra_order(&ractl, ra, 0);
+ return fpin;
+}
+
+/*
+ * Asynchronous readahead happens when we find the page and PG_readahead,
+ * so we want to possibly extend the readahead further. We return the file that
+ * was pinned if we have to drop the mmap_lock in order to do IO.
+ */
+static struct file *do_async_mmap_readahead(struct vm_fault *vmf,
+ struct folio *folio)
+{
+ struct file *file = vmf->vma->vm_file;
+ struct file_ra_state *ra = &file->f_ra;
+ DEFINE_READAHEAD(ractl, file, ra, file->f_mapping, vmf->pgoff);
+ struct file *fpin = NULL;
+ unsigned int mmap_miss;
+
+ /* If we don't want any read-ahead, don't bother */
+ if (vmf->vma->vm_flags & VM_RAND_READ || !ra->ra_pages)
+ return fpin;
+
+ mmap_miss = READ_ONCE(ra->mmap_miss);
+ if (mmap_miss)
+ WRITE_ONCE(ra->mmap_miss, --mmap_miss);
+
+ if (folio_test_readahead(folio)) {
+ fpin = maybe_unlock_mmap_for_io(vmf, fpin);
+ page_cache_async_ra(&ractl, folio, ra->ra_pages);
+ }
+ return fpin;
+}
+
+/**
+ * filemap_fault - read in file data for page fault handling
+ * @vmf: struct vm_fault containing details of the fault
+ *
+ * filemap_fault() is invoked via the vma operations vector for a
+ * mapped memory region to read in file data during a page fault.
+ *
+ * The goto's are kind of ugly, but this streamlines the normal case of having
+ * it in the page cache, and handles the special cases reasonably without
+ * having a lot of duplicated code.
+ *
+ * vma->vm_mm->mmap_lock must be held on entry.
+ *
+ * If our return value has VM_FAULT_RETRY set, it's because the mmap_lock
+ * may be dropped before doing I/O or by lock_folio_maybe_drop_mmap().
+ *
+ * If our return value does not have VM_FAULT_RETRY set, the mmap_lock
+ * has not been released.
+ *
+ * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
+ *
+ * Return: bitwise-OR of %VM_FAULT_ codes.
+ */
+vm_fault_t filemap_fault(struct vm_fault *vmf)
+{
+ int error;
+ struct file *file = vmf->vma->vm_file;
+ struct file *fpin = NULL;
+ struct address_space *mapping = file->f_mapping;
+ struct inode *inode = mapping->host;
+ pgoff_t max_idx, index = vmf->pgoff;
+ struct folio *folio;
+ vm_fault_t ret = 0;
+ bool mapping_locked = false;
+
+ max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+ if (unlikely(index >= max_idx))
+ return VM_FAULT_SIGBUS;
+
+ /*
+ * Do we have something in the page cache already?
+ */
+ folio = filemap_get_folio(mapping, index);
+ if (likely(folio)) {
+ /*
+ * We found the page, so try async readahead before waiting for
+ * the lock.
+ */
+ if (!(vmf->flags & FAULT_FLAG_TRIED))
+ fpin = do_async_mmap_readahead(vmf, folio);
+ if (unlikely(!folio_test_uptodate(folio))) {
+ filemap_invalidate_lock_shared(mapping);
+ mapping_locked = true;
+ }
+ } else {
+ /* No page in the page cache at all */
+ count_vm_event(PGMAJFAULT);
+ count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT);
+ ret = VM_FAULT_MAJOR;
+ fpin = do_sync_mmap_readahead(vmf);
+retry_find:
+ /*
+ * See comment in filemap_create_folio() why we need
+ * invalidate_lock
+ */
+ if (!mapping_locked) {
+ filemap_invalidate_lock_shared(mapping);
+ mapping_locked = true;
+ }
+ folio = __filemap_get_folio(mapping, index,
+ FGP_CREAT|FGP_FOR_MMAP,
+ vmf->gfp_mask);
+ if (!folio) {
+ if (fpin)
+ goto out_retry;
+ filemap_invalidate_unlock_shared(mapping);
+ return VM_FAULT_OOM;
+ }
+ }
+
+ if (!lock_folio_maybe_drop_mmap(vmf, folio, &fpin))
+ goto out_retry;
+
+ /* Did it get truncated? */
+ if (unlikely(folio->mapping != mapping)) {
+ folio_unlock(folio);
+ folio_put(folio);
+ goto retry_find;
+ }
+ VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio);
+
+ /*
+ * We have a locked page in the page cache, now we need to check
+ * that it's up-to-date. If not, it is going to be due to an error.
+ */
+ if (unlikely(!folio_test_uptodate(folio))) {
+ /*
+ * The page was in cache and uptodate and now it is not.
+ * Strange but possible since we didn't hold the page lock all
+ * the time. Let's drop everything get the invalidate lock and
+ * try again.
+ */
+ if (!mapping_locked) {
+ folio_unlock(folio);
+ folio_put(folio);
+ goto retry_find;
+ }
+ goto page_not_uptodate;
+ }
+
+ /*
+ * We've made it this far and we had to drop our mmap_lock, now is the
+ * time to return to the upper layer and have it re-find the vma and
+ * redo the fault.
+ */
+ if (fpin) {
+ folio_unlock(folio);
+ goto out_retry;
+ }
+ if (mapping_locked)
+ filemap_invalidate_unlock_shared(mapping);
+
+ /*
+ * Found the page and have a reference on it.
+ * We must recheck i_size under page lock.
+ */
+ max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+ if (unlikely(index >= max_idx)) {
+ folio_unlock(folio);
+ folio_put(folio);
+ return VM_FAULT_SIGBUS;
+ }
+
+ vmf->page = folio_file_page(folio, index);
+ return ret | VM_FAULT_LOCKED;
+
+page_not_uptodate:
+ /*
+ * Umm, take care of errors if the page isn't up-to-date.
+ * Try to re-read it _once_. We do this synchronously,
+ * because there really aren't any performance issues here
+ * and we need to check for errors.
+ */
+ fpin = maybe_unlock_mmap_for_io(vmf, fpin);
+ error = filemap_read_folio(file, mapping->a_ops->read_folio, folio);
+ if (fpin)
+ goto out_retry;
+ folio_put(folio);
+
+ if (!error || error == AOP_TRUNCATED_PAGE)
+ goto retry_find;
+ filemap_invalidate_unlock_shared(mapping);
+
+ return VM_FAULT_SIGBUS;
+
+out_retry:
+ /*
+ * We dropped the mmap_lock, we need to return to the fault handler to
+ * re-find the vma and come back and find our hopefully still populated
+ * page.
+ */
+ if (folio)
+ folio_put(folio);
+ if (mapping_locked)
+ filemap_invalidate_unlock_shared(mapping);
+ if (fpin)
+ fput(fpin);
+ return ret | VM_FAULT_RETRY;
+}
+EXPORT_SYMBOL(filemap_fault);
+
+static bool filemap_map_pmd(struct vm_fault *vmf, struct page *page)
+{
+ struct mm_struct *mm = vmf->vma->vm_mm;
+
+ /* Huge page is mapped? No need to proceed. */
+ if (pmd_trans_huge(*vmf->pmd)) {
+ unlock_page(page);
+ put_page(page);
+ return true;
+ }
+
+ if (pmd_none(*vmf->pmd) && PageTransHuge(page)) {
+ vm_fault_t ret = do_set_pmd(vmf, page);
+ if (!ret) {
+ /* The page is mapped successfully, reference consumed. */
+ unlock_page(page);
+ return true;
+ }
+ }
+
+ if (pmd_none(*vmf->pmd) && vmf->prealloc_pte)
+ pmd_install(mm, vmf->pmd, &vmf->prealloc_pte);
+
+ /* See comment in handle_pte_fault() */
+ if (pmd_devmap_trans_unstable(vmf->pmd)) {
+ unlock_page(page);
+ put_page(page);
+ return true;
+ }
+
+ return false;
+}
+
+static struct folio *next_uptodate_page(struct folio *folio,
+ struct address_space *mapping,
+ struct xa_state *xas, pgoff_t end_pgoff)
+{
+ unsigned long max_idx;
+
+ do {
+ if (!folio)
+ return NULL;
+ if (xas_retry(xas, folio))
+ continue;
+ if (xa_is_value(folio))
+ continue;
+ if (folio_test_locked(folio))
+ continue;
+ if (!folio_try_get_rcu(folio))
+ continue;
+ /* Has the page moved or been split? */
+ if (unlikely(folio != xas_reload(xas)))
+ goto skip;
+ if (!folio_test_uptodate(folio) || folio_test_readahead(folio))
+ goto skip;
+ if (!folio_trylock(folio))
+ goto skip;
+ if (folio->mapping != mapping)
+ goto unlock;
+ if (!folio_test_uptodate(folio))
+ goto unlock;
+ max_idx = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
+ if (xas->xa_index >= max_idx)
+ goto unlock;
+ return folio;
+unlock:
+ folio_unlock(folio);
+skip:
+ folio_put(folio);
+ } while ((folio = xas_next_entry(xas, end_pgoff)) != NULL);
+
+ return NULL;
+}
+
+static inline struct folio *first_map_page(struct address_space *mapping,
+ struct xa_state *xas,
+ pgoff_t end_pgoff)
+{
+ return next_uptodate_page(xas_find(xas, end_pgoff),
+ mapping, xas, end_pgoff);
+}
+
+static inline struct folio *next_map_page(struct address_space *mapping,
+ struct xa_state *xas,
+ pgoff_t end_pgoff)
+{
+ return next_uptodate_page(xas_next_entry(xas, end_pgoff),
+ mapping, xas, end_pgoff);
+}
+
+vm_fault_t filemap_map_pages(struct vm_fault *vmf,
+ pgoff_t start_pgoff, pgoff_t end_pgoff)
+{
+ struct vm_area_struct *vma = vmf->vma;
+ struct file *file = vma->vm_file;
+ struct address_space *mapping = file->f_mapping;
+ pgoff_t last_pgoff = start_pgoff;
+ unsigned long addr;
+ XA_STATE(xas, &mapping->i_pages, start_pgoff);
+ struct folio *folio;
+ struct page *page;
+ unsigned int mmap_miss = READ_ONCE(file->f_ra.mmap_miss);
+ vm_fault_t ret = 0;
+
+ rcu_read_lock();
+ folio = first_map_page(mapping, &xas, end_pgoff);
+ if (!folio)
+ goto out;
+
+ if (filemap_map_pmd(vmf, &folio->page)) {
+ ret = VM_FAULT_NOPAGE;
+ goto out;
+ }
+
+ addr = vma->vm_start + ((start_pgoff - vma->vm_pgoff) << PAGE_SHIFT);
+ vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, addr, &vmf->ptl);
+ do {
+again:
+ page = folio_file_page(folio, xas.xa_index);
+ if (PageHWPoison(page))
+ goto unlock;
+
+ if (mmap_miss > 0)
+ mmap_miss--;
+
+ addr += (xas.xa_index - last_pgoff) << PAGE_SHIFT;
+ vmf->pte += xas.xa_index - last_pgoff;
+ last_pgoff = xas.xa_index;
+
+ /*
+ * NOTE: If there're PTE markers, we'll leave them to be
+ * handled in the specific fault path, and it'll prohibit the
+ * fault-around logic.
+ */
+ if (!pte_none(*vmf->pte))
+ goto unlock;
+
+ /* We're about to handle the fault */
+ if (vmf->address == addr)
+ ret = VM_FAULT_NOPAGE;
+
+ do_set_pte(vmf, page, addr);
+ /* no need to invalidate: a not-present page won't be cached */
+ update_mmu_cache(vma, addr, vmf->pte);
+ if (folio_more_pages(folio, xas.xa_index, end_pgoff)) {
+ xas.xa_index++;
+ folio_ref_inc(folio);
+ goto again;
+ }
+ folio_unlock(folio);
+ continue;
+unlock:
+ if (folio_more_pages(folio, xas.xa_index, end_pgoff)) {
+ xas.xa_index++;
+ goto again;
+ }
+ folio_unlock(folio);
+ folio_put(folio);
+ } while ((folio = next_map_page(mapping, &xas, end_pgoff)) != NULL);
+ pte_unmap_unlock(vmf->pte, vmf->ptl);
+out:
+ rcu_read_unlock();
+ WRITE_ONCE(file->f_ra.mmap_miss, mmap_miss);
+ return ret;
+}
+EXPORT_SYMBOL(filemap_map_pages);
+
+vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf)
+{
+ struct address_space *mapping = vmf->vma->vm_file->f_mapping;
+ struct folio *folio = page_folio(vmf->page);
+ vm_fault_t ret = VM_FAULT_LOCKED;
+
+ sb_start_pagefault(mapping->host->i_sb);
+ file_update_time(vmf->vma->vm_file);
+ folio_lock(folio);
+ if (folio->mapping != mapping) {
+ folio_unlock(folio);
+ ret = VM_FAULT_NOPAGE;
+ goto out;
+ }
+ /*
+ * We mark the folio dirty already here so that when freeze is in
+ * progress, we are guaranteed that writeback during freezing will
+ * see the dirty folio and writeprotect it again.
+ */
+ folio_mark_dirty(folio);
+ folio_wait_stable(folio);
+out:
+ sb_end_pagefault(mapping->host->i_sb);
+ return ret;
+}
+
+const struct vm_operations_struct generic_file_vm_ops = {
+ .fault = filemap_fault,
+ .map_pages = filemap_map_pages,
+ .page_mkwrite = filemap_page_mkwrite,
+};
+
+/* This is used for a general mmap of a disk file */
+
+int generic_file_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ struct address_space *mapping = file->f_mapping;
+
+ if (!mapping->a_ops->read_folio)
+ return -ENOEXEC;
+ file_accessed(file);
+ vma->vm_ops = &generic_file_vm_ops;
+ return 0;
+}
+
+/*
+ * This is for filesystems which do not implement ->writepage.
+ */
+int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
+ return -EINVAL;
+ return generic_file_mmap(file, vma);
+}
+#else
+vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf)
+{
+ return VM_FAULT_SIGBUS;
+}
+int generic_file_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ return -ENOSYS;
+}
+int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ return -ENOSYS;
+}
+#endif /* CONFIG_MMU */
+
+EXPORT_SYMBOL(filemap_page_mkwrite);
+EXPORT_SYMBOL(generic_file_mmap);
+EXPORT_SYMBOL(generic_file_readonly_mmap);
+
+static struct folio *do_read_cache_folio(struct address_space *mapping,
+ pgoff_t index, filler_t filler, struct file *file, gfp_t gfp)
+{
+ struct folio *folio;
+ int err;
+
+ if (!filler)
+ filler = mapping->a_ops->read_folio;
+repeat:
+ folio = filemap_get_folio(mapping, index);
+ if (!folio) {
+ folio = filemap_alloc_folio(gfp, 0);
+ if (!folio)
+ return ERR_PTR(-ENOMEM);
+ err = filemap_add_folio(mapping, folio, index, gfp);
+ if (unlikely(err)) {
+ folio_put(folio);
+ if (err == -EEXIST)
+ goto repeat;
+ /* Presumably ENOMEM for xarray node */
+ return ERR_PTR(err);
+ }
+
+ goto filler;
+ }
+ if (folio_test_uptodate(folio))
+ goto out;
+
+ if (!folio_trylock(folio)) {
+ folio_put_wait_locked(folio, TASK_UNINTERRUPTIBLE);
+ goto repeat;
+ }
+
+ /* Folio was truncated from mapping */
+ if (!folio->mapping) {
+ folio_unlock(folio);
+ folio_put(folio);
+ goto repeat;
+ }
+
+ /* Someone else locked and filled the page in a very small window */
+ if (folio_test_uptodate(folio)) {
+ folio_unlock(folio);
+ goto out;
+ }
+
+filler:
+ err = filemap_read_folio(file, filler, folio);
+ if (err) {
+ folio_put(folio);
+ if (err == AOP_TRUNCATED_PAGE)
+ goto repeat;
+ return ERR_PTR(err);
+ }
+
+out:
+ folio_mark_accessed(folio);
+ return folio;
+}
+
+/**
+ * read_cache_folio - Read into page cache, fill it if needed.
+ * @mapping: The address_space to read from.
+ * @index: The index to read.
+ * @filler: Function to perform the read, or NULL to use aops->read_folio().
+ * @file: Passed to filler function, may be NULL if not required.
+ *
+ * Read one page into the page cache. If it succeeds, the folio returned
+ * will contain @index, but it may not be the first page of the folio.
+ *
+ * If the filler function returns an error, it will be returned to the
+ * caller.
+ *
+ * Context: May sleep. Expects mapping->invalidate_lock to be held.
+ * Return: An uptodate folio on success, ERR_PTR() on failure.
+ */
+struct folio *read_cache_folio(struct address_space *mapping, pgoff_t index,
+ filler_t filler, struct file *file)
+{
+ return do_read_cache_folio(mapping, index, filler, file,
+ mapping_gfp_mask(mapping));
+}
+EXPORT_SYMBOL(read_cache_folio);
+
+static struct page *do_read_cache_page(struct address_space *mapping,
+ pgoff_t index, filler_t *filler, struct file *file, gfp_t gfp)
+{
+ struct folio *folio;
+
+ folio = do_read_cache_folio(mapping, index, filler, file, gfp);
+ if (IS_ERR(folio))
+ return &folio->page;
+ return folio_file_page(folio, index);
+}
+
+struct page *read_cache_page(struct address_space *mapping,
+ pgoff_t index, filler_t *filler, struct file *file)
+{
+ return do_read_cache_page(mapping, index, filler, file,
+ mapping_gfp_mask(mapping));
+}
+EXPORT_SYMBOL(read_cache_page);
+
+/**
+ * read_cache_page_gfp - read into page cache, using specified page allocation flags.
+ * @mapping: the page's address_space
+ * @index: the page index
+ * @gfp: the page allocator flags to use if allocating
+ *
+ * This is the same as "read_mapping_page(mapping, index, NULL)", but with
+ * any new page allocations done using the specified allocation flags.
+ *
+ * If the page does not get brought uptodate, return -EIO.
+ *
+ * The function expects mapping->invalidate_lock to be already held.
+ *
+ * Return: up to date page on success, ERR_PTR() on failure.
+ */
+struct page *read_cache_page_gfp(struct address_space *mapping,
+ pgoff_t index,
+ gfp_t gfp)
+{
+ return do_read_cache_page(mapping, index, NULL, NULL, gfp);
+}
+EXPORT_SYMBOL(read_cache_page_gfp);
+
+/*
+ * Warn about a page cache invalidation failure during a direct I/O write.
+ */
+void dio_warn_stale_pagecache(struct file *filp)
+{
+ static DEFINE_RATELIMIT_STATE(_rs, 86400 * HZ, DEFAULT_RATELIMIT_BURST);
+ char pathname[128];
+ char *path;
+
+ errseq_set(&filp->f_mapping->wb_err, -EIO);
+ if (__ratelimit(&_rs)) {
+ path = file_path(filp, pathname, sizeof(pathname));
+ if (IS_ERR(path))
+ path = "(unknown)";
+ pr_crit("Page cache invalidation failure on direct I/O. Possible data corruption due to collision with buffered I/O!\n");
+ pr_crit("File: %s PID: %d Comm: %.20s\n", path, current->pid,
+ current->comm);
+ }
+}
+
+ssize_t
+generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
+{
+ struct file *file = iocb->ki_filp;
+ struct address_space *mapping = file->f_mapping;
+ struct inode *inode = mapping->host;
+ loff_t pos = iocb->ki_pos;
+ ssize_t written;
+ size_t write_len;
+ pgoff_t end;
+
+ write_len = iov_iter_count(from);
+ end = (pos + write_len - 1) >> PAGE_SHIFT;
+
+ if (iocb->ki_flags & IOCB_NOWAIT) {
+ /* If there are pages to writeback, return */
+ if (filemap_range_has_page(file->f_mapping, pos,
+ pos + write_len - 1))
+ return -EAGAIN;
+ } else {
+ written = filemap_write_and_wait_range(mapping, pos,
+ pos + write_len - 1);
+ if (written)
+ goto out;
+ }
+
+ /*
+ * After a write we want buffered reads to be sure to go to disk to get
+ * the new data. We invalidate clean cached page from the region we're
+ * about to write. We do this *before* the write so that we can return
+ * without clobbering -EIOCBQUEUED from ->direct_IO().
+ */
+ written = invalidate_inode_pages2_range(mapping,
+ pos >> PAGE_SHIFT, end);
+ /*
+ * If a page can not be invalidated, return 0 to fall back
+ * to buffered write.
+ */
+ if (written) {
+ if (written == -EBUSY)
+ return 0;
+ goto out;
+ }
+
+ written = mapping->a_ops->direct_IO(iocb, from);
+
+ /*
+ * Finally, try again to invalidate clean pages which might have been
+ * cached by non-direct readahead, or faulted in by get_user_pages()
+ * if the source of the write was an mmap'ed region of the file
+ * we're writing. Either one is a pretty crazy thing to do,
+ * so we don't support it 100%. If this invalidation
+ * fails, tough, the write still worked...
+ *
+ * Most of the time we do not need this since dio_complete() will do
+ * the invalidation for us. However there are some file systems that
+ * do not end up with dio_complete() being called, so let's not break
+ * them by removing it completely.
+ *
+ * Noticeable example is a blkdev_direct_IO().
+ *
+ * Skip invalidation for async writes or if mapping has no pages.
+ */
+ if (written > 0 && mapping->nrpages &&
+ invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT, end))
+ dio_warn_stale_pagecache(file);
+
+ if (written > 0) {
+ pos += written;
+ write_len -= written;
+ if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
+ i_size_write(inode, pos);
+ mark_inode_dirty(inode);
+ }
+ iocb->ki_pos = pos;
+ }
+ if (written != -EIOCBQUEUED)
+ iov_iter_revert(from, write_len - iov_iter_count(from));
+out:
+ return written;
+}
+EXPORT_SYMBOL(generic_file_direct_write);
+
+ssize_t generic_perform_write(struct kiocb *iocb, struct iov_iter *i)
+{
+ struct file *file = iocb->ki_filp;
+ loff_t pos = iocb->ki_pos;
+ struct address_space *mapping = file->f_mapping;
+ const struct address_space_operations *a_ops = mapping->a_ops;
+ long status = 0;
+ ssize_t written = 0;
+
+ do {
+ struct page *page;
+ unsigned long offset; /* Offset into pagecache page */
+ unsigned long bytes; /* Bytes to write to page */
+ size_t copied; /* Bytes copied from user */
+ void *fsdata = NULL;
+
+ offset = (pos & (PAGE_SIZE - 1));
+ bytes = min_t(unsigned long, PAGE_SIZE - offset,
+ iov_iter_count(i));
+
+again:
+ /*
+ * Bring in the user page that we will copy from _first_.
+ * Otherwise there's a nasty deadlock on copying from the
+ * same page as we're writing to, without it being marked
+ * up-to-date.
+ */
+ if (unlikely(fault_in_iov_iter_readable(i, bytes) == bytes)) {
+ status = -EFAULT;
+ break;
+ }
+
+ if (fatal_signal_pending(current)) {
+ status = -EINTR;
+ break;
+ }
+
+ status = a_ops->write_begin(file, mapping, pos, bytes,
+ &page, &fsdata);
+ if (unlikely(status < 0))
+ break;
+
+ if (mapping_writably_mapped(mapping))
+ flush_dcache_page(page);
+
+ copied = copy_page_from_iter_atomic(page, offset, bytes, i);
+ flush_dcache_page(page);
+
+ status = a_ops->write_end(file, mapping, pos, bytes, copied,
+ page, fsdata);
+ if (unlikely(status != copied)) {
+ iov_iter_revert(i, copied - max(status, 0L));
+ if (unlikely(status < 0))
+ break;
+ }
+ cond_resched();
+
+ if (unlikely(status == 0)) {
+ /*
+ * A short copy made ->write_end() reject the
+ * thing entirely. Might be memory poisoning
+ * halfway through, might be a race with munmap,
+ * might be severe memory pressure.
+ */
+ if (copied)
+ bytes = copied;
+ goto again;
+ }
+ pos += status;
+ written += status;
+
+ balance_dirty_pages_ratelimited(mapping);
+ } while (iov_iter_count(i));
+
+ return written ? written : status;
+}
+EXPORT_SYMBOL(generic_perform_write);
+
+/**
+ * __generic_file_write_iter - write data to a file
+ * @iocb: IO state structure (file, offset, etc.)
+ * @from: iov_iter with data to write
+ *
+ * This function does all the work needed for actually writing data to a
+ * file. It does all basic checks, removes SUID from the file, updates
+ * modification times and calls proper subroutines depending on whether we
+ * do direct IO or a standard buffered write.
+ *
+ * It expects i_rwsem to be grabbed unless we work on a block device or similar
+ * object which does not need locking at all.
+ *
+ * This function does *not* take care of syncing data in case of O_SYNC write.
+ * A caller has to handle it. This is mainly due to the fact that we want to
+ * avoid syncing under i_rwsem.
+ *
+ * Return:
+ * * number of bytes written, even for truncated writes
+ * * negative error code if no data has been written at all
+ */
+ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+ struct file *file = iocb->ki_filp;
+ struct address_space *mapping = file->f_mapping;
+ struct inode *inode = mapping->host;
+ ssize_t written = 0;
+ ssize_t err;
+ ssize_t status;
+
+ /* We can write back this queue in page reclaim */
+ current->backing_dev_info = inode_to_bdi(inode);
+ err = file_remove_privs(file);
+ if (err)
+ goto out;
+
+ err = file_update_time(file);
+ if (err)
+ goto out;
+
+ if (iocb->ki_flags & IOCB_DIRECT) {
+ loff_t pos, endbyte;
+
+ written = generic_file_direct_write(iocb, from);
+ /*
+ * If the write stopped short of completing, fall back to
+ * buffered writes. Some filesystems do this for writes to
+ * holes, for example. For DAX files, a buffered write will
+ * not succeed (even if it did, DAX does not handle dirty
+ * page-cache pages correctly).
+ */
+ if (written < 0 || !iov_iter_count(from) || IS_DAX(inode))
+ goto out;
+
+ pos = iocb->ki_pos;
+ status = generic_perform_write(iocb, from);
+ /*
+ * If generic_perform_write() returned a synchronous error
+ * then we want to return the number of bytes which were
+ * direct-written, or the error code if that was zero. Note
+ * that this differs from normal direct-io semantics, which
+ * will return -EFOO even if some bytes were written.
+ */
+ if (unlikely(status < 0)) {
+ err = status;
+ goto out;
+ }
+ /*
+ * We need to ensure that the page cache pages are written to
+ * disk and invalidated to preserve the expected O_DIRECT
+ * semantics.
+ */
+ endbyte = pos + status - 1;
+ err = filemap_write_and_wait_range(mapping, pos, endbyte);
+ if (err == 0) {
+ iocb->ki_pos = endbyte + 1;
+ written += status;
+ invalidate_mapping_pages(mapping,
+ pos >> PAGE_SHIFT,
+ endbyte >> PAGE_SHIFT);
+ } else {
+ /*
+ * We don't know how much we wrote, so just return
+ * the number of bytes which were direct-written
+ */
+ }
+ } else {
+ written = generic_perform_write(iocb, from);
+ if (likely(written > 0))
+ iocb->ki_pos += written;
+ }
+out:
+ current->backing_dev_info = NULL;
+ return written ? written : err;
+}
+EXPORT_SYMBOL(__generic_file_write_iter);
+
+/**
+ * generic_file_write_iter - write data to a file
+ * @iocb: IO state structure
+ * @from: iov_iter with data to write
+ *
+ * This is a wrapper around __generic_file_write_iter() to be used by most
+ * filesystems. It takes care of syncing the file in case of O_SYNC file
+ * and acquires i_rwsem as needed.
+ * Return:
+ * * negative error code if no data has been written at all of
+ * vfs_fsync_range() failed for a synchronous write
+ * * number of bytes written, even for truncated writes
+ */
+ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+ struct file *file = iocb->ki_filp;
+ struct inode *inode = file->f_mapping->host;
+ ssize_t ret;
+
+ inode_lock(inode);
+ ret = generic_write_checks(iocb, from);
+ if (ret > 0)
+ ret = __generic_file_write_iter(iocb, from);
+ inode_unlock(inode);
+
+ if (ret > 0)
+ ret = generic_write_sync(iocb, ret);
+ return ret;
+}
+EXPORT_SYMBOL(generic_file_write_iter);
+
+/**
+ * filemap_release_folio() - Release fs-specific metadata on a folio.
+ * @folio: The folio which the kernel is trying to free.
+ * @gfp: Memory allocation flags (and I/O mode).
+ *
+ * The address_space is trying to release any data attached to a folio
+ * (presumably at folio->private).
+ *
+ * This will also be called if the private_2 flag is set on a page,
+ * indicating that the folio has other metadata associated with it.
+ *
+ * The @gfp argument specifies whether I/O may be performed to release
+ * this page (__GFP_IO), and whether the call may block
+ * (__GFP_RECLAIM & __GFP_FS).
+ *
+ * Return: %true if the release was successful, otherwise %false.
+ */
+bool filemap_release_folio(struct folio *folio, gfp_t gfp)
+{
+ struct address_space * const mapping = folio->mapping;
+
+ BUG_ON(!folio_test_locked(folio));
+ if (!folio_needs_release(folio))
+ return true;
+ if (folio_test_writeback(folio))
+ return false;
+
+ if (mapping && mapping->a_ops->release_folio)
+ return mapping->a_ops->release_folio(folio, gfp);
+ return try_to_free_buffers(folio);
+}
+EXPORT_SYMBOL(filemap_release_folio);