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Diffstat (limited to 'mm/filemap.c')
| -rw-r--r-- | mm/filemap.c | 3536 |
1 files changed, 3536 insertions, 0 deletions
diff --git a/mm/filemap.c b/mm/filemap.c new file mode 100644 index 000000000..3b0d8c6dd --- /dev/null +++ b/mm/filemap.c @@ -0,0 +1,3536 @@ +// 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/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/blkdev.h> +#include <linux/security.h> +#include <linux/cpuset.h> +#include <linux/hugetlb.h> +#include <linux/memcontrol.h> +#include <linux/cleancache.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 "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->__set_page_dirty_buffers) + * ->swap_lock (exclusive_swap_page, others) + * ->i_pages lock + * + * ->i_mutex + * ->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 + * ->lock_page (access_process_vm) + * + * ->i_mutex (generic_perform_write) + * ->mmap_lock (fault_in_pages_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) + * ->pgdat->lru_lock (follow_page->mark_page_accessed) + * ->pgdat->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->__set_page_dirty_buffers) + * + * ->i_mmap_rwsem + * ->tasklist_lock (memory_failure, collect_procs_ao) + */ + +static void page_cache_delete(struct address_space *mapping, + struct page *page, void *shadow) +{ + XA_STATE(xas, &mapping->i_pages, page->index); + unsigned int nr = 1; + + mapping_set_update(&xas, mapping); + + /* hugetlb pages are represented by a single entry in the xarray */ + if (!PageHuge(page)) { + xas_set_order(&xas, page->index, compound_order(page)); + nr = compound_nr(page); + } + + VM_BUG_ON_PAGE(!PageLocked(page), page); + VM_BUG_ON_PAGE(PageTail(page), page); + VM_BUG_ON_PAGE(nr != 1 && shadow, page); + + xas_store(&xas, shadow); + xas_init_marks(&xas); + + page->mapping = NULL; + /* Leave page->index set: truncation lookup relies upon it */ + + if (shadow) { + mapping->nrexceptional += nr; + /* + * Make sure the nrexceptional update is committed before + * the nrpages update so that final truncate racing + * with reclaim does not see both counters 0 at the + * same time and miss a shadow entry. + */ + smp_wmb(); + } + mapping->nrpages -= nr; +} + +static void unaccount_page_cache_page(struct address_space *mapping, + struct page *page) +{ + int nr; + + /* + * if we're uptodate, flush out into the cleancache, otherwise + * invalidate any existing cleancache entries. We can't leave + * stale data around in the cleancache once our page is gone + */ + if (PageUptodate(page) && PageMappedToDisk(page)) + cleancache_put_page(page); + else + cleancache_invalidate_page(mapping, page); + + VM_BUG_ON_PAGE(PageTail(page), page); + VM_BUG_ON_PAGE(page_mapped(page), page); + if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(page_mapped(page))) { + int mapcount; + + pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n", + current->comm, page_to_pfn(page)); + dump_page(page, "still mapped when deleted"); + dump_stack(); + add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); + + mapcount = page_mapcount(page); + if (mapping_exiting(mapping) && + page_count(page) >= mapcount + 2) { + /* + * All vmas have already been torn down, so it's + * a good bet that actually the page is unmapped, + * and we'd prefer not to leak it: if we're wrong, + * some other bad page check should catch it later. + */ + page_mapcount_reset(page); + page_ref_sub(page, mapcount); + } + } + + /* hugetlb pages do not participate in page cache accounting. */ + if (PageHuge(page)) + return; + + nr = thp_nr_pages(page); + + __mod_lruvec_page_state(page, NR_FILE_PAGES, -nr); + if (PageSwapBacked(page)) { + __mod_lruvec_page_state(page, NR_SHMEM, -nr); + if (PageTransHuge(page)) + __dec_node_page_state(page, NR_SHMEM_THPS); + } else if (PageTransHuge(page)) { + __dec_node_page_state(page, NR_FILE_THPS); + filemap_nr_thps_dec(mapping); + } + + /* + * At this point page must be either written or cleaned by + * truncate. Dirty page here signals a bug and loss of + * unwritten data. + * + * This fixes dirty accounting after removing the page entirely + * but leaves PageDirty set: it has no effect for truncated + * page and anyway will be cleared before returning page into + * buddy allocator. + */ + if (WARN_ON_ONCE(PageDirty(page))) + account_page_cleaned(page, mapping, 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 __delete_from_page_cache(struct page *page, void *shadow) +{ + struct address_space *mapping = page->mapping; + + trace_mm_filemap_delete_from_page_cache(page); + + unaccount_page_cache_page(mapping, page); + page_cache_delete(mapping, page, shadow); +} + +static void page_cache_free_page(struct address_space *mapping, + struct page *page) +{ + void (*freepage)(struct page *); + + freepage = mapping->a_ops->freepage; + if (freepage) + freepage(page); + + if (PageTransHuge(page) && !PageHuge(page)) { + page_ref_sub(page, thp_nr_pages(page)); + VM_BUG_ON_PAGE(page_count(page) <= 0, page); + } else { + put_page(page); + } +} + +/** + * delete_from_page_cache - delete page from page cache + * @page: the page which the kernel is trying to remove from page cache + * + * This must be called only on pages that have been verified to be in the page + * cache and locked. It will never put the page into the free list, the caller + * has a reference on the page. + */ +void delete_from_page_cache(struct page *page) +{ + struct address_space *mapping = page_mapping(page); + unsigned long flags; + + BUG_ON(!PageLocked(page)); + xa_lock_irqsave(&mapping->i_pages, flags); + __delete_from_page_cache(page, NULL); + xa_unlock_irqrestore(&mapping->i_pages, flags); + + page_cache_free_page(mapping, page); +} +EXPORT_SYMBOL(delete_from_page_cache); + +/* + * page_cache_delete_batch - delete several pages from page cache + * @mapping: the mapping to which pages belong + * @pvec: pagevec with pages to delete + * + * The function walks over mapping->i_pages and removes pages passed in @pvec + * from the mapping. The function expects @pvec to be sorted by page index + * and is optimised for it to be dense. + * It tolerates holes in @pvec (mapping entries at those indices are not + * modified). The function expects only THP head pages to be present in the + * @pvec. + * + * The function expects the i_pages lock to be held. + */ +static void page_cache_delete_batch(struct address_space *mapping, + struct pagevec *pvec) +{ + XA_STATE(xas, &mapping->i_pages, pvec->pages[0]->index); + int total_pages = 0; + int i = 0; + struct page *page; + + mapping_set_update(&xas, mapping); + xas_for_each(&xas, page, ULONG_MAX) { + if (i >= pagevec_count(pvec)) + break; + + /* A swap/dax/shadow entry got inserted? Skip it. */ + if (xa_is_value(page)) + 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 (page != pvec->pages[i]) { + VM_BUG_ON_PAGE(page->index > pvec->pages[i]->index, + page); + continue; + } + + WARN_ON_ONCE(!PageLocked(page)); + + if (page->index == xas.xa_index) + page->mapping = NULL; + /* Leave page->index set: truncation lookup relies on it */ + + /* + * Move to the next page in the vector if this is a regular + * page or the index is of the last sub-page of this compound + * page. + */ + if (page->index + compound_nr(page) - 1 == xas.xa_index) + i++; + xas_store(&xas, NULL); + total_pages++; + } + mapping->nrpages -= total_pages; +} + +void delete_from_page_cache_batch(struct address_space *mapping, + struct pagevec *pvec) +{ + int i; + unsigned long flags; + + if (!pagevec_count(pvec)) + return; + + xa_lock_irqsave(&mapping->i_pages, flags); + for (i = 0; i < pagevec_count(pvec); i++) { + trace_mm_filemap_delete_from_page_cache(pvec->pages[i]); + + unaccount_page_cache_page(mapping, pvec->pages[i]); + } + page_cache_delete_batch(mapping, pvec); + xa_unlock_irqrestore(&mapping->i_pages, flags); + + for (i = 0; i < pagevec_count(pvec); i++) + page_cache_free_page(mapping, pvec->pages[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_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) +{ + int ret; + struct writeback_control wbc = { + .sync_mode = sync_mode, + .nr_to_write = LONG_MAX, + .range_start = start, + .range_end = end, + }; + + 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; +} + +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) +{ + if (dax_mapping(mapping)) + return mapping->nrexceptional; + + return mapping->nrpages; +} + +/** + * 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; + + 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) { + int err2 = filemap_fdatawait_range(mapping, + lstart, lend); + if (!err) + err = err2; + } else { + /* Clear any previously stored errors */ + filemap_check_errors(mapping); + } + } else { + err = filemap_check_errors(mapping); + } + 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 + * @gfp_mask: allocation mode + * + * 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. + * + * Return: %0 + */ +int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask) +{ + struct address_space *mapping = old->mapping; + void (*freepage)(struct page *) = mapping->a_ops->freepage; + pgoff_t offset = old->index; + XA_STATE(xas, &mapping->i_pages, offset); + unsigned long flags; + + 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(old, new); + + xas_lock_irqsave(&xas, flags); + 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_irqrestore(&xas, flags); + if (freepage) + freepage(old); + put_page(old); + + return 0; +} +EXPORT_SYMBOL_GPL(replace_page_cache_page); + +noinline int __add_to_page_cache_locked(struct page *page, + struct address_space *mapping, + pgoff_t offset, gfp_t gfp, + void **shadowp) +{ + XA_STATE(xas, &mapping->i_pages, offset); + int huge = PageHuge(page); + int error; + bool charged = false; + + VM_BUG_ON_PAGE(!PageLocked(page), page); + VM_BUG_ON_PAGE(PageSwapBacked(page), page); + mapping_set_update(&xas, mapping); + + get_page(page); + page->mapping = mapping; + page->index = offset; + + if (!huge) { + error = mem_cgroup_charge(page, current->mm, gfp); + if (error) + goto error; + charged = true; + } + + gfp &= GFP_RECLAIM_MASK; + + do { + unsigned int order = xa_get_order(xas.xa, xas.xa_index); + void *entry, *old = NULL; + + if (order > thp_order(page)) + 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 > thp_order(page)) { + xas_split(&xas, old, order); + xas_reset(&xas); + } + } + + xas_store(&xas, page); + if (xas_error(&xas)) + goto unlock; + + if (old) + mapping->nrexceptional--; + mapping->nrpages++; + + /* hugetlb pages do not participate in page cache accounting */ + if (!huge) + __inc_lruvec_page_state(page, NR_FILE_PAGES); +unlock: + xas_unlock_irq(&xas); + } while (xas_nomem(&xas, gfp)); + + if (xas_error(&xas)) { + error = xas_error(&xas); + if (charged) + mem_cgroup_uncharge(page); + goto error; + } + + trace_mm_filemap_add_to_page_cache(page); + return 0; +error: + page->mapping = NULL; + /* Leave page->index set: truncation relies upon it */ + put_page(page); + return error; +} +ALLOW_ERROR_INJECTION(__add_to_page_cache_locked, ERRNO); + +/** + * add_to_page_cache_locked - add a locked page to the pagecache + * @page: page to add + * @mapping: the page's address_space + * @offset: page index + * @gfp_mask: page allocation mode + * + * This function is used to add a page to the pagecache. It must be locked. + * This function does not add the page to the LRU. The caller must do that. + * + * Return: %0 on success, negative error code otherwise. + */ +int add_to_page_cache_locked(struct page *page, struct address_space *mapping, + pgoff_t offset, gfp_t gfp_mask) +{ + return __add_to_page_cache_locked(page, mapping, offset, + gfp_mask, NULL); +} +EXPORT_SYMBOL(add_to_page_cache_locked); + +int add_to_page_cache_lru(struct page *page, struct address_space *mapping, + pgoff_t offset, gfp_t gfp_mask) +{ + void *shadow = NULL; + int ret; + + __SetPageLocked(page); + ret = __add_to_page_cache_locked(page, mapping, offset, + gfp_mask, &shadow); + if (unlikely(ret)) + __ClearPageLocked(page); + else { + /* + * The page might have been evicted from cache only + * recently, in which case it should be activated like + * any other repeatedly accessed page. + * The exception is pages 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(PageActive(page)); + if (!(gfp_mask & __GFP_WRITE) && shadow) + workingset_refault(page, shadow); + lru_cache_add(page); + } + return ret; +} +EXPORT_SYMBOL_GPL(add_to_page_cache_lru); + +#ifdef CONFIG_NUMA +struct page *__page_cache_alloc(gfp_t gfp) +{ + int n; + struct page *page; + + if (cpuset_do_page_mem_spread()) { + unsigned int cpuset_mems_cookie; + do { + cpuset_mems_cookie = read_mems_allowed_begin(); + n = cpuset_mem_spread_node(); + page = __alloc_pages_node(n, gfp, 0); + } while (!page && read_mems_allowed_retry(cpuset_mems_cookie)); + + return page; + } + return alloc_pages(gfp, 0); +} +EXPORT_SYMBOL(__page_cache_alloc); +#endif + +/* + * 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 page_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned; + +static wait_queue_head_t *page_waitqueue(struct page *page) +{ + return &page_wait_table[hash_ptr(page, PAGE_WAIT_TABLE_BITS)]; +} + +void __init pagecache_init(void) +{ + int i; + + for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++) + init_waitqueue_head(&page_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->page->flags)) + return -1; + if (flags & WQ_FLAG_CUSTOM) { + if (test_and_set_bit(key->bit_nr, &key->page->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 wait_on_page_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 wake_up_page_bit(struct page *page, int bit_nr) +{ + wait_queue_head_t *q = page_waitqueue(page); + struct wait_page_key key; + unsigned long flags; + wait_queue_entry_t bookmark; + + key.page = page; + 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 is possible for other pages to have collided on the waitqueue + * hash, so in that case check for a page match. That prevents a long- + * term waiter + * + * It is still possible to miss a case here, when we woke page waiters + * and removed them from the waitqueue, but there are still other + * page waiters. + */ + if (!waitqueue_active(q) || !key.page_match) { + ClearPageWaiters(page); + /* + * 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. + */ + } + spin_unlock_irqrestore(&q->lock, flags); +} + +static void wake_up_page(struct page *page, int bit) +{ + if (!PageWaiters(page)) + return; + wake_up_page_bit(page, bit); +} + +/* + * A choice of three behaviors for wait_on_page_bit_common(): + */ +enum behavior { + EXCLUSIVE, /* Hold ref to page and take the bit when woken, like + * __lock_page() waiting on then setting PG_locked. + */ + SHARED, /* Hold ref to page and check the bit when woken, like + * wait_on_page_writeback() waiting on PG_writeback. + */ + DROP, /* Drop ref to page before wait, no check when woken, + * like put_and_wait_on_page_locked() on PG_locked. + */ +}; + +/* + * Attempt to check (or get) the page bit, and mark us done + * if successful. + */ +static inline bool trylock_page_bit_common(struct page *page, int bit_nr, + struct wait_queue_entry *wait) +{ + if (wait->flags & WQ_FLAG_EXCLUSIVE) { + if (test_and_set_bit(bit_nr, &page->flags)) + return false; + } else if (test_bit(bit_nr, &page->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 wait_on_page_bit_common(wait_queue_head_t *q, + struct page *page, int bit_nr, int state, enum behavior behavior) +{ + int unfairness = sysctl_page_lock_unfairness; + struct wait_page_queue wait_page; + wait_queue_entry_t *wait = &wait_page.wait; + bool thrashing = false; + bool delayacct = false; + unsigned long pflags; + + if (bit_nr == PG_locked && + !PageUptodate(page) && PageWorkingset(page)) { + if (!PageSwapBacked(page)) { + delayacct_thrashing_start(); + delayacct = true; + } + psi_memstall_enter(&pflags); + thrashing = true; + } + + init_wait(wait); + wait->func = wake_page_function; + wait_page.page = page; + 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 SetPageWaiters() 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); + SetPageWaiters(page); + if (!trylock_page_bit_common(page, 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 page. + */ + if (behavior == DROP) + put_page(page); + + /* + * 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, &page->flags))) + 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 PageWaiters 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) { + if (delayacct) + delayacct_thrashing_end(); + 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; +} + +void wait_on_page_bit(struct page *page, int bit_nr) +{ + wait_queue_head_t *q = page_waitqueue(page); + wait_on_page_bit_common(q, page, bit_nr, TASK_UNINTERRUPTIBLE, SHARED); +} +EXPORT_SYMBOL(wait_on_page_bit); + +int wait_on_page_bit_killable(struct page *page, int bit_nr) +{ + wait_queue_head_t *q = page_waitqueue(page); + return wait_on_page_bit_common(q, page, bit_nr, TASK_KILLABLE, SHARED); +} +EXPORT_SYMBOL(wait_on_page_bit_killable); + +static int __wait_on_page_locked_async(struct page *page, + struct wait_page_queue *wait, bool set) +{ + struct wait_queue_head *q = page_waitqueue(page); + int ret = 0; + + wait->page = page; + wait->bit_nr = PG_locked; + + spin_lock_irq(&q->lock); + __add_wait_queue_entry_tail(q, &wait->wait); + SetPageWaiters(page); + if (set) + ret = !trylock_page(page); + else + ret = PageLocked(page); + /* + * If we were succesful 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; +} + +static int wait_on_page_locked_async(struct page *page, + struct wait_page_queue *wait) +{ + if (!PageLocked(page)) + return 0; + return __wait_on_page_locked_async(compound_head(page), wait, false); +} + +/** + * put_and_wait_on_page_locked - Drop a reference and wait for it to be unlocked + * @page: The page to wait for. + * + * The caller should hold a reference on @page. 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 page to + * come unlocked. After this function returns, the caller should not + * dereference @page. + */ +void put_and_wait_on_page_locked(struct page *page) +{ + wait_queue_head_t *q; + + page = compound_head(page); + q = page_waitqueue(page); + wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE, DROP); +} + +/** + * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue + * @page: Page defining the wait queue of interest + * @waiter: Waiter to add to the queue + * + * Add an arbitrary @waiter to the wait queue for the nominated @page. + */ +void add_page_wait_queue(struct page *page, wait_queue_entry_t *waiter) +{ + wait_queue_head_t *q = page_waitqueue(page); + unsigned long flags; + + spin_lock_irqsave(&q->lock, flags); + __add_wait_queue_entry_tail(q, waiter); + SetPageWaiters(page); + spin_unlock_irqrestore(&q->lock, flags); +} +EXPORT_SYMBOL_GPL(add_page_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 + +/** + * unlock_page - unlock a locked page + * @page: the page + * + * Unlocks the page and wakes up sleepers in wait_on_page_locked(). + * Also wakes sleepers in wait_on_page_writeback() because the wakeup + * mechanism between PageLocked pages and PageWriteback pages is shared. + * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep. + * + * Note that this depends on PG_waiters being the sign bit in the byte + * that contains PG_locked - thus the BUILD_BUG_ON(). That allows us to + * clear the PG_locked bit and test PG_waiters at the same time fairly + * portably (architectures that do LL/SC can test any bit, while x86 can + * test the sign bit). + */ +void unlock_page(struct page *page) +{ + BUILD_BUG_ON(PG_waiters != 7); + page = compound_head(page); + VM_BUG_ON_PAGE(!PageLocked(page), page); + if (clear_bit_unlock_is_negative_byte(PG_locked, &page->flags)) + wake_up_page_bit(page, PG_locked); +} +EXPORT_SYMBOL(unlock_page); + +/** + * end_page_writeback - end writeback against a page + * @page: the page + */ +void end_page_writeback(struct page *page) +{ + /* + * TestClearPageReclaim could be used here but it is an atomic + * operation and overkill in this particular case. Failing to + * shuffle a page marked for immediate reclaim is too mild to + * justify taking an atomic operation penalty at the end of + * ever page writeback. + */ + if (PageReclaim(page)) { + ClearPageReclaim(page); + rotate_reclaimable_page(page); + } + + /* + * Writeback does not hold a page reference of its own, relying + * on truncation to wait for the clearing of PG_writeback. + * But here we must make sure that the page is not freed and + * reused before the wake_up_page(). + */ + get_page(page); + if (!test_clear_page_writeback(page)) + BUG(); + + smp_mb__after_atomic(); + wake_up_page(page, PG_writeback); + put_page(page); +} +EXPORT_SYMBOL(end_page_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) +{ + if (!is_write) { + if (!err) { + SetPageUptodate(page); + } else { + ClearPageUptodate(page); + SetPageError(page); + } + unlock_page(page); + } else { + if (err) { + struct address_space *mapping; + + SetPageError(page); + mapping = page_mapping(page); + if (mapping) + mapping_set_error(mapping, err); + } + end_page_writeback(page); + } +} +EXPORT_SYMBOL_GPL(page_endio); + +/** + * __lock_page - get a lock on the page, assuming we need to sleep to get it + * @__page: the page to lock + */ +void __lock_page(struct page *__page) +{ + struct page *page = compound_head(__page); + wait_queue_head_t *q = page_waitqueue(page); + wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE, + EXCLUSIVE); +} +EXPORT_SYMBOL(__lock_page); + +int __lock_page_killable(struct page *__page) +{ + struct page *page = compound_head(__page); + wait_queue_head_t *q = page_waitqueue(page); + return wait_on_page_bit_common(q, page, PG_locked, TASK_KILLABLE, + EXCLUSIVE); +} +EXPORT_SYMBOL_GPL(__lock_page_killable); + +int __lock_page_async(struct page *page, struct wait_page_queue *wait) +{ + return __wait_on_page_locked_async(page, wait, true); +} + +/* + * Return values: + * 1 - page is locked; mmap_lock is still held. + * 0 - page 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 1 + * with the page locked and the mmap_lock unperturbed. + */ +int __lock_page_or_retry(struct page *page, 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 0; + + mmap_read_unlock(mm); + if (flags & FAULT_FLAG_KILLABLE) + wait_on_page_locked_killable(page); + else + wait_on_page_locked(page); + return 0; + } else { + if (flags & FAULT_FLAG_KILLABLE) { + int ret; + + ret = __lock_page_killable(page); + if (ret) { + mmap_read_unlock(mm); + return 0; + } + } else + __lock_page(page); + return 1; + } +} + +/** + * 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); + +/** + * find_get_entry - find and get a page cache entry + * @mapping: the address_space to search + * @index: The page cache index. + * + * Looks up the page cache slot at @mapping & @offset. If there is a + * page cache page, the head page is returned with an increased refcount. + * + * If the slot holds a shadow entry of a previously evicted page, or a + * swap entry from shmem/tmpfs, it is returned. + * + * Return: The head page or shadow entry, %NULL if nothing is found. + */ +struct page *find_get_entry(struct address_space *mapping, pgoff_t index) +{ + XA_STATE(xas, &mapping->i_pages, index); + struct page *page; + + rcu_read_lock(); +repeat: + xas_reset(&xas); + page = xas_load(&xas); + if (xas_retry(&xas, page)) + 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 (!page || xa_is_value(page)) + goto out; + + if (!page_cache_get_speculative(page)) + goto repeat; + + /* + * Has the page moved or been split? + * This is part of the lockless pagecache protocol. See + * include/linux/pagemap.h for details. + */ + if (unlikely(page != xas_reload(&xas))) { + put_page(page); + goto repeat; + } +out: + rcu_read_unlock(); + + return page; +} + +/** + * find_lock_entry - Locate and lock a page cache entry. + * @mapping: The address_space to search. + * @index: The page cache index. + * + * Looks up the page at @mapping & @index. If there is a page in the + * cache, the head page is returned locked and with an increased refcount. + * + * If the slot holds a shadow entry of a previously evicted page, or a + * swap entry from shmem/tmpfs, it is returned. + * + * Context: May sleep. + * Return: The head page or shadow entry, %NULL if nothing is found. + */ +struct page *find_lock_entry(struct address_space *mapping, pgoff_t index) +{ + struct page *page; + +repeat: + page = find_get_entry(mapping, index); + if (page && !xa_is_value(page)) { + lock_page(page); + /* Has the page been truncated? */ + if (unlikely(page->mapping != mapping)) { + unlock_page(page); + put_page(page); + goto repeat; + } + VM_BUG_ON_PAGE(!thp_contains(page, index), page); + } + return page; +} + +/** + * pagecache_get_page - Find and get a reference to a page. + * @mapping: The address_space to search. + * @index: The page index. + * @fgp_flags: %FGP flags modify how the page is returned. + * @gfp_mask: 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 page will be marked accessed. + * * %FGP_LOCK - The page is returned locked. + * * %FGP_HEAD - If the page is present and a THP, return the head page + * rather than the exact page specified by the index. + * * %FGP_CREAT - If no page is present then a new page is allocated using + * @gfp_mask 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 + * * %FGP_NOFS - __GFP_FS will get cleared in gfp mask + * * %FGP_NOWAIT - Don't get blocked by page lock + * + * 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 page or %NULL otherwise. + */ +struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index, + int fgp_flags, gfp_t gfp_mask) +{ + struct page *page; + +repeat: + page = find_get_entry(mapping, index); + if (xa_is_value(page)) + page = NULL; + if (!page) + goto no_page; + + if (fgp_flags & FGP_LOCK) { + if (fgp_flags & FGP_NOWAIT) { + if (!trylock_page(page)) { + put_page(page); + return NULL; + } + } else { + lock_page(page); + } + + /* Has the page been truncated? */ + if (unlikely(page->mapping != mapping)) { + unlock_page(page); + put_page(page); + goto repeat; + } + VM_BUG_ON_PAGE(!thp_contains(page, index), page); + } + + if (fgp_flags & FGP_ACCESSED) + mark_page_accessed(page); + else if (fgp_flags & FGP_WRITE) { + /* Clear idle flag for buffer write */ + if (page_is_idle(page)) + clear_page_idle(page); + } + if (!(fgp_flags & FGP_HEAD)) + page = find_subpage(page, index); + +no_page: + if (!page && (fgp_flags & FGP_CREAT)) { + int err; + if ((fgp_flags & FGP_WRITE) && mapping_can_writeback(mapping)) + gfp_mask |= __GFP_WRITE; + if (fgp_flags & FGP_NOFS) + gfp_mask &= ~__GFP_FS; + + page = __page_cache_alloc(gfp_mask); + if (!page) + 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) + __SetPageReferenced(page); + + err = add_to_page_cache_lru(page, mapping, index, gfp_mask); + if (unlikely(err)) { + put_page(page); + page = NULL; + if (err == -EEXIST) + goto repeat; + } + + /* + * add_to_page_cache_lru locks the page, and for mmap we expect + * an unlocked page. + */ + if (page && (fgp_flags & FGP_FOR_MMAP)) + unlock_page(page); + } + + return page; +} +EXPORT_SYMBOL(pagecache_get_page); + +/** + * find_get_entries - gang pagecache lookup + * @mapping: The address_space to search + * @start: The starting page cache index + * @nr_entries: The maximum number of entries + * @entries: 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 group of up to + * @nr_entries entries in the mapping. The entries are placed at + * @entries. find_get_entries() takes a reference against any actual + * pages it returns. + * + * The search returns a group of mapping-contiguous page cache entries + * with ascending indexes. There may be holes in the indices due to + * not-present pages. + * + * Any shadow entries of evicted pages, or swap entries from + * shmem/tmpfs, are included in the returned array. + * + * If it finds a Transparent Huge Page, head or tail, find_get_entries() + * stops at that page: the caller is likely to have a better way to handle + * the compound page as a whole, and then skip its extent, than repeatedly + * calling find_get_entries() to return all its tails. + * + * Return: the number of pages and shadow entries which were found. + */ +unsigned find_get_entries(struct address_space *mapping, + pgoff_t start, unsigned int nr_entries, + struct page **entries, pgoff_t *indices) +{ + XA_STATE(xas, &mapping->i_pages, start); + struct page *page; + unsigned int ret = 0; + + if (!nr_entries) + return 0; + + rcu_read_lock(); + xas_for_each(&xas, page, ULONG_MAX) { + if (xas_retry(&xas, page)) + continue; + /* + * 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 (xa_is_value(page)) + goto export; + + if (!page_cache_get_speculative(page)) + goto retry; + + /* Has the page moved or been split? */ + if (unlikely(page != xas_reload(&xas))) + goto put_page; + + /* + * Terminate early on finding a THP, to allow the caller to + * handle it all at once; but continue if this is hugetlbfs. + */ + if (PageTransHuge(page) && !PageHuge(page)) { + page = find_subpage(page, xas.xa_index); + nr_entries = ret + 1; + } +export: + indices[ret] = xas.xa_index; + entries[ret] = page; + if (++ret == nr_entries) + break; + continue; +put_page: + put_page(page); +retry: + xas_reset(&xas); + } + rcu_read_unlock(); + return ret; +} + +/** + * find_get_pages_range - gang pagecache lookup + * @mapping: The address_space to search + * @start: The starting page index + * @end: The final page index (inclusive) + * @nr_pages: The maximum number of pages + * @pages: Where the resulting pages are placed + * + * find_get_pages_range() will search for and return a group of up to @nr_pages + * pages in the mapping starting at index @start and up to index @end + * (inclusive). The pages are placed at @pages. find_get_pages_range() takes + * a reference against the returned pages. + * + * The search returns a group of mapping-contiguous pages with ascending + * indexes. There may be holes in the indices due to not-present pages. + * We also update @start to index the next page for the traversal. + * + * Return: the number of pages which were found. If this number is + * smaller than @nr_pages, the end of specified range has been + * reached. + */ +unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start, + pgoff_t end, unsigned int nr_pages, + struct page **pages) +{ + XA_STATE(xas, &mapping->i_pages, *start); + struct page *page; + unsigned ret = 0; + + if (unlikely(!nr_pages)) + return 0; + + rcu_read_lock(); + xas_for_each(&xas, page, end) { + if (xas_retry(&xas, page)) + continue; + /* Skip over shadow, swap and DAX entries */ + if (xa_is_value(page)) + continue; + + if (!page_cache_get_speculative(page)) + goto retry; + + /* Has the page moved or been split? */ + if (unlikely(page != xas_reload(&xas))) + goto put_page; + + pages[ret] = find_subpage(page, xas.xa_index); + if (++ret == nr_pages) { + *start = xas.xa_index + 1; + goto out; + } + continue; +put_page: + put_page(page); +retry: + xas_reset(&xas); + } + + /* + * 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 ret; +} + +/** + * find_get_pages_contig - gang contiguous pagecache lookup + * @mapping: The address_space to search + * @index: The starting page index + * @nr_pages: The maximum number of pages + * @pages: Where the resulting pages are placed + * + * find_get_pages_contig() works exactly like find_get_pages(), except + * that the returned number of pages are guaranteed to be contiguous. + * + * Return: the number of pages which were found. + */ +unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index, + unsigned int nr_pages, struct page **pages) +{ + XA_STATE(xas, &mapping->i_pages, index); + struct page *page; + unsigned int ret = 0; + + if (unlikely(!nr_pages)) + return 0; + + rcu_read_lock(); + for (page = xas_load(&xas); page; page = xas_next(&xas)) { + if (xas_retry(&xas, page)) + continue; + /* + * If the entry has been swapped out, we can stop looking. + * No current caller is looking for DAX entries. + */ + if (xa_is_value(page)) + break; + + if (!page_cache_get_speculative(page)) + goto retry; + + /* Has the page moved or been split? */ + if (unlikely(page != xas_reload(&xas))) + goto put_page; + + pages[ret] = find_subpage(page, xas.xa_index); + if (++ret == nr_pages) + break; + continue; +put_page: + put_page(page); +retry: + xas_reset(&xas); + } + rcu_read_unlock(); + return ret; +} +EXPORT_SYMBOL(find_get_pages_contig); + +/** + * find_get_pages_range_tag - find and return pages in given range 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, except we only return pages which are tagged with + * @tag. We update @index to index the next page for the traversal. + * + * 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 page *page; + unsigned ret = 0; + + if (unlikely(!nr_pages)) + return 0; + + rcu_read_lock(); + xas_for_each_marked(&xas, page, end, tag) { + if (xas_retry(&xas, page)) + continue; + /* + * 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(page)) + continue; + + if (!page_cache_get_speculative(page)) + goto retry; + + /* Has the page moved or been split? */ + if (unlikely(page != xas_reload(&xas))) + goto put_page; + + pages[ret] = find_subpage(page, xas.xa_index); + if (++ret == nr_pages) { + *index = xas.xa_index + 1; + goto out; + } + continue; +put_page: + put_page(page); +retry: + xas_reset(&xas); + } + + /* + * 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; +} + +/** + * generic_file_buffered_read - generic file read routine + * @iocb: the iocb to read + * @iter: data destination + * @written: already copied + * + * This is a generic file read routine, and uses the + * mapping->a_ops->readpage() function for the actual low-level stuff. + * + * This is really ugly. But the goto's actually try to clarify some + * of the logic when it comes to error handling etc. + * + * Return: + * * total number of bytes copied, including those the were already @written + * * negative error code if nothing was copied + */ +ssize_t generic_file_buffered_read(struct kiocb *iocb, + struct iov_iter *iter, ssize_t written) +{ + struct file *filp = iocb->ki_filp; + struct address_space *mapping = filp->f_mapping; + struct inode *inode = mapping->host; + struct file_ra_state *ra = &filp->f_ra; + loff_t *ppos = &iocb->ki_pos; + pgoff_t index; + pgoff_t last_index; + pgoff_t prev_index; + unsigned long offset; /* offset into pagecache page */ + unsigned int prev_offset; + int error = 0; + + if (unlikely(*ppos >= inode->i_sb->s_maxbytes)) + return 0; + if (unlikely(!iov_iter_count(iter))) + return 0; + + iov_iter_truncate(iter, inode->i_sb->s_maxbytes); + + index = *ppos >> PAGE_SHIFT; + prev_index = ra->prev_pos >> PAGE_SHIFT; + prev_offset = ra->prev_pos & (PAGE_SIZE-1); + last_index = (*ppos + iter->count + PAGE_SIZE-1) >> PAGE_SHIFT; + offset = *ppos & ~PAGE_MASK; + + /* + * 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 (written && (iocb->ki_flags & IOCB_WAITQ)) + iocb->ki_flags |= IOCB_NOWAIT; + + for (;;) { + struct page *page; + pgoff_t end_index; + loff_t isize; + unsigned long nr, ret; + + cond_resched(); +find_page: + if (fatal_signal_pending(current)) { + error = -EINTR; + goto out; + } + + page = find_get_page(mapping, index); + if (!page) { + if (iocb->ki_flags & IOCB_NOIO) + goto would_block; + page_cache_sync_readahead(mapping, + ra, filp, + index, last_index - index); + page = find_get_page(mapping, index); + if (unlikely(page == NULL)) + goto no_cached_page; + } + if (PageReadahead(page)) { + if (iocb->ki_flags & IOCB_NOIO) { + put_page(page); + goto out; + } + page_cache_async_readahead(mapping, + ra, filp, page, + index, last_index - index); + } + if (!PageUptodate(page)) { + /* + * See comment in do_read_cache_page on why + * wait_on_page_locked is used to avoid unnecessarily + * serialisations and why it's safe. + */ + if (iocb->ki_flags & IOCB_WAITQ) { + if (written) { + put_page(page); + goto out; + } + error = wait_on_page_locked_async(page, + iocb->ki_waitq); + } else { + if (iocb->ki_flags & IOCB_NOWAIT) { + put_page(page); + goto would_block; + } + error = wait_on_page_locked_killable(page); + } + if (unlikely(error)) + goto readpage_error; + if (PageUptodate(page)) + goto page_ok; + + if (inode->i_blkbits == PAGE_SHIFT || + !mapping->a_ops->is_partially_uptodate) + goto page_not_up_to_date; + /* pipes can't handle partially uptodate pages */ + if (unlikely(iov_iter_is_pipe(iter))) + goto page_not_up_to_date; + if (!trylock_page(page)) + goto page_not_up_to_date; + /* Did it get truncated before we got the lock? */ + if (!page->mapping) + goto page_not_up_to_date_locked; + if (!mapping->a_ops->is_partially_uptodate(page, + offset, iter->count)) + goto page_not_up_to_date_locked; + unlock_page(page); + } +page_ok: + /* + * i_size must be checked after we know the page is 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); + end_index = (isize - 1) >> PAGE_SHIFT; + if (unlikely(!isize || index > end_index)) { + put_page(page); + goto out; + } + + /* nr is the maximum number of bytes to copy from this page */ + nr = PAGE_SIZE; + if (index == end_index) { + nr = ((isize - 1) & ~PAGE_MASK) + 1; + if (nr <= offset) { + put_page(page); + goto out; + } + } + nr = nr - offset; + + /* If users can be writing to this page using arbitrary + * virtual addresses, take care about potential aliasing + * before reading the page on the kernel side. + */ + if (mapping_writably_mapped(mapping)) + flush_dcache_page(page); + + /* + * When a sequential read accesses a page several times, + * only mark it as accessed the first time. + */ + if (prev_index != index || offset != prev_offset) + mark_page_accessed(page); + prev_index = index; + + /* + * Ok, we have the page, and it's up-to-date, so + * now we can copy it to user space... + */ + + ret = copy_page_to_iter(page, offset, nr, iter); + offset += ret; + index += offset >> PAGE_SHIFT; + offset &= ~PAGE_MASK; + prev_offset = offset; + + put_page(page); + written += ret; + if (!iov_iter_count(iter)) + goto out; + if (ret < nr) { + error = -EFAULT; + goto out; + } + continue; + +page_not_up_to_date: + /* Get exclusive access to the page ... */ + if (iocb->ki_flags & IOCB_WAITQ) { + if (written) { + put_page(page); + goto out; + } + error = lock_page_async(page, iocb->ki_waitq); + } else { + error = lock_page_killable(page); + } + if (unlikely(error)) + goto readpage_error; + +page_not_up_to_date_locked: + /* Did it get truncated before we got the lock? */ + if (!page->mapping) { + unlock_page(page); + put_page(page); + continue; + } + + /* Did somebody else fill it already? */ + if (PageUptodate(page)) { + unlock_page(page); + goto page_ok; + } + +readpage: + if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT)) { + unlock_page(page); + put_page(page); + goto would_block; + } + /* + * A previous I/O error may have been due to temporary + * failures, eg. multipath errors. + * PG_error will be set again if readpage fails. + */ + ClearPageError(page); + /* Start the actual read. The read will unlock the page. */ + error = mapping->a_ops->readpage(filp, page); + + if (unlikely(error)) { + if (error == AOP_TRUNCATED_PAGE) { + put_page(page); + error = 0; + goto find_page; + } + goto readpage_error; + } + + if (!PageUptodate(page)) { + if (iocb->ki_flags & IOCB_WAITQ) { + if (written) { + put_page(page); + goto out; + } + error = lock_page_async(page, iocb->ki_waitq); + } else { + error = lock_page_killable(page); + } + + if (unlikely(error)) + goto readpage_error; + if (!PageUptodate(page)) { + if (page->mapping == NULL) { + /* + * invalidate_mapping_pages got it + */ + unlock_page(page); + put_page(page); + goto find_page; + } + unlock_page(page); + shrink_readahead_size_eio(ra); + error = -EIO; + goto readpage_error; + } + unlock_page(page); + } + + goto page_ok; + +readpage_error: + /* UHHUH! A synchronous read error occurred. Report it */ + put_page(page); + goto out; + +no_cached_page: + /* + * Ok, it wasn't cached, so we need to create a new + * page.. + */ + page = page_cache_alloc(mapping); + if (!page) { + error = -ENOMEM; + goto out; + } + error = add_to_page_cache_lru(page, mapping, index, + mapping_gfp_constraint(mapping, GFP_KERNEL)); + if (error) { + put_page(page); + if (error == -EEXIST) { + error = 0; + goto find_page; + } + goto out; + } + goto readpage; + } + +would_block: + error = -EAGAIN; +out: + ra->prev_pos = prev_index; + ra->prev_pos <<= PAGE_SHIFT; + ra->prev_pos |= prev_offset; + + *ppos = ((loff_t)index << PAGE_SHIFT) + offset; + file_accessed(filp); + return written ? written : error; +} +EXPORT_SYMBOL_GPL(generic_file_buffered_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) + goto out; /* 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; + loff_t size; + + size = i_size_read(inode); + if (iocb->ki_flags & IOCB_NOWAIT) { + if (filemap_range_has_page(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) + goto out; + } + + file_accessed(file); + + retval = mapping->a_ops->direct_IO(iocb, iter); + if (retval >= 0) { + iocb->ki_pos += retval; + count -= retval; + } + 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 || iocb->ki_pos >= size || + IS_DAX(inode)) + goto out; + } + + retval = generic_file_buffered_read(iocb, iter, retval); +out: + return retval; +} +EXPORT_SYMBOL(generic_file_read_iter); + +#ifdef CONFIG_MMU +#define MMAP_LOTSAMISS (100) +/* + * lock_page_maybe_drop_mmap - lock the page, possibly dropping the mmap_lock + * @vmf - the vm_fault for this fault. + * @page - the page to lock. + * @fpin - the pointer to the file we may pin (or is already pinned). + * + * This works similar to lock_page_or_retry in that it can drop the mmap_lock. + * It differs in that it actually returns the page locked if it returns 1 and 0 + * if it couldn't lock the page. 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_page_maybe_drop_mmap(struct vm_fault *vmf, struct page *page, + struct file **fpin) +{ + if (trylock_page(page)) + 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 (__lock_page_killable(page)) { + /* + * 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 + __lock_page(page); + 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, 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) + return fpin; + if (!ra->ra_pages) + return fpin; + + if (vmf->vma->vm_flags & VM_SEQ_READ) { + fpin = maybe_unlock_mmap_for_io(vmf, fpin); + page_cache_sync_ra(&ractl, ra, 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; + do_page_cache_ra(&ractl, ra->size, ra->async_size); + 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 page *page) +{ + struct file *file = vmf->vma->vm_file; + struct file_ra_state *ra = &file->f_ra; + struct address_space *mapping = file->f_mapping; + struct file *fpin = NULL; + unsigned int mmap_miss; + pgoff_t offset = vmf->pgoff; + + /* 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 (PageReadahead(page)) { + fpin = maybe_unlock_mmap_for_io(vmf, fpin); + page_cache_async_readahead(mapping, ra, file, + page, offset, 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_page_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 file_ra_state *ra = &file->f_ra; + struct inode *inode = mapping->host; + pgoff_t offset = vmf->pgoff; + pgoff_t max_off; + struct page *page; + vm_fault_t ret = 0; + + max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); + if (unlikely(offset >= max_off)) + return VM_FAULT_SIGBUS; + + /* + * Do we have something in the page cache already? + */ + page = find_get_page(mapping, offset); + if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) { + /* + * We found the page, so try async readahead before + * waiting for the lock. + */ + fpin = do_async_mmap_readahead(vmf, page); + } else if (!page) { + /* 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: + page = pagecache_get_page(mapping, offset, + FGP_CREAT|FGP_FOR_MMAP, + vmf->gfp_mask); + if (!page) { + if (fpin) + goto out_retry; + return VM_FAULT_OOM; + } + } + + if (!lock_page_maybe_drop_mmap(vmf, page, &fpin)) + goto out_retry; + + /* Did it get truncated? */ + if (unlikely(compound_head(page)->mapping != mapping)) { + unlock_page(page); + put_page(page); + goto retry_find; + } + VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page); + + /* + * 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(!PageUptodate(page))) + 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) { + unlock_page(page); + goto out_retry; + } + + /* + * Found the page and have a reference on it. + * We must recheck i_size under page lock. + */ + max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); + if (unlikely(offset >= max_off)) { + unlock_page(page); + put_page(page); + return VM_FAULT_SIGBUS; + } + + vmf->page = page; + 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. + */ + ClearPageError(page); + fpin = maybe_unlock_mmap_for_io(vmf, fpin); + error = mapping->a_ops->readpage(file, page); + if (!error) { + wait_on_page_locked(page); + if (!PageUptodate(page)) + error = -EIO; + } + if (fpin) + goto out_retry; + put_page(page); + + if (!error || error == AOP_TRUNCATED_PAGE) + goto retry_find; + + shrink_readahead_size_eio(ra); + 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 (page) + put_page(page); + if (fpin) + fput(fpin); + return ret | VM_FAULT_RETRY; +} +EXPORT_SYMBOL(filemap_fault); + +void filemap_map_pages(struct vm_fault *vmf, + pgoff_t start_pgoff, pgoff_t end_pgoff) +{ + struct file *file = vmf->vma->vm_file; + struct address_space *mapping = file->f_mapping; + pgoff_t last_pgoff = start_pgoff; + unsigned long max_idx; + XA_STATE(xas, &mapping->i_pages, start_pgoff); + struct page *head, *page; + unsigned int mmap_miss = READ_ONCE(file->f_ra.mmap_miss); + + rcu_read_lock(); + xas_for_each(&xas, head, end_pgoff) { + if (xas_retry(&xas, head)) + continue; + if (xa_is_value(head)) + goto next; + + /* + * Check for a locked page first, as a speculative + * reference may adversely influence page migration. + */ + if (PageLocked(head)) + goto next; + if (!page_cache_get_speculative(head)) + goto next; + + /* Has the page moved or been split? */ + if (unlikely(head != xas_reload(&xas))) + goto skip; + page = find_subpage(head, xas.xa_index); + + if (!PageUptodate(head) || + PageReadahead(page) || + PageHWPoison(page)) + goto skip; + if (!trylock_page(head)) + goto skip; + + if (head->mapping != mapping || !PageUptodate(head)) + goto unlock; + + max_idx = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE); + if (xas.xa_index >= max_idx) + goto unlock; + + if (mmap_miss > 0) + mmap_miss--; + + vmf->address += (xas.xa_index - last_pgoff) << PAGE_SHIFT; + if (vmf->pte) + vmf->pte += xas.xa_index - last_pgoff; + last_pgoff = xas.xa_index; + if (alloc_set_pte(vmf, page)) + goto unlock; + unlock_page(head); + goto next; +unlock: + unlock_page(head); +skip: + put_page(head); +next: + /* Huge page is mapped? No need to proceed. */ + if (pmd_trans_huge(*vmf->pmd)) + break; + } + rcu_read_unlock(); + WRITE_ONCE(file->f_ra.mmap_miss, mmap_miss); +} +EXPORT_SYMBOL(filemap_map_pages); + +vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf) +{ + struct page *page = vmf->page; + struct inode *inode = file_inode(vmf->vma->vm_file); + vm_fault_t ret = VM_FAULT_LOCKED; + + sb_start_pagefault(inode->i_sb); + file_update_time(vmf->vma->vm_file); + lock_page(page); + if (page->mapping != inode->i_mapping) { + unlock_page(page); + ret = VM_FAULT_NOPAGE; + goto out; + } + /* + * We mark the page dirty already here so that when freeze is in + * progress, we are guaranteed that writeback during freezing will + * see the dirty page and writeprotect it again. + */ + set_page_dirty(page); + wait_for_stable_page(page); +out: + sb_end_pagefault(inode->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->readpage) + 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 page *wait_on_page_read(struct page *page) +{ + if (!IS_ERR(page)) { + wait_on_page_locked(page); + if (!PageUptodate(page)) { + put_page(page); + page = ERR_PTR(-EIO); + } + } + return page; +} + +static struct page *do_read_cache_page(struct address_space *mapping, + pgoff_t index, + int (*filler)(void *, struct page *), + void *data, + gfp_t gfp) +{ + struct page *page; + int err; +repeat: + page = find_get_page(mapping, index); + if (!page) { + page = __page_cache_alloc(gfp); + if (!page) + return ERR_PTR(-ENOMEM); + err = add_to_page_cache_lru(page, mapping, index, gfp); + if (unlikely(err)) { + put_page(page); + if (err == -EEXIST) + goto repeat; + /* Presumably ENOMEM for xarray node */ + return ERR_PTR(err); + } + +filler: + if (filler) + err = filler(data, page); + else + err = mapping->a_ops->readpage(data, page); + + if (err < 0) { + put_page(page); + return ERR_PTR(err); + } + + page = wait_on_page_read(page); + if (IS_ERR(page)) + return page; + goto out; + } + if (PageUptodate(page)) + goto out; + + /* + * Page is not up to date and may be locked due to one of the following + * case a: Page is being filled and the page lock is held + * case b: Read/write error clearing the page uptodate status + * case c: Truncation in progress (page locked) + * case d: Reclaim in progress + * + * Case a, the page will be up to date when the page is unlocked. + * There is no need to serialise on the page lock here as the page + * is pinned so the lock gives no additional protection. Even if the + * page is truncated, the data is still valid if PageUptodate as + * it's a race vs truncate race. + * Case b, the page will not be up to date + * Case c, the page may be truncated but in itself, the data may still + * be valid after IO completes as it's a read vs truncate race. The + * operation must restart if the page is not uptodate on unlock but + * otherwise serialising on page lock to stabilise the mapping gives + * no additional guarantees to the caller as the page lock is + * released before return. + * Case d, similar to truncation. If reclaim holds the page lock, it + * will be a race with remove_mapping that determines if the mapping + * is valid on unlock but otherwise the data is valid and there is + * no need to serialise with page lock. + * + * As the page lock gives no additional guarantee, we optimistically + * wait on the page to be unlocked and check if it's up to date and + * use the page if it is. Otherwise, the page lock is required to + * distinguish between the different cases. The motivation is that we + * avoid spurious serialisations and wakeups when multiple processes + * wait on the same page for IO to complete. + */ + wait_on_page_locked(page); + if (PageUptodate(page)) + goto out; + + /* Distinguish between all the cases under the safety of the lock */ + lock_page(page); + + /* Case c or d, restart the operation */ + if (!page->mapping) { + unlock_page(page); + put_page(page); + goto repeat; + } + + /* Someone else locked and filled the page in a very small window */ + if (PageUptodate(page)) { + unlock_page(page); + goto out; + } + + /* + * A previous I/O error may have been due to temporary + * failures. + * Clear page error before actual read, PG_error will be + * set again if read page fails. + */ + ClearPageError(page); + goto filler; + +out: + mark_page_accessed(page); + return page; +} + +/** + * read_cache_page - read into page cache, fill it if needed + * @mapping: the page's address_space + * @index: the page index + * @filler: function to perform the read + * @data: first arg to filler(data, page) function, often left as NULL + * + * Read into the page cache. If a page already exists, and PageUptodate() is + * not set, try to fill the page and wait for it to become unlocked. + * + * If the page does not get brought uptodate, return -EIO. + * + * Return: up to date page on success, ERR_PTR() on failure. + */ +struct page *read_cache_page(struct address_space *mapping, + pgoff_t index, + int (*filler)(void *, struct page *), + void *data) +{ + return do_read_cache_page(mapping, index, filler, data, + 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. + * + * 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); + +int pagecache_write_begin(struct file *file, struct address_space *mapping, + loff_t pos, unsigned len, unsigned flags, + struct page **pagep, void **fsdata) +{ + const struct address_space_operations *aops = mapping->a_ops; + + return aops->write_begin(file, mapping, pos, len, flags, + pagep, fsdata); +} +EXPORT_SYMBOL(pagecache_write_begin); + +int pagecache_write_end(struct file *file, struct address_space *mapping, + loff_t pos, unsigned len, unsigned copied, + struct page *page, void *fsdata) +{ + const struct address_space_operations *aops = mapping->a_ops; + + return aops->write_end(file, mapping, pos, len, copied, page, fsdata); +} +EXPORT_SYMBOL(pagecache_write_end); + +/* + * 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]; + struct inode *inode = file_inode(filp); + char *path; + + errseq_set(&inode->i_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(inode->i_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; + } + iov_iter_revert(from, write_len - iov_iter_count(from)); +out: + return written; +} +EXPORT_SYMBOL(generic_file_direct_write); + +/* + * Find or create a page at the given pagecache position. Return the locked + * page. This function is specifically for buffered writes. + */ +struct page *grab_cache_page_write_begin(struct address_space *mapping, + pgoff_t index, unsigned flags) +{ + struct page *page; + int fgp_flags = FGP_LOCK|FGP_WRITE|FGP_CREAT; + + if (flags & AOP_FLAG_NOFS) + fgp_flags |= FGP_NOFS; + + page = pagecache_get_page(mapping, index, fgp_flags, + mapping_gfp_mask(mapping)); + if (page) + wait_for_stable_page(page); + + return page; +} +EXPORT_SYMBOL(grab_cache_page_write_begin); + +ssize_t generic_perform_write(struct file *file, + struct iov_iter *i, loff_t 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; + unsigned int flags = 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. + * + * Not only is this an optimisation, but it is also required + * to check that the address is actually valid, when atomic + * usercopies are used, below. + */ + if (unlikely(iov_iter_fault_in_readable(i, bytes))) { + status = -EFAULT; + break; + } + + if (fatal_signal_pending(current)) { + status = -EINTR; + break; + } + + status = a_ops->write_begin(file, mapping, pos, bytes, flags, + &page, &fsdata); + if (unlikely(status < 0)) + break; + + if (mapping_writably_mapped(mapping)) + flush_dcache_page(page); + + copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); + flush_dcache_page(page); + + status = a_ops->write_end(file, mapping, pos, bytes, copied, + page, fsdata); + if (unlikely(status < 0)) + break; + copied = status; + + cond_resched(); + + iov_iter_advance(i, copied); + if (unlikely(copied == 0)) { + /* + * If we were unable to copy any data at all, we must + * fall back to a single segment length write. + * + * If we didn't fallback here, we could livelock + * because not all segments in the iov can be copied at + * once without a pagefault. + */ + bytes = min_t(unsigned long, PAGE_SIZE - offset, + iov_iter_single_seg_count(i)); + goto again; + } + pos += copied; + written += copied; + + 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_mutex 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_mutex. + * + * 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; + + status = generic_perform_write(file, from, pos = iocb->ki_pos); + /* + * 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(file, from, iocb->ki_pos); + 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_mutex 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); + +/** + * try_to_release_page() - release old fs-specific metadata on a page + * + * @page: the page which the kernel is trying to free + * @gfp_mask: memory allocation flags (and I/O mode) + * + * The address_space is to try to release any data against the page + * (presumably at page->private). + * + * This may also be called if PG_fscache is set on a page, indicating that the + * page is known to the local caching routines. + * + * The @gfp_mask 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: %1 if the release was successful, otherwise return zero. + */ +int try_to_release_page(struct page *page, gfp_t gfp_mask) +{ + struct address_space * const mapping = page->mapping; + + BUG_ON(!PageLocked(page)); + if (PageWriteback(page)) + return 0; + + if (mapping && mapping->a_ops->releasepage) + return mapping->a_ops->releasepage(page, gfp_mask); + return try_to_free_buffers(page); +} + +EXPORT_SYMBOL(try_to_release_page); |