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Diffstat (limited to 'mm/truncate.c')
| -rw-r--r-- | mm/truncate.c | 916 |
1 files changed, 916 insertions, 0 deletions
diff --git a/mm/truncate.c b/mm/truncate.c new file mode 100644 index 000000000..43c73db17 --- /dev/null +++ b/mm/truncate.c @@ -0,0 +1,916 @@ +/* + * mm/truncate.c - code for taking down pages from address_spaces + * + * Copyright (C) 2002, Linus Torvalds + * + * 10Sep2002 Andrew Morton + * Initial version. + */ + +#include <linux/kernel.h> +#include <linux/backing-dev.h> +#include <linux/dax.h> +#include <linux/gfp.h> +#include <linux/mm.h> +#include <linux/swap.h> +#include <linux/export.h> +#include <linux/pagemap.h> +#include <linux/highmem.h> +#include <linux/pagevec.h> +#include <linux/task_io_accounting_ops.h> +#include <linux/buffer_head.h> /* grr. try_to_release_page, + do_invalidatepage */ +#include <linux/shmem_fs.h> +#include <linux/cleancache.h> +#include <linux/rmap.h> +#include "internal.h" + +/* + * Regular page slots are stabilized by the page lock even without the tree + * itself locked. These unlocked entries need verification under the tree + * lock. + */ +static inline void __clear_shadow_entry(struct address_space *mapping, + pgoff_t index, void *entry) +{ + struct radix_tree_node *node; + void **slot; + + if (!__radix_tree_lookup(&mapping->i_pages, index, &node, &slot)) + return; + if (*slot != entry) + return; + __radix_tree_replace(&mapping->i_pages, node, slot, NULL, + workingset_update_node); + mapping->nrexceptional--; +} + +static void clear_shadow_entry(struct address_space *mapping, pgoff_t index, + void *entry) +{ + xa_lock_irq(&mapping->i_pages); + __clear_shadow_entry(mapping, index, entry); + xa_unlock_irq(&mapping->i_pages); +} + +/* + * Unconditionally remove exceptional entries. Usually called from truncate + * path. Note that the pagevec may be altered by this function by removing + * exceptional entries similar to what pagevec_remove_exceptionals does. + */ +static void truncate_exceptional_pvec_entries(struct address_space *mapping, + struct pagevec *pvec, pgoff_t *indices, + pgoff_t end) +{ + int i, j; + bool dax, lock; + + /* Handled by shmem itself */ + if (shmem_mapping(mapping)) + return; + + for (j = 0; j < pagevec_count(pvec); j++) + if (radix_tree_exceptional_entry(pvec->pages[j])) + break; + + if (j == pagevec_count(pvec)) + return; + + dax = dax_mapping(mapping); + lock = !dax && indices[j] < end; + if (lock) + xa_lock_irq(&mapping->i_pages); + + for (i = j; i < pagevec_count(pvec); i++) { + struct page *page = pvec->pages[i]; + pgoff_t index = indices[i]; + + if (!radix_tree_exceptional_entry(page)) { + pvec->pages[j++] = page; + continue; + } + + if (index >= end) + continue; + + if (unlikely(dax)) { + dax_delete_mapping_entry(mapping, index); + continue; + } + + __clear_shadow_entry(mapping, index, page); + } + + if (lock) + xa_unlock_irq(&mapping->i_pages); + pvec->nr = j; +} + +/* + * Invalidate exceptional entry if easily possible. This handles exceptional + * entries for invalidate_inode_pages(). + */ +static int invalidate_exceptional_entry(struct address_space *mapping, + pgoff_t index, void *entry) +{ + /* Handled by shmem itself, or for DAX we do nothing. */ + if (shmem_mapping(mapping) || dax_mapping(mapping)) + return 1; + clear_shadow_entry(mapping, index, entry); + return 1; +} + +/* + * Invalidate exceptional entry if clean. This handles exceptional entries for + * invalidate_inode_pages2() so for DAX it evicts only clean entries. + */ +static int invalidate_exceptional_entry2(struct address_space *mapping, + pgoff_t index, void *entry) +{ + /* Handled by shmem itself */ + if (shmem_mapping(mapping)) + return 1; + if (dax_mapping(mapping)) + return dax_invalidate_mapping_entry_sync(mapping, index); + clear_shadow_entry(mapping, index, entry); + return 1; +} + +/** + * do_invalidatepage - invalidate part or all of a page + * @page: the page which is affected + * @offset: start of the range to invalidate + * @length: length of the range to invalidate + * + * do_invalidatepage() is called when all or part of the page has become + * invalidated by a truncate operation. + * + * do_invalidatepage() does not have to release all buffers, but it must + * ensure that no dirty buffer is left outside @offset and that no I/O + * is underway against any of the blocks which are outside the truncation + * point. Because the caller is about to free (and possibly reuse) those + * blocks on-disk. + */ +void do_invalidatepage(struct page *page, unsigned int offset, + unsigned int length) +{ + void (*invalidatepage)(struct page *, unsigned int, unsigned int); + + invalidatepage = page->mapping->a_ops->invalidatepage; +#ifdef CONFIG_BLOCK + if (!invalidatepage) + invalidatepage = block_invalidatepage; +#endif + if (invalidatepage) + (*invalidatepage)(page, offset, length); +} + +/* + * If truncate cannot remove the fs-private metadata from the page, the page + * becomes orphaned. It will be left on the LRU and may even be mapped into + * user pagetables if we're racing with filemap_fault(). + * + * We need to bale out if page->mapping is no longer equal to the original + * mapping. This happens a) when the VM reclaimed the page while we waited on + * its lock, b) when a concurrent invalidate_mapping_pages got there first and + * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space. + */ +static void truncate_cleanup_page(struct page *page) +{ + if (page_mapped(page)) + unmap_mapping_page(page); + + if (page_has_private(page)) + do_invalidatepage(page, 0, PAGE_SIZE); + + /* + * Some filesystems seem to re-dirty the page even after + * the VM has canceled the dirty bit (eg ext3 journaling). + * Hence dirty accounting check is placed after invalidation. + */ + cancel_dirty_page(page); + ClearPageMappedToDisk(page); +} + +/* + * This is for invalidate_mapping_pages(). That function can be called at + * any time, and is not supposed to throw away dirty pages. But pages can + * be marked dirty at any time too, so use remove_mapping which safely + * discards clean, unused pages. + * + * Returns non-zero if the page was successfully invalidated. + */ +static int +invalidate_complete_page(struct address_space *mapping, struct page *page) +{ + int ret; + + if (page->mapping != mapping) + return 0; + + if (page_has_private(page) && !try_to_release_page(page, 0)) + return 0; + + ret = remove_mapping(mapping, page); + + return ret; +} + +int truncate_inode_page(struct address_space *mapping, struct page *page) +{ + VM_BUG_ON_PAGE(PageTail(page), page); + + if (page->mapping != mapping) + return -EIO; + + truncate_cleanup_page(page); + delete_from_page_cache(page); + return 0; +} + +/* + * Used to get rid of pages on hardware memory corruption. + */ +int generic_error_remove_page(struct address_space *mapping, struct page *page) +{ + if (!mapping) + return -EINVAL; + /* + * Only punch for normal data pages for now. + * Handling other types like directories would need more auditing. + */ + if (!S_ISREG(mapping->host->i_mode)) + return -EIO; + return truncate_inode_page(mapping, page); +} +EXPORT_SYMBOL(generic_error_remove_page); + +/* + * Safely invalidate one page from its pagecache mapping. + * It only drops clean, unused pages. The page must be locked. + * + * Returns 1 if the page is successfully invalidated, otherwise 0. + */ +int invalidate_inode_page(struct page *page) +{ + struct address_space *mapping = page_mapping(page); + if (!mapping) + return 0; + if (PageDirty(page) || PageWriteback(page)) + return 0; + if (page_mapped(page)) + return 0; + return invalidate_complete_page(mapping, page); +} + +/** + * truncate_inode_pages_range - truncate range of pages specified by start & end byte offsets + * @mapping: mapping to truncate + * @lstart: offset from which to truncate + * @lend: offset to which to truncate (inclusive) + * + * Truncate the page cache, removing the pages that are between + * specified offsets (and zeroing out partial pages + * if lstart or lend + 1 is not page aligned). + * + * Truncate takes two passes - the first pass is nonblocking. It will not + * block on page locks and it will not block on writeback. The second pass + * will wait. This is to prevent as much IO as possible in the affected region. + * The first pass will remove most pages, so the search cost of the second pass + * is low. + * + * We pass down the cache-hot hint to the page freeing code. Even if the + * mapping is large, it is probably the case that the final pages are the most + * recently touched, and freeing happens in ascending file offset order. + * + * Note that since ->invalidatepage() accepts range to invalidate + * truncate_inode_pages_range is able to handle cases where lend + 1 is not + * page aligned properly. + */ +void truncate_inode_pages_range(struct address_space *mapping, + loff_t lstart, loff_t lend) +{ + pgoff_t start; /* inclusive */ + pgoff_t end; /* exclusive */ + unsigned int partial_start; /* inclusive */ + unsigned int partial_end; /* exclusive */ + struct pagevec pvec; + pgoff_t indices[PAGEVEC_SIZE]; + pgoff_t index; + int i; + + if (mapping->nrpages == 0 && mapping->nrexceptional == 0) + goto out; + + /* Offsets within partial pages */ + partial_start = lstart & (PAGE_SIZE - 1); + partial_end = (lend + 1) & (PAGE_SIZE - 1); + + /* + * 'start' and 'end' always covers the range of pages to be fully + * truncated. Partial pages are covered with 'partial_start' at the + * start of the range and 'partial_end' at the end of the range. + * Note that 'end' is exclusive while 'lend' is inclusive. + */ + start = (lstart + PAGE_SIZE - 1) >> PAGE_SHIFT; + if (lend == -1) + /* + * lend == -1 indicates end-of-file so we have to set 'end' + * to the highest possible pgoff_t and since the type is + * unsigned we're using -1. + */ + end = -1; + else + end = (lend + 1) >> PAGE_SHIFT; + + pagevec_init(&pvec); + index = start; + while (index < end && pagevec_lookup_entries(&pvec, mapping, index, + min(end - index, (pgoff_t)PAGEVEC_SIZE), + indices)) { + /* + * Pagevec array has exceptional entries and we may also fail + * to lock some pages. So we store pages that can be deleted + * in a new pagevec. + */ + struct pagevec locked_pvec; + + pagevec_init(&locked_pvec); + for (i = 0; i < pagevec_count(&pvec); i++) { + struct page *page = pvec.pages[i]; + + /* We rely upon deletion not changing page->index */ + index = indices[i]; + if (index >= end) + break; + + if (radix_tree_exceptional_entry(page)) + continue; + + if (!trylock_page(page)) + continue; + WARN_ON(page_to_index(page) != index); + if (PageWriteback(page)) { + unlock_page(page); + continue; + } + if (page->mapping != mapping) { + unlock_page(page); + continue; + } + pagevec_add(&locked_pvec, page); + } + for (i = 0; i < pagevec_count(&locked_pvec); i++) + truncate_cleanup_page(locked_pvec.pages[i]); + delete_from_page_cache_batch(mapping, &locked_pvec); + for (i = 0; i < pagevec_count(&locked_pvec); i++) + unlock_page(locked_pvec.pages[i]); + truncate_exceptional_pvec_entries(mapping, &pvec, indices, end); + pagevec_release(&pvec); + cond_resched(); + index++; + } + if (partial_start) { + struct page *page = find_lock_page(mapping, start - 1); + if (page) { + unsigned int top = PAGE_SIZE; + if (start > end) { + /* Truncation within a single page */ + top = partial_end; + partial_end = 0; + } + wait_on_page_writeback(page); + zero_user_segment(page, partial_start, top); + cleancache_invalidate_page(mapping, page); + if (page_has_private(page)) + do_invalidatepage(page, partial_start, + top - partial_start); + unlock_page(page); + put_page(page); + } + } + if (partial_end) { + struct page *page = find_lock_page(mapping, end); + if (page) { + wait_on_page_writeback(page); + zero_user_segment(page, 0, partial_end); + cleancache_invalidate_page(mapping, page); + if (page_has_private(page)) + do_invalidatepage(page, 0, + partial_end); + unlock_page(page); + put_page(page); + } + } + /* + * If the truncation happened within a single page no pages + * will be released, just zeroed, so we can bail out now. + */ + if (start >= end) + goto out; + + index = start; + for ( ; ; ) { + cond_resched(); + if (!pagevec_lookup_entries(&pvec, mapping, index, + min(end - index, (pgoff_t)PAGEVEC_SIZE), indices)) { + /* If all gone from start onwards, we're done */ + if (index == start) + break; + /* Otherwise restart to make sure all gone */ + index = start; + continue; + } + if (index == start && indices[0] >= end) { + /* All gone out of hole to be punched, we're done */ + pagevec_remove_exceptionals(&pvec); + pagevec_release(&pvec); + break; + } + + for (i = 0; i < pagevec_count(&pvec); i++) { + struct page *page = pvec.pages[i]; + + /* We rely upon deletion not changing page->index */ + index = indices[i]; + if (index >= end) { + /* Restart punch to make sure all gone */ + index = start - 1; + break; + } + + if (radix_tree_exceptional_entry(page)) + continue; + + lock_page(page); + WARN_ON(page_to_index(page) != index); + wait_on_page_writeback(page); + truncate_inode_page(mapping, page); + unlock_page(page); + } + truncate_exceptional_pvec_entries(mapping, &pvec, indices, end); + pagevec_release(&pvec); + index++; + } + +out: + cleancache_invalidate_inode(mapping); +} +EXPORT_SYMBOL(truncate_inode_pages_range); + +/** + * truncate_inode_pages - truncate *all* the pages from an offset + * @mapping: mapping to truncate + * @lstart: offset from which to truncate + * + * Called under (and serialised by) inode->i_mutex. + * + * Note: When this function returns, there can be a page in the process of + * deletion (inside __delete_from_page_cache()) in the specified range. Thus + * mapping->nrpages can be non-zero when this function returns even after + * truncation of the whole mapping. + */ +void truncate_inode_pages(struct address_space *mapping, loff_t lstart) +{ + truncate_inode_pages_range(mapping, lstart, (loff_t)-1); +} +EXPORT_SYMBOL(truncate_inode_pages); + +/** + * truncate_inode_pages_final - truncate *all* pages before inode dies + * @mapping: mapping to truncate + * + * Called under (and serialized by) inode->i_mutex. + * + * Filesystems have to use this in the .evict_inode path to inform the + * VM that this is the final truncate and the inode is going away. + */ +void truncate_inode_pages_final(struct address_space *mapping) +{ + unsigned long nrexceptional; + unsigned long nrpages; + + /* + * Page reclaim can not participate in regular inode lifetime + * management (can't call iput()) and thus can race with the + * inode teardown. Tell it when the address space is exiting, + * so that it does not install eviction information after the + * final truncate has begun. + */ + mapping_set_exiting(mapping); + + /* + * When reclaim installs eviction entries, it increases + * nrexceptional first, then decreases nrpages. Make sure we see + * this in the right order or we might miss an entry. + */ + nrpages = mapping->nrpages; + smp_rmb(); + nrexceptional = mapping->nrexceptional; + + if (nrpages || nrexceptional) { + /* + * As truncation uses a lockless tree lookup, cycle + * the tree lock to make sure any ongoing tree + * modification that does not see AS_EXITING is + * completed before starting the final truncate. + */ + xa_lock_irq(&mapping->i_pages); + xa_unlock_irq(&mapping->i_pages); + } + + /* + * Cleancache needs notification even if there are no pages or shadow + * entries. + */ + truncate_inode_pages(mapping, 0); +} +EXPORT_SYMBOL(truncate_inode_pages_final); + +/** + * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode + * @mapping: the address_space which holds the pages to invalidate + * @start: the offset 'from' which to invalidate + * @end: the offset 'to' which to invalidate (inclusive) + * + * This function only removes the unlocked pages, if you want to + * remove all the pages of one inode, you must call truncate_inode_pages. + * + * invalidate_mapping_pages() will not block on IO activity. It will not + * invalidate pages which are dirty, locked, under writeback or mapped into + * pagetables. + */ +unsigned long invalidate_mapping_pages(struct address_space *mapping, + pgoff_t start, pgoff_t end) +{ + pgoff_t indices[PAGEVEC_SIZE]; + struct pagevec pvec; + pgoff_t index = start; + unsigned long ret; + unsigned long count = 0; + int i; + + pagevec_init(&pvec); + while (index <= end && pagevec_lookup_entries(&pvec, mapping, index, + min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1, + indices)) { + for (i = 0; i < pagevec_count(&pvec); i++) { + struct page *page = pvec.pages[i]; + + /* We rely upon deletion not changing page->index */ + index = indices[i]; + if (index > end) + break; + + if (radix_tree_exceptional_entry(page)) { + invalidate_exceptional_entry(mapping, index, + page); + continue; + } + + if (!trylock_page(page)) + continue; + + WARN_ON(page_to_index(page) != index); + + /* Middle of THP: skip */ + if (PageTransTail(page)) { + unlock_page(page); + continue; + } else if (PageTransHuge(page)) { + index += HPAGE_PMD_NR - 1; + i += HPAGE_PMD_NR - 1; + /* + * 'end' is in the middle of THP. Don't + * invalidate the page as the part outside of + * 'end' could be still useful. + */ + if (index > end) { + unlock_page(page); + continue; + } + } + + ret = invalidate_inode_page(page); + unlock_page(page); + /* + * Invalidation is a hint that the page is no longer + * of interest and try to speed up its reclaim. + */ + if (!ret) + deactivate_file_page(page); + count += ret; + } + pagevec_remove_exceptionals(&pvec); + pagevec_release(&pvec); + cond_resched(); + index++; + } + return count; +} +EXPORT_SYMBOL(invalidate_mapping_pages); + +/* + * This is like invalidate_complete_page(), except it ignores the page's + * refcount. We do this because invalidate_inode_pages2() needs stronger + * invalidation guarantees, and cannot afford to leave pages behind because + * shrink_page_list() has a temp ref on them, or because they're transiently + * sitting in the lru_cache_add() pagevecs. + */ +static int +invalidate_complete_page2(struct address_space *mapping, struct page *page) +{ + unsigned long flags; + + if (page->mapping != mapping) + return 0; + + if (page_has_private(page) && !try_to_release_page(page, GFP_KERNEL)) + return 0; + + xa_lock_irqsave(&mapping->i_pages, flags); + if (PageDirty(page)) + goto failed; + + BUG_ON(page_has_private(page)); + __delete_from_page_cache(page, NULL); + xa_unlock_irqrestore(&mapping->i_pages, flags); + + if (mapping->a_ops->freepage) + mapping->a_ops->freepage(page); + + put_page(page); /* pagecache ref */ + return 1; +failed: + xa_unlock_irqrestore(&mapping->i_pages, flags); + return 0; +} + +static int do_launder_page(struct address_space *mapping, struct page *page) +{ + if (!PageDirty(page)) + return 0; + if (page->mapping != mapping || mapping->a_ops->launder_page == NULL) + return 0; + return mapping->a_ops->launder_page(page); +} + +/** + * invalidate_inode_pages2_range - remove range of pages from an address_space + * @mapping: the address_space + * @start: the page offset 'from' which to invalidate + * @end: the page offset 'to' which to invalidate (inclusive) + * + * Any pages which are found to be mapped into pagetables are unmapped prior to + * invalidation. + * + * Returns -EBUSY if any pages could not be invalidated. + */ +int invalidate_inode_pages2_range(struct address_space *mapping, + pgoff_t start, pgoff_t end) +{ + pgoff_t indices[PAGEVEC_SIZE]; + struct pagevec pvec; + pgoff_t index; + int i; + int ret = 0; + int ret2 = 0; + int did_range_unmap = 0; + + if (mapping->nrpages == 0 && mapping->nrexceptional == 0) + goto out; + + pagevec_init(&pvec); + index = start; + while (index <= end && pagevec_lookup_entries(&pvec, mapping, index, + min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1, + indices)) { + for (i = 0; i < pagevec_count(&pvec); i++) { + struct page *page = pvec.pages[i]; + + /* We rely upon deletion not changing page->index */ + index = indices[i]; + if (index > end) + break; + + if (radix_tree_exceptional_entry(page)) { + if (!invalidate_exceptional_entry2(mapping, + index, page)) + ret = -EBUSY; + continue; + } + + if (!did_range_unmap && page_mapped(page)) { + /* + * If page is mapped, before taking its lock, + * zap the rest of the file in one hit. + */ + unmap_mapping_pages(mapping, index, + (1 + end - index), false); + did_range_unmap = 1; + } + + lock_page(page); + WARN_ON(page_to_index(page) != index); + if (page->mapping != mapping) { + unlock_page(page); + continue; + } + wait_on_page_writeback(page); + + if (page_mapped(page)) + unmap_mapping_page(page); + BUG_ON(page_mapped(page)); + + ret2 = do_launder_page(mapping, page); + if (ret2 == 0) { + if (!invalidate_complete_page2(mapping, page)) + ret2 = -EBUSY; + } + if (ret2 < 0) + ret = ret2; + unlock_page(page); + } + pagevec_remove_exceptionals(&pvec); + pagevec_release(&pvec); + cond_resched(); + index++; + } + /* + * For DAX we invalidate page tables after invalidating radix tree. We + * could invalidate page tables while invalidating each entry however + * that would be expensive. And doing range unmapping before doesn't + * work as we have no cheap way to find whether radix tree entry didn't + * get remapped later. + */ + if (dax_mapping(mapping)) { + unmap_mapping_pages(mapping, start, end - start + 1, false); + } +out: + cleancache_invalidate_inode(mapping); + return ret; +} +EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range); + +/** + * invalidate_inode_pages2 - remove all pages from an address_space + * @mapping: the address_space + * + * Any pages which are found to be mapped into pagetables are unmapped prior to + * invalidation. + * + * Returns -EBUSY if any pages could not be invalidated. + */ +int invalidate_inode_pages2(struct address_space *mapping) +{ + return invalidate_inode_pages2_range(mapping, 0, -1); +} +EXPORT_SYMBOL_GPL(invalidate_inode_pages2); + +/** + * truncate_pagecache - unmap and remove pagecache that has been truncated + * @inode: inode + * @newsize: new file size + * + * inode's new i_size must already be written before truncate_pagecache + * is called. + * + * This function should typically be called before the filesystem + * releases resources associated with the freed range (eg. deallocates + * blocks). This way, pagecache will always stay logically coherent + * with on-disk format, and the filesystem would not have to deal with + * situations such as writepage being called for a page that has already + * had its underlying blocks deallocated. + */ +void truncate_pagecache(struct inode *inode, loff_t newsize) +{ + struct address_space *mapping = inode->i_mapping; + loff_t holebegin = round_up(newsize, PAGE_SIZE); + + /* + * unmap_mapping_range is called twice, first simply for + * efficiency so that truncate_inode_pages does fewer + * single-page unmaps. However after this first call, and + * before truncate_inode_pages finishes, it is possible for + * private pages to be COWed, which remain after + * truncate_inode_pages finishes, hence the second + * unmap_mapping_range call must be made for correctness. + */ + unmap_mapping_range(mapping, holebegin, 0, 1); + truncate_inode_pages(mapping, newsize); + unmap_mapping_range(mapping, holebegin, 0, 1); +} +EXPORT_SYMBOL(truncate_pagecache); + +/** + * truncate_setsize - update inode and pagecache for a new file size + * @inode: inode + * @newsize: new file size + * + * truncate_setsize updates i_size and performs pagecache truncation (if + * necessary) to @newsize. It will be typically be called from the filesystem's + * setattr function when ATTR_SIZE is passed in. + * + * Must be called with a lock serializing truncates and writes (generally + * i_mutex but e.g. xfs uses a different lock) and before all filesystem + * specific block truncation has been performed. + */ +void truncate_setsize(struct inode *inode, loff_t newsize) +{ + loff_t oldsize = inode->i_size; + + i_size_write(inode, newsize); + if (newsize > oldsize) + pagecache_isize_extended(inode, oldsize, newsize); + truncate_pagecache(inode, newsize); +} +EXPORT_SYMBOL(truncate_setsize); + +/** + * pagecache_isize_extended - update pagecache after extension of i_size + * @inode: inode for which i_size was extended + * @from: original inode size + * @to: new inode size + * + * Handle extension of inode size either caused by extending truncate or by + * write starting after current i_size. We mark the page straddling current + * i_size RO so that page_mkwrite() is called on the nearest write access to + * the page. This way filesystem can be sure that page_mkwrite() is called on + * the page before user writes to the page via mmap after the i_size has been + * changed. + * + * The function must be called after i_size is updated so that page fault + * coming after we unlock the page will already see the new i_size. + * The function must be called while we still hold i_mutex - this not only + * makes sure i_size is stable but also that userspace cannot observe new + * i_size value before we are prepared to store mmap writes at new inode size. + */ +void pagecache_isize_extended(struct inode *inode, loff_t from, loff_t to) +{ + int bsize = i_blocksize(inode); + loff_t rounded_from; + struct page *page; + pgoff_t index; + + WARN_ON(to > inode->i_size); + + if (from >= to || bsize == PAGE_SIZE) + return; + /* Page straddling @from will not have any hole block created? */ + rounded_from = round_up(from, bsize); + if (to <= rounded_from || !(rounded_from & (PAGE_SIZE - 1))) + return; + + index = from >> PAGE_SHIFT; + page = find_lock_page(inode->i_mapping, index); + /* Page not cached? Nothing to do */ + if (!page) + return; + /* + * See clear_page_dirty_for_io() for details why set_page_dirty() + * is needed. + */ + if (page_mkclean(page)) + set_page_dirty(page); + unlock_page(page); + put_page(page); +} +EXPORT_SYMBOL(pagecache_isize_extended); + +/** + * truncate_pagecache_range - unmap and remove pagecache that is hole-punched + * @inode: inode + * @lstart: offset of beginning of hole + * @lend: offset of last byte of hole + * + * This function should typically be called before the filesystem + * releases resources associated with the freed range (eg. deallocates + * blocks). This way, pagecache will always stay logically coherent + * with on-disk format, and the filesystem would not have to deal with + * situations such as writepage being called for a page that has already + * had its underlying blocks deallocated. + */ +void truncate_pagecache_range(struct inode *inode, loff_t lstart, loff_t lend) +{ + struct address_space *mapping = inode->i_mapping; + loff_t unmap_start = round_up(lstart, PAGE_SIZE); + loff_t unmap_end = round_down(1 + lend, PAGE_SIZE) - 1; + /* + * This rounding is currently just for example: unmap_mapping_range + * expands its hole outwards, whereas we want it to contract the hole + * inwards. However, existing callers of truncate_pagecache_range are + * doing their own page rounding first. Note that unmap_mapping_range + * allows holelen 0 for all, and we allow lend -1 for end of file. + */ + + /* + * Unlike in truncate_pagecache, unmap_mapping_range is called only + * once (before truncating pagecache), and without "even_cows" flag: + * hole-punching should not remove private COWed pages from the hole. + */ + if ((u64)unmap_end > (u64)unmap_start) + unmap_mapping_range(mapping, unmap_start, + 1 + unmap_end - unmap_start, 0); + truncate_inode_pages_range(mapping, lstart, lend); +} +EXPORT_SYMBOL(truncate_pagecache_range); |