![Lukas Czerner](/assets/img/avatar_default.png)
Currently there is no way to truncate partial page where the end truncate point is not at the end of the page. This is because it was not needed and the functionality was enough for file system truncate operation to work properly. However more file systems now support punch hole feature and it can benefit from mm supporting truncating page just up to the certain point. Specifically, with this functionality truncate_inode_pages_range() can be changed so it supports truncating partial page at the end of the range (currently it will BUG_ON() if 'end' is not at the end of the page). This commit changes the invalidatepage() address space operation prototype to accept range to be invalidated and update all the instances for it. We also change the block_invalidatepage() in the same way and actually make a use of the new length argument implementing range invalidation. Actual file system implementations will follow except the file systems where the changes are really simple and should not change the behaviour in any way .Implementation for truncate_page_range() which will be able to accept page unaligned ranges will follow as well. Signed-off-by: Lukas Czerner <lczerner@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Hugh Dickins <hughd@google.com>
621 lines
18 KiB
C
621 lines
18 KiB
C
/*
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* mm/truncate.c - code for taking down pages from address_spaces
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*
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* Copyright (C) 2002, Linus Torvalds
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*
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* 10Sep2002 Andrew Morton
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* Initial version.
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*/
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#include <linux/kernel.h>
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#include <linux/backing-dev.h>
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#include <linux/gfp.h>
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#include <linux/mm.h>
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#include <linux/swap.h>
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#include <linux/export.h>
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#include <linux/pagemap.h>
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#include <linux/highmem.h>
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#include <linux/pagevec.h>
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#include <linux/task_io_accounting_ops.h>
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#include <linux/buffer_head.h> /* grr. try_to_release_page,
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do_invalidatepage */
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#include <linux/cleancache.h>
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#include "internal.h"
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/**
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* do_invalidatepage - invalidate part or all of a page
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* @page: the page which is affected
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* @offset: start of the range to invalidate
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* @length: length of the range to invalidate
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*
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* do_invalidatepage() is called when all or part of the page has become
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* invalidated by a truncate operation.
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*
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* do_invalidatepage() does not have to release all buffers, but it must
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* ensure that no dirty buffer is left outside @offset and that no I/O
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* is underway against any of the blocks which are outside the truncation
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* point. Because the caller is about to free (and possibly reuse) those
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* blocks on-disk.
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*/
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void do_invalidatepage(struct page *page, unsigned int offset,
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unsigned int length)
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{
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void (*invalidatepage)(struct page *, unsigned int, unsigned int);
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invalidatepage = page->mapping->a_ops->invalidatepage;
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#ifdef CONFIG_BLOCK
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if (!invalidatepage)
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invalidatepage = block_invalidatepage;
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#endif
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if (invalidatepage)
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(*invalidatepage)(page, offset, length);
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}
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static inline void truncate_partial_page(struct page *page, unsigned partial)
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{
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zero_user_segment(page, partial, PAGE_CACHE_SIZE);
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cleancache_invalidate_page(page->mapping, page);
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if (page_has_private(page))
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do_invalidatepage(page, partial, PAGE_CACHE_SIZE - partial);
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}
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/*
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* This cancels just the dirty bit on the kernel page itself, it
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* does NOT actually remove dirty bits on any mmap's that may be
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* around. It also leaves the page tagged dirty, so any sync
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* activity will still find it on the dirty lists, and in particular,
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* clear_page_dirty_for_io() will still look at the dirty bits in
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* the VM.
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*
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* Doing this should *normally* only ever be done when a page
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* is truncated, and is not actually mapped anywhere at all. However,
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* fs/buffer.c does this when it notices that somebody has cleaned
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* out all the buffers on a page without actually doing it through
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* the VM. Can you say "ext3 is horribly ugly"? Tought you could.
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*/
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void cancel_dirty_page(struct page *page, unsigned int account_size)
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{
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if (TestClearPageDirty(page)) {
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struct address_space *mapping = page->mapping;
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if (mapping && mapping_cap_account_dirty(mapping)) {
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dec_zone_page_state(page, NR_FILE_DIRTY);
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dec_bdi_stat(mapping->backing_dev_info,
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BDI_RECLAIMABLE);
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if (account_size)
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task_io_account_cancelled_write(account_size);
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}
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}
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}
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EXPORT_SYMBOL(cancel_dirty_page);
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/*
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* If truncate cannot remove the fs-private metadata from the page, the page
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* becomes orphaned. It will be left on the LRU and may even be mapped into
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* user pagetables if we're racing with filemap_fault().
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*
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* We need to bale out if page->mapping is no longer equal to the original
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* mapping. This happens a) when the VM reclaimed the page while we waited on
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* its lock, b) when a concurrent invalidate_mapping_pages got there first and
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* c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
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*/
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static int
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truncate_complete_page(struct address_space *mapping, struct page *page)
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{
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if (page->mapping != mapping)
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return -EIO;
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if (page_has_private(page))
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do_invalidatepage(page, 0, PAGE_CACHE_SIZE);
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cancel_dirty_page(page, PAGE_CACHE_SIZE);
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ClearPageMappedToDisk(page);
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delete_from_page_cache(page);
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return 0;
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}
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/*
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* This is for invalidate_mapping_pages(). That function can be called at
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* any time, and is not supposed to throw away dirty pages. But pages can
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* be marked dirty at any time too, so use remove_mapping which safely
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* discards clean, unused pages.
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*
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* Returns non-zero if the page was successfully invalidated.
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*/
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static int
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invalidate_complete_page(struct address_space *mapping, struct page *page)
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{
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int ret;
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if (page->mapping != mapping)
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return 0;
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if (page_has_private(page) && !try_to_release_page(page, 0))
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return 0;
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ret = remove_mapping(mapping, page);
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return ret;
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}
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int truncate_inode_page(struct address_space *mapping, struct page *page)
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{
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if (page_mapped(page)) {
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unmap_mapping_range(mapping,
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(loff_t)page->index << PAGE_CACHE_SHIFT,
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PAGE_CACHE_SIZE, 0);
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}
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return truncate_complete_page(mapping, page);
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}
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/*
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* Used to get rid of pages on hardware memory corruption.
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*/
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int generic_error_remove_page(struct address_space *mapping, struct page *page)
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{
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if (!mapping)
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return -EINVAL;
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/*
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* Only punch for normal data pages for now.
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* Handling other types like directories would need more auditing.
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*/
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if (!S_ISREG(mapping->host->i_mode))
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return -EIO;
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return truncate_inode_page(mapping, page);
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}
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EXPORT_SYMBOL(generic_error_remove_page);
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/*
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* Safely invalidate one page from its pagecache mapping.
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* It only drops clean, unused pages. The page must be locked.
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*
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* Returns 1 if the page is successfully invalidated, otherwise 0.
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*/
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int invalidate_inode_page(struct page *page)
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{
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struct address_space *mapping = page_mapping(page);
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if (!mapping)
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return 0;
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if (PageDirty(page) || PageWriteback(page))
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return 0;
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if (page_mapped(page))
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return 0;
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return invalidate_complete_page(mapping, page);
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}
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/**
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* truncate_inode_pages_range - truncate range of pages specified by start & end byte offsets
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* @mapping: mapping to truncate
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* @lstart: offset from which to truncate
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* @lend: offset to which to truncate
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*
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* Truncate the page cache, removing the pages that are between
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* specified offsets (and zeroing out partial page
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* (if lstart is not page aligned)).
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*
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* Truncate takes two passes - the first pass is nonblocking. It will not
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* block on page locks and it will not block on writeback. The second pass
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* will wait. This is to prevent as much IO as possible in the affected region.
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* The first pass will remove most pages, so the search cost of the second pass
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* is low.
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*
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* We pass down the cache-hot hint to the page freeing code. Even if the
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* mapping is large, it is probably the case that the final pages are the most
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* recently touched, and freeing happens in ascending file offset order.
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*/
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void truncate_inode_pages_range(struct address_space *mapping,
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loff_t lstart, loff_t lend)
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{
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const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
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const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);
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struct pagevec pvec;
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pgoff_t index;
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pgoff_t end;
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int i;
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cleancache_invalidate_inode(mapping);
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if (mapping->nrpages == 0)
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return;
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BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1));
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end = (lend >> PAGE_CACHE_SHIFT);
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pagevec_init(&pvec, 0);
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index = start;
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while (index <= end && pagevec_lookup(&pvec, mapping, index,
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min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
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mem_cgroup_uncharge_start();
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for (i = 0; i < pagevec_count(&pvec); i++) {
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struct page *page = pvec.pages[i];
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/* We rely upon deletion not changing page->index */
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index = page->index;
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if (index > end)
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break;
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if (!trylock_page(page))
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continue;
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WARN_ON(page->index != index);
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if (PageWriteback(page)) {
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unlock_page(page);
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continue;
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}
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truncate_inode_page(mapping, page);
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unlock_page(page);
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}
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pagevec_release(&pvec);
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mem_cgroup_uncharge_end();
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cond_resched();
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index++;
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}
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if (partial) {
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struct page *page = find_lock_page(mapping, start - 1);
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if (page) {
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wait_on_page_writeback(page);
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truncate_partial_page(page, partial);
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unlock_page(page);
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page_cache_release(page);
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}
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}
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index = start;
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for ( ; ; ) {
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cond_resched();
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if (!pagevec_lookup(&pvec, mapping, index,
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min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
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if (index == start)
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break;
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index = start;
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continue;
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}
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if (index == start && pvec.pages[0]->index > end) {
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pagevec_release(&pvec);
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break;
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}
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mem_cgroup_uncharge_start();
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for (i = 0; i < pagevec_count(&pvec); i++) {
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struct page *page = pvec.pages[i];
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/* We rely upon deletion not changing page->index */
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index = page->index;
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if (index > end)
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break;
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lock_page(page);
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WARN_ON(page->index != index);
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wait_on_page_writeback(page);
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truncate_inode_page(mapping, page);
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unlock_page(page);
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}
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pagevec_release(&pvec);
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mem_cgroup_uncharge_end();
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index++;
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}
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cleancache_invalidate_inode(mapping);
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}
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EXPORT_SYMBOL(truncate_inode_pages_range);
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/**
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* truncate_inode_pages - truncate *all* the pages from an offset
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* @mapping: mapping to truncate
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* @lstart: offset from which to truncate
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*
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* Called under (and serialised by) inode->i_mutex.
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*
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* Note: When this function returns, there can be a page in the process of
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* deletion (inside __delete_from_page_cache()) in the specified range. Thus
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* mapping->nrpages can be non-zero when this function returns even after
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* truncation of the whole mapping.
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*/
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void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
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{
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truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
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}
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EXPORT_SYMBOL(truncate_inode_pages);
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/**
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* invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
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* @mapping: the address_space which holds the pages to invalidate
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* @start: the offset 'from' which to invalidate
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* @end: the offset 'to' which to invalidate (inclusive)
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*
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* This function only removes the unlocked pages, if you want to
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* remove all the pages of one inode, you must call truncate_inode_pages.
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*
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* invalidate_mapping_pages() will not block on IO activity. It will not
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* invalidate pages which are dirty, locked, under writeback or mapped into
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* pagetables.
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*/
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unsigned long invalidate_mapping_pages(struct address_space *mapping,
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pgoff_t start, pgoff_t end)
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{
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struct pagevec pvec;
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pgoff_t index = start;
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unsigned long ret;
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unsigned long count = 0;
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int i;
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/*
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* Note: this function may get called on a shmem/tmpfs mapping:
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* pagevec_lookup() might then return 0 prematurely (because it
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* got a gangful of swap entries); but it's hardly worth worrying
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* about - it can rarely have anything to free from such a mapping
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* (most pages are dirty), and already skips over any difficulties.
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*/
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pagevec_init(&pvec, 0);
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while (index <= end && pagevec_lookup(&pvec, mapping, index,
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min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
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mem_cgroup_uncharge_start();
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for (i = 0; i < pagevec_count(&pvec); i++) {
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struct page *page = pvec.pages[i];
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/* We rely upon deletion not changing page->index */
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index = page->index;
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if (index > end)
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break;
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if (!trylock_page(page))
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continue;
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WARN_ON(page->index != index);
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ret = invalidate_inode_page(page);
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unlock_page(page);
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/*
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* Invalidation is a hint that the page is no longer
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* of interest and try to speed up its reclaim.
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*/
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if (!ret)
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deactivate_page(page);
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count += ret;
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}
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pagevec_release(&pvec);
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mem_cgroup_uncharge_end();
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cond_resched();
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index++;
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}
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return count;
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}
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EXPORT_SYMBOL(invalidate_mapping_pages);
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/*
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* This is like invalidate_complete_page(), except it ignores the page's
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* refcount. We do this because invalidate_inode_pages2() needs stronger
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* invalidation guarantees, and cannot afford to leave pages behind because
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* shrink_page_list() has a temp ref on them, or because they're transiently
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* sitting in the lru_cache_add() pagevecs.
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*/
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static int
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invalidate_complete_page2(struct address_space *mapping, struct page *page)
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{
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if (page->mapping != mapping)
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return 0;
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if (page_has_private(page) && !try_to_release_page(page, GFP_KERNEL))
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return 0;
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spin_lock_irq(&mapping->tree_lock);
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if (PageDirty(page))
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goto failed;
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BUG_ON(page_has_private(page));
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__delete_from_page_cache(page);
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spin_unlock_irq(&mapping->tree_lock);
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mem_cgroup_uncharge_cache_page(page);
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if (mapping->a_ops->freepage)
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mapping->a_ops->freepage(page);
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page_cache_release(page); /* pagecache ref */
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return 1;
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failed:
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spin_unlock_irq(&mapping->tree_lock);
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return 0;
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}
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static int do_launder_page(struct address_space *mapping, struct page *page)
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{
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if (!PageDirty(page))
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return 0;
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if (page->mapping != mapping || mapping->a_ops->launder_page == NULL)
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return 0;
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return mapping->a_ops->launder_page(page);
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}
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/**
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* invalidate_inode_pages2_range - remove range of pages from an address_space
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* @mapping: the address_space
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* @start: the page offset 'from' which to invalidate
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* @end: the page offset 'to' which to invalidate (inclusive)
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*
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* Any pages which are found to be mapped into pagetables are unmapped prior to
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* invalidation.
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*
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* Returns -EBUSY if any pages could not be invalidated.
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*/
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int invalidate_inode_pages2_range(struct address_space *mapping,
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pgoff_t start, pgoff_t end)
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{
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struct pagevec pvec;
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pgoff_t index;
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int i;
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int ret = 0;
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int ret2 = 0;
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int did_range_unmap = 0;
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cleancache_invalidate_inode(mapping);
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pagevec_init(&pvec, 0);
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index = start;
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while (index <= end && pagevec_lookup(&pvec, mapping, index,
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min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
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mem_cgroup_uncharge_start();
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for (i = 0; i < pagevec_count(&pvec); i++) {
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struct page *page = pvec.pages[i];
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/* We rely upon deletion not changing page->index */
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index = page->index;
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if (index > end)
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break;
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lock_page(page);
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WARN_ON(page->index != index);
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if (page->mapping != mapping) {
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unlock_page(page);
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continue;
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}
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wait_on_page_writeback(page);
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if (page_mapped(page)) {
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if (!did_range_unmap) {
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/*
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* Zap the rest of the file in one hit.
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*/
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unmap_mapping_range(mapping,
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(loff_t)index << PAGE_CACHE_SHIFT,
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(loff_t)(1 + end - index)
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<< PAGE_CACHE_SHIFT,
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0);
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did_range_unmap = 1;
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} else {
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/*
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* Just zap this page
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*/
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unmap_mapping_range(mapping,
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(loff_t)index << PAGE_CACHE_SHIFT,
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PAGE_CACHE_SIZE, 0);
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}
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}
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BUG_ON(page_mapped(page));
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ret2 = do_launder_page(mapping, page);
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if (ret2 == 0) {
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if (!invalidate_complete_page2(mapping, page))
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ret2 = -EBUSY;
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}
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if (ret2 < 0)
|
|
ret = ret2;
|
|
unlock_page(page);
|
|
}
|
|
pagevec_release(&pvec);
|
|
mem_cgroup_uncharge_end();
|
|
cond_resched();
|
|
index++;
|
|
}
|
|
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
|
|
* @oldsize: old file size
|
|
* @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 oldsize, 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 inode_mutex held and before all filesystem specific
|
|
* block truncation has been performed.
|
|
*/
|
|
void truncate_setsize(struct inode *inode, loff_t newsize)
|
|
{
|
|
loff_t oldsize;
|
|
|
|
oldsize = inode->i_size;
|
|
i_size_write(inode, newsize);
|
|
|
|
truncate_pagecache(inode, oldsize, newsize);
|
|
}
|
|
EXPORT_SYMBOL(truncate_setsize);
|
|
|
|
/**
|
|
* 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; and truncate_inode_pages_range
|
|
* currently BUGs if lend is not pagealigned-1 (it handles partial
|
|
* page at start of hole, but not partial page at end of hole). Note
|
|
* unmap_mapping_range allows holelen 0 for all, and we allow lend -1.
|
|
*/
|
|
|
|
/*
|
|
* 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);
|