diff options
author | Konstantin Khlebnikov <khlebnikov@yandex-team.ru> | 2015-04-14 22:45:27 (GMT) |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-04-14 23:49:01 (GMT) |
commit | b9ea25152e56365ce149b9a39637cd7a16eec556 (patch) | |
tree | e8ab83d71a0bea5330d38e77e948170c0054d2a3 /mm | |
parent | ca0984caa8235762dc4e22c1c47ae6719dcc4064 (diff) | |
download | linux-b9ea25152e56365ce149b9a39637cd7a16eec556.tar.xz |
page_writeback: clean up mess around cancel_dirty_page()
This patch replaces cancel_dirty_page() with a helper function
account_page_cleaned() which only updates counters. It's called from
truncate_complete_page() and from try_to_free_buffers() (hack for ext3).
Page is locked in both cases, page-lock protects against concurrent
dirtiers: see commit 2d6d7f982846 ("mm: protect set_page_dirty() from
ongoing truncation").
Delete_from_page_cache() shouldn't be called for dirty pages, they must
be handled by caller (either written or truncated). This patch treats
final dirty accounting fixup at the end of __delete_from_page_cache() as
a debug check and adds WARN_ON_ONCE() around it. If something removes
dirty pages without proper handling that might be a bug and unwritten
data might be lost.
Hugetlbfs has no dirty pages accounting, ClearPageDirty() is enough
here.
cancel_dirty_page() in nfs_wb_page_cancel() is redundant. This is
helper for nfs_invalidate_page() and it's called only in case complete
invalidation.
The mess was started in v2.6.20 after commits 46d2277c796f ("Clean up
and make try_to_free_buffers() not race with dirty pages") and
3e67c0987d75 ("truncate: clear page dirtiness before running
try_to_free_buffers()") first was reverted right in v2.6.20 in commit
ecdfc9787fe5 ("Resurrect 'try_to_free_buffers()' VM hackery"), second in
v2.6.25 commit a2b345642f53 ("Fix dirty page accounting leak with ext3
data=journal").
Custom fixes were introduced between these points. NFS in v2.6.23, commit
1b3b4a1a2deb ("NFS: Fix a write request leak in nfs_invalidate_page()").
Kludge in __delete_from_page_cache() in v2.6.24, commit 3a6927906f1b ("Do
dirty page accounting when removing a page from the page cache"). Since
v2.6.25 all of them are redundant.
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Tejun Heo <tj@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r-- | mm/filemap.c | 15 | ||||
-rw-r--r-- | mm/page-writeback.c | 19 | ||||
-rw-r--r-- | mm/truncate.c | 37 |
3 files changed, 33 insertions, 38 deletions
diff --git a/mm/filemap.c b/mm/filemap.c index ad72420..434dba3 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -203,16 +203,15 @@ void __delete_from_page_cache(struct page *page, void *shadow) BUG_ON(page_mapped(page)); /* - * Some filesystems seem to re-dirty the page even after - * the VM has canceled the dirty bit (eg ext3 journaling). + * At this point page must be either written or cleaned by truncate. + * Dirty page here signals a bug and loss of unwritten data. * - * Fix it up by doing a final dirty accounting check after - * having removed the page entirely. + * 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 (PageDirty(page) && mapping_cap_account_dirty(mapping)) { - dec_zone_page_state(page, NR_FILE_DIRTY); - dec_bdi_stat(inode_to_bdi(mapping->host), BDI_RECLAIMABLE); - } + if (WARN_ON_ONCE(PageDirty(page))) + account_page_cleaned(page, mapping); } /** diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 644bcb6..0372411 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -2111,6 +2111,25 @@ void account_page_dirtied(struct page *page, struct address_space *mapping) EXPORT_SYMBOL(account_page_dirtied); /* + * Helper function for deaccounting dirty page without writeback. + * + * Doing this should *normally* only ever be done when a page + * is truncated, and is not actually mapped anywhere at all. However, + * fs/buffer.c does this when it notices that somebody has cleaned + * out all the buffers on a page without actually doing it through + * the VM. Can you say "ext3 is horribly ugly"? Thought you could. + */ +void account_page_cleaned(struct page *page, struct address_space *mapping) +{ + if (mapping_cap_account_dirty(mapping)) { + dec_zone_page_state(page, NR_FILE_DIRTY); + dec_bdi_stat(inode_to_bdi(mapping->host), BDI_RECLAIMABLE); + task_io_account_cancelled_write(PAGE_CACHE_SIZE); + } +} +EXPORT_SYMBOL(account_page_cleaned); + +/* * For address_spaces which do not use buffers. Just tag the page as dirty in * its radix tree. * diff --git a/mm/truncate.c b/mm/truncate.c index ddec5a5..7a9d8a3 100644 --- a/mm/truncate.c +++ b/mm/truncate.c @@ -93,35 +93,6 @@ void do_invalidatepage(struct page *page, unsigned int offset, } /* - * This cancels just the dirty bit on the kernel page itself, it - * does NOT actually remove dirty bits on any mmap's that may be - * around. It also leaves the page tagged dirty, so any sync - * activity will still find it on the dirty lists, and in particular, - * clear_page_dirty_for_io() will still look at the dirty bits in - * the VM. - * - * Doing this should *normally* only ever be done when a page - * is truncated, and is not actually mapped anywhere at all. However, - * fs/buffer.c does this when it notices that somebody has cleaned - * out all the buffers on a page without actually doing it through - * the VM. Can you say "ext3 is horribly ugly"? Tought you could. - */ -void cancel_dirty_page(struct page *page, unsigned int account_size) -{ - if (TestClearPageDirty(page)) { - struct address_space *mapping = page->mapping; - if (mapping && mapping_cap_account_dirty(mapping)) { - dec_zone_page_state(page, NR_FILE_DIRTY); - dec_bdi_stat(inode_to_bdi(mapping->host), - BDI_RECLAIMABLE); - if (account_size) - task_io_account_cancelled_write(account_size); - } - } -} -EXPORT_SYMBOL(cancel_dirty_page); - -/* * 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(). @@ -140,7 +111,13 @@ truncate_complete_page(struct address_space *mapping, struct page *page) if (page_has_private(page)) do_invalidatepage(page, 0, PAGE_CACHE_SIZE); - cancel_dirty_page(page, PAGE_CACHE_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. + */ + if (TestClearPageDirty(page)) + account_page_cleaned(page, mapping); ClearPageMappedToDisk(page); delete_from_page_cache(page); |