From b9ea25152e56365ce149b9a39637cd7a16eec556 Mon Sep 17 00:00:00 2001 From: Konstantin Khlebnikov Date: Tue, 14 Apr 2015 15:45:27 -0700 Subject: 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 Cc: Tejun Heo Cc: Jan Kara Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/filemap.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) (limited to 'mm/filemap.c') diff --git a/mm/filemap.c b/mm/filemap.c index ad7242043bdb..434dba317400 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); } /** -- cgit v1.2.3