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authorKonstantin Khlebnikov <khlebnikov@yandex-team.ru>2015-04-14 15:45:27 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-04-14 16:49:01 -0700
commitb9ea25152e56365ce149b9a39637cd7a16eec556 (patch)
treee8ab83d71a0bea5330d38e77e948170c0054d2a3 /mm/page-writeback.c
parentca0984caa8235762dc4e22c1c47ae6719dcc4064 (diff)
downloadlwn-b9ea25152e56365ce149b9a39637cd7a16eec556.tar.gz
lwn-b9ea25152e56365ce149b9a39637cd7a16eec556.zip
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/page-writeback.c')
-rw-r--r--mm/page-writeback.c19
1 files changed, 19 insertions, 0 deletions
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 644bcb665773..0372411f38fc 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.
*