Messages in this thread Patch in this message | | | Date | Tue, 3 Oct 2006 13:51:49 -0400 (EDT) | From | Chip Coldwell <> | Subject | direct IO regression in 2.6.18 |
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Hi,
The following commit caused a regression in direct IO:
commit 016eb4a0ed06a3677d67a584da901f0e9a63c666 Author: Andrew Morton <akpm@osdl.org> Date: Fri Sep 8 09:48:38 2006 -0700
[PATCH] invalidate_complete_page() race fix
If a CPU faults this page into pagetables after invalidate_mapping_pages() checked page_mapped(), invalidate_complete_page() will still proceed to remove the page from pagecache. This leaves the page-faulting process with a detached page. If it was MAP_SHARED then file data loss will ensue.
Fix that up by checking the page's refcount after taking tree_lock.
Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Hugh Dickins <hugh@veritas.com> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/mm/truncate.c b/mm/truncate.c index cf1b015..c6ab55e 100644 --- a/mm/truncate.c +++ b/mm/truncate.c @@ -68,10 +68,10 @@ invalidate_complete_page(struct address_ return 0;
write_lock_irq(&mapping->tree_lock); - if (PageDirty(page)) { - write_unlock_irq(&mapping->tree_lock); - return 0; - } + if (PageDirty(page)) + goto failed; + if (page_count(page) != 2) /* caller's ref + pagecache ref */ + goto failed;
BUG_ON(PagePrivate(page)); __remove_from_page_cache(page); @@ -79,6 +79,9 @@ invalidate_complete_page(struct address_ ClearPageUptodate(page); page_cache_release(page); /* pagecache ref */ return 1; +failed: + write_unlock_irq(&mapping->tree_lock); + return 0; }
/**
The issue is that invalidate_complete_page is in two different code paths, the normal one (prune_icache calls invalidate_inode_pages calls invalidate_mapping_pages calls invalidate_complete_page) and also via direct IO (generic_file_direct_write calls generic_file_direct_IO calls invalidate_inode_pages2_range calls invalidate_complete_page). In the latter case, the page is (usually) not even in the page cache and the refcount can legitimately != 2.
Chip
-- Charles M. "Chip" Coldwell Senior Software Engineer Red Hat, Inc 978-392-2426
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