From 87df7241bd547da5d4d4a4e5397866dfe422e439 Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Tue, 30 Jan 2007 14:36:27 +1100 Subject: [PATCH] Fix try_to_free_buffer() locking Fix commit ecdfc9787fe527491baefc22dce8b2dbd5b2908d Not to put too fine a point on it, but in a nutshell... __set_page_dirty_buffers() | try_to_free_buffers() ---------------------------+--------------------------- | spin_lock(private_lock); | drop_bufers() | spin_unlock(private_lock); spin_lock(private_lock) | !page_has_buffers() | spin_unlock(private_lock) | SetPageDirty() | | cancel_dirty_page() oops! Signed-off-by: Nick Piggin Acked-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/buffer.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/fs/buffer.c b/fs/buffer.c index 460f1c43238..1ad674fd348 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -2844,7 +2844,6 @@ int try_to_free_buffers(struct page *page) spin_lock(&mapping->private_lock); ret = drop_buffers(page, &buffers_to_free); - spin_unlock(&mapping->private_lock); /* * If the filesystem writes its buffers by hand (eg ext3) @@ -2855,9 +2854,14 @@ int try_to_free_buffers(struct page *page) * Also, during truncate, discard_buffer will have marked all * the page's buffers clean. We discover that here and clean * the page also. + * + * private_lock must be held over this entire operation in order + * to synchronise against __set_page_dirty_buffers and prevent the + * dirty bit from being lost. */ if (ret) cancel_dirty_page(page, PAGE_CACHE_SIZE); + spin_unlock(&mapping->private_lock); out: if (buffers_to_free) { struct buffer_head *bh = buffers_to_free; -- cgit v1.2.3