From: Nick Piggin Date: Thu, 5 May 2005 23:15:45 +0000 (-0700) Subject: [PATCH] fix race in __block_prepare_write X-Git-Tag: v2.6.12-rc4~71 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f3ddbdc6267c32223035ea9bb8456a2d86f65ba1;p=linux-2.6 [PATCH] fix race in __block_prepare_write Fix a race where __block_prepare_write can leak out an in-flight read against a bh if get_block returns an error. This can lead to the page becoming unlocked while the buffer is locked and the read still in flight. __mpage_writepage BUGs on this condition. BUG sighted on a 2-way Itanium2 system with 16K PAGE_SIZE running fsstress -v -d $DIR/tmp -n 1000 -p 1000 -l 2 where $DIR is a new ext2 filesystem with 4K blocks that is quite small (causing get_block to fail often with -ENOSPC). Signed-off-by: Nick Piggin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/fs/buffer.c b/fs/buffer.c index 6ed59497fd..af7c51ded2 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -1953,7 +1953,7 @@ static int __block_prepare_write(struct inode *inode, struct page *page, if (!buffer_mapped(bh)) { err = get_block(inode, block, bh, 1); if (err) - goto out; + break; if (buffer_new(bh)) { clear_buffer_new(bh); unmap_underlying_metadata(bh->b_bdev, @@ -1995,10 +1995,12 @@ static int __block_prepare_write(struct inode *inode, struct page *page, while(wait_bh > wait) { wait_on_buffer(*--wait_bh); if (!buffer_uptodate(*wait_bh)) - return -EIO; + err = -EIO; } - return 0; -out: + if (!err) + return err; + + /* Error case: */ /* * Zero out any newly allocated blocks to avoid exposing stale * data. If BH_New is set, we know that the block was newly