From: Miao Xie Date: Thu, 21 Feb 2013 09:48:22 +0000 (-0700) Subject: Btrfs: fix wrong outstanding_extents when doing DIO write X-Git-Tag: v3.9-rc1~17^2~23 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=172a50497ffaf84d60dff37fbeb03894268fe5c2;p=pandora-kernel.git Btrfs: fix wrong outstanding_extents when doing DIO write When running the 083th case of xfstests on the filesystem with "compress-force=lzo", the following WARNINGs were triggered. WARNING: at fs/btrfs/inode.c:7908 WARNING: at fs/btrfs/inode.c:7909 WARNING: at fs/btrfs/inode.c:7911 WARNING: at fs/btrfs/extent-tree.c:4510 WARNING: at fs/btrfs/extent-tree.c:4511 This problem was introduced by the patch "Btrfs: fix deadlock due to unsubmitted". In this patch, there are two bugs which caused the above problem. The 1st one is a off-by-one bug, if the DIO write return 0, it is also a short write, we need release the reserved space for it. But we didn't do it in that patch. Fix it by change "ret > 0" to "ret >= 0". The 2nd one is ->outstanding_extents was increased twice when a short write happened. As we know, ->outstanding_extents is a counter to keep track of the number of extent items we may use duo to delalloc, when we reserve the free space for a delalloc write, we assume that the write will introduce just one extent item, so we increase ->outstanding_extents by 1 at that time. And then we will increase it every time we split the write, it is done at the beginning of btrfs_get_blocks_direct(). So when a short write happens, we needn't increase ->outstanding_extents again. But this patch done. In order to fix the 2nd problem, I re-write the logic for ->outstanding_extents operation. We don't increase it at the beginning of btrfs_get_blocks_direct(), instead, we just increase it when the split actually happens. Reported-by: Mitch Harder Signed-off-by: Miao Xie Signed-off-by: Chris Mason --- Reading git-diff-tree failed