From 1bfd8d04190c615bb8d1d98188dead0c09702208 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Sat, 26 Mar 2011 09:13:55 +1100 Subject: xfs: introduce inode cluster buffer trylocks for xfs_iflush There is an ABBA deadlock between synchronous inode flushing in xfs_reclaim_inode and xfs_icluster_free. xfs_icluster_free locks the buffer, then takes inode ilocks, whilst synchronous reclaim takes the ilock followed by the buffer lock in xfs_iflush(). To avoid this deadlock, separate the inode cluster buffer locking semantics from the synchronous inode flush semantics, allowing callers to attempt to lock the buffer but still issue synchronous IO if it can get the buffer. This requires xfs_iflush() calls that currently use non-blocking semantics to pass SYNC_TRYLOCK rather than 0 as the flags parameter. This allows xfs_reclaim_inode to avoid the deadlock on the buffer lock and detect the failure so that it can drop the inode ilock and restart the reclaim attempt on the inode. This allows xfs_ifree_cluster to obtain the inode lock, mark the inode stale and release it and hence defuse the deadlock situation. It also has the pleasant side effect of avoiding IO in xfs_reclaim_inode when it tries to next reclaim the inode as it is now marked stale. Signed-off-by: Dave Chinner Reviewed-by: Christoph Hellwig Reviewed-by: Alex Elder --- fs/xfs/xfs_inode_item.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'fs/xfs/xfs_inode_item.c') diff --git a/fs/xfs/xfs_inode_item.c b/fs/xfs/xfs_inode_item.c index fd4f398bd6f1..46cc40131d4a 100644 --- a/fs/xfs/xfs_inode_item.c +++ b/fs/xfs/xfs_inode_item.c @@ -760,11 +760,11 @@ xfs_inode_item_push( * Push the inode to it's backing buffer. This will not remove the * inode from the AIL - a further push will be required to trigger a * buffer push. However, this allows all the dirty inodes to be pushed - * to the buffer before it is pushed to disk. THe buffer IO completion - * will pull th einode from the AIL, mark it clean and unlock the flush + * to the buffer before it is pushed to disk. The buffer IO completion + * will pull the inode from the AIL, mark it clean and unlock the flush * lock. */ - (void) xfs_iflush(ip, 0); + (void) xfs_iflush(ip, SYNC_TRYLOCK); xfs_iunlock(ip, XFS_ILOCK_SHARED); } -- cgit v1.2.3-58-ga151