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authorDave Chinner <dchinner@redhat.com>2011-07-04 05:27:36 +0000
committerAlex Elder <aelder@sgi.com>2011-07-06 15:44:40 -0500
commit1316d4da3f632d5843d5a446203e73067dc40f09 (patch)
tree6ccaf36953d67749ab5943898cac345cf35ea738 /fs/xfs/xfs_inode_item.c
parent4a33821236f2ef3af0081e8a5eec1301cbed3125 (diff)
xfs: unpin stale inodes directly in IOP_COMMITTED
When inodes are marked stale in a transaction, they are treated specially when the inode log item is being inserted into the AIL. It tries to avoid moving the log item forward in the AIL due to a race condition with the writing the underlying buffer back to disk. The was "fixed" in commit de25c18 ("xfs: avoid moving stale inodes in the AIL"). To avoid moving the item forward, we return a LSN smaller than the commit_lsn of the completing transaction, thereby trying to trick the commit code into not moving the inode forward at all. I'm not sure this ever worked as intended - it assumes the inode is already in the AIL, but I don't think the returned LSN would have been small enough to prevent moving the inode. It appears that the reason it worked is that the lower LSN of the inodes meant they were inserted into the AIL and flushed before the inode buffer (which was moved to the commit_lsn of the transaction). The big problem is that with delayed logging, the returning of the different LSN means insertion takes the slow, non-bulk path. Worse yet is that insertion is to a position -before- the commit_lsn so it is doing a AIL traversal on every insertion, and has to walk over all the items that have already been inserted into the AIL. It's expensive. To compound the matter further, with delayed logging inodes are likely to go from clean to stale in a single checkpoint, which means they aren't even in the AIL at all when we come across them at AIL insertion time. Hence these were all getting inserted into the AIL when they simply do not need to be as inodes marked XFS_ISTALE are never written back. Transactional/recovery integrity is maintained in this case by the other items in the unlink transaction that were modified (e.g. the AGI btree blocks) and committed in the same checkpoint. So to fix this, simply unpin the stale inodes directly in xfs_inode_item_committed() and return -1 to indicate that the AIL insertion code does not need to do any further processing of these inodes. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alex Elder <aelder@sgi.com>
Diffstat (limited to 'fs/xfs/xfs_inode_item.c')
-rw-r--r--fs/xfs/xfs_inode_item.c14
1 files changed, 8 insertions, 6 deletions
diff --git a/fs/xfs/xfs_inode_item.c b/fs/xfs/xfs_inode_item.c
index 09983a3344a5..b1e88d56069c 100644
--- a/fs/xfs/xfs_inode_item.c
+++ b/fs/xfs/xfs_inode_item.c
@@ -681,15 +681,15 @@ xfs_inode_item_unlock(
* where the cluster buffer may be unpinned before the inode is inserted into
* the AIL during transaction committed processing. If the buffer is unpinned
* before the inode item has been committed and inserted, then it is possible
- * for the buffer to be written and IO completions before the inode is inserted
+ * for the buffer to be written and IO completes before the inode is inserted
* into the AIL. In that case, we'd be inserting a clean, stale inode into the
* AIL which will never get removed. It will, however, get reclaimed which
* triggers an assert in xfs_inode_free() complaining about freein an inode
* still in the AIL.
*
- * To avoid this, return a lower LSN than the one passed in so that the
- * transaction committed code will not move the inode forward in the AIL but
- * will still unpin it properly.
+ * To avoid this, just unpin the inode directly and return a LSN of -1 so the
+ * transaction committed code knows that it does not need to do any further
+ * processing on the item.
*/
STATIC xfs_lsn_t
xfs_inode_item_committed(
@@ -699,8 +699,10 @@ xfs_inode_item_committed(
struct xfs_inode_log_item *iip = INODE_ITEM(lip);
struct xfs_inode *ip = iip->ili_inode;
- if (xfs_iflags_test(ip, XFS_ISTALE))
- return lsn - 1;
+ if (xfs_iflags_test(ip, XFS_ISTALE)) {
+ xfs_inode_item_unpin(lip, 0);
+ return -1;
+ }
return lsn;
}