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authorDave Chinner <dchinner@redhat.com>2022-07-14 11:47:26 +1000
committerDave Chinner <david@fromorbit.com>2022-07-14 11:47:26 +1000
commitfad743d7cd8bd92d03c09e71f29eace860f50415 (patch)
treef8a23c586653a20917e9c335b503a67bd7e5c9f7 /fs/xfs/xfs_trans.h
parent062efdb0803adac3fad039d681789c5e01818bef (diff)
xfs: add log item precommit operation
For inodes that are dirty, we have an attached cluster buffer that we want to use to track the dirty inode through the AIL. Unfortunately, locking the cluster buffer and adding it to the transaction when the inode is first logged in a transaction leads to buffer lock ordering inversions. The specific problem is ordering against the AGI buffer. When modifying unlinked lists, the buffer lock order is AGI -> inode cluster buffer as the AGI buffer lock serialises all access to the unlinked lists. Unfortunately, functionality like xfs_droplink() logs the inode before calling xfs_iunlink(), as do various directory manipulation functions. The inode can be logged way down in the stack as far as the bmapi routines and hence, without a major rewrite of lots of APIs there's no way we can avoid the inode being logged by something until after the AGI has been logged. As we are going to be using ordered buffers for inode AIL tracking, there isn't a need to actually lock that buffer against modification as all the modifications are captured by logging the inode item itself. Hence we don't actually need to join the cluster buffer into the transaction until just before it is committed. This means we do not perturb any of the existing buffer lock orders in transactions, and the inode cluster buffer is always locked last in a transaction that doesn't otherwise touch inode cluster buffers. We do this by introducing a precommit log item method. This commit just introduces the mechanism; the inode item implementation is in followup commits. The precommit items need to be sorted into consistent order as we may be locking multiple items here. Hence if we have two dirty inodes in cluster buffers A and B, and some other transaction has two separate dirty inodes in the same cluster buffers, locking them in different orders opens us up to ABBA deadlocks. Hence we sort the items on the transaction based on the presence of a sort log item method. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de>
Diffstat (limited to 'fs/xfs/xfs_trans.h')
-rw-r--r--fs/xfs/xfs_trans.h6
1 files changed, 4 insertions, 2 deletions
diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h
index 9561f193e7e1..64062e3b788b 100644
--- a/fs/xfs/xfs_trans.h
+++ b/fs/xfs/xfs_trans.h
@@ -71,10 +71,12 @@ struct xfs_item_ops {
void (*iop_format)(struct xfs_log_item *, struct xfs_log_vec *);
void (*iop_pin)(struct xfs_log_item *);
void (*iop_unpin)(struct xfs_log_item *, int remove);
- uint (*iop_push)(struct xfs_log_item *, struct list_head *);
+ uint64_t (*iop_sort)(struct xfs_log_item *lip);
+ int (*iop_precommit)(struct xfs_trans *tp, struct xfs_log_item *lip);
void (*iop_committing)(struct xfs_log_item *lip, xfs_csn_t seq);
- void (*iop_release)(struct xfs_log_item *);
xfs_lsn_t (*iop_committed)(struct xfs_log_item *, xfs_lsn_t);
+ uint (*iop_push)(struct xfs_log_item *, struct list_head *);
+ void (*iop_release)(struct xfs_log_item *);
int (*iop_recover)(struct xfs_log_item *lip,
struct list_head *capture_list);
bool (*iop_match)(struct xfs_log_item *item, uint64_t id);