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xfs: only run precommits once per transaction object

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Committing a transaction tx0 with a defer ops chain of (A, B, C)
creates a chain of transactions that looks like this:

tx0 -> txA -> txB -> txC

Prior to commit cb04211748, __xfs_trans_commit would run precommits
on tx0, then call xfs_defer_finish_noroll to convert A-C to tx[A-C].
Unfortunately, after the finish_noroll loop we forgot to run precommits
on txC.  That was fixed by adding the second precommit call.

Unfortunately, none of us remembered that xfs_defer_finish_noroll
calls __xfs_trans_commit a second time to commit tx0 before finishing
work A in txA and committing that.  In other words, we run precommits
twice on tx0:

xfs_trans_commit(tx0)
    __xfs_trans_commit(tx0, false)
        xfs_trans_run_precommits(tx0)
        xfs_defer_finish_noroll(tx0)
            xfs_trans_roll(tx0)
                txA = xfs_trans_dup(tx0)
                __xfs_trans_commit(tx0, true)
                xfs_trans_run_precommits(tx0)

This currently isn't an issue because the inode item precommit is
idempotent; the iunlink item precommit deletes itself so it can't be
called again; and the buffer/dquot item precommits only check the incore
objects for corruption.  However, it doesn't make sense to run
precommits twice.

Fix this situation by only running precommits after finish_noroll.

Cc: <stable@vger.kernel.org> # v6.4
Fixes: cb04211748 ("xfs: defered work could create precommits")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Darrick J. Wong 2024-12-02 10:57:33 -08:00
parent 53b001a21c
commit 44d9b07e52
1 changed files with 4 additions and 12 deletions
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16
fs/xfs/xfs_trans.c
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@ -860,13 +860,6 @@ __xfs_trans_commit(
trace_xfs_trans_commit(tp, _RET_IP_);
error = xfs_trans_run_precommits(tp);
if (error) {
if (tp->t_flags & XFS_TRANS_PERM_LOG_RES)
xfs_defer_cancel(tp);
goto out_unreserve;
}
/*
* Finish deferred items on final commit. Only permanent transactions
* should ever have deferred ops.
@ -877,13 +870,12 @@ __xfs_trans_commit(
error = xfs_defer_finish_noroll(&tp);
if (error)
goto out_unreserve;
/* Run precommits from final tx in defer chain. */
error = xfs_trans_run_precommits(tp);
if (error)
goto out_unreserve;
}
error = xfs_trans_run_precommits(tp);
if (error)
goto out_unreserve;
/*
* If there is nothing to be logged by the transaction,
* then unlock all of the items associated with the