When xfs_defer_finish calls ->finish_item, it's possible that
(refcount) won't be able to finish all the work in a single
transaction. When this happens, the ->finish_item handler should
shorten the log done item's list count, update the work item to
reflect where work should continue, and return -EAGAIN so that
defer_finish knows to retain the pending item on the pending list,
roll the transaction, and restart processing where we left off.
Plumb in the code and document how this mechanism is supposed to work.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Christoph reports slab corruption when a deferred refcount update
aborts during _defer_finish(). The cause of this was broken log item
state tracking in xfs_defer_pending -- upon an abort,
_defer_trans_abort() will call abort_intent on all intent items,
including the ones that have already had a done item attached.
This is incorrect because each intent item has 2 refcount: the first
is released when the intent item is committed to the log; and the
second is released when the _done_ item is committed to the log, or
by the intent creator if there is no done item. In other words, once
we log the done item, responsibility for releasing the intent item's
second refcount is transferred to the done item and /must not/ be
performed by anything else.
The dfp_committed flag should have been tracking whether or not we had
a done item so that _defer_trans_abort could decide if it needs to
abort the intent item, but due to a thinko this was not the case. Rip
it out and track the done item directly so that we do the right thing
w.r.t. intent item freeing.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reported-by: Christoph Hellwig <hch@infradead.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Add tracepoints for the internals of the deferred ops mechanism
and tracepoint classes for clients of the dops, to make debugging
easier.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
All the code around struct xfs_bmap_free basically implements a
deferred operation framework through which we can roll transactions
(to unlock buffers and avoid violating lock order rules) while
managing all the necessary log redo items. Previously we only used
this code to free extents after some sort of mapping operation, but
with the advent of rmap and reflink, we suddenly need to do more than
that.
With that in mind, xfs_bmap_free really becomes a deferred ops control
structure. Rename the structure and move the deferred ops into their
own file to avoid further bloating of the bmap code.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
