Now that AGFL block frees are deferred when dfops is set in the
transaction, start deferring AGFL block frees from contexts that are
known to push the limits of existing log reservations.

The first such context is deferred operation processing itself. This
primarily targets deferred extent frees (such as file extents and
inode chunks), but in doing so covers all allocation operations that
occur in deferred operation processing context.

Update xfs_defer_finish() to set and reset ->t_agfl_dfops across the
processing sequence. This means that any AGFL block frees due to
allocation events result in the addition of new EFIs to the dfops
rather than being processed immediately. xfs_defer_finish() rolls
the transaction at least once more to process the frees of the AGFL
blocks back to the allocation btrees and returns once the AGFL is
rectified.
Signed-off-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

In certain cases, defer_ops callers will lock a buffer and want to hold
the lock across transaction rolls.  Similar to ijoined inodes, we want
to dirty & join the buffer with each transaction roll in defer_finish so
that afterwards the caller still owns the buffer lock and we haven't
inadvertently pinned the log.
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>

And instead require callers to explicitly join the inode using
xfs_defer_ijoin.  Also consolidate the defer error handling in
a few places using a goto label.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

Split xfs_trans_roll into a low-level helper that just rolls the
actual transaction and a new higher level xfs_trans_roll_inode
that takes care of logging and rejoining the inode.  This gets
rid of the NULL inode case, and allows to simplify the special
cases in the deferred operation code.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

If the deferred ops transaction roll fails, we need to abort the intent
items if we haven't already logged a done item for it, regardless of
whether or not the deferred ops has had a transaction committed.  Dave
found this while running generic/388.

Move the tracepoint to make it easier to track object lifetimes.
Reported-by: NDave Chinner <david@fromorbit.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NDave Chinner <david@fromorbit.com>

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: NDarrick 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: NDarrick J. Wong <darrick.wong@oracle.com>
Reported-by: NChristoph Hellwig <hch@infradead.org>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NDave 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: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NDave 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: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NDave Chinner <david@fromorbit.com>