xfs: use xfs_defer_pending objects to recover intent items

One thing I never quite got around to doing is porting the log intent
item recovery code to reconstruct the deferred pending work state.  As a
result, each intent item open codes xfs_defer_finish_one in its recovery
method, because that's what the EFI code did before xfs_defer.c even
existed.

This is a gross thing to have left unfixed -- if an EFI cannot proceed
due to busy extents, we end up creating separate new EFIs for each
unfinished work item, which is a change in behavior from what runtime
would have done.

Worse yet, Long Li pointed out that there's a UAF in the recovery code.
The ->commit_pass2 function adds the intent item to the AIL and drops
the refcount.  The one remaining refcount is now owned by the recovery
mechanism (aka the log intent items in the AIL) with the intent of
giving the refcount to the intent done item in the ->iop_recover
function.

However, if something fails later in recovery, xlog_recover_finish will
walk the recovered intent items in the AIL and release them.  If the CIL
hasn't been pushed before that point (which is possible since we don't
force the log until later) then the intent done release will try to free
its associated intent, which has already been freed.

This patch starts to address this mess by having the ->commit_pass2
functions recreate the xfs_defer_pending state.  The next few patches
will fix the recovery functions.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
index fa3ad1d7b31c..e30c06ec20e3 100644
--- a/fs/xfs/xfs_log_priv.h
+++ b/fs/xfs/xfs_log_priv.h
@@ -407,6 +407,7 @@ struct xlog {
 	long			l_opstate;	/* operational state */
 	uint			l_quotaoffs_flag; /* XFS_DQ_*, for QUOTAOFFs */
 	struct list_head	*l_buf_cancel_table;
+	struct list_head	r_dfops;	/* recovered log intent items */
 	int			l_iclog_hsize;  /* size of iclog header */
 	int			l_iclog_heads;  /* # of iclog header sectors */
 	uint			l_sectBBsize;   /* sector size in BBs (2^n) */