xfs: refactor inode creation transaction/inode/quota allocation idiom

For file creation, create a new helper xfs_trans_alloc_icreate that
allocates a transaction and reserves the appropriate amount of quota
against that transction.  Replace all the open-coded idioms with a
single call to this helper so that we can contain the retry loops in the
next patchset.

This changes the locking behavior for non-tempfile creation slightly, in
that we now make the quota reservation without holding the directory
ILOCK.  While the dquots chosen for inode creation are based on the
directory state at a given point in time, the directory ILOCK was
released as soon as the dquot references are picked up.  Hence it was
never necessary to hold the directory ILOCK for the quota reservation.

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

1 files changed, 33 insertions, 0 deletions

diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index 151f274eee43..6c68635cc6ac 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -21,6 +21,8 @@
 #include "xfs_error.h"
 #include "xfs_defer.h"
 #include "xfs_inode.h"
+#include "xfs_dquot_item.h"
+#include "xfs_dquot.h"
 
 kmem_zone_t	*xfs_trans_zone;
 
@@ -1074,3 +1076,34 @@ out_cancel:
 	xfs_iunlock(ip, XFS_ILOCK_EXCL);
 	return error;
 }
+
+/*
+ * Allocate an transaction in preparation for inode creation by reserving quota
+ * against the given dquots.  Callers are not required to hold any inode locks.
+ */
+int
+xfs_trans_alloc_icreate(
+	struct xfs_mount	*mp,
+	struct xfs_trans_res	*resv,
+	struct xfs_dquot	*udqp,
+	struct xfs_dquot	*gdqp,
+	struct xfs_dquot	*pdqp,
+	unsigned int		dblocks,
+	struct xfs_trans	**tpp)
+{
+	struct xfs_trans	*tp;
+	int			error;
+
+	error = xfs_trans_alloc(mp, resv, dblocks, 0, 0, &tp);
+	if (error)
+		return error;
+
+	error = xfs_trans_reserve_quota_icreate(tp, udqp, gdqp, pdqp, dblocks);
+	if (error) {
+		xfs_trans_cancel(tp);
+		return error;
+	}
+
+	*tpp = tp;
+	return 0;
+}