xfs: always return -ENOSPC on project quota reservation failure

XFS project quota treats project hierarchies as "mini filesysems" and
so rather than -EDQUOT, the intent is to return -ENOSPC when a quota
reservation fails, but this behavior is not consistent.

The only place we make a decision between -EDQUOT and -ENOSPC
returns based on quota type is in xfs_trans_dqresv().

This behavior is currently controlled by whether or not the
XFS_QMOPT_ENOSPC flag gets passed into the quota reservation.  However,
its use is not consistent; paths such as xfs_create() and xfs_symlink()
don't set the flag, so a reservation failure will return -EDQUOT for
project quota reservation failures rather than -ENOSPC for these sorts
of operations, even for project quota:

# mkdir mnt/project
# xfs_quota -x -c "project -s -p mnt/project 42" mnt
# xfs_quota -x -c 'limit -p isoft=2 ihard=3 42' mnt
# touch mnt/project/file{1,2,3}
touch: cannot touch ‘mnt/project/file3’: Disk quota exceeded

We can make this consistent by not requiring the flag to be set at the
top of the callchain; instead we can simply test whether we are
reserving a project quota with XFS_QM_ISPDQ in xfs_trans_dqresv and if
so, return -ENOSPC for that failure.  This removes the need for the
XFS_QMOPT_ENOSPC altogether and simplifies the code a fair bit.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c
index fc93f88..27a9076 100644
--- a/fs/xfs/xfs_qm.c
+++ b/fs/xfs/xfs_qm.c
@@ -1808,7 +1808,7 @@ xfs_qm_vop_chown_reserve(
 {
 	struct xfs_mount	*mp = ip->i_mount;
 	uint64_t		delblks;
-	unsigned int		blkflags, prjflags = 0;
+	unsigned int		blkflags;
 	struct xfs_dquot	*udq_unres = NULL;
 	struct xfs_dquot	*gdq_unres = NULL;
 	struct xfs_dquot	*pdq_unres = NULL;
@@ -1849,7 +1849,6 @@ xfs_qm_vop_chown_reserve(
 
 	if (XFS_IS_PQUOTA_ON(ip->i_mount) && pdqp &&
 	    ip->i_d.di_projid != be32_to_cpu(pdqp->q_core.d_id)) {
-		prjflags = XFS_QMOPT_ENOSPC;
 		pdq_delblks = pdqp;
 		if (delblks) {
 			ASSERT(ip->i_pdquot);
@@ -1859,8 +1858,7 @@ xfs_qm_vop_chown_reserve(
 
 	error = xfs_trans_reserve_quota_bydquots(tp, ip->i_mount,
 				udq_delblks, gdq_delblks, pdq_delblks,
-				ip->i_d.di_nblocks, 1,
-				flags | blkflags | prjflags);
+				ip->i_d.di_nblocks, 1, flags | blkflags);
 	if (error)
 		return error;
 
@@ -1878,8 +1876,7 @@ xfs_qm_vop_chown_reserve(
 		ASSERT(udq_unres || gdq_unres || pdq_unres);
 		error = xfs_trans_reserve_quota_bydquots(NULL, ip->i_mount,
 			    udq_delblks, gdq_delblks, pdq_delblks,
-			    (xfs_qcnt_t)delblks, 0,
-			    flags | blkflags | prjflags);
+			    (xfs_qcnt_t)delblks, 0, flags | blkflags);
 		if (error)
 			return error;
 		xfs_trans_reserve_quota_bydquots(NULL, ip->i_mount,