xfs: rewrite xfs_dq_get_next_id using xfs_iext_lookup_extent

This goes straight to a single lookup in the extent list and avoids a
roundtrip through two layers that don't add any value for the simple
quoata file that just has data or holes and no page cache, delayed
allocation, unwritten extent or COW fork (which btw, doesn't seem to
be handled by the existing SEEK HOLE/DATA code).
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/xfs_dquot.c

@@ -701,21 +701,18 @@ xfs_qm_dqread(
  */
 static int
 xfs_dq_get_next_id(
-	xfs_mount_t		*mp,
+	struct xfs_mount	*mp,
 	uint			type,
-	xfs_dqid_t		*id,
-	loff_t			eof)
+	xfs_dqid_t		*id)
 {
-	struct xfs_inode	*quotip;
+	struct xfs_inode	*quotip = xfs_quota_inode(mp, type);
+	xfs_dqid_t		next_id = *id + 1; /* simple advance */
+	uint			lock_flags;
+	struct xfs_bmbt_irec	got;
+	xfs_extnum_t		idx;
 	xfs_fsblock_t		start;
-	loff_t			offset;
-	uint			lock;
-	xfs_dqid_t		next_id;
 	int			error = 0;
 
-	/* Simple advance */
-	next_id = *id + 1;
-
 	/* If we'd wrap past the max ID, stop */
 	if (next_id < *id)
 		return -ENOENT;
@@ -729,23 +726,20 @@ xfs_dq_get_next_id(
 	/* Nope, next_id is now past the current chunk, so find the next one */
 	start = (xfs_fsblock_t)next_id / mp->m_quotainfo->qi_dqperchunk;
 
-	quotip = xfs_quota_inode(mp, type);
-	lock = xfs_ilock_data_map_shared(quotip);
-
-	offset = __xfs_seek_hole_data(VFS_I(quotip), XFS_FSB_TO_B(mp, start),
-				      eof, SEEK_DATA);
-	if (offset < 0)
-		error = offset;
-
-	xfs_iunlock(quotip, lock);
+	lock_flags = xfs_ilock_data_map_shared(quotip);
+	if (!(quotip->i_df.if_flags & XFS_IFEXTENTS)) {
+		error = xfs_iread_extents(NULL, quotip, XFS_DATA_FORK);
+		if (error)
+			return error;
+	}
 
-	/* -ENXIO is essentially "no more data" */
-	if (error)
-		return (error == -ENXIO ? -ENOENT: error);
+	if (xfs_iext_lookup_extent(quotip, &quotip->i_df, start, &idx, &got))
+		*id = got.br_startoff * mp->m_quotainfo->qi_dqperchunk;
+	else
+		error = -ENOENT;
+	xfs_iunlock(quotip, lock_flags);
 
-	/* Convert next data offset back to a quota id */
-	*id = XFS_B_TO_FSB(mp, offset) * mp->m_quotainfo->qi_dqperchunk;
-	return 0;
+	return error;
 }
 
 /*
@@ -768,7 +762,6 @@ xfs_qm_dqget(
 	struct xfs_quotainfo	*qi = mp->m_quotainfo;
 	struct radix_tree_root *tree = xfs_dquot_tree(qi, type);
 	struct xfs_dquot	*dqp;
-	loff_t			eof = 0;
 	int			error;
 
 	ASSERT(XFS_IS_QUOTA_RUNNING(mp));
@@ -796,21 +789,6 @@ xfs_qm_dqget(
 	}
 #endif
 
-	/* Get the end of the quota file if we need it */
-	if (flags & XFS_QMOPT_DQNEXT) {
-		struct xfs_inode	*quotip;
-		xfs_fileoff_t		last;
-		uint			lock_mode;
-
-		quotip = xfs_quota_inode(mp, type);
-		lock_mode = xfs_ilock_data_map_shared(quotip);
-		error = xfs_bmap_last_offset(quotip, &last, XFS_DATA_FORK);
-		xfs_iunlock(quotip, lock_mode);
-		if (error)
-			return error;
-		eof = XFS_FSB_TO_B(mp, last);
-	}
-
 restart:
 	mutex_lock(&qi->qi_tree_lock);
 	dqp = radix_tree_lookup(tree, id);
@@ -829,7 +807,7 @@ xfs_qm_dqget(
 			if (XFS_IS_DQUOT_UNINITIALIZED(dqp)) {
 				xfs_dqunlock(dqp);
 				mutex_unlock(&qi->qi_tree_lock);
-				error = xfs_dq_get_next_id(mp, type, &id, eof);
+				error = xfs_dq_get_next_id(mp, type, &id);
 				if (error)
 					return error;
 				goto restart;
@@ -864,7 +842,7 @@ xfs_qm_dqget(
 
 	/* If we are asked to find next active id, keep looking */
 	if (error == -ENOENT && (flags & XFS_QMOPT_DQNEXT)) {
-		error = xfs_dq_get_next_id(mp, type, &id, eof);
+		error = xfs_dq_get_next_id(mp, type, &id);
 		if (!error)
 			goto restart;
 	}
@@ -923,7 +901,7 @@ xfs_qm_dqget(
 	if (flags & XFS_QMOPT_DQNEXT) {
 		if (XFS_IS_DQUOT_UNINITIALIZED(dqp)) {
 			xfs_qm_dqput(dqp);
-			error = xfs_dq_get_next_id(mp, type, &id, eof);
+			error = xfs_dq_get_next_id(mp, type, &id);
 			if (error)
 				return error;
 			goto restart;