[PATCH V11 04/14] xfs: Check for extent overflow when adding/removing xattrs

[Chandan Babu R <chandanrlinux@xxxxxxxxx>]

Adding/removing an xattr can cause XFS_DA_NODE_MAXDEPTH extents to be
added. One extra extent for dabtree in case a local attr is large enough
to cause a double split.  It can also cause extent count to increase
proportional to the size of a remote xattr's value.

To be able to always remove an existing xattr, when adding an xattr we
make sure to reserve inode fork extent count required for removing max
sized xattr in addition to that required by the xattr add operation.

Signed-off-by: Chandan Babu R <chandanrlinux@xxxxxxxxx>
---
 fs/xfs/libxfs/xfs_attr.c       | 20 ++++++++++++++++++++
 fs/xfs/libxfs/xfs_inode_fork.h | 10 ++++++++++
 2 files changed, 30 insertions(+)

diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
index fd8e6418a0d3..d53b3867b308 100644
--- a/fs/xfs/libxfs/xfs_attr.c
+++ b/fs/xfs/libxfs/xfs_attr.c
@@ -396,6 +396,8 @@ xfs_attr_set(
 	struct xfs_trans_res	tres;
 	bool			rsvd = (args->attr_filter & XFS_ATTR_ROOT);
 	int			error, local;
+	int			iext_cnt;
+	int			rmt_blks;
 	unsigned int		total;
 
 	if (XFS_FORCED_SHUTDOWN(dp->i_mount))
@@ -416,6 +418,9 @@ xfs_attr_set(
 	 */
 	args->op_flags = XFS_DA_OP_OKNOENT;
 
+	rmt_blks = xfs_attr3_rmt_blocks(mp, XFS_XATTR_SIZE_MAX);
+	iext_cnt = XFS_IEXT_ATTR_MANIP_CNT(rmt_blks);
+
 	if (args->value) {
 		XFS_STATS_INC(mp, xs_attr_set);
 
@@ -442,6 +447,13 @@ xfs_attr_set(
 		tres.tr_logcount = XFS_ATTRSET_LOG_COUNT;
 		tres.tr_logflags = XFS_TRANS_PERM_LOG_RES;
 		total = args->total;
+
+		if (local)
+			rmt_blks = 0;
+		else
+			rmt_blks = xfs_attr3_rmt_blocks(mp, args->valuelen);
+
+		iext_cnt += XFS_IEXT_ATTR_MANIP_CNT(rmt_blks);
 	} else {
 		XFS_STATS_INC(mp, xs_attr_remove);
 
@@ -460,6 +472,14 @@ xfs_attr_set(
 
 	xfs_ilock(dp, XFS_ILOCK_EXCL);
 	xfs_trans_ijoin(args->trans, dp, 0);
+
+	if (args->value || xfs_inode_hasattr(dp)) {
+		error = xfs_iext_count_may_overflow(dp, XFS_ATTR_FORK,
+				iext_cnt);
+		if (error)
+			goto out_trans_cancel;
+	}
+
 	if (args->value) {
 		unsigned int	quota_flags = XFS_QMOPT_RES_REGBLKS;
 
diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
index bcac769a7df6..5de2f07d0dd5 100644
--- a/fs/xfs/libxfs/xfs_inode_fork.h
+++ b/fs/xfs/libxfs/xfs_inode_fork.h
@@ -47,6 +47,16 @@ struct xfs_ifork {
  */
 #define XFS_IEXT_PUNCH_HOLE_CNT		(1)
 
+/*
+ * Adding/removing an xattr can cause XFS_DA_NODE_MAXDEPTH extents to
+ * be added. One extra extent for dabtree in case a local attr is
+ * large enough to cause a double split.  It can also cause extent
+ * count to increase proportional to the size of a remote xattr's
+ * value.
+ */
+#define XFS_IEXT_ATTR_MANIP_CNT(rmt_blks) \
+	(XFS_DA_NODE_MAXDEPTH + max(1, rmt_blks))
+
 /*
  * Fork handling.
  */
-- 
2.28.0