[PATCH V3 10/10] xfs: Check for extent overflow when swapping extents

[Chandan Babu R <chandanrlinux@gmail.com>]

Removing an initial range of source/donor file's extent and adding a new
extent (from donor/source file) in its place will cause extent count to
increase by 1.

Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>
---
 fs/xfs/libxfs/xfs_inode_fork.h |  6 ++++++
 fs/xfs/xfs_bmap_util.c         | 11 +++++++++++
 2 files changed, 17 insertions(+)

diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
index d1c675cf803a..4219b01f1034 100644
--- a/fs/xfs/libxfs/xfs_inode_fork.h
+++ b/fs/xfs/libxfs/xfs_inode_fork.h
@@ -100,6 +100,12 @@ struct xfs_ifork {
  */
 #define XFS_IEXT_REFLINK_REMAP_CNT(smap_real, dmap_written) \
 	(((smap_real) ? 1 : 0) + ((dmap_written) ? 1 : 0))
+/*
+ * Removing an initial range of source/donor file's extent and adding a new
+ * extent (from donor/source file) in its place will cause extent count to
+ * increase by 1.
+ */
+#define XFS_IEXT_SWAP_RMAP_CNT		(1)
 
 /*
  * Fork handling.
diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index e682eecebb1f..7105525dadd5 100644
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -1375,6 +1375,17 @@ xfs_swap_extent_rmap(
 		/* Unmap the old blocks in the source file. */
 		while (tirec.br_blockcount) {
 			ASSERT(tp->t_firstblock == NULLFSBLOCK);
+
+			error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK,
+					XFS_IEXT_SWAP_RMAP_CNT);
+			if (error)
+				goto out;
+
+			error = xfs_iext_count_may_overflow(tip, XFS_DATA_FORK,
+					XFS_IEXT_SWAP_RMAP_CNT);
+			if (error)
+				goto out;
+
 			trace_xfs_swap_extent_rmap_remap_piece(tip, &tirec);
 
 			/* Read extent from the source file */
-- 
2.28.0