[PATCH V3 03/10] xfs: Check for extent overflow when deleting an extent

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

Deleting a file range from the middle of an existing extent can cause
the per-inode extent count to increase by 1. This commit checks for
extent count overflow in such cases.

Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>
---
 fs/xfs/libxfs/xfs_inode_fork.h | 6 ++++++
 fs/xfs/xfs_bmap_item.c         | 4 ++++
 fs/xfs/xfs_bmap_util.c         | 5 +++++
 3 files changed, 15 insertions(+)

diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
index 7fc2b129a2e7..2642e4847ee0 100644
--- a/fs/xfs/libxfs/xfs_inode_fork.h
+++ b/fs/xfs/libxfs/xfs_inode_fork.h
@@ -39,6 +39,12 @@ struct xfs_ifork {
  * extent to a fork and there's no possibility of splitting an existing mapping.
  */
 #define XFS_IEXT_ADD_NOSPLIT_CNT	(1)
+/*
+ * Removing an extent from the middle of an existing extent can cause the extent
+ * count to increase by 1.
+ * i.e. | Old extent | Hole | Old extent |
+ */
+#define XFS_IEXT_REMOVE_CNT		(1)
 
 /*
  * Fork handling.
diff --git a/fs/xfs/xfs_bmap_item.c b/fs/xfs/xfs_bmap_item.c
index ec3691372e7c..b9c35fb10de4 100644
--- a/fs/xfs/xfs_bmap_item.c
+++ b/fs/xfs/xfs_bmap_item.c
@@ -519,6 +519,10 @@ xfs_bui_item_recover(
 	}
 	xfs_trans_ijoin(tp, ip, 0);
 
+	error = xfs_iext_count_may_overflow(ip, whichfork, XFS_IEXT_REMOVE_CNT);
+	if (error)
+		goto err_inode;
+
 	count = bmap->me_len;
 	error = xfs_trans_log_finish_bmap_update(tp, budp, type, ip, whichfork,
 			bmap->me_startoff, bmap->me_startblock, &count, state);
diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index 7b76a48b0885..59d4da38aadf 100644
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -891,6 +891,11 @@ xfs_unmap_extent(
 
 	xfs_trans_ijoin(tp, ip, 0);
 
+	error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK,
+			XFS_IEXT_REMOVE_CNT);
+	if (error)
+		goto out_trans_cancel;
+
 	error = xfs_bunmapi(tp, ip, startoffset_fsb, len_fsb, 0, 2, done);
 	if (error)
 		goto out_trans_cancel;
-- 
2.28.0