[V2,09/10] xfs: Check for extent overflow when remapping an extent
diff mbox series

Message ID 20200814080833.84760-10-chandanrlinux@gmail.com
State Superseded
Headers show
Series
  • Bail out if transaction can cause extent count to overflow
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Commit Message

Chandan Babu R Aug. 14, 2020, 8:08 a.m. UTC
Remapping an extent involves unmapping the existing extent and mapping
in the new extent. When unmapping, an extent containing the entire unmap
range can be split into two extents,
i.e. | Old extent | hole | Old extent |
Hence extent count increases by 1.

Mapping in the new extent into the destination file can increase the
extent count by 1.

Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>
---
 fs/xfs/libxfs/xfs_inode_fork.h | 15 +++++++++++++++
 fs/xfs/xfs_reflink.c           |  5 +++++
 2 files changed, 20 insertions(+)

Patch
diff mbox series

diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
index d750bdff17c9..afff20703270 100644
--- a/fs/xfs/libxfs/xfs_inode_fork.h
+++ b/fs/xfs/libxfs/xfs_inode_fork.h
@@ -85,6 +85,21 @@  struct xfs_ifork {
  * Hence number of extents increases by 2.
  */
 #define XFS_IEXT_REFLINK_END_COW_CNT 2
+/*
+ * Remapping an extent involves unmapping the existing extent and
+ * mapping in the new extent.
+ * When unmapping, an extent containing the entire unmap
+ * range can be split into two extents,
+ * i.e. | Old extent | hole | Old extent |
+ * Hence extent count increases by 1.
+ *
+ * Mapping in the new extent into the destination file can increase
+ * the extent count by 1.
+ */
+#define XFS_IEXT_REFLINK_REMAP_CNT(smap_real, dmap_written) \
+	(((smap_real) ? 1 : 0) + ((dmap_written) ? 1 : 0))
+
+
 /*
  * Fork handling.
  */
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 04a7754ee681..134d49f8c941 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1100,6 +1100,11 @@  xfs_reflink_remap_extent(
 			goto out_cancel;
 	}
 
+	error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK,
+			XFS_IEXT_REFLINK_REMAP_CNT(smap_real, dmap_written));
+	if (error)
+		goto out_cancel;
+
 	if (smap_real) {
 		/*
 		 * If the extent we're unmapping is backed by storage (written