[PATCH V4 09/10] 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_bmap.c       | 18 +++++++++---------
 fs/xfs/libxfs/xfs_bmap.h       |  1 +
 fs/xfs/libxfs/xfs_inode_fork.h |  7 +++++++
 fs/xfs/xfs_bmap_util.c         | 17 +++++++++++++++++
 4 files changed, 34 insertions(+), 9 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 51c2d2690f05..9c665e379dfc 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -6104,15 +6104,6 @@ xfs_bmap_split_extent(
 	return error;
 }
 
-/* Deferred mapping is only for real extents in the data fork. */
-static bool
-xfs_bmap_is_update_needed(
-	struct xfs_bmbt_irec	*bmap)
-{
-	return  bmap->br_startblock != HOLESTARTBLOCK &&
-		bmap->br_startblock != DELAYSTARTBLOCK;
-}
-
 /* Record a bmap intent. */
 static int
 __xfs_bmap_add(
@@ -6144,6 +6135,15 @@ __xfs_bmap_add(
 	return 0;
 }
 
+/* Deferred mapping is only for real extents in the data fork. */
+bool
+xfs_bmap_is_update_needed(
+	struct xfs_bmbt_irec	*bmap)
+{
+	return  bmap->br_startblock != HOLESTARTBLOCK &&
+		bmap->br_startblock != DELAYSTARTBLOCK;
+}
+
 /* Map an extent into a file. */
 void
 xfs_bmap_map_extent(
diff --git a/fs/xfs/libxfs/xfs_bmap.h b/fs/xfs/libxfs/xfs_bmap.h
index e1bd484e5548..60fbe184d5f4 100644
--- a/fs/xfs/libxfs/xfs_bmap.h
+++ b/fs/xfs/libxfs/xfs_bmap.h
@@ -263,6 +263,7 @@ struct xfs_bmap_intent {
 	struct xfs_bmbt_irec			bi_bmap;
 };
 
+bool	xfs_bmap_is_update_needed(struct xfs_bmbt_irec *bmap);
 int	xfs_bmap_finish_one(struct xfs_trans *tp, struct xfs_inode *ip,
 		enum xfs_bmap_intent_type type, int whichfork,
 		xfs_fileoff_t startoff, xfs_fsblock_t startblock,
diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
index ded3c1b56c94..837c01595439 100644
--- a/fs/xfs/libxfs/xfs_inode_fork.h
+++ b/fs/xfs/libxfs/xfs_inode_fork.h
@@ -102,6 +102,13 @@ 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 0776abd0103c..542f990247c4 100644
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -28,6 +28,7 @@
 #include "xfs_icache.h"
 #include "xfs_iomap.h"
 #include "xfs_reflink.h"
+#include "xfs_bmap.h"
 
 /* Kernel only BMAP related definitions and functions */
 
@@ -1407,6 +1408,22 @@ xfs_swap_extent_rmap(
 					irec.br_blockcount);
 			trace_xfs_swap_extent_rmap_remap_piece(tip, &uirec);
 
+			if (xfs_bmap_is_update_needed(&uirec)) {
+				error = xfs_iext_count_may_overflow(ip,
+						XFS_DATA_FORK,
+						XFS_IEXT_SWAP_RMAP_CNT);
+				if (error)
+					goto out;
+			}
+
+			if (xfs_bmap_is_update_needed(&irec)) {
+				error = xfs_iext_count_may_overflow(tip,
+						XFS_DATA_FORK,
+						XFS_IEXT_SWAP_RMAP_CNT);
+				if (error)
+					goto out;
+			}
+
 			/* Remove the mapping from the donor file. */
 			xfs_bmap_unmap_extent(tp, tip, &uirec);
 
-- 
2.28.0