[PATCH V8 03/14] xfs: Check for extent overflow when punching a hole

Chandan Babu R
2020-10-29T10:14:34Z

The extent mapping the file offset at which a hole has to be
inserted will be split into two extents causing extent count to
increase by 1.

Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>
---
fs/xfs/libxfs/xfs_inode_fork.h | 7 +++++++
fs/xfs/xfs_bmap_item.c | 15 +++++++++------
fs/xfs/xfs_bmap_util.c | 10 ++++++++++
3 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
index 7fc2b129a2e7..bcac769a7df6 100644
--- a/fs/xfs/libxfs/xfs_inode_fork.h
+++ b/fs/xfs/libxfs/xfs_inode_fork.h
@@ -40,6 +40,13 @@ struct xfs_ifork {
*/
#define XFS_IEXT_ADD_NOSPLIT_CNT (1)

+/*
+ * Punching out 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_PUNCH_HOLE_CNT (1)
+
/*
* Fork handling.
*/
diff --git a/fs/xfs/xfs_bmap_item.c b/fs/xfs/xfs_bmap_item.c
index 1610d6ad089b..80d828394158 100644
--- a/fs/xfs/xfs_bmap_item.c
+++ b/fs/xfs/xfs_bmap_item.c
@@ -439,6 +439,7 @@ xfs_bui_item_recover(
xfs_exntst_t state;
unsigned int bui_type;
int whichfork;
+ int iext_delta;
int error = 0;

/* Only one mapping operation per BUI... */
@@ -497,12 +498,14 @@ xfs_bui_item_recover(
xfs_ilock(ip, XFS_ILOCK_EXCL);
xfs_trans_ijoin(tp, ip, 0);

- if (bui_type == XFS_BMAP_MAP) {
- error = xfs_iext_count_may_overflow(ip, whichfork,
- XFS_IEXT_ADD_NOSPLIT_CNT);
- if (error)
- goto err_cancel;
- }
+ if (bui_type == XFS_BMAP_MAP)
+ iext_delta = XFS_IEXT_ADD_NOSPLIT_CNT;
+ else
+ iext_delta = XFS_IEXT_PUNCH_HOLE_CNT;
+
+ error = xfs_iext_count_may_overflow(ip, whichfork, iext_delta);
+ if (error)
+ goto err_cancel;

count = bmap->me_len;
error = xfs_trans_log_finish_bmap_update(tp, budp, bui_type, ip,
diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index dcd6e61df711..0776abd0103c 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_PUNCH_HOLE_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;
@@ -1176,6 +1181,11 @@ xfs_insert_file_space(
xfs_ilock(ip, XFS_ILOCK_EXCL);
xfs_trans_ijoin(tp, ip, 0);

+ error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK,
+ XFS_IEXT_PUNCH_HOLE_CNT);
+ if (error)
+ goto out_trans_cancel;
+
/*
* The extent shifting code works on extent granularity. So, if stop_fsb
* is not the starting block of extent, we need to split the extent at
--
2.28.0