From: Chandan Babu R <chandanrlinux@gmail.com>
Date: Mon, 5 Apr 2021 21:58:16 +0000 (-0400)
Subject: xfs: Check for extent overflow when writing to unwritten extent
X-Git-Tag: v5.12.0-rc0~17
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=b4024c158d4c5bf8efc1cac965783fd8444b032e;p=thirdparty%2Fxfsprogs-dev.git

xfs: Check for extent overflow when writing to unwritten extent

Source kernel commit: c442f3086d5a108b7ff086c8ade1923a8f389db5

A write to a sub-interval of an existing unwritten extent causes
the original extent to be split into 3 extents
i.e. | Unwritten | Real | Unwritten |
Hence extent count can increase by 2.

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>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
---

diff --git a/libxfs/xfs_inode_fork.h b/libxfs/xfs_inode_fork.h
index 8d89838e2..917e289ad 100644
--- a/libxfs/xfs_inode_fork.h
+++ b/libxfs/xfs_inode_fork.h
@@ -70,6 +70,15 @@ struct xfs_ifork {
 #define XFS_IEXT_ATTR_MANIP_CNT(rmt_blks) \
 	(XFS_DA_NODE_MAXDEPTH + max(1, rmt_blks))
 
+/*
+ * A write to a sub-interval of an existing unwritten extent causes the original
+ * extent to be split into 3 extents
+ * i.e. | Unwritten | Real | Unwritten |
+ * Hence extent count can increase by 2.
+ */
+#define XFS_IEXT_WRITE_UNWRITTEN_CNT	(2)
+
+
 /*
  * Fork handling.
  */