Commit 5147ef30 authored Mar 25, 2021 by Chandan Babu R Committed by Darrick J. Wong Apr 07, 2021

xfs: Fix dax inode extent calculation when direct write is performed on an unwritten extent



With dax enabled filesystems, a direct write operation into an existing
unwritten extent results in xfs_iomap_write_direct() zero-ing and converting
the extent into a normal extent before the actual data is copied from the
userspace buffer.

The inode extent count can increase by 2 if the extent range being written to
maps to the middle of the existing unwritten extent range. Hence this commit
uses XFS_IEXT_WRITE_UNWRITTEN_CNT as the extent count delta when such a write
operation is being performed.

Fixes: 727e1acd ("xfs: Check for extent overflow when trivally adding a new extent")
Reported-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

parent 25dfa65f

fs/xfs/xfs_iomap.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -198,6 +198,7 @@ xfs_iomap_write_direct(
		bool force = false;
		int error;
		int bmapi_flags = XFS_BMAPI_PREALLOC;
		int nr_exts = XFS_IEXT_ADD_NOSPLIT_CNT;

		ASSERT(count_fsb > 0);

		@@ -232,6 +233,7 @@ xfs_iomap_write_direct(
		bmapi_flags = XFS_BMAPI_CONVERT \| XFS_BMAPI_ZERO;
		if (imap->br_state == XFS_EXT_UNWRITTEN) {
		force = true;
		nr_exts = XFS_IEXT_WRITE_UNWRITTEN_CNT;
		dblocks = XFS_DIOSTRAT_SPACE_RES(mp, 0) << 1;
		}
		}
		@@ -241,8 +243,7 @@ xfs_iomap_write_direct(
		if (error)
		return error;

		error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK,
		XFS_IEXT_ADD_NOSPLIT_CNT);
		error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK, nr_exts);
		if (error)
		goto out_trans_cancel;