[PATCH 08/26] xfs: don't call xfs_exchange_range_finish for a dry run

[Eduard Zateev <hackerowskiy@gmail.com>]

From: "Darrick J. Wong" <djwong@kernel.org>

LOLLM noticed that we strip file privileges and whatnot even for a dry
run.  We also shouldn't flush dirty data to disk or trim COW staging
events for a dry run.  Neither of those behaviors are allowed by the
manpage, so fix that by exiting early on DRY_RUN in various functions.

Cc: stable@vger.kernel.org # v6.10
Fixes: 42672471f938cd ("xfs: bind together the front and back ends of the file range exchange code")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Assisted-by: LOLLM # finding obvious bugs
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
---
 fs/xfs/xfs_exchrange.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/fs/xfs/xfs_exchrange.c b/fs/xfs/xfs_exchrange.c
index 07090487c581..fafb4e3f065c 100644
--- a/fs/xfs/xfs_exchrange.c
+++ b/fs/xfs/xfs_exchrange.c
@@ -633,6 +633,9 @@ xfs_exchrange_prep(
 	if (error)
 		return error;
 
+	if (fxr->flags & XFS_EXCHANGE_RANGE_DRY_RUN)
+		return 0;
+
 	trace_xfs_exchrange_flush(fxr, ip1, ip2);
 
 	/* Flush the relevant ranges of both files. */
@@ -709,9 +712,11 @@ xfs_exchrange_contents(
 	 * other file write would do.  This may involve turning on support for
 	 * logged xattrs if either file has security capabilities.
 	 */
-	error = xfs_exchange_range_finish(fxr);
-	if (error)
-		goto out_unlock;
+	if (!(fxr->flags & XFS_EXCHANGE_RANGE_DRY_RUN)) {
+		error = xfs_exchange_range_finish(fxr);
+		if (error)
+			goto out_unlock;
+	}
 
 out_unlock:
 	xfs_iunlock2_io_mmap(ip1, ip2);
-- 
2.55.0