[PATCH v2 03/23] xfs: fix exchmaps reservation limit check

[Andrey Albershteyn <aalbersh@kernel.org>]

From: Yingjie Gao <gaoyingjie@uniontech.com>

Source kernel commit: 0a5213bbff62b51c7d4999ac8c7e11ea57d00d45

xfs_exchmaps_estimate_overhead() adds the bmbt and rmapbt
overhead to a local resblks variable, but the final UINT_MAX
check still tests req->resblks.  That is the reservation value
from before the overhead was added.

The computed value is stored back in req->resblks and later passed
to xfs_trans_alloc(), whose block reservation argument is unsigned
int.  Check the computed reservation so the existing limit applies
to the value that will be used.

Fixes: 966ceafc7a43 ("xfs: create deferred log items for file mapping exchanges")
Signed-off-by: Yingjie Gao <gaoyingjie@uniontech.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 libxfs/xfs_exchmaps.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libxfs/xfs_exchmaps.c b/libxfs/xfs_exchmaps.c
index 5566f9faf456..651c3784caba 100644
--- a/libxfs/xfs_exchmaps.c
+++ b/libxfs/xfs_exchmaps.c
@@ -708,7 +708,7 @@ xfs_exchmaps_estimate_overhead(
 		return -ENOSPC;
 
 	/* Can't actually reserve more than UINT_MAX blocks. */
-	if (req->resblks > UINT_MAX)
+	if (resblks > UINT_MAX)
 		return -ENOSPC;
 
 	req->resblks = resblks;
-- 
2.55.0