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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "stable@vger.kernel.org" <stable@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     John Pittman <jpittman@redhat.com>,
        Mike Snitzer <snitzer@redhat.com>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL 4.18 093/131] dm cache: only allow a single io_mode
 cache feature to be requested
Thread-Topic: [PATCH AUTOSEL 4.18 093/131] dm cache: only allow a single
 io_mode cache feature to be requested
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Date:   Sun, 2 Sep 2018 13:05:01 +0000
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From: John Pittman <jpittman@redhat.com>

[ Upstream commit af9313c32c0fa2a0ac3b113669273833d60cc9de ]

More than one io_mode feature can be requested when creating a dm cache
device (as is: last one wins).  The io_mode selections are incompatible
with one another, we should force them to be selected exclusively.  Add
a counter to check for more than one io_mode selection.

Fixes: 629d0a8a1a10 ("dm cache metadata: add "metadata2" feature")
Signed-off-by: John Pittman <jpittman@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 drivers/md/dm-cache-target.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index ce14a3d1f609..44df244807e5 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -2250,7 +2250,7 @@ static int parse_features(struct cache_args *ca, stru=
ct dm_arg_set *as,
 		{0, 2, "Invalid number of cache feature arguments"},
 	};
=20
-	int r;
+	int r, mode_ctr =3D 0;
 	unsigned argc;
 	const char *arg;
 	struct cache_features *cf =3D &ca->features;
@@ -2264,14 +2264,20 @@ static int parse_features(struct cache_args *ca, st=
ruct dm_arg_set *as,
 	while (argc--) {
 		arg =3D dm_shift_arg(as);
=20
-		if (!strcasecmp(arg, "writeback"))
+		if (!strcasecmp(arg, "writeback")) {
 			cf->io_mode =3D CM_IO_WRITEBACK;
+			mode_ctr++;
+		}
=20
-		else if (!strcasecmp(arg, "writethrough"))
+		else if (!strcasecmp(arg, "writethrough")) {
 			cf->io_mode =3D CM_IO_WRITETHROUGH;
+			mode_ctr++;
+		}
=20
-		else if (!strcasecmp(arg, "passthrough"))
+		else if (!strcasecmp(arg, "passthrough")) {
 			cf->io_mode =3D CM_IO_PASSTHROUGH;
+			mode_ctr++;
+		}
=20
 		else if (!strcasecmp(arg, "metadata2"))
 			cf->metadata_version =3D 2;
@@ -2282,6 +2288,11 @@ static int parse_features(struct cache_args *ca, str=
uct dm_arg_set *as,
 		}
 	}
=20
+	if (mode_ctr > 1) {
+		*error =3D "Duplicate cache io_mode features requested";
+		return -EINVAL;
+	}
+
 	return 0;
 }
=20
--=20
2.17.1