linux-kernel - [PATCH 3.12 080/119] dm flakey: fix reads to be issued if drop

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Message-Id: <bc45be8519f7dd6a0aa98c95e37a0b3a74c62423.1475144721.git.jslaby@suse.cz>
Date:   Thu, 29 Sep 2016 12:25:16 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Mike Snitzer <snitzer@...hat.com>,
        Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 080/119] dm flakey: fix reads to be issued if drop_writes configured

From: Mike Snitzer <snitzer@...hat.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 299f6230bc6d0ccd5f95bb0fb865d80a9c7d5ccc upstream.

v4.8-rc3 commit 99f3c90d0d ("dm flakey: error READ bios during the
down_interval") overlooked the 'drop_writes' feature, which is meant to
allow reads to be issued rather than errored, during the down_interval.

Fixes: 99f3c90d0d ("dm flakey: error READ bios during the down_interval")
Reported-by: Qu Wenruo <quwenruo@...fujitsu.com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 drivers/md/dm-flakey.c | 27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/drivers/md/dm-flakey.c b/drivers/md/dm-flakey.c
index 8e36248f729f..c8ac0ed9d206 100644
--- a/drivers/md/dm-flakey.c
+++ b/drivers/md/dm-flakey.c
@@ -286,15 +286,13 @@ static int flakey_map(struct dm_target *ti, struct bio *bio)
 		pb->bio_submitted = true;
 
 		/*
-		 * Map reads as normal only if corrupt_bio_byte set.
+		 * Error reads if neither corrupt_bio_byte or drop_writes are set.
+		 * Otherwise, flakey_end_io() will decide if the reads should be modified.
 		 */
 		if (bio_data_dir(bio) == READ) {
-			/* If flags were specified, only corrupt those that match. */
-			if (fc->corrupt_bio_byte && (fc->corrupt_bio_rw == READ) &&
-			    all_corrupt_bio_flags_match(bio, fc))
-				goto map_bio;
-			else
+			if (!fc->corrupt_bio_byte && !test_bit(DROP_WRITES, &fc->flags))
 				return -EIO;
+			goto map_bio;
 		}
 
 		/*
@@ -331,14 +329,21 @@ static int flakey_end_io(struct dm_target *ti, struct bio *bio, int error)
 	struct flakey_c *fc = ti->private;
 	struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
 
-	/*
-	 * Corrupt successful READs while in down state.
-	 */
 	if (!error && pb->bio_submitted && (bio_data_dir(bio) == READ)) {
-		if (fc->corrupt_bio_byte)
+		if (fc->corrupt_bio_byte && (fc->corrupt_bio_rw == READ) &&
+		    all_corrupt_bio_flags_match(bio, fc)) {
+			/*
+			 * Corrupt successful matching READs while in down state.
+			 */
 			corrupt_bio_data(bio, fc);
-		else
+
+		} else if (!test_bit(DROP_WRITES, &fc->flags)) {
+			/*
+			 * Error read during the down_interval if drop_writes
+			 * wasn't configured.
+			 */
 			return -EIO;
+		}
 	}
 
 	return error;
-- 
2.10.0