[PATCH 4.7 056/184] dm flakey: fix reads to be issued if drop_writes configured

[Greg Kroah-Hartman]

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

------------------

From: Mike Snitzer <snit...@redhat.com>

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 <quwen...@cn.fujitsu.com>
Signed-off-by: Mike Snitzer <snit...@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/md/dm-flakey.c |   27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

--- a/drivers/md/dm-flakey.c
+++ b/drivers/md/dm-flakey.c
@@ -289,15 +289,13 @@ static int flakey_map(struct dm_target *
                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;
                }
 
                /*
@@ -334,14 +332,21 @@ static int flakey_end_io(struct dm_targe
        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;