dm: simplify dm_request loop

Refactor the code in dm_request().

Require the new DMF_BLOCK_FOR_SUSPEND flag on readahead bios we will
discard so we don't drop such bios while processing a barrier.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 7 insertions, 11 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 7cac7220937f..bb97ec8d6644 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -929,7 +929,6 @@ out:
  */
 static int dm_request(struct request_queue *q, struct bio *bio)
 {
-        int r = -EIO;
         int rw = bio_data_dir(bio);
         struct mapped_device *md = q->queuedata;
         int cpu;
@@ -957,11 +956,14 @@ static int dm_request(struct request_queue *q, struct bio *bio)
         while (test_bit(DMF_QUEUE_IO_TO_THREAD, &md->flags)) {
                 up_read(&md->io_lock);
 
-                if (bio_rw(bio) != READA)
-                        r = queue_io(md, bio);
+                if (unlikely(test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags)) &&
+                    bio_rw(bio) == READA) {
+                        bio_io_error(bio);
+                        return 0;
+                }
 
-                if (r <= 0)
-                        goto out_req;
+                if (!queue_io(md, bio))
+                        return 0;
 
                 /*
                  * We're in a while loop, because someone could suspend
@@ -973,12 +975,6 @@ static int dm_request(struct request_queue *q, struct bio *bio)
         __split_and_process_bio(md, bio);
         up_read(&md->io_lock);
         return 0;
-
-out_req:
-        if (r < 0)
-                bio_io_error(bio);
-
-        return 0;
 }
 
 static void dm_unplug_all(struct request_queue *q)