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>

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 7cac7220937f72792b916d5cf597cd8c0d59d233..bb97ec8d664488fb796b56494f17cff433072f0e 100644 (file)
--- 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)