[Xen-devel] [PATCH] xen-blkback: fix dispatch_rw_block_io() error path

["Jan Beulich" <JBeulich@xxxxxxxx>]

Commit 7708992 ("xen/blkback: Seperate the bio allocation and the bio
submission") consolidated the pendcnt updates to just a single write,
neglecting the fact that the error path relied on it getting set to 1
up front (such that the decrement in __end_block_io_op() would actually
drop the count to zero, triggering the necessary cleanup actions).

Also remove a misleading and a stale (after said commit) comment.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

---
 drivers/block/xen-blkback/blkback.c |    7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

--- 3.9-rc2/drivers/block/xen-blkback/blkback.c
+++ 3.9-rc2-xen-blkback-error-path-refcnt/drivers/block/xen-blkback/blkback.c
@@ -977,13 +977,7 @@ static int dispatch_rw_block_io(struct x
                bio->bi_end_io  = end_block_io_op;
        }
 
-       /*
-        * We set it one so that the last submit_bio does not have to call
-        * atomic_inc.
-        */
        atomic_set(&pending_req->pendcnt, nbio);
-
-       /* Get a reference count for the disk queue and start sending I/O */
        blk_start_plug(&plug);
 
        for (i = 0; i < nbio; i++)
@@ -1011,6 +1005,7 @@ static int dispatch_rw_block_io(struct x
  fail_put_bio:
        for (i = 0; i < nbio; i++)
                bio_put(biolist[i]);
+       atomic_set(&pending_req->pendcnt, 1);
        __end_block_io_op(pending_req, -EINVAL);
        msleep(1); /* back off a bit */
        return -EIO;

Attachment: linux-3.9-rc2-xen-blkback-error-path-refcnt.patch
Description: Text document

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