ide-disk: Fix request requeuing

Simon Kirby reported that on his RAID setup with idedisk underneath
the box OOMs after a couple of days of runtime. Running with
CONFIG_DEBUG_KMEMLEAK pointed to idedisk_prep_fn() which unconditionally
allocates an ide_cmd struct. However, ide_requeue_and_plug() can be
called more than once per request, either from the request issue or the
IRQ handler path and do blk_peek_request() ends up in idedisk_prep_fn()
repeatedly, allocating a struct ide_cmd everytime and "forgetting" the
previous pointer.

Make sure the code reuses the old allocated chunk.

Reported-and-tested-by: Simon Kirby <sim@hostway.ca>
Cc: <stable@kernel.org> [ 39.x, 3.0.x ]
Link: http://marc.info/?l=linux-kernel&m=131667641517919
Link: http://lkml.kernel.org/r/20110922072643.GA27232@hostway.ca
Signed-off-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/ide/ide-disk.c b/drivers/ide/ide-disk.c
index 274798068a54..16f69be820c7 100644
--- a/drivers/ide/ide-disk.c
+++ b/drivers/ide/ide-disk.c
@@ -435,7 +435,12 @@ static int idedisk_prep_fn(struct request_queue *q, struct request *rq)
         if (!(rq->cmd_flags & REQ_FLUSH))
                 return BLKPREP_OK;
 
-        cmd = kzalloc(sizeof(*cmd), GFP_ATOMIC);
+        if (rq->special) {
+                cmd = rq->special;
+                memset(cmd, 0, sizeof(*cmd));
+        } else {
+                cmd = kzalloc(sizeof(*cmd), GFP_ATOMIC);
+        }
 
         /* FIXME: map struct ide_taskfile on rq->cmd[] */
         BUG_ON(cmd == NULL);