On Mon, Jan 05, 2015 at 12:00:58PM -0700, Jens Axboe wrote:
> That's not quite true, the only guarantee is that it WILL execute on the
> CPU (or CPUs) that are set in the mask. So unless it ends up offloading
> the run to a specific workqueue, we'll disable preempt in the current
> path before ->queue_rq() is called.
Oops. Indeed, with those recent changes ->queue_rq can't safely block
for memory allocatios anymore.
The patch below should fix it:
---
From: Christoph Hellwig <hch@xxxxxx>
Subject: scsi: ->queue_rq can't sleep
Since Linux 3.19 blk-mq may disable preemption before calling into
->queue_rq, so we can't actually sleep anymore.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
drivers/scsi/scsi_lib.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 9ea95dd..6d5c0b8 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -591,7 +591,6 @@ static void scsi_free_sgtable(struct scsi_data_buffer *sdb, bool mq)
static int scsi_alloc_sgtable(struct scsi_data_buffer *sdb, int nents, bool mq)
{
struct scatterlist *first_chunk = NULL;
- gfp_t gfp_mask = mq ? GFP_NOIO : GFP_ATOMIC;
int ret;
BUG_ON(!nents);
@@ -606,7 +605,7 @@ static int scsi_alloc_sgtable(struct scsi_data_buffer *sdb, int nents, bool mq)
}
ret = __sg_alloc_table(&sdb->table, nents, SCSI_MAX_SG_SEGMENTS,
- first_chunk, gfp_mask, scsi_sg_alloc);
+ first_chunk, GFP_ATOMIC, scsi_sg_alloc);
if (unlikely(ret))
scsi_free_sgtable(sdb, mq);
return ret;
--
1.9.1
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