01_scsi_reqfn_consolidate_error_handling.patch
This patch fixes a queue stall bug which occurred when sgtable
allocation failed and device_busy == 0. When scsi_init_io()
returns BLKPREP_DEFER or BLKPREP_KILL, it's supposed to free
resources itself. This patch consolidates defer and kill
handling into scsi_prep_fn().
Note that this patch doesn't consolidate state defer/kill
handlings in scsi_prep_fn(). They were omitted as all state
checks will be moved into scsi_reques_fn() by the following
reqfn_reimpl patch.
ret value checking was changed to switch() as in James's
patch. Also, kill: comment is copied from James's patch.
Signed-off-by: Tejun Heo <htejun@xxxxxxxxx>
scsi_lib.c | 46 +++++++++++++++++++++++++++++++---------------
1 files changed, 31 insertions(+), 15 deletions(-)
Index: scsi-reqfn-export/drivers/scsi/scsi_lib.c
===================================================================
--- scsi-reqfn-export.orig/drivers/scsi/scsi_lib.c 2005-04-12 19:27:55.000000000 +0900
+++ scsi-reqfn-export/drivers/scsi/scsi_lib.c 2005-04-12 19:27:55.000000000 +0900
@@ -945,10 +945,8 @@ static int scsi_init_io(struct scsi_cmnd
* if sg table allocation fails, requeue request later.
*/
sgpnt = scsi_alloc_sgtable(cmd, GFP_ATOMIC);
- if (unlikely(!sgpnt)) {
- req->flags |= REQ_SOFTBARRIER;
+ if (unlikely(!sgpnt))
return BLKPREP_DEFER;
- }
cmd->request_buffer = (char *) sgpnt;
cmd->request_bufflen = req->nr_sectors << 9;
@@ -975,9 +973,6 @@ static int scsi_init_io(struct scsi_cmnd
printk(KERN_ERR "req nr_sec %lu, cur_nr_sec %u\n", req->nr_sectors,
req->current_nr_sectors);
- /* release the command and kill it */
- scsi_release_buffers(cmd);
- scsi_put_command(cmd);
return BLKPREP_KILL;
}
@@ -1145,18 +1140,24 @@ static int scsi_prep_fn(struct request_q
* required).
*/
ret = scsi_init_io(cmd);
- if (ret) /* BLKPREP_KILL return also releases the command */
- return ret;
+ switch (ret) {
+ case 0:
+ /* Successful initialization. */
+ break;
+ case BLKPREP_DEFER:
+ goto defer;
+ default:
+ /* Unknown return value, fall through. */
+ case BLKPREP_KILL:
+ goto kill;
+ }
/*
* Initialize the actual SCSI command for this request.
*/
drv = *(struct scsi_driver **)req->rq_disk->private_data;
- if (unlikely(!drv->init_command(cmd))) {
- scsi_release_buffers(cmd);
- scsi_put_command(cmd);
- return BLKPREP_KILL;
- }
+ if (unlikely(!drv->init_command(cmd)))
+ goto kill;
}
/*
@@ -1166,12 +1167,27 @@ static int scsi_prep_fn(struct request_q
return BLKPREP_OK;
defer:
- /* If we defer, the elv_next_request() returns NULL, but the
+ /*
+ * If we defer, the elv_next_request() returns NULL, but the
* queue must be restarted, so we plug here if no returning
- * command will automatically do that. */
+ * command will automatically do that. Also, the request may
+ * have its cmd allocated, so we set REQ_SOFTBARRIER.
+ */
if (sdev->device_busy == 0)
blk_plug_device(q);
+ req->flags |= REQ_SOFTBARRIER;
return BLKPREP_DEFER;
+
+ kill:
+ /*
+ * Here we have to release every resource associated with the
+ * request because this will complete at the request level
+ * (req->end_io), not the scsi command level, so no scsi
+ * routine will get to free the associated resources.
+ */
+ scsi_release_buffers(cmd);
+ scsi_put_command(cmd);
+ return BLKPREP_KILL;
}
/*
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