[SCSI] bug fix for free list handling

commit:

commit 542bd1377a
Author: James Bottomley <James.Bottomley@HansenPartnership.com>
Date:   Mon Apr 21 10:57:20 2008 -0500

    [SCSI] fix SLUB WARN_ON

Fixed another problem in free list handling by moving list allocation
from scsi_host_alloc() to scsi_add_host().  Unfortunately it
introduced a new failure mode in that hosts can pass straight from
alloc to put without going through add, leaving the free list
uninitialised.

Fix by checking shost->cmd_pool on the release path to see if it got
initialised.

Signed-off-by: Alan D. Brunelle <alan.brunelle@hp.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

drivers/scsi/scsi.c

@@ -469,6 +469,7 @@ int scsi_setup_command_freelist(struct Scsi_Host *shost)
 	cmd = scsi_pool_alloc_command(shost->cmd_pool, gfp_mask);
 	if (!cmd) {
 		scsi_put_host_cmd_pool(gfp_mask);
+		shost->cmd_pool = NULL;
 		return -ENOMEM;
 	}
 	list_add(&cmd->list, &shost->free_list);
@@ -481,6 +482,13 @@ int scsi_setup_command_freelist(struct Scsi_Host *shost)
  */
 void scsi_destroy_command_freelist(struct Scsi_Host *shost)
 {
+	/*
+	 * If cmd_pool is NULL the free list was not initialized, so
+	 * do not attempt to release resources.
+	 */
+	if (!shost->cmd_pool)
+		return;
+
 	while (!list_empty(&shost->free_list)) {
 		struct scsi_cmnd *cmd;