scsi: lpfc: Fix invalid sleeping context in lpfc_sli4_nvmet_alloc()

The following calltrace was seen:

BUG: sleeping function called from invalid context at mm/slab.h:494
...
Call Trace:
 dump_stack+0x9a/0xf0
 ___might_sleep.cold.63+0x13d/0x178
 slab_pre_alloc_hook+0x6a/0x90
 kmem_cache_alloc_trace+0x3a/0x2d0
 lpfc_sli4_nvmet_alloc+0x4c/0x280 [lpfc]
 lpfc_post_rq_buffer+0x2e7/0xa60 [lpfc]
 lpfc_sli4_hba_setup+0x6b4c/0xa4b0 [lpfc]
 lpfc_pci_probe_one_s4.isra.15+0x14f8/0x2280 [lpfc]
 lpfc_pci_probe_one+0x260/0x2880 [lpfc]
 local_pci_probe+0xd4/0x180
 work_for_cpu_fn+0x51/0xa0
 process_one_work+0x8f0/0x17b0
 worker_thread+0x536/0xb50
 kthread+0x30c/0x3d0
 ret_from_fork+0x3a/0x50

A prior patch introduced a spin_lock_irqsave(hbalock) in the
lpfc_post_rq_buffer() routine. Call trace is seen as the hbalock is held
with interrupts disabled during a GFP_KERNEL allocation in
lpfc_sli4_nvmet_alloc().

Fix by reordering locking so that hbalock not held when calling
sli4_nvmet_alloc() (aka rqb_buf_list()).

Link: https://lore.kernel.org/r/20201020202719.54726-2-james.smart@broadcom.com
Fixes: 411de511 ("scsi: lpfc: Fix RQ empty firmware trap")
Cc: <stable@vger.kernel.org> # v4.17+
Co-developed-by: NDick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: NDick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: NJames Smart <james.smart@broadcom.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/lpfc/lpfc_mem.c

@@ -588,8 +588,6 @@ lpfc_sli4_rb_free(struct lpfc_hba *phba, struct hbq_dmabuf *dmab)
  * Description: Allocates a DMA-mapped receive buffer from the lpfc_hrb_pool PCI
  * pool along a non-DMA-mapped container for it.
  *
- * Notes: Not interrupt-safe.  Must be called with no locks held.
- *
  * Returns:
  *   pointer to HBQ on success
  *   NULL on failure
@@ -599,7 +597,7 @@ lpfc_sli4_nvmet_alloc(struct lpfc_hba *phba)
 {
 	struct rqb_dmabuf *dma_buf;
 
-	dma_buf = kzalloc(sizeof(struct rqb_dmabuf), GFP_KERNEL);
+	dma_buf = kzalloc(sizeof(*dma_buf), GFP_KERNEL);
 	if (!dma_buf)
 		return NULL;
 

drivers/scsi/lpfc/lpfc_sli.c

@@ -7248,12 +7248,16 @@ lpfc_post_rq_buffer(struct lpfc_hba *phba, struct lpfc_queue *hrq,
 	struct rqb_dmabuf *rqb_buffer;
 	LIST_HEAD(rqb_buf_list);
 
-	spin_lock_irqsave(&phba->hbalock, flags);
 	rqbp = hrq->rqbp;
 	for (i = 0; i < count; i++) {
+		spin_lock_irqsave(&phba->hbalock, flags);
 		/* IF RQ is already full, don't bother */
-		if (rqbp->buffer_count + i >= rqbp->entry_count - 1)
+		if (rqbp->buffer_count + i >= rqbp->entry_count - 1) {
+			spin_unlock_irqrestore(&phba->hbalock, flags);
 			break;
+		}
+		spin_unlock_irqrestore(&phba->hbalock, flags);
+
 		rqb_buffer = rqbp->rqb_alloc_buffer(phba);
 		if (!rqb_buffer)
 			break;
@@ -7262,6 +7266,8 @@ lpfc_post_rq_buffer(struct lpfc_hba *phba, struct lpfc_queue *hrq,
 		rqb_buffer->idx = idx;
 		list_add_tail(&rqb_buffer->hbuf.list, &rqb_buf_list);
 	}
+
+	spin_lock_irqsave(&phba->hbalock, flags);
 	while (!list_empty(&rqb_buf_list)) {
 		list_remove_head(&rqb_buf_list, rqb_buffer, struct rqb_dmabuf,
 				 hbuf.list);