block,scsi: fixup blk_get_request dead queue scenarios

The blk_get_request function may fail in low-memory conditions or during
device removal (even if __GFP_WAIT is set). To distinguish between these
errors, modify the blk_get_request call stack to return the appropriate
ERR_PTR. Verify that all callers check the return status and consider
IS_ERR instead of a simple NULL pointer check.

For consistency, make a similar change to the blk_mq_alloc_request leg
of blk_get_request.  It may fail if the queue is dead, or the caller was
unwilling to wait.

Signed-off-by: Joe Lawrence <joe.lawrence@stratus.com>
Acked-by: Jiri Kosina <jkosina@suse.cz> [for pktdvd]
Acked-by: Boaz Harrosh <bharrosh@panasas.com> [for osd]
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

16 files changed, 22 insertions, 22 deletions

diff --git a/drivers/block/paride/pd.c b/drivers/block/paride/pd.c
index ca831f741d89..d48715b287e6 100644
--- a/drivers/block/paride/pd.c
+++ b/drivers/block/paride/pd.c
@@ -722,8 +722,8 @@ static int pd_special_command(struct pd_unit *disk,
         int err = 0;
 
         rq = blk_get_request(disk->gd->queue, READ, __GFP_WAIT);
-        if (!rq)
-                return -ENODEV;
+        if (IS_ERR(rq))
+                return PTR_ERR(rq);
 
         rq->cmd_type = REQ_TYPE_SPECIAL;
         rq->special = func;
diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
index 7fa8c80e8982..09e628dafd9d 100644
--- a/drivers/block/pktcdvd.c
+++ b/drivers/block/pktcdvd.c
@@ -704,8 +704,8 @@ static int pkt_generic_packet(struct pktcdvd_device *pd, struct packet_command *
 
         rq = blk_get_request(q, (cgc->data_direction == CGC_DATA_WRITE) ?
                              WRITE : READ, __GFP_WAIT);
-        if (!rq)
-                return -ENODEV;
+        if (IS_ERR(rq))
+                return PTR_ERR(rq);
         blk_rq_set_block_pc(rq);
 
         if (cgc->buflen) {
diff --git a/drivers/block/sx8.c b/drivers/block/sx8.c
index d5e2d12b9d9e..5d552857de41 100644
--- a/drivers/block/sx8.c
+++ b/drivers/block/sx8.c
@@ -568,7 +568,7 @@ static struct carm_request *carm_get_special(struct carm_host *host)
                 return NULL;
 
         rq = blk_get_request(host->oob_q, WRITE /* bogus */, GFP_KERNEL);
-        if (!rq) {
+        if (IS_ERR(rq)) {
                 spin_lock_irqsave(&host->lock, flags);
                 carm_put_request(host, crq);
                 spin_unlock_irqrestore(&host->lock, flags);
diff --git a/drivers/cdrom/cdrom.c b/drivers/cdrom/cdrom.c
index 898b84bba28a..5d28a45d2960 100644
--- a/drivers/cdrom/cdrom.c
+++ b/drivers/cdrom/cdrom.c
@@ -2180,8 +2180,8 @@ static int cdrom_read_cdda_bpc(struct cdrom_device_info *cdi, __u8 __user *ubuf,
                 len = nr * CD_FRAMESIZE_RAW;
 
                 rq = blk_get_request(q, READ, GFP_KERNEL);
-                if (!rq) {
-                        ret = -ENOMEM;
+                if (IS_ERR(rq)) {
+                        ret = PTR_ERR(rq);
                         break;
                 }
                 blk_rq_set_block_pc(rq);
diff --git a/drivers/ide/ide-park.c b/drivers/ide/ide-park.c
index f41558a0bcd1..ca958604cda2 100644
--- a/drivers/ide/ide-park.c
+++ b/drivers/ide/ide-park.c
@@ -46,7 +46,7 @@ static void issue_park_cmd(ide_drive_t *drive, unsigned long timeout)
          * timeout has expired, so power management will be reenabled.
          */
         rq = blk_get_request(q, READ, GFP_NOWAIT);
-        if (unlikely(!rq))
+        if (IS_ERR(rq))
                 goto out;
 
         rq->cmd[0] = REQ_UNPARK_HEADS;
diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 7bcf67eec921..e99507ed0e3c 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -115,7 +115,7 @@ static struct request *get_alua_req(struct scsi_device *sdev,
 
         rq = blk_get_request(q, rw, GFP_NOIO);
 
-        if (!rq) {
+        if (IS_ERR(rq)) {
                 sdev_printk(KERN_INFO, sdev,
                             "%s: blk_get_request failed\n", __func__);
                 return NULL;
diff --git a/drivers/scsi/device_handler/scsi_dh_emc.c b/drivers/scsi/device_handler/scsi_dh_emc.c
index 6f07f7fe3aa1..84765384c47c 100644
--- a/drivers/scsi/device_handler/scsi_dh_emc.c
+++ b/drivers/scsi/device_handler/scsi_dh_emc.c
@@ -275,7 +275,7 @@ static struct request *get_req(struct scsi_device *sdev, int cmd,
 
         rq = blk_get_request(sdev->request_queue,
                         (cmd != INQUIRY) ? WRITE : READ, GFP_NOIO);
-        if (!rq) {
+        if (IS_ERR(rq)) {
                 sdev_printk(KERN_INFO, sdev, "get_req: blk_get_request failed");
                 return NULL;
         }
diff --git a/drivers/scsi/device_handler/scsi_dh_hp_sw.c b/drivers/scsi/device_handler/scsi_dh_hp_sw.c
index e9d9fea9e272..4ee2759f5299 100644
--- a/drivers/scsi/device_handler/scsi_dh_hp_sw.c
+++ b/drivers/scsi/device_handler/scsi_dh_hp_sw.c
@@ -117,7 +117,7 @@ static int hp_sw_tur(struct scsi_device *sdev, struct hp_sw_dh_data *h)
 
 retry:
         req = blk_get_request(sdev->request_queue, WRITE, GFP_NOIO);
-        if (!req)
+        if (IS_ERR(req))
                 return SCSI_DH_RES_TEMP_UNAVAIL;
 
         blk_rq_set_block_pc(req);
@@ -247,7 +247,7 @@ static int hp_sw_start_stop(struct hp_sw_dh_data *h)
         struct request *req;
 
         req = blk_get_request(h->sdev->request_queue, WRITE, GFP_ATOMIC);
-        if (!req)
+        if (IS_ERR(req))
                 return SCSI_DH_RES_TEMP_UNAVAIL;
 
         blk_rq_set_block_pc(req);
diff --git a/drivers/scsi/device_handler/scsi_dh_rdac.c b/drivers/scsi/device_handler/scsi_dh_rdac.c
index 826069db9848..1b5bc9293e37 100644
--- a/drivers/scsi/device_handler/scsi_dh_rdac.c
+++ b/drivers/scsi/device_handler/scsi_dh_rdac.c
@@ -274,7 +274,7 @@ static struct request *get_rdac_req(struct scsi_device *sdev,
 
         rq = blk_get_request(q, rw, GFP_NOIO);
 
-        if (!rq) {
+        if (IS_ERR(rq)) {
                 sdev_printk(KERN_INFO, sdev,
                                 "get_rdac_req: blk_get_request failed.\n");
                 return NULL;
diff --git a/drivers/scsi/osd/osd_initiator.c b/drivers/scsi/osd/osd_initiator.c
index 5f4cbf0c4759..fd19fd8468ac 100644
--- a/drivers/scsi/osd/osd_initiator.c
+++ b/drivers/scsi/osd/osd_initiator.c
@@ -1567,8 +1567,8 @@ static struct request *_make_request(struct request_queue *q, bool has_write,
                 struct request *req;
 
                 req = blk_get_request(q, has_write ? WRITE : READ, flags);
-                if (unlikely(!req))
-                        return ERR_PTR(-ENOMEM);
+                if (IS_ERR(req))
+                        return req;
 
                 blk_rq_set_block_pc(req);
                 return req;
diff --git a/drivers/scsi/osst.c b/drivers/scsi/osst.c
index 0727ea7cc387..dff37a250d79 100644
--- a/drivers/scsi/osst.c
+++ b/drivers/scsi/osst.c
@@ -362,7 +362,7 @@ static int osst_execute(struct osst_request *SRpnt, const unsigned char *cmd,
         int write = (data_direction == DMA_TO_DEVICE);