[PATCH v3 2/2] block,scsi: fixup blk_get_request dead queue scenarios

From: Joe Lawrence
Date: Wed Jul 02 2014 - 15:39:38 EST

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@xxxxxxxxxxx>
Acked-by: Jiri Kosina <jkosina@xxxxxxx> [for pktdvd]
Acked-by: Boaz Harrosh <bharrosh@xxxxxxxxxxx> [for osd]
Reviewed-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
---
block/blk-core.c | 34 +++++++++++++--------------
block/blk-mq.c | 8 +++++--
block/bsg.c | 8 +++----
block/scsi_ioctl.c | 12 +++++-----
drivers/block/paride/pd.c | 4 ++--
drivers/block/pktcdvd.c | 4 ++--
drivers/block/sx8.c | 2 +-
drivers/cdrom/cdrom.c | 4 ++--
drivers/ide/ide-park.c | 2 +-
drivers/scsi/device_handler/scsi_dh_alua.c | 2 +-
drivers/scsi/device_handler/scsi_dh_emc.c | 2 +-
drivers/scsi/device_handler/scsi_dh_hp_sw.c | 4 ++--
drivers/scsi/device_handler/scsi_dh_rdac.c | 2 +-
drivers/scsi/osd/osd_initiator.c | 4 ++--
drivers/scsi/osst.c | 2 +-
drivers/scsi/scsi_error.c | 2 +-
drivers/scsi/scsi_lib.c | 2 +-
drivers/scsi/scsi_tgt_lib.c | 2 +-
drivers/scsi/sg.c | 4 ++--
drivers/scsi/st.c | 2 +-
drivers/target/target_core_pscsi.c | 2 +-
21 files changed, 56 insertions(+), 52 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 6f8dba1..7dd4692 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -930,9 +930,9 @@ static struct io_context *rq_ioc(struct bio *bio)
* Get a free request from @q. This function may fail under memory
* pressure or if @q is dead.
*
- * Must be callled with @q->queue_lock held and,
- * Returns %NULL on failure, with @q->queue_lock held.
- * Returns !%NULL on success, with @q->queue_lock *not held*.
+ * Must be called with @q->queue_lock held and,
+ * Returns ERR_PTR on failure, with @q->queue_lock held.
+ * Returns request pointer on success, with @q->queue_lock *not held*.
*/
static struct request *__get_request(struct request_list *rl, int rw_flags,
struct bio *bio, gfp_t gfp_mask)
@@ -946,7 +946,7 @@ static struct request *__get_request(struct request_list *rl, int rw_flags,
int may_queue;

if (unlikely(blk_queue_dying(q)))
- return NULL;
+ return ERR_PTR(-ENODEV);

may_queue = elv_may_queue(q, rw_flags);
if (may_queue == ELV_MQUEUE_NO)
@@ -971,7 +971,7 @@ static struct request *__get_request(struct request_list *rl, int rw_flags,
* process is not a "batcher", and not
* exempted by the IO scheduler
*/
- return NULL;
+ return ERR_PTR(-ENOMEM);
}
}
}
@@ -989,7 +989,7 @@ static struct request *__get_request(struct request_list *rl, int rw_flags,
* allocated with any setting of ->nr_requests
*/
if (rl->count[is_sync] >= (3 * q->nr_requests / 2))
- return NULL;
+ return ERR_PTR(-ENOMEM);

q->nr_rqs[is_sync]++;
rl->count[is_sync]++;
@@ -1094,7 +1094,7 @@ fail_alloc:
rq_starved:
if (unlikely(rl->count[is_sync] == 0))
rl->starved[is_sync] = 1;
- return NULL;
+ return ERR_PTR(-ENOMEM);
}

/**
@@ -1107,9 +1107,9 @@ rq_starved:
* Get a free request from @q. If %__GFP_WAIT is set in @gfp_mask, this
* function keeps retrying under memory pressure and fails iff @q is dead.
*
- * Must be callled with @q->queue_lock held and,
- * Returns %NULL on failure, with @q->queue_lock held.
- * Returns !%NULL on success, with @q->queue_lock *not held*.
+ * Must be called with @q->queue_lock held and,
+ * Returns ERR_PTR on failure, with @q->queue_lock held.
+ * Returns request pointer on success, with @q->queue_lock *not held*.
*/
static struct request *get_request(struct request_queue *q, int rw_flags,
struct bio *bio, gfp_t gfp_mask)
@@ -1122,12 +1122,12 @@ static struct request *get_request(struct request_queue *q, int rw_flags,
rl = blk_get_rl(q, bio); /* transferred to @rq on success */
retry:
rq = __get_request(rl, rw_flags, bio, gfp_mask);
- if (rq)
+ if (!IS_ERR(rq))
return rq;

if (!(gfp_mask & __GFP_WAIT) || unlikely(blk_queue_dying(q))) {
blk_put_rl(rl);
- return NULL;
+ return rq;
}

/* wait on @rl and retry */
@@ -1164,7 +1164,7 @@ static struct request *blk_old_get_request(struct request_queue *q, int rw,

spin_lock_irq(q->queue_lock);
rq = get_request(q, rw, NULL, gfp_mask);
- if (!rq)
+ if (IS_ERR(rq))
spin_unlock_irq(q->queue_lock);
/* q->queue_lock is unlocked at this point */

@@ -1216,8 +1216,8 @@ struct request *blk_make_request(struct request_queue *q, struct bio *bio,
{
struct request *rq = blk_get_request(q, bio_data_dir(bio), gfp_mask);

- if (unlikely(!rq))
- return ERR_PTR(-ENOMEM);
+ if (IS_ERR(rq))
+ return rq;

blk_rq_set_block_pc(rq);

@@ -1612,8 +1612,8 @@ get_rq:
* Returns with the queue unlocked.
*/
req = get_request(q, rw_flags, bio, GFP_NOIO);
- if (unlikely(!req)) {
- bio_endio(bio, -ENODEV); /* @q is dead */
+ if (IS_ERR(req)) {
+ bio_endio(bio, PTR_ERR(req)); /* @q is dead */
goto out_unlock;
}

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 0ef2dc7..eaec14b 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -240,9 +240,11 @@ struct request *blk_mq_alloc_request(struct request_queue *q, int rw, gfp_t gfp,
struct blk_mq_hw_ctx *hctx;
struct request *rq;
struct blk_mq_alloc_data alloc_data;
+ int ret;

- if (blk_mq_queue_enter(q))
- return NULL;
+ ret = blk_mq_queue_enter(q);
+ if (ret)
+ return ERR_PTR(ret);

ctx = blk_mq_get_ctx(q);
hctx = q->mq_ops->map_queue(q, ctx->cpu);
@@ -262,6 +264,8 @@ struct request *blk_mq_alloc_request(struct request_queue *q, int rw, gfp_t gfp,
ctx = alloc_data.ctx;
}
blk_mq_put_ctx(ctx);
+ if (!rq)
+ return ERR_PTR(-EWOULDBLOCK);
return rq;
}
EXPORT_SYMBOL(blk_mq_alloc_request);
diff --git a/block/bsg.c b/block/bsg.c
index ff46add..73c78fd 100644
--- a/block/bsg.c
+++ b/block/bsg.c
@@ -270,8 +270,8 @@ bsg_map_hdr(struct bsg_device *bd, struct sg_io_v4 *hdr, fmode_t has_write_perm,
* map scatter-gather elements separately and string them to request
*/
rq = blk_get_request(q, rw, GFP_KERNEL);
- if (!rq)
- return ERR_PTR(-ENOMEM);
+ if (IS_ERR(rq))
+ return rq;
blk_rq_set_block_pc(rq);

ret = blk_fill_sgv4_hdr_rq(q, rq, hdr, bd, has_write_perm);
@@ -285,8 +285,8 @@ bsg_map_hdr(struct bsg_device *bd, struct sg_io_v4 *hdr, fmode_t has_write_perm,
}

next_rq = blk_get_request(q, READ, GFP_KERNEL);
- if (!next_rq) {
- ret = -ENOMEM;
+ if (IS_ERR(next_rq)) {
+ ret = PTR_ERR(next_rq);
goto out;
}
rq->next_rq = next_rq;
diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
index 3e1d80c..531cbe5 100644
--- a/block/scsi_ioctl.c
+++ b/block/scsi_ioctl.c
@@ -308,8 +308,8 @@ static int sg_io(struct request_queue *q, struct gendisk *bd_disk,
}

rq = blk_get_request(q, writing ? WRITE : READ, GFP_KERNEL);
- if (!rq)
- return -ENOMEM;
+ if (IS_ERR(rq))
+ return PTR_ERR(rq);
blk_rq_set_block_pc(rq);

if (blk_fill_sghdr_rq(q, rq, hdr, mode)) {
@@ -438,8 +438,8 @@ int sg_scsi_ioctl(struct request_queue *q, struct gendisk *disk, fmode_t mode,
}

rq = blk_get_request(q, in_len ? WRITE : READ, __GFP_WAIT);
- if (!rq) {
- err = -ENODEV;
+ if (IS_ERR(rq)) {
+ err = PTR_ERR(rq);
goto error_free_buffer;
}

@@ -529,8 +529,8 @@ static int __blk_send_generic(struct request_queue *q, struct gendisk *bd_disk,
int err;

rq = blk_get_request(q, WRITE, __GFP_WAIT);
- if (!rq)
- return -ENODEV;
+ if (IS_ERR(rq))
+ return PTR_ERR(rq);
blk_rq_set_block_pc(rq);
rq->timeout = BLK_DEFAULT_SG_TIMEOUT;
rq->cmd[0] = cmd;
diff --git a/drivers/block/paride/pd.c b/drivers/block/paride/pd.c
index ca831f7..d48715b 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 7fa8c80..09e628da 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 d5e2d12..5d55285 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 898b84b..5d28a45 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 f41558a..ca95860 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 7bcf67e..e99507e 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 6f07f7f..8476538 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 e9d9fea..4ee2759 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 826069d..1b5bc92 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 5f4cbf0..fd19fd8 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 0727ea7..dff37a25 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);

req = blk_get_request(SRpnt->stp->device->request_queue, write, GFP_KERNEL);
- if (!req)
+ if (IS_ERR(req))
return DRIVER_ERROR << 24;

blk_rq_set_block_pc(req);
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index b403b04..641ffde 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -1951,7 +1951,7 @@ static void scsi_eh_lock_door(struct scsi_device *sdev)
* request becomes available
*/
req = blk_get_request(sdev->request_queue, READ, GFP_KERNEL);
- if (!req)
+ if (IS_ERR(req))
return;

blk_rq_set_block_pc(req);
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index f7e3163..b64bba3 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -193,7 +193,7 @@ int scsi_execute(struct scsi_device *sdev, const unsigned char *cmd,
int ret = DRIVER_ERROR << 24;

req = blk_get_request(sdev->request_queue, write, __GFP_WAIT);
- if (!req)
+ if (IS_ERR(req))
return ret;
blk_rq_set_block_pc(req);

diff --git a/drivers/scsi/scsi_tgt_lib.c b/drivers/scsi/scsi_tgt_lib.c
index e51add0..b14c15b 100644
--- a/drivers/scsi/scsi_tgt_lib.c
+++ b/drivers/scsi/scsi_tgt_lib.c
@@ -97,7 +97,7 @@ struct scsi_cmnd *scsi_host_get_command(struct Scsi_Host *shost,
* we are in target mode we want the opposite.
*/
rq = blk_get_request(shost->uspace_req_q, !write, gfp_mask);
- if (!rq)
+ if (IS_ERR(rq))
goto free_tcmd;

cmd = __scsi_get_command(shost, gfp_mask);
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 53268aa..dec00f6 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -1650,8 +1650,8 @@ static int sg_start_req(Sg_request *srp, unsigned char *cmd)
dxfer_len));

rq = blk_get_request(q, rw, GFP_ATOMIC);
- if (!rq)
- return -ENOMEM;
+ if (IS_ERR(rq))
+ return PTR_ERR(rq);

blk_rq_set_block_pc(rq);
memcpy(rq->cmd, cmd, hp->cmd_len);
diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
index 14eb4b2..54f74b0 100644
--- a/drivers/scsi/st.c
+++ b/drivers/scsi/st.c
@@ -481,7 +481,7 @@ static int st_scsi_execute(struct st_request *SRpnt, const unsigned char *cmd,

req = blk_get_request(SRpnt->stp->device->request_queue, write,
GFP_KERNEL);
- if (!req)
+ if (IS_ERR(req))
return DRIVER_ERROR << 24;

blk_rq_set_block_pc(req);
diff --git a/drivers/target/target_core_pscsi.c b/drivers/target/target_core_pscsi.c
index 94d00df..b2bdced 100644
--- a/drivers/target/target_core_pscsi.c
+++ b/drivers/target/target_core_pscsi.c
@@ -1050,7 +1050,7 @@ pscsi_execute_cmd(struct se_cmd *cmd)
req = blk_get_request(pdv->pdv_sd->request_queue,
(data_direction == DMA_TO_DEVICE),
GFP_KERNEL);
- if (!req) {
+ if (IS_ERR(req)) {
pr_err("PSCSI: blk_get_request() failed\n");
ret = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
goto fail;
--
1.7.10.4

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