Re: [PATCH 2/2] block,scsi: convert and handle ERR_PTR from blk_get_request

From: Jeff Moyer
Date: Tue Jun 03 2014 - 15:45:51 EST

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Joe Lawrence <joe.lawrence@xxxxxxxxxxx> writes:

> 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.

I'm curious to know what testing you did, and what code paths do
anything different for ENOMEM vs EIO. I guess ENOMEM may make it all
the way back to userspace?

-Jeff

>
> Signed-off-by: Joe Lawrence <joe.lawrence@xxxxxxxxxxx>
> Acked-by: Jiri Kosina <jkosina@xxxxxxx> [for pktdvd]
> Acked-by: Boaz Harrosh <bharrosh@xxxxxxxxxxx> [for osd]
> ---
> block/blk-core.c | 34 ++++++++++++++---------------
> 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 +-
> 20 files changed, 50 insertions(+), 50 deletions(-)
>
> diff --git a/block/blk-core.c b/block/blk-core.c
> index a0e3096..cd0e9f3 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -891,9 +891,9 @@ 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)
> @@ -907,7 +907,7 @@ 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)
> @@ -932,7 +932,7 @@ 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);
> }
> }
> }
> @@ -950,7 +950,7 @@ 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]++;
> @@ -1055,7 +1055,7 @@ fail_alloc:
> rq_starved:
> if (unlikely(rl->count[is_sync] == 0))
> rl->starved[is_sync] = 1;
> - return NULL;
> + return ERR_PTR(-ENOMEM);
> }
>
> /**
> @@ -1068,9 +1068,9 @@ 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)
> @@ -1083,12 +1083,12 @@ 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 */
> @@ -1125,7 +1125,7 @@ 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 */
>
> @@ -1177,8 +1177,8 @@ 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;
>
> for_each_bio(bio) {
> struct bio *bounce_bio = bio;
> @@ -1559,8 +1559,8 @@ 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/bsg.c b/block/bsg.c
> index 420a5a9..2b1c322 100644
> --- a/block/bsg.c
> +++ b/block/bsg.c
> @@ -271,8 +271,8 @@ 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;
> ret = blk_fill_sgv4_hdr_rq(q, rq, hdr, bd, has_write_perm);
> if (ret)
> goto out;
> @@ -284,8 +284,8 @@ 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(rq);
> goto out;
> }
> rq->next_rq = next_rq;
> diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
> index e6485c9..f901fb5 100644
> --- a/block/scsi_ioctl.c
> +++ b/block/scsi_ioctl.c
> @@ -313,8 +313,8 @@ 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);
>
> if (blk_fill_sghdr_rq(q, rq, hdr, mode)) {
> blk_put_request(rq);
> @@ -442,8 +442,8 @@ 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;
> }
>
> @@ -533,8 +533,8 @@ 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);
> rq->cmd_type = REQ_TYPE_BLOCK_PC;
> 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 856178a..2af4101 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 ff39837..1de6e90 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);
>
> if (cgc->buflen) {
> ret = blk_rq_map_kern(q, rq, cgc->buffer, 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 8a3aff7..85e63d3 100644
> --- a/drivers/cdrom/cdrom.c
> +++ b/drivers/cdrom/cdrom.c
> @@ -2161,8 +2161,8 @@ 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;
> }
>
> 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 5248c88..5aefcf9 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 e1c8be0..2ec3261 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 084062b..1cf4019 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;
>
> req->cmd_type = REQ_TYPE_BLOCK_PC;
> @@ -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;
>
> req->cmd_type = REQ_TYPE_BLOCK_PC;
> diff --git a/drivers/scsi/device_handler/scsi_dh_rdac.c b/drivers/scsi/device_handler/scsi_dh_rdac.c
> index 4b9cf93..5f6e5d8 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 bac04c2..831f1f9 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;
>
> return req;
> }
> diff --git a/drivers/scsi/osst.c b/drivers/scsi/osst.c
> index 21883a2..826cda9 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;
>
> req->cmd_type = REQ_TYPE_BLOCK_PC;
> diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
> index d50531f..ca038ee 100644
> --- a/drivers/scsi/scsi_error.c
> +++ b/drivers/scsi/scsi_error.c
> @@ -1950,7 +1950,7 @@ 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;
>
> req->cmd[0] = ALLOW_MEDIUM_REMOVAL;
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 9db097a..b25fab0b 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;
>
> if (bufflen && blk_rq_map_kern(sdev->request_queue, 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 df5e961..2e54684 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);
>
> memcpy(rq->cmd, cmd, hp->cmd_len);
>
> diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
> index afc834e..48a6cef 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;
>
> req->cmd_type = REQ_TYPE_BLOCK_PC;
> diff --git a/drivers/target/target_core_pscsi.c b/drivers/target/target_core_pscsi.c
> index 0f199f6..23d340d 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;
--
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