[PATCH v3 00/12] SCSI patches for kernel v4.13

[PATCH v3 00/12] SCSI patches for kernel v4.13

[Bart Van Assche]

Hello Martin,

This patch series consists of the bug fixes and improvements I came up with
during the past two months. This patch series has been developed on top of
your 4.13/scsi-queue branch. Please consider these patches for kernel v4.13.

Thanks,

Bart.

The changes compared to v2 of this patch series are:
- Addressed Christoph's review comments: added an explanation to patch
  "Protect SCSI device state changes with a mutex" of why that change is
  needed. Removed a printk() from patch "Make __scsi_remove_device go
  straight from BLOCKED to DEL". For scsi-mq, moved the initialization of
  .prot_sdb from scsi_mq_prep_fn() into scsi_init_request(). Fixed the
  driver name in the virtio_scsi patch.

Between v1 and v2:
- Left out the block layer patches from this series.
- Reworked this patch series such that it applies cleanly on the 4.13 SCSI
  patch queue and no longer depends on any block layer changes that are not
  yet upstream.
- In patch "Avoid that scsi_exit_rq() triggers a use-after-free", make the
  prep functions save and restore the SCMD_UNCHECKED_ISA_DMA flag.
- Added patch "Introduce scsi_start_queue()".

Bart Van Assche (12):
  Avoid that scsi_exit_rq() triggers a use-after-free
  Split scsi_internal_device_block()
  Create two versions of scsi_internal_device_unblock()
  Protect SCSI device state changes with a mutex
  Introduce scsi_start_queue()
  Make __scsi_remove_device go straight from BLOCKED to DEL
  Only add commands to the device command list if required by the LLD
  Introduce scsi_mq_sgl_size()
  Make scsi_mq_prep_fn() call scsi_init_command()
  snic: Remove code that zeroes driver-private command data
  virtio_scsi: Remove code that zeroes driver-private command data
  xen/scsifront: Remove code that zeroes driver-private command data

 drivers/scsi/mpt3sas/mpt3sas_scsih.c |   8 +-
 drivers/scsi/scsi.c                  |   9 +-
 drivers/scsi/scsi_error.c            |   8 +-
 drivers/scsi/scsi_lib.c              | 306 ++++++++++++++++++++++-------------
 drivers/scsi/scsi_priv.h             |   3 +
 drivers/scsi/scsi_scan.c             |  16 +-
 drivers/scsi/scsi_sysfs.c            |  34 +++-
 drivers/scsi/scsi_transport_srp.c    |   7 +-
 drivers/scsi/sd.c                    |   7 +-
 drivers/scsi/snic/snic_scsi.c        |   2 -
 drivers/scsi/virtio_scsi.c           |   1 -
 drivers/scsi/xen-scsifront.c         |   1 -
 include/scsi/scsi_cmnd.h             |   1 +
 include/scsi/scsi_device.h           |   7 +-
 14 files changed, 258 insertions(+), 152 deletions(-)

-- 
2.12.2

[PATCH v3 01/12] Avoid that scsi_exit_rq() triggers a use-after-free

[Bart Van Assche]

Dereferencing shost from scsi_exit_rq() is not safe because the
SCSI host may already have been freed when scsi_exit_rq() is
called. Increasing the shost reference count in scsi_init_rq()
and dropping that reference in scsi_exit_rq() is nontrivial since
scsi_host_dev_release() may sleep and since scsi_exit_rq() may
be called from interrupt context. Since scsi_exit_rq() only needs
a single bit from shost, copy that bit into struct scsi_cmnd.

Reported-by: Scott Bauer <scott.bauer@intel.com>
Fixes: e9c787e65c0c ("scsi: allocate scsi_cmnd structures as part of struct request")
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Scott Bauer <scott.bauer@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: <stable@vger.kernel.org>
---
 drivers/scsi/scsi_lib.c  | 47 +++++++++++++++++++++++++++++------------------
 include/scsi/scsi_cmnd.h |  1 +
 2 files changed, 30 insertions(+), 18 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 814a4bd8405d..cc9f792cd12b 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -44,23 +44,23 @@ static struct kmem_cache *scsi_sense_isadma_cache;
 static DEFINE_MUTEX(scsi_sense_cache_mutex);
 
 static inline struct kmem_cache *
-scsi_select_sense_cache(struct Scsi_Host *shost)
+scsi_select_sense_cache(bool unchecked_isa_dma)
 {
-	return shost->unchecked_isa_dma ?
-		scsi_sense_isadma_cache : scsi_sense_cache;
+	return unchecked_isa_dma ? scsi_sense_isadma_cache : scsi_sense_cache;
 }
 
-static void scsi_free_sense_buffer(struct Scsi_Host *shost,
-		unsigned char *sense_buffer)
+static void scsi_free_sense_buffer(bool unchecked_isa_dma,
+				   unsigned char *sense_buffer)
 {
-	kmem_cache_free(scsi_select_sense_cache(shost), sense_buffer);
+	kmem_cache_free(scsi_select_sense_cache(unchecked_isa_dma),
+			sense_buffer);
 }
 
-static unsigned char *scsi_alloc_sense_buffer(struct Scsi_Host *shost,
+static unsigned char *scsi_alloc_sense_buffer(bool unchecked_isa_dma,
 	gfp_t gfp_mask, int numa_node)
 {
-	return kmem_cache_alloc_node(scsi_select_sense_cache(shost), gfp_mask,
-			numa_node);
+	return kmem_cache_alloc_node(scsi_select_sense_cache(unchecked_isa_dma),
+				     gfp_mask, numa_node);
 }
 
 int scsi_init_sense_cache(struct Scsi_Host *shost)
@@ -68,7 +68,7 @@ int scsi_init_sense_cache(struct Scsi_Host *shost)
 	struct kmem_cache *cache;
 	int ret = 0;
 
-	cache = scsi_select_sense_cache(shost);
+	cache = scsi_select_sense_cache(shost->unchecked_isa_dma);
 	if (cache)
 		return 0;
 
@@ -1137,6 +1137,7 @@ void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd)
 {
 	void *buf = cmd->sense_buffer;
 	void *prot = cmd->prot_sdb;
+	unsigned int unchecked_isa_dma = cmd->flags & SCMD_UNCHECKED_ISA_DMA;
 	unsigned long flags;
 
 	/* zero out the cmd, except for the embedded scsi_request */
@@ -1146,6 +1147,7 @@ void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd)
 	cmd->device = dev;
 	cmd->sense_buffer = buf;
 	cmd->prot_sdb = prot;
+	cmd->flags = unchecked_isa_dma;
 	INIT_DELAYED_WORK(&cmd->abort_work, scmd_eh_abort_handler);
 	cmd->jiffies_at_alloc = jiffies;
 
@@ -1846,6 +1848,7 @@ static int scsi_mq_prep_fn(struct request *req)
 	struct scsi_device *sdev = req->q->queuedata;
 	struct Scsi_Host *shost = sdev->host;
 	unsigned char *sense_buf = cmd->sense_buffer;
+	unsigned int unchecked_isa_dma = cmd->flags & SCMD_UNCHECKED_ISA_DMA;
 	struct scatterlist *sg;
 
 	/* zero out the cmd, except for the embedded scsi_request */
@@ -1857,6 +1860,7 @@ static int scsi_mq_prep_fn(struct request *req)
 	cmd->request = req;
 	cmd->device = sdev;
 	cmd->sense_buffer = sense_buf;
+	cmd->flags = unchecked_isa_dma;
 
 	cmd->tag = req->tag;
 
@@ -2003,10 +2007,13 @@ static int scsi_init_request(struct blk_mq_tag_set *set, struct request *rq,
 		unsigned int hctx_idx, unsigned int numa_node)
 {
 	struct Scsi_Host *shost = set->driver_data;
+	const bool unchecked_isa_dma = shost->unchecked_isa_dma;
 	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
 
-	cmd->sense_buffer =
-		scsi_alloc_sense_buffer(shost, GFP_KERNEL, numa_node);
+	if (unchecked_isa_dma)
+		cmd->flags |= SCMD_UNCHECKED_ISA_DMA;
+	cmd->sense_buffer = scsi_alloc_sense_buffer(unchecked_isa_dma,
+						    GFP_KERNEL, numa_node);
 	if (!cmd->sense_buffer)
 		return -ENOMEM;
 	cmd->req.sense = cmd->sense_buffer;
@@ -2016,10 +2023,10 @@ static int scsi_init_request(struct blk_mq_tag_set *set, struct request *rq,
 static void scsi_exit_request(struct blk_mq_tag_set *set, struct request *rq,
 		unsigned int hctx_idx)
 {
-	struct Scsi_Host *shost = set->driver_data;
 	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
 
-	scsi_free_sense_buffer(shost, cmd->sense_buffer);
+	scsi_free_sense_buffer(cmd->flags & SCMD_UNCHECKED_ISA_DMA,
+			       cmd->sense_buffer);
 }
 
 static int scsi_map_queues(struct blk_mq_tag_set *set)
@@ -2092,11 +2099,15 @@ EXPORT_SYMBOL_GPL(__scsi_init_queue);
 static int scsi_init_rq(struct request_queue *q, struct request *rq, gfp_t gfp)
 {
 	struct Scsi_Host *shost = q->rq_alloc_data;
+	const bool unchecked_isa_dma = shost->unchecked_isa_dma;
 	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
 
 	memset(cmd, 0, sizeof(*cmd));
 
-	cmd->sense_buffer = scsi_alloc_sense_buffer(shost, gfp, NUMA_NO_NODE);
+	if (unchecked_isa_dma)
+		cmd->flags |= SCMD_UNCHECKED_ISA_DMA;
+	cmd->sense_buffer = scsi_alloc_sense_buffer(unchecked_isa_dma, gfp,
+						    NUMA_NO_NODE);
 	if (!cmd->sense_buffer)
 		goto fail;
 	cmd->req.sense = cmd->sense_buffer;
@@ -2110,19 +2121,19 @@ static int scsi_init_rq(struct request_queue *q, struct request *rq, gfp_t gfp)
 	return 0;
 
 fail_free_sense:
-	scsi_free_sense_buffer(shost, cmd->sense_buffer);
+	scsi_free_sense_buffer(unchecked_isa_dma, cmd->sense_buffer);
 fail:
 	return -ENOMEM;
 }
 
 static void scsi_exit_rq(struct request_queue *q, struct request *rq)
 {
-	struct Scsi_Host *shost = q->rq_alloc_data;
 	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
 
 	if (cmd->prot_sdb)
 		kmem_cache_free(scsi_sdb_cache, cmd->prot_sdb);
-	scsi_free_sense_buffer(shost, cmd->sense_buffer);
+	scsi_free_sense_buffer(cmd->flags & SCMD_UNCHECKED_ISA_DMA,
+			       cmd->sense_buffer);
 }
 
 struct request_queue *scsi_alloc_queue(struct scsi_device *sdev)
diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index b379f93a2c48..16351de31243 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -56,6 +56,7 @@ struct scsi_pointer {
 
 /* for scmd->flags */
 #define SCMD_TAGGED		(1 << 0)
+#define SCMD_UNCHECKED_ISA_DMA	(1 << 1)
 
 struct scsi_cmnd {
 	struct scsi_request req;
-- 
2.12.2

[PATCH v3 01/12] Avoid that scsi_exit_rq() triggers a use-after-free

[Bart Van Assche]

Dereferencing shost from scsi_exit_rq() is not safe because the
SCSI host may already have been freed when scsi_exit_rq() is
called. Increasing the shost reference count in scsi_init_rq()
and dropping that reference in scsi_exit_rq() is nontrivial since
scsi_host_dev_release() may sleep and since scsi_exit_rq() may
be called from interrupt context. Since scsi_exit_rq() only needs
a single bit from shost, copy that bit into struct scsi_cmnd.

Reported-by: Scott Bauer <scott.bauer@intel.com>
Fixes: e9c787e65c0c ("scsi: allocate scsi_cmnd structures as part of struct request")
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Scott Bauer <scott.bauer@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: <stable@vger.kernel.org>
---
 drivers/scsi/scsi_lib.c  | 47 +++++++++++++++++++++++++++++------------------
 include/scsi/scsi_cmnd.h |  1 +
 2 files changed, 30 insertions(+), 18 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 814a4bd8405d..cc9f792cd12b 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -44,23 +44,23 @@ static struct kmem_cache *scsi_sense_isadma_cache;
 static DEFINE_MUTEX(scsi_sense_cache_mutex);
 
 static inline struct kmem_cache *
-scsi_select_sense_cache(struct Scsi_Host *shost)
+scsi_select_sense_cache(bool unchecked_isa_dma)
 {
-	return shost->unchecked_isa_dma ?
-		scsi_sense_isadma_cache : scsi_sense_cache;
+	return unchecked_isa_dma ? scsi_sense_isadma_cache : scsi_sense_cache;
 }
 
-static void scsi_free_sense_buffer(struct Scsi_Host *shost,
-		unsigned char *sense_buffer)
+static void scsi_free_sense_buffer(bool unchecked_isa_dma,
+				   unsigned char *sense_buffer)
 {
-	kmem_cache_free(scsi_select_sense_cache(shost), sense_buffer);
+	kmem_cache_free(scsi_select_sense_cache(unchecked_isa_dma),
+			sense_buffer);
 }
 
-static unsigned char *scsi_alloc_sense_buffer(struct Scsi_Host *shost,
+static unsigned char *scsi_alloc_sense_buffer(bool unchecked_isa_dma,
 	gfp_t gfp_mask, int numa_node)
 {
-	return kmem_cache_alloc_node(scsi_select_sense_cache(shost), gfp_mask,
-			numa_node);
+	return kmem_cache_alloc_node(scsi_select_sense_cache(unchecked_isa_dma),
+				     gfp_mask, numa_node);
 }
 
 int scsi_init_sense_cache(struct Scsi_Host *shost)
@@ -68,7 +68,7 @@ int scsi_init_sense_cache(struct Scsi_Host *shost)
 	struct kmem_cache *cache;
 	int ret = 0;
 
-	cache = scsi_select_sense_cache(shost);
+	cache = scsi_select_sense_cache(shost->unchecked_isa_dma);
 	if (cache)
 		return 0;
 
@@ -1137,6 +1137,7 @@ void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd)
 {
 	void *buf = cmd->sense_buffer;
 	void *prot = cmd->prot_sdb;
+	unsigned int unchecked_isa_dma = cmd->flags & SCMD_UNCHECKED_ISA_DMA;
 	unsigned long flags;
 
 	/* zero out the cmd, except for the embedded scsi_request */
@@ -1146,6 +1147,7 @@ void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd)
 	cmd->device = dev;
 	cmd->sense_buffer = buf;
 	cmd->prot_sdb = prot;
+	cmd->flags = unchecked_isa_dma;
 	INIT_DELAYED_WORK(&cmd->abort_work, scmd_eh_abort_handler);
 	cmd->jiffies_at_alloc = jiffies;
 
@@ -1846,6 +1848,7 @@ static int scsi_mq_prep_fn(struct request *req)
 	struct scsi_device *sdev = req->q->queuedata;
 	struct Scsi_Host *shost = sdev->host;
 	unsigned char *sense_buf = cmd->sense_buffer;
+	unsigned int unchecked_isa_dma = cmd->flags & SCMD_UNCHECKED_ISA_DMA;
 	struct scatterlist *sg;
 
 	/* zero out the cmd, except for the embedded scsi_request */
@@ -1857,6 +1860,7 @@ static int scsi_mq_prep_fn(struct request *req)
 	cmd->request = req;
 	cmd->device = sdev;
 	cmd->sense_buffer = sense_buf;
+	cmd->flags = unchecked_isa_dma;
 
 	cmd->tag = req->tag;
 
@@ -2003,10 +2007,13 @@ static int scsi_init_request(struct blk_mq_tag_set *set, struct request *rq,
 		unsigned int hctx_idx, unsigned int numa_node)
 {
 	struct Scsi_Host *shost = set->driver_data;
+	const bool unchecked_isa_dma = shost->unchecked_isa_dma;
 	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
 
-	cmd->sense_buffer =
-		scsi_alloc_sense_buffer(shost, GFP_KERNEL, numa_node);
+	if (unchecked_isa_dma)
+		cmd->flags |= SCMD_UNCHECKED_ISA_DMA;
+	cmd->sense_buffer = scsi_alloc_sense_buffer(unchecked_isa_dma,
+						    GFP_KERNEL, numa_node);
 	if (!cmd->sense_buffer)
 		return -ENOMEM;
 	cmd->req.sense = cmd->sense_buffer;
@@ -2016,10 +2023,10 @@ static int scsi_init_request(struct blk_mq_tag_set *set, struct request *rq,
 static void scsi_exit_request(struct blk_mq_tag_set *set, struct request *rq,
 		unsigned int hctx_idx)
 {
-	struct Scsi_Host *shost = set->driver_data;
 	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
 
-	scsi_free_sense_buffer(shost, cmd->sense_buffer);
+	scsi_free_sense_buffer(cmd->flags & SCMD_UNCHECKED_ISA_DMA,
+			       cmd->sense_buffer);
 }
 
 static int scsi_map_queues(struct blk_mq_tag_set *set)
@@ -2092,11 +2099,15 @@ EXPORT_SYMBOL_GPL(__scsi_init_queue);
 static int scsi_init_rq(struct request_queue *q, struct request *rq, gfp_t gfp)
 {
 	struct Scsi_Host *shost = q->rq_alloc_data;
+	const bool unchecked_isa_dma = shost->unchecked_isa_dma;
 	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
 
 	memset(cmd, 0, sizeof(*cmd));
 
-	cmd->sense_buffer = scsi_alloc_sense_buffer(shost, gfp, NUMA_NO_NODE);
+	if (unchecked_isa_dma)
+		cmd->flags |= SCMD_UNCHECKED_ISA_DMA;
+	cmd->sense_buffer = scsi_alloc_sense_buffer(unchecked_isa_dma, gfp,
+						    NUMA_NO_NODE);
 	if (!cmd->sense_buffer)
 		goto fail;
 	cmd->req.sense = cmd->sense_buffer;
@@ -2110,19 +2121,19 @@ static int scsi_init_rq(struct request_queue *q, struct request *rq, gfp_t gfp)
 	return 0;
 
 fail_free_sense:
-	scsi_free_sense_buffer(shost, cmd->sense_buffer);
+	scsi_free_sense_buffer(unchecked_isa_dma, cmd->sense_buffer);
 fail:
 	return -ENOMEM;
 }
 
 static void scsi_exit_rq(struct request_queue *q, struct request *rq)
 {
-	struct Scsi_Host *shost = q->rq_alloc_data;
 	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
 
 	if (cmd->prot_sdb)
 		kmem_cache_free(scsi_sdb_cache, cmd->prot_sdb);
-	scsi_free_sense_buffer(shost, cmd->sense_buffer);
+	scsi_free_sense_buffer(cmd->flags & SCMD_UNCHECKED_ISA_DMA,
+			       cmd->sense_buffer);
 }
 
 struct request_queue *scsi_alloc_queue(struct scsi_device *sdev)
diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index b379f93a2c48..16351de31243 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -56,6 +56,7 @@ struct scsi_pointer {
 
 /* for scmd->flags */
 #define SCMD_TAGGED		(1 << 0)
+#define SCMD_UNCHECKED_ISA_DMA	(1 << 1)
 
 struct scsi_cmnd {
 	struct scsi_request req;
-- 
2.12.2

[PATCH v3 02/12] Split scsi_internal_device_block()

[Bart Van Assche]

Instead of passing a "wait" argument to scsi_internal_device_block(),
split this function into a function that waits and a function that
doesn't wait. This will make it easier to serialize SCSI device state
changes through a mutex.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Sreekanth Reddy <sreekanth.reddy@broadcom.com>
---
 drivers/scsi/mpt3sas/mpt3sas_scsih.c |  4 +-
 drivers/scsi/scsi_lib.c              | 73 +++++++++++++++++++++++-------------
 include/scsi/scsi_device.h           |  2 +-
 3 files changed, 50 insertions(+), 29 deletions(-)

diff --git a/drivers/scsi/mpt3sas/mpt3sas_scsih.c b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
index a5d872664257..c63bc5ccce37 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_scsih.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
@@ -2859,7 +2859,7 @@ _scsih_internal_device_block(struct scsi_device *sdev,
 	    sas_device_priv_data->sas_target->handle);
 	sas_device_priv_data->block = 1;
 
-	r = scsi_internal_device_block(sdev, false);
+	r = scsi_internal_device_block_nowait(sdev);
 	if (r == -EINVAL)
 		sdev_printk(KERN_WARNING, sdev,
 		    "device_block failed with return(%d) for handle(0x%04x)\n",
@@ -2895,7 +2895,7 @@ _scsih_internal_device_unblock(struct scsi_device *sdev,
 		    "performing a block followed by an unblock\n",
 		    r, sas_device_priv_data->sas_target->handle);
 		sas_device_priv_data->block = 1;
-		r = scsi_internal_device_block(sdev, false);
+		r = scsi_internal_device_block_nowait(sdev);
 		if (r)
 			sdev_printk(KERN_WARNING, sdev, "retried device_block "
 			    "failed with return(%d) for handle(0x%04x)\n",
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index cc9f792cd12b..c9ce36d16df0 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2943,28 +2943,20 @@ scsi_target_resume(struct scsi_target *starget)
 EXPORT_SYMBOL(scsi_target_resume);
 
 /**
- * scsi_internal_device_block - internal function to put a device temporarily into the SDEV_BLOCK state
- * @sdev:	device to block
- * @wait:	Whether or not to wait until ongoing .queuecommand() /
- *		.queue_rq() calls have finished.
+ * scsi_internal_device_block_nowait - try to transition to the SDEV_BLOCK state
+ * @sdev: device to block
  *
- * Block request made by scsi lld's to temporarily stop all
- * scsi commands on the specified device. May sleep.
+ * Pause SCSI command processing on the specified device. Does not sleep.
  *
- * Returns zero if successful or error if not
+ * Returns zero if successful or a negative error code upon failure.
  *
- * Notes:       
- *	This routine transitions the device to the SDEV_BLOCK state
- *	(which must be a legal transition).  When the device is in this
- *	state, all commands are deferred until the scsi lld reenables
- *	the device with scsi_device_unblock or device_block_tmo fires.
- *
- * To do: avoid that scsi_send_eh_cmnd() calls queuecommand() after
- * scsi_internal_device_block() has blocked a SCSI device and also
- * remove the rport mutex lock and unlock calls from srp_queuecommand().
+ * Notes:
+ * This routine transitions the device to the SDEV_BLOCK state (which must be
+ * a legal transition). When the device is in this state, command processing
+ * is paused until the device leaves the SDEV_BLOCK state. See also
+ * scsi_internal_device_unblock_nowait().
  */
-int
-scsi_internal_device_block(struct scsi_device *sdev, bool wait)
+int scsi_internal_device_block_nowait(struct scsi_device *sdev)
 {
 	struct request_queue *q = sdev->request_queue;
 	unsigned long flags;
@@ -2984,21 +2976,50 @@ scsi_internal_device_block(struct scsi_device *sdev, bool wait)
 	 * request queue. 
 	 */
 	if (q->mq_ops) {
-		if (wait)
-			blk_mq_quiesce_queue(q);
-		else
-			blk_mq_stop_hw_queues(q);
+		blk_mq_stop_hw_queues(q);
 	} else {
 		spin_lock_irqsave(q->queue_lock, flags);
 		blk_stop_queue(q);
 		spin_unlock_irqrestore(q->queue_lock, flags);
-		if (wait)
-			scsi_wait_for_queuecommand(sdev);
 	}
 
 	return 0;
 }
-EXPORT_SYMBOL_GPL(scsi_internal_device_block);
+EXPORT_SYMBOL_GPL(scsi_internal_device_block_nowait);
+
+/**
+ * scsi_internal_device_block - try to transition to the SDEV_BLOCK state
+ * @sdev: device to block
+ *
+ * Pause SCSI command processing on the specified device and wait until all
+ * ongoing scsi_request_fn() / scsi_queue_rq() calls have finished. May sleep.
+ *
+ * Returns zero if successful or a negative error code upon failure.
+ *
+ * Note:
+ * This routine transitions the device to the SDEV_BLOCK state (which must be
+ * a legal transition). When the device is in this state, command processing
+ * is paused until the device leaves the SDEV_BLOCK state. See also
+ * scsi_internal_device_unblock().
+ *
+ * To do: avoid that scsi_send_eh_cmnd() calls queuecommand() after
+ * scsi_internal_device_block() has blocked a SCSI device and also
+ * remove the rport mutex lock and unlock calls from srp_queuecommand().
+ */
+static int scsi_internal_device_block(struct scsi_device *sdev)
+{
+	struct request_queue *q = sdev->request_queue;
+	int err;
+
+	err = scsi_internal_device_block_nowait(sdev);
+	if (err == 0) {
+		if (q->mq_ops)
+			blk_mq_quiesce_queue(q);
+		else
+			scsi_wait_for_queuecommand(sdev);
+	}
+	return err;
+}
  
 /**
  * scsi_internal_device_unblock - resume a device after a block request
@@ -3055,7 +3076,7 @@ EXPORT_SYMBOL_GPL(scsi_internal_device_unblock);
 static void
 device_block(struct scsi_device *sdev, void *data)
 {
-	scsi_internal_device_block(sdev, true);
+	scsi_internal_device_block(sdev);
 }
 
 static int
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 05641aebd181..6ce6888f3c69 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -472,7 +472,7 @@ static inline int scsi_device_created(struct scsi_device *sdev)
 		sdev->sdev_state == SDEV_CREATED_BLOCK;
 }
 
-int scsi_internal_device_block(struct scsi_device *sdev, bool wait);
+int scsi_internal_device_block_nowait(struct scsi_device *sdev);
 int scsi_internal_device_unblock(struct scsi_device *sdev,
 				 enum scsi_device_state new_state);
 
-- 
2.12.2

[PATCH v3 03/12] Create two versions of scsi_internal_device_unblock()

[Bart Van Assche]

This will make it easier to serialize SCSI device state changes
through a mutex.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Sreekanth Reddy <sreekanth.reddy@broadcom.com>
---
 drivers/scsi/mpt3sas/mpt3sas_scsih.c |  4 ++--
 drivers/scsi/scsi_lib.c              | 46 +++++++++++++++++++++++++-----------
 include/scsi/scsi_device.h           |  4 ++--
 3 files changed, 36 insertions(+), 18 deletions(-)

diff --git a/drivers/scsi/mpt3sas/mpt3sas_scsih.c b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
index c63bc5ccce37..22998cbd538f 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_scsih.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
@@ -2883,7 +2883,7 @@ _scsih_internal_device_unblock(struct scsi_device *sdev,
 	sdev_printk(KERN_WARNING, sdev, "device_unblock and setting to running, "
 	    "handle(0x%04x)\n", sas_device_priv_data->sas_target->handle);
 	sas_device_priv_data->block = 0;
-	r = scsi_internal_device_unblock(sdev, SDEV_RUNNING);
+	r = scsi_internal_device_unblock_nowait(sdev, SDEV_RUNNING);
 	if (r == -EINVAL) {
 		/* The device has been set to SDEV_RUNNING by SD layer during
 		 * device addition but the request queue is still stopped by
@@ -2902,7 +2902,7 @@ _scsih_internal_device_unblock(struct scsi_device *sdev,
 			    r, sas_device_priv_data->sas_target->handle);
 
 		sas_device_priv_data->block = 0;
-		r = scsi_internal_device_unblock(sdev, SDEV_RUNNING);
+		r = scsi_internal_device_unblock_nowait(sdev, SDEV_RUNNING);
 		if (r)
 			sdev_printk(KERN_WARNING, sdev, "retried device_unblock"
 			    " failed with return(%d) for handle(0x%04x)\n",
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index c9ce36d16df0..aa84b77e41dc 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -3022,24 +3022,22 @@ static int scsi_internal_device_block(struct scsi_device *sdev)
 }
  
 /**
- * scsi_internal_device_unblock - resume a device after a block request
+ * scsi_internal_device_unblock_nowait - resume a device after a block request
  * @sdev:	device to resume
- * @new_state:	state to set devices to after unblocking
+ * @new_state:	state to set the device to after unblocking
  *
- * Called by scsi lld's or the midlayer to restart the device queue
- * for the previously suspended scsi device.  Called from interrupt or
- * normal process context.
+ * Restart the device queue for a previously suspended SCSI device. Does not
+ * sleep.
  *
- * Returns zero if successful or error if not.
+ * Returns zero if successful or a negative error code upon failure.
  *
- * Notes:       
- *	This routine transitions the device to the SDEV_RUNNING state
- *	or to one of the offline states (which must be a legal transition)
- *	allowing the midlayer to goose the queue for this device.
+ * Notes:
+ * This routine transitions the device to the SDEV_RUNNING state or to one of
+ * the offline states (which must be a legal transition) allowing the midlayer
+ * to goose the queue for this device.
  */
-int
-scsi_internal_device_unblock(struct scsi_device *sdev,
-			     enum scsi_device_state new_state)
+int scsi_internal_device_unblock_nowait(struct scsi_device *sdev,
+					enum scsi_device_state new_state)
 {
 	struct request_queue *q = sdev->request_queue; 
 	unsigned long flags;
@@ -3071,7 +3069,27 @@ scsi_internal_device_unblock(struct scsi_device *sdev,
 
 	return 0;
 }
-EXPORT_SYMBOL_GPL(scsi_internal_device_unblock);
+EXPORT_SYMBOL_GPL(scsi_internal_device_unblock_nowait);
+
+/**
+ * scsi_internal_device_unblock - resume a device after a block request
+ * @sdev:	device to resume
+ * @new_state:	state to set the device to after unblocking
+ *
+ * Restart the device queue for a previously suspended SCSI device. May sleep.
+ *
+ * Returns zero if successful or a negative error code upon failure.
+ *
+ * Notes:
+ * This routine transitions the device to the SDEV_RUNNING state or to one of
+ * the offline states (which must be a legal transition) allowing the midlayer
+ * to goose the queue for this device.
+ */
+static int scsi_internal_device_unblock(struct scsi_device *sdev,
+					enum scsi_device_state new_state)
+{
+	return scsi_internal_device_unblock_nowait(sdev, new_state);
+}
 
 static void
 device_block(struct scsi_device *sdev, void *data)
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 6ce6888f3c69..5f24dae2a8e1 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -473,8 +473,8 @@ static inline int scsi_device_created(struct scsi_device *sdev)
 }
 
 int scsi_internal_device_block_nowait(struct scsi_device *sdev);
-int scsi_internal_device_unblock(struct scsi_device *sdev,
-				 enum scsi_device_state new_state);
+int scsi_internal_device_unblock_nowait(struct scsi_device *sdev,
+					enum scsi_device_state new_state);
 
 /* accessor functions for the SCSI parameters */
 static inline int scsi_device_sync(struct scsi_device *sdev)
-- 
2.12.2

[PATCH v3 04/12] Protect SCSI device state changes with a mutex

[Bart Van Assche]

Serializing SCSI device state changes avoids that two state changes
can occur concurrently, e.g. the state changes in scsi_target_block()
and __scsi_remove_device(). This serialization is essential to make
patch "Make __scsi_remove_device go straight from BLOCKED to DEL"
work reliably.

Enable this mechanism for all scsi_target_*block() callers but not
for the scsi_internal_device_unblock() calls from the mpt3sas driver
because that driver can call scsi_internal_device_unblock() from
atomic context.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
---
 drivers/scsi/scsi_error.c         |  8 +++++++-
 drivers/scsi/scsi_lib.c           | 27 +++++++++++++++++++++------
 drivers/scsi/scsi_scan.c          | 16 +++++++++-------
 drivers/scsi/scsi_sysfs.c         | 24 +++++++++++++++++++-----
 drivers/scsi/scsi_transport_srp.c |  7 ++++---
 drivers/scsi/sd.c                 |  7 +++++--
 include/scsi/scsi_device.h        |  1 +
 7 files changed, 66 insertions(+), 24 deletions(-)

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index ecc07dab893d..ac3196420435 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -1628,11 +1628,17 @@ static void scsi_eh_offline_sdevs(struct list_head *work_q,
 				  struct list_head *done_q)
 {
 	struct scsi_cmnd *scmd, *next;
+	struct scsi_device *sdev;
 
 	list_for_each_entry_safe(scmd, next, work_q, eh_entry) {
 		sdev_printk(KERN_INFO, scmd->device, "Device offlined - "
 			    "not ready after error recovery\n");
-		scsi_device_set_state(scmd->device, SDEV_OFFLINE);
+		sdev = scmd->device;
+
+		mutex_lock(&sdev->state_mutex);
+		scsi_device_set_state(sdev, SDEV_OFFLINE);
+		mutex_unlock(&sdev->state_mutex);
+
 		scsi_eh_finish_cmd(scmd, done_q);
 	}
 	return;
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index aa84b77e41dc..845d47244e70 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2881,7 +2881,12 @@ static void scsi_wait_for_queuecommand(struct scsi_device *sdev)
 int
 scsi_device_quiesce(struct scsi_device *sdev)
 {
-	int err = scsi_device_set_state(sdev, SDEV_QUIESCE);
+	int err;
+
+	mutex_lock(&sdev->state_mutex);
+	err = scsi_device_set_state(sdev, SDEV_QUIESCE);
+	mutex_unlock(&sdev->state_mutex);
+
 	if (err)
 		return err;
 
@@ -2909,10 +2914,11 @@ void scsi_device_resume(struct scsi_device *sdev)
 	 * so assume the state is being managed elsewhere (for example
 	 * device deleted during suspend)
 	 */
-	if (sdev->sdev_state != SDEV_QUIESCE ||
-	    scsi_device_set_state(sdev, SDEV_RUNNING))
-		return;
-	scsi_run_queue(sdev->request_queue);
+	mutex_lock(&sdev->state_mutex);
+	if (sdev->sdev_state == SDEV_QUIESCE &&
+	    scsi_device_set_state(sdev, SDEV_RUNNING) == 0)
+		scsi_run_queue(sdev->request_queue);
+	mutex_unlock(&sdev->state_mutex);
 }
 EXPORT_SYMBOL(scsi_device_resume);
 
@@ -3011,6 +3017,7 @@ static int scsi_internal_device_block(struct scsi_device *sdev)
 	struct request_queue *q = sdev->request_queue;
 	int err;
 
+	mutex_lock(&sdev->state_mutex);
 	err = scsi_internal_device_block_nowait(sdev);
 	if (err == 0) {
 		if (q->mq_ops)
@@ -3018,6 +3025,8 @@ static int scsi_internal_device_block(struct scsi_device *sdev)
 		else
 			scsi_wait_for_queuecommand(sdev);
 	}
+	mutex_unlock(&sdev->state_mutex);
+
 	return err;
 }
  
@@ -3088,7 +3097,13 @@ EXPORT_SYMBOL_GPL(scsi_internal_device_unblock_nowait);
 static int scsi_internal_device_unblock(struct scsi_device *sdev,
 					enum scsi_device_state new_state)
 {
-	return scsi_internal_device_unblock_nowait(sdev, new_state);
+	int ret;
+
+	mutex_lock(&sdev->state_mutex);
+	ret = scsi_internal_device_unblock_nowait(sdev, new_state);
+	mutex_unlock(&sdev->state_mutex);
+
+	return ret;
 }
 
 static void
diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 6f7128f49c30..e6de4eee97a3 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -231,6 +231,7 @@ static struct scsi_device *scsi_alloc_sdev(struct scsi_target *starget,
 	sdev->id = starget->id;
 	sdev->lun = lun;
 	sdev->channel = starget->channel;
+	mutex_init(&sdev->state_mutex);
 	sdev->sdev_state = SDEV_CREATED;
 	INIT_LIST_HEAD(&sdev->siblings);
 	INIT_LIST_HEAD(&sdev->same_target_siblings);
@@ -943,16 +944,17 @@ static int scsi_add_lun(struct scsi_device *sdev, unsigned char *inq_result,
 
 	/* set the device running here so that slave configure
 	 * may do I/O */
+	mutex_lock(&sdev->state_mutex);
 	ret = scsi_device_set_state(sdev, SDEV_RUNNING);
-	if (ret) {
+	if (ret)
 		ret = scsi_device_set_state(sdev, SDEV_BLOCK);
+	mutex_unlock(&sdev->state_mutex);
 
-		if (ret) {
-			sdev_printk(KERN_ERR, sdev,
-				    "in wrong state %s to complete scan\n",
-				    scsi_device_state_name(sdev->sdev_state));
-			return SCSI_SCAN_NO_RESPONSE;
-		}
+	if (ret) {
+		sdev_printk(KERN_ERR, sdev,
+			    "in wrong state %s to complete scan\n",
+			    scsi_device_state_name(sdev->sdev_state));
+		return SCSI_SCAN_NO_RESPONSE;
 	}
 
 	if (*bflags & BLIST_MS_192_BYTES_FOR_3F)
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 82dfe07b1d47..a91537a3abbf 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -719,7 +719,7 @@ static ssize_t
 store_state_field(struct device *dev, struct device_attribute *attr,
 		  const char *buf, size_t count)
 {
-	int i;
+	int i, ret;
 	struct scsi_device *sdev = to_scsi_device(dev);
 	enum scsi_device_state state = 0;
 
@@ -734,9 +734,11 @@ store_state_field(struct device *dev, struct device_attribute *attr,
 	if (!state)
 		return -EINVAL;
 
-	if (scsi_device_set_state(sdev, state))
-		return -EINVAL;
-	return count;
+	mutex_lock(&sdev->state_mutex);
+	ret = scsi_device_set_state(sdev, state);
+	mutex_unlock(&sdev->state_mutex);
+
+	return ret == 0 ? count : -EINVAL;
 }
 
 static ssize_t
@@ -1272,6 +1274,7 @@ int scsi_sysfs_add_sdev(struct scsi_device *sdev)
 void __scsi_remove_device(struct scsi_device *sdev)
 {
 	struct device *dev = &sdev->sdev_gendev;
+	int res;
 
 	/*
 	 * This cleanup path is not reentrant and while it is impossible
@@ -1282,7 +1285,15 @@ void __scsi_remove_device(struct scsi_device *sdev)
 		return;
 
 	if (sdev->is_visible) {
-		if (scsi_device_set_state(sdev, SDEV_CANCEL) != 0)
+		/*
+		 * If scsi_internal_target_block() is running concurrently,
+		 * wait until it has finished before changing the device state.
+		 */
+		mutex_lock(&sdev->state_mutex);
+		res = scsi_device_set_state(sdev, SDEV_CANCEL);
+		mutex_unlock(&sdev->state_mutex);
+
+		if (res != 0)
 			return;
 
 		bsg_unregister_queue(sdev->request_queue);
@@ -1298,7 +1309,10 @@ void __scsi_remove_device(struct scsi_device *sdev)
 	 * scsi_run_queue() invocations have finished before tearing down the
 	 * device.
 	 */
+	mutex_lock(&sdev->state_mutex);
 	scsi_device_set_state(sdev, SDEV_DEL);
+	mutex_unlock(&sdev->state_mutex);
+
 	blk_cleanup_queue(sdev->request_queue);
 	cancel_work_sync(&sdev->requeue_work);
 
diff --git a/drivers/scsi/scsi_transport_srp.c b/drivers/scsi/scsi_transport_srp.c
index 3c5d89852e9f..f617021c94f7 100644
--- a/drivers/scsi/scsi_transport_srp.c
+++ b/drivers/scsi/scsi_transport_srp.c
@@ -554,11 +554,12 @@ int srp_reconnect_rport(struct srp_rport *rport)
 		 * invoking scsi_target_unblock() won't change the state of
 		 * these devices into running so do that explicitly.
 		 */
-		spin_lock_irq(shost->host_lock);
-		__shost_for_each_device(sdev, shost)
+		shost_for_each_device(sdev, shost) {
+			mutex_lock(&sdev->state_mutex);
 			if (sdev->sdev_state == SDEV_OFFLINE)
 				sdev->sdev_state = SDEV_RUNNING;
-		spin_unlock_irq(shost->host_lock);
+			mutex_unlock(&sdev->state_mutex);
+		}
 	} else if (rport->state == SRP_RPORT_RUNNING) {
 		/*
 		 * srp_reconnect_rport() has been invoked with fast_io_fail
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index f9d1432d7cc5..aea55f5afed0 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -1798,8 +1798,9 @@ static void sd_eh_reset(struct scsi_cmnd *scmd)
 static int sd_eh_action(struct scsi_cmnd *scmd, int eh_disp)
 {
 	struct scsi_disk *sdkp = scsi_disk(scmd->request->rq_disk);
+	struct scsi_device *sdev = scmd->device;
 
-	if (!scsi_device_online(scmd->device) ||
+	if (!scsi_device_online(sdev) ||
 	    !scsi_medium_access_command(scmd) ||
 	    host_byte(scmd->result) != DID_TIME_OUT ||
 	    eh_disp != SUCCESS)
@@ -1825,7 +1826,9 @@ static int sd_eh_action(struct scsi_cmnd *scmd, int eh_disp)
 	if (sdkp->medium_access_timed_out >= sdkp->max_medium_access_timeouts) {
 		scmd_printk(KERN_ERR, scmd,
 			    "Medium access timeout failure. Offlining disk!\n");
-		scsi_device_set_state(scmd->device, SDEV_OFFLINE);
+		mutex_lock(&sdev->state_mutex);
+		scsi_device_set_state(sdev, SDEV_OFFLINE);
+		mutex_unlock(&sdev->state_mutex);
 
 		return SUCCESS;
 	}
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 5f24dae2a8e1..d13bc80825b1 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -207,6 +207,7 @@ struct scsi_device {
 	void			*handler_data;
 
 	unsigned char		access_state;
+	struct mutex		state_mutex;
 	enum scsi_device_state sdev_state;
 	unsigned long		sdev_data[0];
 } __attribute__((aligned(sizeof(unsigned long))));
-- 
2.12.2

[PATCH v3 05/12] Introduce scsi_start_queue()

[Bart Van Assche]

This patch does not change any functionality.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Israel Rukshin <israelr@mellanox.com>
Cc: Max Gurtovoy <maxg@mellanox.com>
Cc: Benjamin Block <bblock@linux.vnet.ibm.com>
---
 drivers/scsi/scsi_lib.c  | 25 +++++++++++++++----------
 drivers/scsi/scsi_priv.h |  1 +
 2 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 845d47244e70..6a58a124714f 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -3030,6 +3030,20 @@ static int scsi_internal_device_block(struct scsi_device *sdev)
 	return err;
 }
  
+void scsi_start_queue(struct scsi_device *sdev)
+{
+	struct request_queue *q = sdev->request_queue;
+	unsigned long flags;
+
+	if (q->mq_ops) {
+		blk_mq_start_stopped_hw_queues(q, false);
+	} else {
+		spin_lock_irqsave(q->queue_lock, flags);
+		blk_start_queue(q);
+		spin_unlock_irqrestore(q->queue_lock, flags);
+	}
+}
+
 /**
  * scsi_internal_device_unblock_nowait - resume a device after a block request
  * @sdev:	device to resume
@@ -3048,9 +3062,6 @@ static int scsi_internal_device_block(struct scsi_device *sdev)
 int scsi_internal_device_unblock_nowait(struct scsi_device *sdev,
 					enum scsi_device_state new_state)
 {
-	struct request_queue *q = sdev->request_queue; 
-	unsigned long flags;
-
 	/*
 	 * Try to transition the scsi device to SDEV_RUNNING or one of the
 	 * offlined states and goose the device queue if successful.
@@ -3068,13 +3079,7 @@ int scsi_internal_device_unblock_nowait(struct scsi_device *sdev,
 		 sdev->sdev_state != SDEV_OFFLINE)
 		return -EINVAL;
 
-	if (q->mq_ops) {
-		blk_mq_start_stopped_hw_queues(q, false);
-	} else {
-		spin_lock_irqsave(q->queue_lock, flags);
-		blk_start_queue(q);
-		spin_unlock_irqrestore(q->queue_lock, flags);
-	}
+	scsi_start_queue(sdev);
 
 	return 0;
 }
diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h
index 59ebc1795bb3..f86057842f9a 100644
--- a/drivers/scsi/scsi_priv.h
+++ b/drivers/scsi/scsi_priv.h
@@ -88,6 +88,7 @@ extern void scsi_run_host_queues(struct Scsi_Host *shost);
 extern void scsi_requeue_run_queue(struct work_struct *work);
 extern struct request_queue *scsi_alloc_queue(struct scsi_device *sdev);
 extern struct request_queue *scsi_mq_alloc_queue(struct scsi_device *sdev);
+extern void scsi_start_queue(struct scsi_device *sdev);
 extern int scsi_mq_setup_tags(struct Scsi_Host *shost);
 extern void scsi_mq_destroy_tags(struct Scsi_Host *shost);
 extern int scsi_init_queue(void);
-- 
2.12.2

[PATCH v3 06/12] Make __scsi_remove_device go straight from BLOCKED to DEL

[Bart Van Assche]

If a device is blocked, make __scsi_remove_device() cause it to
transition to the DEL state. This means that all the commands
issued in .shutdown() will error in the mid-layer, thus making
the removal proceed without being stopped.

This patch is a slightly modified version of a patch from James
Bottomley. This patch avoids that the following lockup occurs:

Call Trace:
 schedule+0x35/0x80
 schedule_timeout+0x237/0x2d0
 io_schedule_timeout+0xa6/0x110
 wait_for_completion_io+0xa3/0x110
 blk_execute_rq+0xdf/0x120
 scsi_execute+0xce/0x150 [scsi_mod]
 scsi_execute_req_flags+0x8f/0xf0 [scsi_mod]
 sd_sync_cache+0xa9/0x190 [sd_mod]
 sd_shutdown+0x6a/0x100 [sd_mod]
 sd_remove+0x64/0xc0 [sd_mod]
 __device_release_driver+0x8d/0x120
 device_release_driver+0x1e/0x30
 bus_remove_device+0xf9/0x170
 device_del+0x127/0x240
 __scsi_remove_device+0xc1/0xd0 [scsi_mod]
 scsi_forget_host+0x57/0x60 [scsi_mod]
 scsi_remove_host+0x72/0x110 [scsi_mod]
 srp_remove_work+0x8b/0x200 [ib_srp]

Reported-by: Israel Rukshin <israelr@mellanox.com>
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Israel Rukshin <israelr@mellanox.com>
Cc: Max Gurtovoy <maxg@mellanox.com>
Cc: Benjamin Block <bblock@linux.vnet.ibm.com>
---
 drivers/scsi/scsi_lib.c   |  2 +-
 drivers/scsi/scsi_sysfs.c | 10 ++++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 6a58a124714f..8665eccd2fc8 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2624,7 +2624,6 @@ scsi_device_set_state(struct scsi_device *sdev, enum scsi_device_state state)
 		case SDEV_QUIESCE:
 		case SDEV_OFFLINE:
 		case SDEV_TRANSPORT_OFFLINE:
-		case SDEV_BLOCK:
 			break;
 		default:
 			goto illegal;
@@ -2638,6 +2637,7 @@ scsi_device_set_state(struct scsi_device *sdev, enum scsi_device_state state)
 		case SDEV_OFFLINE:
 		case SDEV_TRANSPORT_OFFLINE:
 		case SDEV_CANCEL:
+		case SDEV_BLOCK:
 		case SDEV_CREATED_BLOCK:
 			break;
 		default:
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index a91537a3abbf..ce470f62a8ae 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -1290,7 +1290,17 @@ void __scsi_remove_device(struct scsi_device *sdev)
 		 * wait until it has finished before changing the device state.
 		 */
 		mutex_lock(&sdev->state_mutex);
+		/*
+		 * If blocked, we go straight to DEL and restart the queue so
+		 * any commands issued during driver shutdown (like sync
+		 * cache) are errored immediately.
+		 */
 		res = scsi_device_set_state(sdev, SDEV_CANCEL);
+		if (res != 0) {
+			res = scsi_device_set_state(sdev, SDEV_DEL);
+			if (res == 0)
+				scsi_start_queue(sdev);
+		}
 		mutex_unlock(&sdev->state_mutex);
 
 		if (res != 0)
-- 
2.12.2

[PATCH v3 07/12] Only add commands to the device command list if required by the LLD

[Bart Van Assche]

Just like for the scsi-mq code path, in the single queue SCSI code
path only add commands to the per-device command list if required
by the SCSI LLD. This patch will make it easier to merge the
single-queue and multiqueue command initialization code.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
---
 drivers/scsi/scsi.c      |  9 +--------
 drivers/scsi/scsi_lib.c  | 52 +++++++++++++++++++++++++++++-------------------
 drivers/scsi/scsi_priv.h |  2 ++
 3 files changed, 35 insertions(+), 28 deletions(-)

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 7bfbcfa7af40..485684aafb9b 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -108,14 +108,7 @@ EXPORT_SYMBOL(scsi_sd_pm_domain);
  */
 void scsi_put_command(struct scsi_cmnd *cmd)
 {
-	unsigned long flags;
-
-	/* serious error if the command hasn't come from a device list */
-	spin_lock_irqsave(&cmd->device->list_lock, flags);
-	BUG_ON(list_empty(&cmd->list));
-	list_del_init(&cmd->list);
-	spin_unlock_irqrestore(&cmd->device->list_lock, flags);
-
+	scsi_del_cmd_from_list(cmd);
 	BUG_ON(delayed_work_pending(&cmd->abort_work));
 }
 
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 8665eccd2fc8..2c43b500e9f4 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -583,19 +583,9 @@ static void scsi_mq_free_sgtables(struct scsi_cmnd *cmd)
 
 static void scsi_mq_uninit_cmd(struct scsi_cmnd *cmd)
 {
-	struct scsi_device *sdev = cmd->device;
-	struct Scsi_Host *shost = sdev->host;
-	unsigned long flags;
-
 	scsi_mq_free_sgtables(cmd);
 	scsi_uninit_cmd(cmd);
-
-	if (shost->use_cmd_list) {
-		BUG_ON(list_empty(&cmd->list));
-		spin_lock_irqsave(&sdev->list_lock, flags);
-		list_del_init(&cmd->list);
-		spin_unlock_irqrestore(&sdev->list_lock, flags);
-	}
+	scsi_del_cmd_from_list(cmd);
 }
 
 /*
@@ -1133,12 +1123,40 @@ int scsi_init_io(struct scsi_cmnd *cmd)
 }
 EXPORT_SYMBOL(scsi_init_io);
 
+/* Add a command to the list used by the aacraid and dpt_i2o drivers */
+void scsi_add_cmd_to_list(struct scsi_cmnd *cmd)
+{
+	struct scsi_device *sdev = cmd->device;
+	struct Scsi_Host *shost = sdev->host;
+	unsigned long flags;
+
+	if (shost->use_cmd_list) {
+		spin_lock_irqsave(&sdev->list_lock, flags);
+		list_add_tail(&cmd->list, &sdev->cmd_list);
+		spin_unlock_irqrestore(&sdev->list_lock, flags);
+	}
+}
+
+/* Remove a command from the list used by the aacraid and dpt_i2o drivers */
+void scsi_del_cmd_from_list(struct scsi_cmnd *cmd)
+{
+	struct scsi_device *sdev = cmd->device;
+	struct Scsi_Host *shost = sdev->host;
+	unsigned long flags;
+
+	if (shost->use_cmd_list) {
+		spin_lock_irqsave(&sdev->list_lock, flags);
+		BUG_ON(list_empty(&cmd->list));
+		list_del_init(&cmd->list);
+		spin_unlock_irqrestore(&sdev->list_lock, flags);
+	}
+}
+
 void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd)
 {
 	void *buf = cmd->sense_buffer;
 	void *prot = cmd->prot_sdb;
 	unsigned int unchecked_isa_dma = cmd->flags & SCMD_UNCHECKED_ISA_DMA;
-	unsigned long flags;
 
 	/* zero out the cmd, except for the embedded scsi_request */
 	memset((char *)cmd + sizeof(cmd->req), 0,
@@ -1151,9 +1169,7 @@ void scsi_init_command(struct scsi_device *dev, struct scsi_cmnd *cmd)
 	INIT_DELAYED_WORK(&cmd->abort_work, scmd_eh_abort_handler);
 	cmd->jiffies_at_alloc = jiffies;
 
-	spin_lock_irqsave(&dev->list_lock, flags);
-	list_add_tail(&cmd->list, &dev->cmd_list);
-	spin_unlock_irqrestore(&dev->list_lock, flags);
+	scsi_add_cmd_to_list(cmd);
 }
 
 static int scsi_setup_scsi_cmnd(struct scsi_device *sdev, struct request *req)
@@ -1870,11 +1886,7 @@ static int scsi_mq_prep_fn(struct request *req)
 	INIT_DELAYED_WORK(&cmd->abort_work, scmd_eh_abort_handler);
 	cmd->jiffies_at_alloc = jiffies;
 
-	if (shost->use_cmd_list) {
-		spin_lock_irq(&sdev->list_lock);
-		list_add_tail(&cmd->list, &sdev->cmd_list);
-		spin_unlock_irq(&sdev->list_lock);
-	}
+	scsi_add_cmd_to_list(cmd);
 
 	sg = (void *)cmd + sizeof(struct scsi_cmnd) + shost->hostt->cmd_size;
 	cmd->sdb.table.sgl = sg;
diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h
index f86057842f9a..c11c1f9c912c 100644
--- a/drivers/scsi/scsi_priv.h
+++ b/drivers/scsi/scsi_priv.h
@@ -80,6 +80,8 @@ int scsi_eh_get_sense(struct list_head *work_q,
 int scsi_noretry_cmd(struct scsi_cmnd *scmd);
 
 /* scsi_lib.c */
+extern void scsi_add_cmd_to_list(struct scsi_cmnd *cmd);
+extern void scsi_del_cmd_from_list(struct scsi_cmnd *cmd);
 extern int scsi_maybe_unblock_host(struct scsi_device *sdev);
 extern void scsi_device_unbusy(struct scsi_device *sdev);
 extern void scsi_queue_insert(struct scsi_cmnd *cmd, int reason);
-- 
2.12.2

[PATCH v3 08/12] Introduce scsi_mq_sgl_size()

[Bart Van Assche]

This patch does not change any functionality but makes the next
patch easier to read.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
---
 drivers/scsi/scsi_lib.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 2c43b500e9f4..6b4fb48033fb 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1858,6 +1858,13 @@ static inline int prep_to_mq(int ret)
 	}
 }
 
+/* Size in bytes of the sg-list stored in the scsi-mq command-private data. */
+static unsigned int scsi_mq_sgl_size(struct Scsi_Host *shost)
+{
+	return min_t(unsigned int, shost->sg_tablesize, SG_CHUNK_SIZE) *
+		sizeof(struct scatterlist);
+}
+
 static int scsi_mq_prep_fn(struct request *req)
 {
 	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
@@ -1892,10 +1899,7 @@ static int scsi_mq_prep_fn(struct request *req)
 	cmd->sdb.table.sgl = sg;
 
 	if (scsi_host_get_prot(shost)) {
-		cmd->prot_sdb = (void *)sg +
-			min_t(unsigned int,
-			      shost->sg_tablesize, SG_CHUNK_SIZE) *
-			sizeof(struct scatterlist);
+		cmd->prot_sdb = (void *)sg + scsi_mq_sgl_size(shost);
 		memset(cmd->prot_sdb, 0, sizeof(struct scsi_data_buffer));
 
 		cmd->prot_sdb->table.sgl =
@@ -2201,12 +2205,9 @@ struct request_queue *scsi_mq_alloc_queue(struct scsi_device *sdev)
 
 int scsi_mq_setup_tags(struct Scsi_Host *shost)
 {
-	unsigned int cmd_size, sgl_size, tbl_size;
+	unsigned int cmd_size, sgl_size;
 
-	tbl_size = shost->sg_tablesize;
-	if (tbl_size > SG_CHUNK_SIZE)
-		tbl_size = SG_CHUNK_SIZE;
-	sgl_size = tbl_size * sizeof(struct scatterlist);
+	sgl_size = scsi_mq_sgl_size(shost);
 	cmd_size = sizeof(struct scsi_cmnd) + shost->hostt->cmd_size + sgl_size;
 	if (scsi_host_get_prot(shost))
 		cmd_size += sizeof(struct scsi_data_buffer) + sgl_size;
-- 
2.12.2

[PATCH v3 09/12] Make scsi_mq_prep_fn() call scsi_init_command()

[Bart Van Assche]

This patch reduces code duplication. There are two functional changes
in this patch:
- It causes scsi_mq_prep_fn() to clear driver-private
  command data, just like the already upstream commit 1bad6c4a57ef
  ("scsi: zero per-cmd private driver data for each MQ I/O").
- The initialization of .prot_sdb is moved from scsi_mq_prep_fn()
  into scsi_init_request().

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
---
 drivers/scsi/scsi_lib.c | 25 +++++++++----------------
 1 file changed, 9 insertions(+), 16 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 6b4fb48033fb..ef4e33319407 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1870,36 +1870,21 @@ static int scsi_mq_prep_fn(struct request *req)
 	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
 	struct scsi_device *sdev = req->q->queuedata;
 	struct Scsi_Host *shost = sdev->host;
-	unsigned char *sense_buf = cmd->sense_buffer;
-	unsigned int unchecked_isa_dma = cmd->flags & SCMD_UNCHECKED_ISA_DMA;
 	struct scatterlist *sg;
 
-	/* zero out the cmd, except for the embedded scsi_request */
-	memset((char *)cmd + sizeof(cmd->req), 0,
-		sizeof(*cmd) - sizeof(cmd->req));
+	scsi_init_command(sdev, cmd);
 
 	req->special = cmd;
 
 	cmd->request = req;
-	cmd->device = sdev;
-	cmd->sense_buffer = sense_buf;
-	cmd->flags = unchecked_isa_dma;
 
 	cmd->tag = req->tag;
-
 	cmd->prot_op = SCSI_PROT_NORMAL;
 
-	INIT_LIST_HEAD(&cmd->list);
-	INIT_DELAYED_WORK(&cmd->abort_work, scmd_eh_abort_handler);
-	cmd->jiffies_at_alloc = jiffies;
-
-	scsi_add_cmd_to_list(cmd);
-
 	sg = (void *)cmd + sizeof(struct scsi_cmnd) + shost->hostt->cmd_size;
 	cmd->sdb.table.sgl = sg;
 
 	if (scsi_host_get_prot(shost)) {
-		cmd->prot_sdb = (void *)sg + scsi_mq_sgl_size(shost);
 		memset(cmd->prot_sdb, 0, sizeof(struct scsi_data_buffer));
 
 		cmd->prot_sdb->table.sgl =
@@ -2025,6 +2010,7 @@ static int scsi_init_request(struct blk_mq_tag_set *set, struct request *rq,
 	struct Scsi_Host *shost = set->driver_data;
 	const bool unchecked_isa_dma = shost->unchecked_isa_dma;
 	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
+	struct scatterlist *sg;
 
 	if (unchecked_isa_dma)
 		cmd->flags |= SCMD_UNCHECKED_ISA_DMA;
@@ -2033,6 +2019,13 @@ static int scsi_init_request(struct blk_mq_tag_set *set, struct request *rq,
 	if (!cmd->sense_buffer)
 		return -ENOMEM;
 	cmd->req.sense = cmd->sense_buffer;
+
+	if (scsi_host_get_prot(shost)) {
+		sg = (void *)cmd + sizeof(struct scsi_cmnd) +
+			shost->hostt->cmd_size;
+		cmd->prot_sdb = (void *)sg + scsi_mq_sgl_size(shost);
+	}
+
 	return 0;
 }
 
-- 
2.12.2

[PATCH v3 10/12] snic: Remove code that zeroes driver-private command data

[Bart Van Assche]

Since the SCSI core zeroes driver-private command data, remove
that code from the snic driver.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Narsimhulu Musini <nmusini@cisco.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Sesidhar Baddela <sebaddel@cisco.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
---
 drivers/scsi/snic/snic_scsi.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/scsi/snic/snic_scsi.c b/drivers/scsi/snic/snic_scsi.c
index da979a73baa0..05c3a7282d4a 100644
--- a/drivers/scsi/snic/snic_scsi.c
+++ b/drivers/scsi/snic/snic_scsi.c
@@ -359,8 +359,6 @@ snic_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *sc)
 	SNIC_SCSI_DBG(shost, "sc %p Tag %d (sc %0x) lun %lld in snic_qcmd\n",
 		      sc, snic_cmd_tag(sc), sc->cmnd[0], sc->device->lun);
 
-	memset(scsi_cmd_priv(sc), 0, sizeof(struct snic_internal_io_state));
-
 	ret = snic_issue_scsi_req(snic, tgt, sc);
 	if (ret) {
 		SNIC_HOST_ERR(shost, "Failed to Q, Scsi Req w/ err %d.\n", ret);
-- 
2.12.2

[PATCH v3 11/12] virtio_scsi: Remove code that zeroes driver-private command data

[Bart Van Assche]

Since the SCSI core zeroes driver-private command data, remove
that code from the virtio driver.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
---
 drivers/scsi/virtio_scsi.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
index f8dbfeee6c63..dc2e97c543a5 100644
--- a/drivers/scsi/virtio_scsi.c
+++ b/drivers/scsi/virtio_scsi.c
@@ -547,7 +547,6 @@ static int virtscsi_queuecommand(struct virtio_scsi *vscsi,
 	dev_dbg(&sc->device->sdev_gendev,
 		"cmd %p CDB: %#02x\n", sc, sc->cmnd[0]);
 
-	memset(cmd, 0, sizeof(*cmd));
 	cmd->sc = sc;
 
 	BUG_ON(sc->cmd_len > VIRTIO_SCSI_CDB_SIZE);
-- 
2.12.2

[PATCH v3 12/12] xen/scsifront: Remove code that zeroes driver-private command data

[Bart Van Assche]

Since the SCSI core zeroes driver-private command data, remove
that code from the xen-scsifront driver.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: xen-devel@lists.xenproject.org
Cc: Johannes Thumshirn <jthumshirn@suse.de>
---
 drivers/scsi/xen-scsifront.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/scsi/xen-scsifront.c b/drivers/scsi/xen-scsifront.c
index a6a8b60d4902..36f59a1be7e9 100644
--- a/drivers/scsi/xen-scsifront.c
+++ b/drivers/scsi/xen-scsifront.c
@@ -534,7 +534,6 @@ static int scsifront_queuecommand(struct Scsi_Host *shost,
 	int err;
 
 	sc->result = 0;
-	memset(shadow, 0, sizeof(*shadow));
 
 	shadow->sc  = sc;
 	shadow->act = VSCSIIF_ACT_SCSI_CDB;
-- 
2.12.2

[PATCH v3 12/12] xen/scsifront: Remove code that zeroes driver-private command data

[Bart Van Assche]

Since the SCSI core zeroes driver-private command data, remove
that code from the xen-scsifront driver.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: xen-devel@lists.xenproject.org
Cc: Johannes Thumshirn <jthumshirn@suse.de>
---
 drivers/scsi/xen-scsifront.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/scsi/xen-scsifront.c b/drivers/scsi/xen-scsifront.c
index a6a8b60d4902..36f59a1be7e9 100644
--- a/drivers/scsi/xen-scsifront.c
+++ b/drivers/scsi/xen-scsifront.c
@@ -534,7 +534,6 @@ static int scsifront_queuecommand(struct Scsi_Host *shost,
 	int err;
 
 	sc->result = 0;
-	memset(shadow, 0, sizeof(*shadow));
 
 	shadow->sc  = sc;
 	shadow->act = VSCSIIF_ACT_SCSI_CDB;
-- 
2.12.2


_______________________________________________
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Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel

Re: [PATCH v3 04/12] Protect SCSI device state changes with a mutex

[Christoph Hellwig]

On Fri, Jun 02, 2017 at 02:21:55PM -0700, Bart Van Assche wrote:
> Serializing SCSI device state changes avoids that two state changes
> can occur concurrently, e.g. the state changes in scsi_target_block()
> and __scsi_remove_device(). This serialization is essential to make
> patch "Make __scsi_remove_device go straight from BLOCKED to DEL"
> work reliably.
> 
> Enable this mechanism for all scsi_target_*block() callers but not
> for the scsi_internal_device_unblock() calls from the mpt3sas driver
> because that driver can call scsi_internal_device_unblock() from
> atomic context.

And not taking the lock in that path is safe because of what conditions?

Re: [PATCH v3 09/12] Make scsi_mq_prep_fn() call scsi_init_command()

[Christoph Hellwig]

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH v3 04/12] Protect SCSI device state changes with a mutex

[Bart Van Assche]

On Mon, 2017-06-05 at 10:09 +0200, Christoph Hellwig wrote:
> On Fri, Jun 02, 2017 at 02:21:55PM -0700, Bart Van Assche wrote:
> > Serializing SCSI device state changes avoids that two state changes
> > can occur concurrently, e.g. the state changes in scsi_target_block()
> > and __scsi_remove_device(). This serialization is essential to make
> > patch "Make __scsi_remove_device go straight from BLOCKED to DEL"
> > work reliably.
> > 
> > Enable this mechanism for all scsi_target_*block() callers but not
> > for the scsi_internal_device_unblock() calls from the mpt3sas driver
> > because that driver can call scsi_internal_device_unblock() from
> > atomic context.
> 
> And not taking the lock in that path is safe because of what conditions?

Hello Christoph,

The mpt3sas driver is the only driver that calls scsi_internal_device_block()
and scsi_internal_device_unblock() from atomic context. Since it's not an option
to protect the SCSI device state changes with a spinlock I prefer that the
mpt3sas authors convert the scsi_internal_device_block() calls into
scsi_target_block() calls.

Bart.

Re: [PATCH v3 04/12] Protect SCSI device state changes with a mutex

[Bart Van Assche]

On Mon, 2017-06-05 at 15:18 +0000, Bart Van Assche wrote:
> On Mon, 2017-06-05 at 10:09 +0200, Christoph Hellwig wrote:
> > On Fri, Jun 02, 2017 at 02:21:55PM -0700, Bart Van Assche wrote:
> > > Serializing SCSI device state changes avoids that two state changes
> > > can occur concurrently, e.g. the state changes in scsi_target_block()
> > > and __scsi_remove_device(). This serialization is essential to make
> > > patch "Make __scsi_remove_device go straight from BLOCKED to DEL"
> > > work reliably.
> > > 
> > > Enable this mechanism for all scsi_target_*block() callers but not
> > > for the scsi_internal_device_unblock() calls from the mpt3sas driver
> > > because that driver can call scsi_internal_device_unblock() from
> > > atomic context.
> > 
> > And not taking the lock in that path is safe because of what conditions?
> 
> The mpt3sas driver is the only driver that calls scsi_internal_device_block()
> and scsi_internal_device_unblock() from atomic context. Since it's not an option
> to protect the SCSI device state changes with a spinlock I prefer that the
> mpt3sas authors convert the scsi_internal_device_block() calls into
> scsi_target_block() calls.

Please also note that although this patch series doesn't improve the mpt3sas
driver, it doesn't change its behavior.

Bart.

Re: [PATCH v3 04/12] Protect SCSI device state changes with a mutex

[hch]

On Mon, Jun 05, 2017 at 06:36:19PM +0000, Bart Van Assche wrote:
> > The mpt3sas driver is the only driver that calls scsi_internal_device_block()
> > and scsi_internal_device_unblock() from atomic context. Since it's not an option
> > to protect the SCSI device state changes with a spinlock I prefer that the
> > mpt3sas authors convert the scsi_internal_device_block() calls into
> > scsi_target_block() calls.
> 
> Please also note that although this patch series doesn't improve the mpt3sas
> driver, it doesn't change its behavior.

Yes.  And normally we try to get things right.  I guess this series is
useful enough without fixing everyone up, but adding a FIXME or getting
the broadcom folks involved would be even better.

Re: [PATCH v3 00/12] SCSI patches for kernel v4.13

[Martin K. Petersen]

Bart,

> This patch series consists of the bug fixes and improvements I came up
> with during the past two months. This patch series has been developed
> on top of your 4.13/scsi-queue branch. Please consider these patches
> for kernel v4.13.

Applied to 4.13/scsi-queue, thanks!

-- 
Martin K. Petersen	Oracle Linux Engineering