SCSI device removal fixes
Subsystems (2)
v10 cover SCSI device removal fixes
This is version ten of the SCSI device removal patch series. This patch series has been tested by triggering a large number of removals of a SCSI device controlled by the ib_srp LLD and at the same time running an I/O integrity test with fio on a dm device on top of the SRP SCSI device.
Changes compared to v9:
- Added a patch to the series (3/5).
- Updated patch description of patch 2/5, swapped a kfree() and blk_cleanup_queue() call to make the code easier to read and removed the BUG_ON(!sdev) statements from that patch.
Changes compared to v8:
- Replaced the block layer patch (1/4) by a more comprehensive patch from Muthukumar Ratty.
- Added "Reviewed-by: Mike Christie" in patches 2/4..4/4.
Changes compared to v7:
- Made sure that __scsi_queue_insert() processes the request that has been passed to that function. Added a comment in that function too.
- Fixed a typo in the description of the first patch in this series and removed "CC: stable".
Changes compared to v6:
- Added a fix for a race in the block layer.
- Moved a BUG_ON(!sdev) statement up since it's a precondition check.
- Changed return type of scsi_queue_insert() from int to void.
- Added a cancel_work_sync(&sdev->requeue_work) call in __scsi_remove_device().
Changes compared to v5:
- Removed the function scsi_free_queue() and inlined that function in its callers.
- Added two additional patches.
PATCH 1/5 block: Fix blk_execute_rq_nowait() dead queue handling
From: Muthukumar Ratty <[email protected]>
If the queue is dead blk_execute_rq_nowait() doesn't invoke the done() callback function. That will result in blk_execute_rq() being stuck in wait_for_completion(). Avoid this by initializing rq->end_io to the done() callback before we check the queue state. Also, make sure the queue lock is held around the invocation of the done() callback. Found this through source code review.
--- block/blk-exec.c | 11 ++++++++--- 1 files changed, 8 insertions(+), 3 deletions(-)
block/blk-exec.c +8 -3
@@ -43,6 +43,9 @@ static void blk_end_sync_rq(struct request *rq, int error)* Description: * Insert a fully prepared request at the back of the I/O scheduler queue * for execution. Don't wait for completion. +* +* Note: +* This function will invoke @done directly if the queue is dead. */ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk, struct request *rq, int at_head,
@@ -51,18 +54,20 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk,int where = at_head ?ELEVATOR_INSERT_FRONT :ELEVATOR_INSERT_BACK ;WARN_ON (irqs_disabled ()); + + rq->rq_disk = bd_disk; + rq->end_io = done; +spin_lock_irq (q->queue_lock);if (unlikely (blk_queue_dead (q))) { -spin_unlock_irq (q->queue_lock); rq->errors = -ENXIO ;if (rq->end_io) rq->end_io (rq, rq->errors); +spin_unlock_irq (q->queue_lock);return ; } - rq->rq_disk = bd_disk; - rq->end_io = done;__elv_add_request (q, rq, where);__blk_run_queue (q);/* the queue is stopped so it won't be run */
Signature · 1 line
1.7.7
PATCH 2/5 scsi: Fix device removal NULL pointer dereference
In reply to Bart Van AsscheUse blk_queue_dead() to test whether the queue is dead instead of !sdev. Since scsi_prep_fn() may be invoked concurrently with __scsi_remove_device(), keep the queuedata (sdev) pointer in __scsi_remove_device(). This patch fixes a kernel oops that can be triggered by USB device removal. See also
http://www.spinics.net/lists/linux-scsi/msg56254.html.
Other changes included in this patch:
- Swap the blk_cleanup_queue() and kfree() calls in scsi_host_dev_release() to make that code easier to grasp.
- Remove the queue dead check from scsi_run_queue() since the queue state can change anyway at any point in that function where the queue lock is not held.
- Remove the queue dead check from the start of scsi_request_fn() since it is redundant with the scsi_device_online() check.
--- drivers/scsi/hosts.c | 7 ++++--- drivers/scsi/scsi_lib.c | 32 ++++---------------------------- drivers/scsi/scsi_priv.h | 1 - drivers/scsi/scsi_sysfs.c | 5 +---- 4 files changed, 9 insertions(+), 36 deletions(-)
drivers/scsi/hosts.c +4 -3
@@ -290,6 +290,7 @@ static void scsi_host_dev_release(struct device *dev)struct Scsi_Host *shost =dev_to_shost (dev);struct device *parent = dev->parent;struct request_queue *q; +void *queuedata;scsi_proc_hostdir_rm (shost->hostt);
@@ -299,9 +300,9 @@ static void scsi_host_dev_release(struct device *dev)destroy_workqueue (shost->work_q); q = shost->uspace_req_q;if (q) { -kfree (q->queuedata); - q->queuedata =NULL ; -scsi_free_queue (q); + queuedata = q->queuedata; +blk_cleanup_queue (q); +kfree (queuedata); }scsi_destroy_command_freelist (shost);
drivers/scsi/scsi_lib.c +4 -28
@@ -406,10 +406,6 @@ static void scsi_run_queue(struct request_queue *q)LIST_HEAD (starved_list);unsigned long flags; -/* if the device is dead, sdev will be NULL, so no queue to run */ -if (!sdev) -return ; - shost = sdev->host;if (scsi_target (sdev)->single_lun)scsi_single_lun_run (sdev);
@@ -1370,16 +1366,16 @@ static inline int scsi_host_queue_ready(struct request_queue *q,* may be changed after request stacking drivers call the function, * regardless of taking lock or not. * -* When scsi can't dispatch I/Os anymore and needs to kill I/Os -* (e.g. !sdev), scsi needs to return 'not busy'. -* Otherwise, request stacking drivers may hold requests forever. +* When scsi can't dispatch I/Os anymore and needs to kill I/Os scsi +* needs to return 'not busy'. Otherwise, request stacking drivers +* may hold requests forever. */ static int scsi_lld_busy (struct request_queue *q) {struct scsi_device *sdev = q->queuedata;struct Scsi_Host *shost; -if (!sdev) +if (blk_queue_dead (q))return 0 ; shost = sdev->host;
@@ -1490,12 +1486,6 @@ static void scsi_request_fn(struct request_queue *q)struct scsi_cmnd *cmd;struct request *req; -if (!sdev) { -while ((req =blk_peek_request (q)) !=NULL ) -scsi_kill_request (req, q); -return ; - } -if (!get_device (&sdev->sdev_gendev))/* We must be tearing the block queue down already */ return ;
@@ -1697,20 +1687,6 @@ struct request_queue *scsi_alloc_queue(struct scsi_device *sdev)return q; } -void scsi_free_queue (struct request_queue *q) -{ -unsigned long flags; - -WARN_ON (q->queuedata); - -/* cause scsi_request_fn() to kill all non-finished requests */ -spin_lock_irqsave (q->queue_lock, flags); - q->request_fn (q); -spin_unlock_irqrestore (q->queue_lock, flags); - -blk_cleanup_queue (q); -} -/* * Function: scsi_block_requests() *
drivers/scsi/scsi_priv.h +0 -1
@@ -84,7 +84,6 @@ extern void scsi_next_command(struct scsi_cmnd *cmd);extern void scsi_io_completion (struct scsi_cmnd *,unsigned int );extern void scsi_run_host_queues (struct Scsi_Host *shost);extern struct request_queue *scsi_alloc_queue (struct scsi_device *sdev); -extern void scsi_free_queue (struct request_queue *q);extern int scsi_init_queue (void );extern void scsi_exit_queue (void );struct request_queue ;
drivers/scsi/scsi_sysfs.c +1 -4
@@ -971,11 +971,8 @@ void __scsi_remove_device(struct scsi_device *sdev) sdev->host->hostt->slave_destroy (sdev);transport_destroy_device (dev); -/* cause the request function to reject all I/O requests */ - sdev->request_queue->queuedata =NULL ; -/* Freeing the queue signals to block that we're done */ -scsi_free_queue (sdev->request_queue); +blk_cleanup_queue (sdev->request_queue);put_device (dev); }
Signature · 1 line
1.7.7
PATCH 3/5 scsi: Avoid dangling pointer in scsi_requeue_command()
In reply to Bart Van Assche--- drivers/scsi/scsi_lib.c | 9 +++++++++ 1 files changed, 9 insertions(+), 0 deletions(-)
drivers/scsi/scsi_lib.c +9 -0
@@ -479,15 +479,24 @@ void scsi_requeue_run_queue(struct work_struct *work)*/ static void scsi_requeue_command (struct request_queue *q,struct scsi_cmnd *cmd) { +struct scsi_device *sdev = cmd->device;struct request *req = cmd->request;unsigned long flags; +/* +* We need to hold a reference on the device to avoid that the queue +* gets killed after the unlock and before scsi_run_queue is invoked. +*/ +get_device (&sdev->sdev_gendev); +spin_lock_irqsave (q->queue_lock, flags);scsi_unprep_request (req);blk_requeue_request (q, req);spin_unlock_irqrestore (q->queue_lock, flags);scsi_run_queue (q); + +put_device (&sdev->sdev_gendev); }void scsi_next_command (struct scsi_cmnd *cmd)
Signature · 1 line
1.7.7
Re: [PATCH 3/5] scsi: Avoid dangling pointer in scsi_requeue_command()
Quoted 29 lines · Bart Van Assche
Reported-by Mike Christie <[email protected]>Signed-off-by Bart Van Assche <[email protected]>Cc Tejun Heo <[email protected]>Cc James Bottomley <[email protected]>Cc <[email protected]>--- drivers/scsi/scsi_lib.c | 9 +++++++++ 1 files changed, 9 insertions(+), 0 deletions(-)drivers/scsi/scsi_lib.c +7
-0@@ -479,15 +479,24 @@ void scsi_requeue_run_queue(struct work_struct *work)*/ static void scsi_requeue_command (struct request_queue *q,struct scsi_cmnd *cmd) { +struct scsi_device *sdev = cmd->device;struct request *req = cmd->request;unsigned long flags; +/* +* We need to hold a reference on the device to avoid that the queue +* gets killed after the unlock and before scsi_run_queue is invoked. +*/ +get_device (&sdev->sdev_gendev); +spin_lock_irqsave (q->queue_lock, flags);
drivers/scsi/scsi_lib.c void scsi_requeue_run_queue(struct work_struct *work) · line 502
Quoted 10 lines
drivers/scsi/scsi_lib.c +2
-0scsi_unprep_request (req);blk_requeue_request (q, req);spin_unlock_irqrestore (q->queue_lock, flags);scsi_run_queue (q); + +put_device (&sdev->sdev_gendev); }void scsi_next_command (struct scsi_cmnd *cmd)
Looks ok to me
Re: [PATCH 3/5] scsi: Avoid dangling pointer in scsi_requeue_command()
In reply to Bart Van AsscheQuoted 5 lines · Bart Van Assche
Reported-by Mike Christie <[email protected]>Signed-off-by Bart Van Assche <[email protected]>Cc Tejun Heo <[email protected]>Cc James Bottomley <[email protected]>Cc <[email protected]>
Thanks.
Signature · 1 line
tejun
PATCH 4/5 scsi: Change return type of scsi_queue_insert() into void
In reply to Bart Van AsscheThe return value of scsi_queue_insert() is ignored by all its callers, hence change the return type of this function into void.
--- drivers/scsi/scsi_lib.c | 8 +++----- drivers/scsi/scsi_priv.h | 2 +- 2 files changed, 4 insertions(+), 6 deletions(-)
drivers/scsi/scsi_lib.c +3 -5
@@ -109,7 +109,7 @@ static void scsi_unprep_request(struct request *req)* for a requeue after completion, which should only occur in this * file. */ -static int __scsi_queue_insert (struct scsi_cmnd *cmd,int reason,int unbusy) +static void __scsi_queue_insert (struct scsi_cmnd *cmd,int reason,int unbusy) {struct Scsi_Host *host = cmd->device->host;struct scsi_device *device = cmd->device;
@@ -162,8 +162,6 @@ static int __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, int unbusy)spin_unlock_irqrestore (q->queue_lock, flags);kblockd_schedule_work (q, &device->requeue_work); - -return 0 ; }/*
@@ -185,9 +183,9 @@ static int __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, int unbusy)* Notes: This could be called either from an interrupt context or a * normal process context. */ -int scsi_queue_insert (struct scsi_cmnd *cmd,int reason) +void scsi_queue_insert (struct scsi_cmnd *cmd,int reason) { -return __scsi_queue_insert (cmd, reason,1 ); +__scsi_queue_insert (cmd, reason,1 ); }/** * scsi_execute - insert request and wait for the result
drivers/scsi/scsi_priv.h +1 -1
@@ -79,7 +79,7 @@ int scsi_noretry_cmd(struct scsi_cmnd *scmd);/* scsi_lib.c */ extern int scsi_maybe_unblock_host (struct scsi_device *sdev);extern void scsi_device_unbusy (struct scsi_device *sdev); -extern int scsi_queue_insert (struct scsi_cmnd *cmd,int reason); +extern void scsi_queue_insert (struct scsi_cmnd *cmd,int reason);extern void scsi_next_command (struct scsi_cmnd *cmd);extern void scsi_io_completion (struct scsi_cmnd *,unsigned int );extern void scsi_run_host_queues (struct Scsi_Host *shost);
PATCH 5/5 scsi: Stop accepting SCSI requests before removing a device
In reply to Bart Van AsscheAvoid that the code for requeueing SCSI requests triggers a crash by making sure that that code isn't scheduled anymore after a device has been removed.
Also, source code inspection of __scsi_remove_device() revealed a race condition in this function: no new SCSI requests must be accepted for a SCSI device after device removal started.
--- drivers/scsi/scsi_lib.c | 7 ++++--- drivers/scsi/scsi_sysfs.c | 11 +++++++++-- 2 files changed, 13 insertions(+), 5 deletions(-)
drivers/scsi/scsi_lib.c +4 -3
@@ -155,13 +155,14 @@ static void __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, int unbusy)/* * Requeue this command. It will go before all other commands -* that are already in the queue. +* that are already in the queue. Schedule requeue work under +* lock such that the kblockd_schedule_work() call happens +* before blk_cleanup_queue() finishes. */ spin_lock_irqsave (q->queue_lock, flags);blk_requeue_request (q, cmd->request); -spin_unlock_irqrestore (q->queue_lock, flags); -kblockd_schedule_work (q, &device->requeue_work); +spin_unlock_irqrestore (q->queue_lock, flags); }/*
drivers/scsi/scsi_sysfs.c +9 -2
@@ -966,13 +966,20 @@ void __scsi_remove_device(struct scsi_device *sdev)device_del (dev); }else put_device (&sdev->sdev_dev); + +/* +* Stop accepting new requests and wait until all queuecommand() and +* scsi_run_queue() invocations have finished before tearing down the +* device. +*/ scsi_device_set_state (sdev,SDEV_DEL ); +blk_cleanup_queue (sdev->request_queue); +cancel_work_sync (&sdev->requeue_work); +if (sdev->host->hostt->slave_destroy) sdev->host->hostt->slave_destroy (sdev);transport_destroy_device (dev); -/* Freeing the queue signals to block that we're done */ -blk_cleanup_queue (sdev->request_queue);put_device (dev); }
Signature · 1 line
1.7.7