[PATCH] scsi: sd: Revert "Rework asynchronous resume support"

Bart Van Assche
2022-08-16T17:26:48Z

Although patch "Rework asynchronous resume support" eliminates the delay
for some ATA disks after resume, it causes resume of ATA disks to fail
on other setups. See also:
* "Resume process hangs for 5-6 seconds starting sometime in 5.16"
(https://bugzilla.kernel.org/show_bug.cgi?id=215880).
* Geert's regression report
(https://lore.kernel.org/linux-scsi/alpine.DEB.2.22.394.2207191125130.1006766@ramsan.of.borg/).

This is what I understand about this issue:
* During resume, ata_port_pm_resume() starts the SCSI error handler.
This changes the SCSI host state into SHOST_RECOVERY and causes
scsi_queue_rq() to return BLK_STS_RESOURCE.
* sd_resume() calls sd_start_stop_device() for ATA devices. That
function in turn calls sd_submit_start() which tries to submit a START
STOP UNIT command. That command can only be submitted after the SCSI
error handler has changed the SCSI host state back to SHOST_RUNNING.
* The SCSI error handler runs on its own thread and calls
schedule_work(&(ap->scsi_rescan_task)). That causes
ata_scsi_dev_rescan() to be called from the context of a kernel
workqueue. That call hangs in blk_mq_get_tag(). I'm not sure why -
maybe because all available tags have been allocated by
sd_submit_start() calls (this is a guess).

Cc: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: gzhqyz@gmail.com
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reported-by: gzhqyz@gmail.com
Fixes: 88f1669019bd ("scsi: sd: Rework asynchronous resume support"; v6.0-rc1~114^2~68)
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
drivers/scsi/sd.c | 84 ++++++++++-------------------------------------
drivers/scsi/sd.h | 5 ---
2 files changed, 18 insertions(+), 71 deletions(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 8f79fa6318fe..eb76ba055021 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -103,7 +103,6 @@ static void sd_config_discard(struct scsi_disk *, unsigned int);
static void sd_config_write_same(struct scsi_disk *);
static int sd_revalidate_disk(struct gendisk *);
static void sd_unlock_native_capacity(struct gendisk *disk);
-static void sd_start_done_work(struct work_struct *work);
static int sd_probe(struct device *);
static int sd_remove(struct device *);
static void sd_shutdown(struct device *);
@@ -3471,7 +3470,6 @@ static int sd_probe(struct device *dev)
sdkp->max_retries = SD_MAX_RETRIES;
atomic_set(&sdkp->openers, 0);
atomic_set(&sdkp->device->ioerr_cnt, 0);
- INIT_WORK(&sdkp->start_done_work, sd_start_done_work);

if (!sdp->request_queue->rq_timeout) {
if (sdp->type != TYPE_MOD)
@@ -3594,69 +3592,12 @@ static void scsi_disk_release(struct device *dev)
kfree(sdkp);
}

-/* Process sense data after a START command finished. */
-static void sd_start_done_work(struct work_struct *work)
-{
- struct scsi_disk *sdkp = container_of(work, typeof(*sdkp),
- start_done_work);
- struct scsi_sense_hdr sshdr;
- int res = sdkp->start_result;
-
- if (res == 0)
- return;
-
- sd_print_result(sdkp, "Start/Stop Unit failed", res);
-
- if (res < 0)
- return;
-
- if (scsi_normalize_sense(sdkp->start_sense_buffer,
- sdkp->start_sense_len, &sshdr))
- sd_print_sense_hdr(sdkp, &sshdr);
-}
-
-/* A START command finished. May be called from interrupt context. */
-static void sd_start_done(struct request *req, blk_status_t status)
-{
- const struct scsi_cmnd *scmd = blk_mq_rq_to_pdu(req);
- struct scsi_disk *sdkp = scsi_disk(req->q->disk);
-
- sdkp->start_result = scmd->result;
- WARN_ON_ONCE(scmd->sense_len > SCSI_SENSE_BUFFERSIZE);
- sdkp->start_sense_len = scmd->sense_len;
- memcpy(sdkp->start_sense_buffer, scmd->sense_buffer,
- ARRAY_SIZE(sdkp->start_sense_buffer));
- WARN_ON_ONCE(!schedule_work(&sdkp->start_done_work));
-}
-
-/* Submit a START command asynchronously. */
-static int sd_submit_start(struct scsi_disk *sdkp, u8 cmd[], u8 cmd_len)
-{
- struct scsi_device *sdev = sdkp->device;
- struct request_queue *q = sdev->request_queue;
- struct request *req;
- struct scsi_cmnd *scmd;
-
- req = scsi_alloc_request(q, REQ_OP_DRV_IN, BLK_MQ_REQ_PM);
- if (IS_ERR(req))
- return PTR_ERR(req);
-
- scmd = blk_mq_rq_to_pdu(req);
- scmd->cmd_len = cmd_len;
- memcpy(scmd->cmnd, cmd, cmd_len);
- scmd->allowed = sdkp->max_retries;
- req->timeout = SD_TIMEOUT;
- req->rq_flags |= RQF_PM | RQF_QUIET;
- req->end_io = sd_start_done;
- blk_execute_rq_nowait(req, /*at_head=*/true);
-
- return 0;
-}
-
static int sd_start_stop_device(struct scsi_disk *sdkp, int start)
{
unsigned char cmd[6] = { START_STOP }; /* START_VALID */
+ struct scsi_sense_hdr sshdr;
struct scsi_device *sdp = sdkp->device;
+ int res;

if (start)
cmd[4] |= 1; /* START */
@@ -3667,10 +3608,23 @@ static int sd_start_stop_device(struct scsi_disk *sdkp, int start)
if (!scsi_device_online(sdp))
return -ENODEV;

- /* Wait until processing of sense data has finished. */
- flush_work(&sdkp->start_done_work);
+ res = scsi_execute(sdp, cmd, DMA_NONE, NULL, 0, NULL, &sshdr,
+ SD_TIMEOUT, sdkp->max_retries, 0, RQF_PM, NULL);
+ if (res) {
+ sd_print_result(sdkp, "Start/Stop Unit failed", res);
+ if (res > 0 && scsi_sense_valid(&sshdr)) {
+ sd_print_sense_hdr(sdkp, &sshdr);
+ /* 0x3a is medium not present */
+ if (sshdr.asc == 0x3a)
+ res = 0;
+ }
+ }

- return sd_submit_start(sdkp, cmd, sizeof(cmd));
+ /* SCSI error codes must not go to the generic layer */
+ if (res)
+ return -EIO;
+
+ return 0;
}

/*
@@ -3697,8 +3651,6 @@ static void sd_shutdown(struct device *dev)
sd_printk(KERN_NOTICE, sdkp, "Stopping disk\n");
sd_start_stop_device(sdkp, 0);
}
-
- flush_work(&sdkp->start_done_work);
}

static int sd_suspend_common(struct device *dev, bool ignore_stop_errors)
diff --git a/drivers/scsi/sd.h b/drivers/scsi/sd.h
index b89187761d61..5eea762f84d1 100644
--- a/drivers/scsi/sd.h
+++ b/drivers/scsi/sd.h
@@ -150,11 +150,6 @@ struct scsi_disk {
unsigned urswrz : 1;
unsigned security : 1;
unsigned ignore_medium_access_errors : 1;
-
- int start_result;
- u32 start_sense_len;
- u8 start_sense_buffer[SCSI_SENSE_BUFFERSIZE];
- struct work_struct start_done_work;
};
#define to_scsi_disk(obj) container_of(obj, struct scsi_disk, disk_dev)