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scsi: core: Drop using the host_lock to protect async_scan race condition 

Previously, host_lock was used to prevent bit-set conflicts in async_scan,
but this approach introduced naked reads in some code paths.

Convert async_scan from a bitfield to a bool type to eliminate bit-level
conflicts entirely. Use __guarded_by(&scan_mutex) to indicate that the
async_scan variable is protected by scan_mutex.

Signed-off-by: Chaohai Chen <wdhh6@aliyun.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Link: https://patch.msgid.link/20260305025125.3649517-1-wdhh6@aliyun.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
master
Chaohai Chen 2026-03-05 10:51:24 +08:00 committed by Martin K. Petersen
parent 1bf5c303eb
commit 7a3aff163c
2 changed files with 6 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
drivers/scsi/scsi_scan.c
View File

@ -1943,7 +1943,6 @@ static void scsi_sysfs_add_devices(struct Scsi_Host *shost)
static struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost)
{
struct async_scan_data *data = NULL;
unsigned long flags;
if (strncmp(scsi_scan_type, "sync", 4) == 0)
return NULL;
@ -1962,9 +1961,7 @@ static struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost)
goto err;
init_completion(&data->prev_finished);
spin_lock_irqsave(shost->host_lock, flags);
shost->async_scan = 1;
spin_unlock_irqrestore(shost->host_lock, flags);
shost->async_scan = true;
mutex_unlock(&shost->scan_mutex);
spin_lock(&async_scan_lock);
@ -1992,7 +1989,6 @@ static struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost)
static void scsi_finish_async_scan(struct async_scan_data *data)
{
struct Scsi_Host *shost;
unsigned long flags;
if (!data)
return;
@ -2012,9 +2008,7 @@ static void scsi_finish_async_scan(struct async_scan_data *data)
scsi_sysfs_add_devices(shost);
spin_lock_irqsave(shost->host_lock, flags);
shost->async_scan = 0;
spin_unlock_irqrestore(shost->host_lock, flags);
shost->async_scan = false;
mutex_unlock(&shost->scan_mutex);

7
include/scsi/scsi_host.h
View File

@ -660,6 +660,10 @@ struct Scsi_Host {
*/
unsigned nr_hw_queues;
unsigned nr_maps;
/* Asynchronous scan in progress */
bool async_scan __guarded_by(&scan_mutex);
unsigned active_mode:2;
/*
@ -678,9 +682,6 @@ struct Scsi_Host {
/* Task mgmt function in progress */
unsigned tmf_in_progress:1;
/* Asynchronous scan in progress */
unsigned async_scan:1;
/* Don't resume host in EH */
unsigned eh_noresume:1;