PM/Hibernate: Wait for SCSI devices scan to complete during resume

There is a race between resume from hibernation and the asynchronous
scanning of SCSI devices and to prevent it from happening we need to
call scsi_complete_async_scans() during resume from hibernation.

In addition, if the resume from hibernation is userland-driven, it's
better to wait for all device probes in the kernel to complete before
attempting to open the resume device.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 17 insertions, 0 deletions

diff --git a/kernel/power/disk.c b/kernel/power/disk.c
index 5f21ab2bbcdf..0854770b63b9 100644
--- a/kernel/power/disk.c
+++ b/kernel/power/disk.c
@@ -22,6 +22,7 @@
 #include <linux/console.h>
 #include <linux/cpu.h>
 #include <linux/freezer.h>
+#include <scsi/scsi_scan.h>
 #include <asm/suspend.h>
 
 #include "power.h"
@@ -645,6 +646,13 @@ static int software_resume(void)
                 return 0;
 
         /*
+         * We can't depend on SCSI devices being available after loading one of
+         * their modules if scsi_complete_async_scans() is not called and the
+         * resume device usually is a SCSI one.
+         */
+        scsi_complete_async_scans();
+
+        /*
          * name_to_dev_t() below takes a sysfs buffer mutex when sysfs
          * is configured into the kernel. Since the regular hibernate
          * trigger path is via sysfs which takes a buffer mutex before
diff --git a/kernel/power/user.c b/kernel/power/user.c
index 6c85359364f2..ed97375daae9 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -24,6 +24,7 @@
 #include <linux/cpu.h>
 #include <linux/freezer.h>
 #include <linux/smp_lock.h>
+#include <scsi/scsi_scan.h>
 
 #include <asm/uaccess.h>
 
@@ -92,6 +93,7 @@ static int snapshot_open(struct inode *inode, struct file *filp)
         filp->private_data = data;
         memset(&data->handle, 0, sizeof(struct snapshot_handle));
         if ((filp->f_flags & O_ACCMODE) == O_RDONLY) {
+                /* Hibernating.  The image device should be accessible. */
                 data->swap = swsusp_resume_device ?
                         swap_type_of(swsusp_resume_device, 0, NULL) : -1;
                 data->mode = O_RDONLY;
@@ -99,6 +101,13 @@ static int snapshot_open(struct inode *inode, struct file *filp)
                 if (error)
                         pm_notifier_call_chain(PM_POST_HIBERNATION);
         } else {
+                /*
+                 * Resuming.  We may need to wait for the image device to
+                 * appear.
+                 */
+                wait_for_device_probe();
+                scsi_complete_async_scans();
+
                 data->swap = -1;
                 data->mode = O_WRONLY;
                 error = pm_notifier_call_chain(PM_RESTORE_PREPARE);