On 10/01/15 09:56, Junichi Nomura wrote:
> With 4.2 kernel, scsi_dh->detach() was not called until the last
> reference has gone. With 4.3-rc3, scsi_dh->detach() is directly called
> from the context of scsi_remove_device(). That's the point.
For my test script in the original post, I can't reproduce the crash
by just swapping the order of scsi_dh_handler_detach() and
device_remove_file() like this:
void scsi_dh_remove_device(struct scsi_device *sdev)
{
device_remove_file(&sdev->sdev_gendev, &scsi_dh_state_attr);
if (sdev->handler)
scsi_dh_handler_detach(sdev);
}
But another workload using dm-multipath still caues the same crash.
I think a patch like the following is needed.
What do you think?
The commit 1bab0de0274f ("dm-mpath, scsi_dh: don't let dm detach device
handlers") removed reference counting of attached scsi device handler.
As a result scsi_dh->detach() is directly called in the context of
scsi_remove_device() where activation request can be still in flight.
This patch moves scsi_dh_handler_detach() to
scsi_device_dev_release_usercontext(), at that point the device
is already in quiesced state.
diff --git a/drivers/scsi/scsi_dh.c b/drivers/scsi/scsi_dh.c
index edb044a..19bf9db 100644
--- a/drivers/scsi/scsi_dh.c
+++ b/drivers/scsi/scsi_dh.c
@@ -232,10 +232,14 @@ int scsi_dh_add_device(struct scsi_device *sdev)
return err;
}
-void scsi_dh_remove_device(struct scsi_device *sdev)
+void scsi_dh_release_device(struct scsi_device *sdev)
{
if (sdev->handler)
scsi_dh_handler_detach(sdev);
+}
+
+void scsi_dh_remove_device(struct scsi_device *sdev)
+{
device_remove_file(&sdev->sdev_gendev, &scsi_dh_state_attr);
}
diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h
index 644bb73..4d01cdb 100644
--- a/drivers/scsi/scsi_priv.h
+++ b/drivers/scsi/scsi_priv.h
@@ -173,9 +173,11 @@ extern struct async_domain scsi_sd_probe_domain;
/* scsi_dh.c */
#ifdef CONFIG_SCSI_DH
int scsi_dh_add_device(struct scsi_device *sdev);
+void scsi_dh_release_device(struct scsi_device *sdev);
void scsi_dh_remove_device(struct scsi_device *sdev);
#else
static inline int scsi_dh_add_device(struct scsi_device *sdev) { return 0; }
+static inline void scsi_dh_release_device(struct scsi_device *sdev) { }
static inline void scsi_dh_remove_device(struct scsi_device *sdev) { }
#endif
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index b333389..dff8faf 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -399,6 +399,8 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work)
sdev = container_of(work, struct scsi_device, ew.work);
+ scsi_dh_release_device(sdev);
+
parent = sdev->sdev_gendev.parent;
spin_lock_irqsave(sdev->host->host_lock, flags);--
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