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Commit 6c10db72 authored by Chandra Seetharaman's avatar Chandra Seetharaman Committed by James Bottomley
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[SCSI] scsi_dh: Reference count scsi_dh_attach 

Problem reported: http://marc.info/?l=dm-devel&m=124585978305866&w=2



scsi_dh does not do a refernce count for attach/detach, and this affects
the way it is supposed to work with multipath when a device is not
in the dev_list of the hardware handler.

This patch adds a reference count that counts each attach.

Signed-off-by: default avatarChandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: default avatarJames Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: default avatarJames Bottomley <James.Bottomley@suse.de>
parent b4567ca6

drivers/scsi/device_handler/scsi_dh.c

+16 −7
Original line number Diff line number Diff line
@@ -153,12 +153,24 @@ static int scsi_dh_handler_attach(struct scsi_device *sdev, 
	if (sdev->scsi_dh_data) {

		if (sdev->scsi_dh_data->scsi_dh != scsi_dh)

			err = -EBUSY;

	} else if (scsi_dh->attach)

		else

			kref_get(&sdev->scsi_dh_data->kref);

	} else if (scsi_dh->attach) {

		err = scsi_dh->attach(sdev);



		if (!err) {

			kref_init(&sdev->scsi_dh_data->kref);

			sdev->scsi_dh_data->sdev = sdev;

		}

	}

	return err;

}



static void __detach_handler (struct kref *kref)

{

	struct scsi_dh_data *scsi_dh_data = container_of(kref, struct scsi_dh_data, kref);

	scsi_dh_data->scsi_dh->detach(scsi_dh_data->sdev);

}



/*

 * scsi_dh_handler_detach - Detach a device handler from a device

 * @sdev - SCSI device the device handler should be detached from
@@ -180,7 +192,7 @@ static void scsi_dh_handler_detach(struct scsi_device *sdev, 
		scsi_dh = sdev->scsi_dh_data->scsi_dh;



	if (scsi_dh && scsi_dh->detach)

		scsi_dh->detach(sdev);

		kref_put(&sdev->scsi_dh_data->kref, __detach_handler);

}



/*
@@ -474,7 +486,6 @@ int scsi_dh_attach(struct request_queue *q, const char *name) 


	if (!err) {

		err = scsi_dh_handler_attach(sdev, scsi_dh);



		put_device(&sdev->sdev_gendev);

	}

	return err;
@@ -505,9 +516,7 @@ void scsi_dh_detach(struct request_queue *q) 
		return;



	if (sdev->scsi_dh_data) {

		/* if sdev is not on internal list, detach */

		scsi_dh = sdev->scsi_dh_data->scsi_dh;

		if (!device_handler_match(scsi_dh, sdev))

		scsi_dh_handler_detach(sdev, scsi_dh);

	}

	put_device(&sdev->sdev_gendev);

include/scsi/scsi_device.h

+2 −0
Original line number Diff line number Diff line
@@ -191,6 +191,8 @@ struct scsi_device_handler { 


struct scsi_dh_data {

	struct scsi_device_handler *scsi_dh;

	struct scsi_device *sdev;

	struct kref kref;

	char buf[0];

};