Commit 2c140a24 authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Mike Snitzer
Browse files

dm: allow remove to be deferred 



This patch allows the removal of an open device to be deferred until
it is closed.  (Previously such a removal attempt would fail.)

The deferred remove functionality is enabled by setting the flag
DM_DEFERRED_REMOVE in the ioctl structure on DM_DEV_REMOVE or
DM_REMOVE_ALL ioctl.

On return from DM_DEV_REMOVE, the flag DM_DEFERRED_REMOVE indicates if
the device was removed immediately or flagged to be removed on close -
if the flag is clear, the device was removed.

On return from DM_DEV_STATUS and other ioctls, the flag
DM_DEFERRED_REMOVE is set if the device is scheduled to be removed on
closure.

A device that is scheduled to be deleted can be revived using the
message "@cancel_deferred_remove". This message clears the
DMF_DEFERRED_REMOVE flag so that the device won't be deleted on close.

Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 7833b08e

drivers/md/dm-ioctl.c

+30 −6
Original line number Diff line number Diff line
@@ -57,7 +57,7 @@ struct vers_iter { 
static struct list_head _name_buckets[NUM_BUCKETS];

static struct list_head _uuid_buckets[NUM_BUCKETS];



static void dm_hash_remove_all(int keep_open_devices);

static void dm_hash_remove_all(bool keep_open_devices, bool mark_deferred, bool only_deferred);



/*

 * Guards access to both hash tables.
@@ -86,7 +86,7 @@ static int dm_hash_init(void) 


static void dm_hash_exit(void)

{

	dm_hash_remove_all(0);

	dm_hash_remove_all(false, false, false);

}



/*-----------------------------------------------------------------
@@ -276,7 +276,7 @@ static struct dm_table *__hash_remove(struct hash_cell *hc) 
	return table;

}



static void dm_hash_remove_all(int keep_open_devices)

static void dm_hash_remove_all(bool keep_open_devices, bool mark_deferred, bool only_deferred)

{

	int i, dev_skipped;

	struct hash_cell *hc;
@@ -293,7 +293,8 @@ retry: 
			md = hc->md;

			dm_get(md);



			if (keep_open_devices && dm_lock_for_deletion(md)) {

			if (keep_open_devices &&

			    dm_lock_for_deletion(md, mark_deferred, only_deferred)) {

				dm_put(md);

				dev_skipped++;

				continue;
@@ -450,6 +451,11 @@ static struct mapped_device *dm_hash_rename(struct dm_ioctl *param, 
	return md;

}



void dm_deferred_remove(void)

{

	dm_hash_remove_all(true, false, true);

}



/*-----------------------------------------------------------------

 * Implementation of the ioctl commands

 *---------------------------------------------------------------*/
@@ -461,7 +467,7 @@ typedef int (*ioctl_fn)(struct dm_ioctl *param, size_t param_size); 


static int remove_all(struct dm_ioctl *param, size_t param_size)

{

	dm_hash_remove_all(1);

	dm_hash_remove_all(true, !!(param->flags & DM_DEFERRED_REMOVE), false);

	param->data_size = 0;

	return 0;

}
@@ -683,6 +689,9 @@ static void __dev_status(struct mapped_device *md, struct dm_ioctl *param) 
	if (dm_suspended_md(md))

		param->flags |= DM_SUSPEND_FLAG;



	if (dm_test_deferred_remove_flag(md))

		param->flags |= DM_DEFERRED_REMOVE;



	param->dev = huge_encode_dev(disk_devt(disk));



	/*
@@ -832,8 +841,13 @@ static int dev_remove(struct dm_ioctl *param, size_t param_size) 
	/*

	 * Ensure the device is not open and nothing further can open it.

	 */

	r = dm_lock_for_deletion(md);

	r = dm_lock_for_deletion(md, !!(param->flags & DM_DEFERRED_REMOVE), false);

	if (r) {

		if (r == -EBUSY && param->flags & DM_DEFERRED_REMOVE) {

			up_write(&_hash_lock);

			dm_put(md);

			return 0;

		}

		DMDEBUG_LIMIT("unable to remove open device %s", hc->name);

		up_write(&_hash_lock);

		dm_put(md);
@@ -848,6 +862,8 @@ static int dev_remove(struct dm_ioctl *param, size_t param_size) 
		dm_table_destroy(t);

	}



	param->flags &= ~DM_DEFERRED_REMOVE;



	if (!dm_kobject_uevent(md, KOBJ_REMOVE, param->event_nr))

		param->flags |= DM_UEVENT_GENERATED_FLAG;
@@ -1469,6 +1485,14 @@ static int message_for_md(struct mapped_device *md, unsigned argc, char **argv, 
	if (**argv != '@')

		return 2; /* no '@' prefix, deliver to target */



	if (!strcasecmp(argv[0], "@cancel_deferred_remove")) {

		if (argc != 1) {

			DMERR("Invalid arguments for @cancel_deferred_remove");

			return -EINVAL;

		}

		return dm_cancel_deferred_remove(md);

	}



	r = dm_stats_message(md, argc, argv, result, maxlen);

	if (r < 2)

		return r;

drivers/md/dm.c

+44 −3
Original line number Diff line number Diff line
@@ -49,6 +49,11 @@ static unsigned int _major = 0; 
static DEFINE_IDR(_minor_idr);



static DEFINE_SPINLOCK(_minor_lock);



static void do_deferred_remove(struct work_struct *w);



static DECLARE_WORK(deferred_remove_work, do_deferred_remove);



/*

 * For bio-based dm.

 * One of these is allocated per bio.
@@ -116,6 +121,7 @@ EXPORT_SYMBOL_GPL(dm_get_rq_mapinfo); 
#define DMF_DELETING 4

#define DMF_NOFLUSH_SUSPENDING 5

#define DMF_MERGE_IS_OPTIONAL 6

#define DMF_DEFERRED_REMOVE 7



/*

 * A dummy definition to make RCU happy.
@@ -299,6 +305,8 @@ out_free_io_cache: 


static void local_exit(void)

{

	flush_scheduled_work();



	kmem_cache_destroy(_rq_tio_cache);

	kmem_cache_destroy(_io_cache);

	unregister_blkdev(_major, _name);
@@ -404,7 +412,10 @@ static void dm_blk_close(struct gendisk *disk, fmode_t mode) 


	spin_lock(&_minor_lock);



	atomic_dec(&md->open_count);

	if (atomic_dec_and_test(&md->open_count) &&

	    (test_bit(DMF_DEFERRED_REMOVE, &md->flags)))

		schedule_work(&deferred_remove_work);



	dm_put(md);



	spin_unlock(&_minor_lock);
@@ -418,14 +429,18 @@ int dm_open_count(struct mapped_device *md) 
/*

 * Guarantees nothing is using the device before it's deleted.

 */

int dm_lock_for_deletion(struct mapped_device *md)

int dm_lock_for_deletion(struct mapped_device *md, bool mark_deferred, bool only_deferred)

{

	int r = 0;



	spin_lock(&_minor_lock);



	if (dm_open_count(md))

	if (dm_open_count(md)) {

		r = -EBUSY;

		if (mark_deferred)

			set_bit(DMF_DEFERRED_REMOVE, &md->flags);

	} else if (only_deferred && !test_bit(DMF_DEFERRED_REMOVE, &md->flags))

		r = -EEXIST;

	else

		set_bit(DMF_DELETING, &md->flags);
@@ -434,6 +449,27 @@ int dm_lock_for_deletion(struct mapped_device *md) 
	return r;

}



int dm_cancel_deferred_remove(struct mapped_device *md)

{

	int r = 0;



	spin_lock(&_minor_lock);



	if (test_bit(DMF_DELETING, &md->flags))

		r = -EBUSY;

	else

		clear_bit(DMF_DEFERRED_REMOVE, &md->flags);



	spin_unlock(&_minor_lock);



	return r;

}



static void do_deferred_remove(struct work_struct *w)

{

	dm_deferred_remove();

}



sector_t dm_get_size(struct mapped_device *md)

{

	return get_capacity(md->disk);
@@ -2894,6 +2930,11 @@ int dm_suspended_md(struct mapped_device *md) 
	return test_bit(DMF_SUSPENDED, &md->flags);

}



int dm_test_deferred_remove_flag(struct mapped_device *md)

{

	return test_bit(DMF_DEFERRED_REMOVE, &md->flags);

}



int dm_suspended(struct dm_target *ti)

{

	return dm_suspended_md(dm_table_get_md(ti->table));

drivers/md/dm.h

+12 −1
Original line number Diff line number Diff line
@@ -128,6 +128,16 @@ int dm_deleting_md(struct mapped_device *md); 
 */

int dm_suspended_md(struct mapped_device *md);



/*

 * Test if the device is scheduled for deferred remove.

 */

int dm_test_deferred_remove_flag(struct mapped_device *md);



/*

 * Try to remove devices marked for deferred removal.

 */

void dm_deferred_remove(void);



/*

 * The device-mapper can be driven through one of two interfaces;

 * ioctl or filesystem, depending which patch you have applied.
@@ -158,7 +168,8 @@ void dm_stripe_exit(void); 
void dm_destroy(struct mapped_device *md);

void dm_destroy_immediate(struct mapped_device *md);

int dm_open_count(struct mapped_device *md);

int dm_lock_for_deletion(struct mapped_device *md);

int dm_lock_for_deletion(struct mapped_device *md, bool mark_deferred, bool only_deferred);

int dm_cancel_deferred_remove(struct mapped_device *md);

int dm_request_based(struct mapped_device *md);

sector_t dm_get_size(struct mapped_device *md);

struct dm_stats *dm_get_stats(struct mapped_device *md);

include/uapi/linux/dm-ioctl.h

+13 −2
Original line number Diff line number Diff line
@@ -267,9 +267,9 @@ enum { 
#define DM_DEV_SET_GEOMETRY	_IOWR(DM_IOCTL, DM_DEV_SET_GEOMETRY_CMD, struct dm_ioctl)



#define DM_VERSION_MAJOR	4

#define DM_VERSION_MINOR	26

#define DM_VERSION_MINOR	27

#define DM_VERSION_PATCHLEVEL	0

#define DM_VERSION_EXTRA	"-ioctl (2013-08-15)"

#define DM_VERSION_EXTRA	"-ioctl (2013-10-30)"



/* Status bits */

#define DM_READONLY_FLAG	(1 << 0) /* In/Out */
@@ -341,4 +341,15 @@ enum { 
 */

#define DM_DATA_OUT_FLAG		(1 << 16) /* Out */



/*

 * If set with DM_DEV_REMOVE or DM_REMOVE_ALL this indicates that if

 * the device cannot be removed immediately because it is still in use

 * it should instead be scheduled for removal when it gets closed.

 *

 * On return from DM_DEV_REMOVE, DM_DEV_STATUS or other ioctls, this

 * flag indicates that the device is scheduled to be removed when it

 * gets closed.

 */

#define DM_DEFERRED_REMOVE		(1 << 17) /* In/Out */



#endif				/* _LINUX_DM_IOCTL_H */

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