From 2c140a246dc0bc085b98eddde978060fcec1080c Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Fri, 1 Nov 2013 18:27:41 -0400 Subject: [PATCH] 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: Mikulas Patocka Signed-off-by: Alasdair G Kergon Signed-off-by: Mike Snitzer --- drivers/md/dm-ioctl.c | 36 +++++++++++++++++++++++++++------ drivers/md/dm.c | 47 ++++++++++++++++++++++++++++++++++++++++--- drivers/md/dm.h | 13 +++++++++++- include/uapi/linux/dm-ioctl.h | 15 ++++++++++++-- 4 files changed, 99 insertions(+), 12 deletions(-) diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c index afe0814..5152142 100644 --- a/drivers/md/dm-ioctl.c +++ b/drivers/md/dm-ioctl.c @@ -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; diff --git a/drivers/md/dm.c b/drivers/md/dm.c index b3e26c7..0704c52 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -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)); diff --git a/drivers/md/dm.h b/drivers/md/dm.h index 1d1ad7b..c57ba55 100644 --- a/drivers/md/dm.h +++ b/drivers/md/dm.h @@ -129,6 +129,16 @@ 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); diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h index f1e12bd..c8a4302 100644 --- a/include/uapi/linux/dm-ioctl.h +++ b/include/uapi/linux/dm-ioctl.h @@ -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 */ -- 2.7.4