dm: allow active and inactive tables to share dm_devs

Until this change, when loading a new DM table, DM core would re-open
all of the devices in the DM table.  Now, DM core will avoid redundant
device opens (and closes when destroying the old table) if the old
table already has a device open using the same mode.  This is achieved
by managing reference counts on the table_devices that DM core now
stores in the mapped_device structure (rather than in the dm_table
structure).  So a mapped_device's active and inactive dm_tables' dm_dev
lists now just point to the dm_devs stored in the mapped_device's
table_devices list.

This improvement in DM core's device reference counting has the
side-effect of fixing a long-standing limitation of the multipath
target: a DM multipath table couldn't include any paths that were unusable
(failed).  For example: if all paths have failed and you add a new,
working, path to the table; you can't use it since the table load would
fail due to it still containing failed paths.  Now a re-load of a
multipath table can include failed devices and when those devices become
active again they can be used instantly.

The device list code in dm.c isn't a straight copy/paste from the code in
dm-table.c, but it's very close (aside from some variable renames).  One
subtle difference is that find_table_device for the tables_devices list
will only match devices with the same name and mode.  This is because we
don't want to upgrade a device's mode in the active table when an
inactive table is loaded.

Access to the mapped_device structure's tables_devices list requires a
mutex (tables_devices_lock), so that tables cannot be created and
destroyed concurrently.

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 51521429fb59d01ea65e8d1243a1151272f9beca..0be9381365d7a7fb6b7672d91246b88677ff489e 100644 (file)
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1418,7 +1418,7 @@ static void retrieve_deps(struct dm_table *table,
        deps->count = count;
        count = 0;
        list_for_each_entry (dd, dm_table_get_devices(table), list)
-               deps->dev[count++] = huge_encode_dev(dd->dm_dev.bdev->bd_dev);
+               deps->dev[count++] = huge_encode_dev(dd->dm_dev->bdev->bd_dev);
 
        param->data_size = param->data_start + needed;
 }

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index f9c6cb8dbcf8c493723f5ddc46af8d4e6fed892b..b2bd1ebf4562902aba2b747c742a5f4da3f659e1 100644 (file)
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -210,15 +210,16 @@ int dm_table_create(struct dm_table **result, fmode_t mode,
        return 0;
 }
 
-static void free_devices(struct list_head *devices)
+static void free_devices(struct list_head *devices, struct mapped_device *md)
 {
        struct list_head *tmp, *next;
 
        list_for_each_safe(tmp, next, devices) {
                struct dm_dev_internal *dd =
                    list_entry(tmp, struct dm_dev_internal, list);
-               DMWARN("dm_table_destroy: dm_put_device call missing for %s",
-                      dd->dm_dev.name);
+               DMWARN("%s: dm_table_destroy: dm_put_device call missing for %s",
+                      dm_device_name(md), dd->dm_dev->name);
+               dm_put_table_device(md, dd->dm_dev);
                kfree(dd);
        }
 }
@@ -247,7 +248,7 @@ void dm_table_destroy(struct dm_table *t)
        vfree(t->highs);
 
        /* free the device list */
-       free_devices(&t->devices);
+       free_devices(&t->devices, t->md);
 
        dm_free_md_mempools(t->mempools);
 
@@ -262,52 +263,12 @@ static struct dm_dev_internal *find_device(struct list_head *l, dev_t dev)
        struct dm_dev_internal *dd;
 
        list_for_each_entry (dd, l, list)
-               if (dd->dm_dev.bdev->bd_dev == dev)
+               if (dd->dm_dev->bdev->bd_dev == dev)
                        return dd;
 
        return NULL;
 }
 
-/*
- * Open a device so we can use it as a map destination.
- */
-static int open_dev(struct dm_dev_internal *d, dev_t dev,
-                   struct mapped_device *md)
-{
-       static char *_claim_ptr = "I belong to device-mapper";
-       struct block_device *bdev;
-
-       int r;
-
-       BUG_ON(d->dm_dev.bdev);
-
-       bdev = blkdev_get_by_dev(dev, d->dm_dev.mode | FMODE_EXCL, _claim_ptr);
-       if (IS_ERR(bdev))
-               return PTR_ERR(bdev);
-
-       r = bd_link_disk_holder(bdev, dm_disk(md));
-       if (r) {
-               blkdev_put(bdev, d->dm_dev.mode | FMODE_EXCL);
-               return r;
-       }
-
-       d->dm_dev.bdev = bdev;
-       return 0;
-}
-
-/*
- * Close a device that we've been using.
- */
-static void close_dev(struct dm_dev_internal *d, struct mapped_device *md)
-{
-       if (!d->dm_dev.bdev)
-               return;
-
-       bd_unlink_disk_holder(d->dm_dev.bdev, dm_disk(md));
-       blkdev_put(d->dm_dev.bdev, d->dm_dev.mode | FMODE_EXCL);
-       d->dm_dev.bdev = NULL;
-}
-
 /*
  * If possible, this checks an area of a destination device is invalid.
  */
@@ -386,19 +347,17 @@ static int upgrade_mode(struct dm_dev_internal *dd, fmode_t new_mode,
                        struct mapped_device *md)
 {
        int r;
-       struct dm_dev_internal dd_new, dd_old;
+       struct dm_dev *old_dev, *new_dev;
 
-       dd_new = dd_old = *dd;
+       old_dev = dd->dm_dev;
 
-       dd_new.dm_dev.mode |= new_mode;
-       dd_new.dm_dev.bdev = NULL;
-
-       r = open_dev(&dd_new, dd->dm_dev.bdev->bd_dev, md);
+       r = dm_get_table_device(md, dd->dm_dev->bdev->bd_dev,
+                               dd->dm_dev->mode | new_mode, &new_dev);
        if (r)
                return r;
 
-       dd->dm_dev.mode |= new_mode;
-       close_dev(&dd_old, md);
+       dd->dm_dev = new_dev;
+       dm_put_table_device(md, old_dev);
 
        return 0;
 }
@@ -440,27 +399,22 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode,
                if (!dd)
                        return -ENOMEM;
 
-               dd->dm_dev.mode = mode;
-               dd->dm_dev.bdev = NULL;
-
-               if ((r = open_dev(dd, dev, t->md))) {
+               if ((r = dm_get_table_device(t->md, dev, mode, &dd->dm_dev))) {
                        kfree(dd);
                        return r;
                }
 
-               format_dev_t(dd->dm_dev.name, dev);
-
                atomic_set(&dd->count, 0);
                list_add(&dd->list, &t->devices);
 
-       } else if (dd->dm_dev.mode != (mode | dd->dm_dev.mode)) {
+       } else if (dd->dm_dev->mode != (mode | dd->dm_dev->mode)) {
                r = upgrade_mode(dd, mode, t->md);
                if (r)
                        return r;
        }
        atomic_inc(&dd->count);
 
-       *result = &dd->dm_dev;
+       *result = dd->dm_dev;
        return 0;
 }
 EXPORT_SYMBOL(dm_get_device);
@@ -505,11 +459,23 @@ static int dm_set_device_limits(struct dm_target *ti, struct dm_dev *dev,
  */
 void dm_put_device(struct dm_target *ti, struct dm_dev *d)
 {
-       struct dm_dev_internal *dd = container_of(d, struct dm_dev_internal,
-                                                 dm_dev);
+       int found = 0;
+       struct list_head *devices = &ti->table->devices;
+       struct dm_dev_internal *dd;
 
+       list_for_each_entry(dd, devices, list) {
+               if (dd->dm_dev == d) {
+                       found = 1;
+                       break;
+               }
+       }
+       if (!found) {
+               DMWARN("%s: device %s not in table devices list",
+                      dm_device_name(ti->table->md), d->name);
+               return;
+       }
        if (atomic_dec_and_test(&dd->count)) {
-               close_dev(dd, ti->table->md);
+               dm_put_table_device(ti->table->md, d);
                list_del(&dd->list);
                kfree(dd);
        }
@@ -906,7 +872,7 @@ static int dm_table_set_type(struct dm_table *t)
        /* Non-request-stackable devices can't be used for request-based dm */
        devices = dm_table_get_devices(t);
        list_for_each_entry(dd, devices, list) {
-               if (!blk_queue_stackable(bdev_get_queue(dd->dm_dev.bdev))) {
+               if (!blk_queue_stackable(bdev_get_queue(dd->dm_dev->bdev))) {
                        DMWARN("table load rejected: including"
                               " non-request-stackable devices");
                        return -EINVAL;
@@ -1043,7 +1009,7 @@ static struct gendisk * dm_table_get_integrity_disk(struct dm_table *t,
        struct gendisk *prev_disk = NULL, *template_disk = NULL;
 
        list_for_each_entry(dd, devices, list) {
-               template_disk = dd->dm_dev.bdev->bd_disk;
+               template_disk = dd->dm_dev->bdev->bd_disk;
                if (!blk_get_integrity(template_disk))
                        goto no_integrity;
                if (!match_all && !blk_integrity_is_initialized(template_disk))
@@ -1629,7 +1595,7 @@ int dm_table_any_congested(struct dm_table *t, int bdi_bits)
        int r = 0;
 
        list_for_each_entry(dd, devices, list) {
-               struct request_queue *q = bdev_get_queue(dd->dm_dev.bdev);
+               struct request_queue *q = bdev_get_queue(dd->dm_dev->bdev);
                char b[BDEVNAME_SIZE];
 
                if (likely(q))
@@ -1637,7 +1603,7 @@ int dm_table_any_congested(struct dm_table *t, int bdi_bits)
                else
                        DMWARN_LIMIT("%s: any_congested: nonexistent device %s",
                                     dm_device_name(t->md),
-                                    bdevname(dd->dm_dev.bdev, b));
+                                    bdevname(dd->dm_dev->bdev, b));
        }
 
        list_for_each_entry(cb, &t->target_callbacks, list)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 56a2c74c9a3f5fb8f0a1427b03c5710edb893aec..58f3927fd7cc98dda4113571fab3e607842e15f3 100644 (file)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -142,6 +142,9 @@ struct mapped_device {
         */
        struct dm_table *map;
 
+       struct list_head table_devices;
+       struct mutex table_devices_lock;
+
        unsigned long flags;
 
        struct request_queue *queue;
@@ -212,6 +215,12 @@ struct dm_md_mempools {
        struct bio_set *bs;
 };
 
+struct table_device {
+       struct list_head list;
+       atomic_t count;
+       struct dm_dev dm_dev;
+};
+
 #define RESERVED_BIO_BASED_IOS         16
 #define RESERVED_REQUEST_BASED_IOS     256
 #define RESERVED_MAX_IOS               1024
@@ -669,6 +678,120 @@ static void dm_put_live_table_fast(struct mapped_device *md) __releases(RCU)
        rcu_read_unlock();
 }
 
+/*
+ * Open a table device so we can use it as a map destination.
+ */
+static int open_table_device(struct table_device *td, dev_t dev,
+                            struct mapped_device *md)
+{
+       static char *_claim_ptr = "I belong to device-mapper";
+       struct block_device *bdev;
+
+       int r;
+
+       BUG_ON(td->dm_dev.bdev);
+
+       bdev = blkdev_get_by_dev(dev, td->dm_dev.mode | FMODE_EXCL, _claim_ptr);
+       if (IS_ERR(bdev))
+               return PTR_ERR(bdev);
+
+       r = bd_link_disk_holder(bdev, dm_disk(md));
+       if (r) {
+               blkdev_put(bdev, td->dm_dev.mode | FMODE_EXCL);
+               return r;
+       }
+
+       td->dm_dev.bdev = bdev;
+       return 0;
+}
+
+/*
+ * Close a table device that we've been using.
+ */
+static void close_table_device(struct table_device *td, struct mapped_device *md)
+{
+       if (!td->dm_dev.bdev)
+               return;
+
+       bd_unlink_disk_holder(td->dm_dev.bdev, dm_disk(md));
+       blkdev_put(td->dm_dev.bdev, td->dm_dev.mode | FMODE_EXCL);
+       td->dm_dev.bdev = NULL;
+}
+
+static struct table_device *find_table_device(struct list_head *l, dev_t dev,
+                                             fmode_t mode) {
+       struct table_device *td;
+
+       list_for_each_entry(td, l, list)
+               if (td->dm_dev.bdev->bd_dev == dev && td->dm_dev.mode == mode)
+                       return td;
+
+       return NULL;
+}
+
+int dm_get_table_device(struct mapped_device *md, dev_t dev, fmode_t mode,
+                       struct dm_dev **result) {
+       int r;
+       struct table_device *td;
+
+       mutex_lock(&md->table_devices_lock);
+       td = find_table_device(&md->table_devices, dev, mode);
+       if (!td) {
+               td = kmalloc(sizeof(*td), GFP_KERNEL);
+               if (!td) {
+                       mutex_unlock(&md->table_devices_lock);
+                       return -ENOMEM;
+               }
+
+               td->dm_dev.mode = mode;
+               td->dm_dev.bdev = NULL;
+
+               if ((r = open_table_device(td, dev, md))) {
+                       mutex_unlock(&md->table_devices_lock);
+                       kfree(td);
+                       return r;
+               }
+
+               format_dev_t(td->dm_dev.name, dev);
+
+               atomic_set(&td->count, 0);
+               list_add(&td->list, &md->table_devices);
+       }
+       atomic_inc(&td->count);
+       mutex_unlock(&md->table_devices_lock);
+
+       *result = &td->dm_dev;
+       return 0;
+}
+EXPORT_SYMBOL_GPL(dm_get_table_device);
+
+void dm_put_table_device(struct mapped_device *md, struct dm_dev *d)
+{
+       struct table_device *td = container_of(d, struct table_device, dm_dev);
+
+       mutex_lock(&md->table_devices_lock);
+       if (atomic_dec_and_test(&td->count)) {
+               close_table_device(td, md);
+               list_del(&td->list);
+               kfree(td);
+       }
+       mutex_unlock(&md->table_devices_lock);
+}
+EXPORT_SYMBOL(dm_put_table_device);
+
+static void free_table_devices(struct list_head *devices)
+{
+       struct list_head *tmp, *next;
+
+       list_for_each_safe(tmp, next, devices) {
+               struct table_device *td = list_entry(tmp, struct table_device, list);
+
+               DMWARN("dm_destroy: %s still exists with %d references",
+                      td->dm_dev.name, atomic_read(&td->count));
+               kfree(td);
+       }
+}
+
 /*
  * Get the geometry associated with a dm device
  */
@@ -1944,12 +2067,14 @@ static struct mapped_device *alloc_dev(int minor)
        md->type = DM_TYPE_NONE;
        mutex_init(&md->suspend_lock);
        mutex_init(&md->type_lock);
+       mutex_init(&md->table_devices_lock);
        spin_lock_init(&md->deferred_lock);
        atomic_set(&md->holders, 1);
        atomic_set(&md->open_count, 0);
        atomic_set(&md->event_nr, 0);
        atomic_set(&md->uevent_seq, 0);
        INIT_LIST_HEAD(&md->uevent_list);
+       INIT_LIST_HEAD(&md->table_devices);
        spin_lock_init(&md->uevent_lock);
 
        md->queue = blk_alloc_queue(GFP_KERNEL);
@@ -2035,6 +2160,7 @@ static void free_dev(struct mapped_device *md)
        blk_integrity_unregister(md->disk);
        del_gendisk(md->disk);
        cleanup_srcu_struct(&md->io_barrier);
+       free_table_devices(&md->table_devices);
        free_minor(minor);
 
        spin_lock(&_minor_lock);

diff --git a/drivers/md/dm.h b/drivers/md/dm.h
index e81d2152fa684198899b1998efe3e5b19554b778..988c7fb7b145bb48338bd4e9bc44fbd06f740bd8 100644 (file)
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -44,7 +44,7 @@
 struct dm_dev_internal {
        struct list_head list;
        atomic_t count;
-       struct dm_dev dm_dev;
+       struct dm_dev *dm_dev;
 };
 
 struct dm_table;
@@ -188,6 +188,9 @@ 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 request_queue *dm_get_md_queue(struct mapped_device *md);
+int dm_get_table_device(struct mapped_device *md, dev_t dev, fmode_t mode,
+                       struct dm_dev **result);
+void dm_put_table_device(struct mapped_device *md, struct dm_dev *d);
 struct dm_stats *dm_get_stats(struct mapped_device *md);
 
 int dm_kobject_uevent(struct mapped_device *md, enum kobject_action action,

diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h
index c8a4302093a394038ac1889148d0b28e20a987a5..3315ab21f7285dcfb218214a2f099949efe85005 100644 (file)
--- 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       27
+#define DM_VERSION_MINOR       28
 #define DM_VERSION_PATCHLEVEL  0
-#define DM_VERSION_EXTRA       "-ioctl (2013-10-30)"
+#define DM_VERSION_EXTRA       "-ioctl (2014-09-17)"
 
 /* Status bits */
 #define DM_READONLY_FLAG       (1 << 0) /* In/Out */