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 5152142..0be9381 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1418,7 +1418,7 @@
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 f9c6cb8..b2bd1eb 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -210,15 +210,16 @@
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 @@
vfree(t->highs);
/* free the device list */
- free_devices(&t->devices);
+ free_devices(&t->devices, t->md);
dm_free_md_mempools(t->mempools);
@@ -262,53 +263,13 @@
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.
*/
static int device_area_is_invalid(struct dm_target *ti, struct dm_dev *dev,
@@ -386,19 +347,17 @@
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 @@
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 @@
*/
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 @@
/* 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 @@
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 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 @@
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 56a2c74..58f3927 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -142,6 +142,9 @@
*/
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 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
@@ -670,6 +679,120 @@
}
/*
+ * 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
*/
int dm_get_geometry(struct mapped_device *md, struct hd_geometry *geo)
@@ -1944,12 +2067,14 @@
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 @@
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 e81d215..988c7fb7 100644
--- 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_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 c8a43020..3315ab2 100644
--- a/include/uapi/linux/dm-ioctl.h
+++ b/include/uapi/linux/dm-ioctl.h
@@ -267,9 +267,9 @@
#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 */
