[PATCH v8 3/4] Adds blk_interposer to md.

From: Sergei Shtepa
Date: Fri Apr 09 2021 - 07:48:35 EST

* The new flag DM_INTERPOSE_FLAG allows to specify that the dm target
will be attached using blk_interposer.
* The [interpose] option allows to specify which device will be
attached via the interposer.
* The connection and disconnection of the interrupter is performed in
the functions __dm_suspend() and __dm_resume(). The flag
DM_SUSPEND_DETACH_IP_FLAG was added for this purpose.
* dm_submit_bio() sets BIO_INTERPOSED for each bio from the interposer.

Signed-off-by: Sergei Shtepa <sergei.shtepa@xxxxxxxxx>
---
drivers/md/dm-core.h | 1 +
drivers/md/dm-ioctl.c | 95 ++++++++++---
drivers/md/dm-table.c | 68 ++++++++-
drivers/md/dm.c | 254 ++++++++++++++++++++++++++++++----
drivers/md/dm.h | 8 +-
include/linux/device-mapper.h | 1 +
include/uapi/linux/dm-ioctl.h | 6 +
7 files changed, 375 insertions(+), 58 deletions(-)

diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h
index 5953ff2bd260..431b82461eae 100644
--- a/drivers/md/dm-core.h
+++ b/drivers/md/dm-core.h
@@ -112,6 +112,7 @@ struct mapped_device {
/* for blk-mq request-based DM support */
struct blk_mq_tag_set *tag_set;
bool init_tio_pdu:1;
+ bool interpose:1;

struct srcu_struct io_barrier;
};
diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 1ca65b434f1f..7ec37526920b 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -294,11 +294,29 @@ static void dm_hash_remove_all(bool keep_open_devices, bool mark_deferred, bool
md = hc->md;
dm_get(md);

- if (keep_open_devices &&
- dm_lock_for_deletion(md, mark_deferred, only_deferred)) {
- dm_put(md);
- dev_skipped++;
- continue;
+ if (md->interpose) {
+ int r;
+
+ /*
+ * Interposer should be suspended and detached
+ * from the interposed block device.
+ */
+ r = dm_suspend(md, DM_SUSPEND_DETACH_IP_FLAG |
+ DM_SUSPEND_LOCKFS_FLAG);
+ if (r) {
+ DMERR("%s: unable to suspend and detach interposer",
+ dm_device_name(md));
+ dm_put(md);
+ dev_skipped++;
+ continue;
+ }
+ } else {
+ if (keep_open_devices &&
+ dm_lock_for_deletion(md, mark_deferred, only_deferred)) {
+ dm_put(md);
+ dev_skipped++;
+ continue;
+ }
}

t = __hash_remove(hc);
@@ -732,6 +750,9 @@ static void __dev_status(struct mapped_device *md, struct dm_ioctl *param)
if (dm_test_deferred_remove_flag(md))
param->flags |= DM_DEFERRED_REMOVE;

+ if (dm_interposer_attached(md))
+ param->flags |= DM_INTERPOSE_FLAG;
+
param->dev = huge_encode_dev(disk_devt(disk));

/*
@@ -878,20 +899,37 @@ static int dev_remove(struct file *filp, struct dm_ioctl *param, size_t param_si

md = hc->md;

- /*
- * Ensure the device is not open and nothing further can open it.
- */
- r = dm_lock_for_deletion(md, !!(param->flags & DM_DEFERRED_REMOVE), false);
- if (r) {
- if (r == -EBUSY && param->flags & DM_DEFERRED_REMOVE) {
+ if (!md->interpose) {
+ /*
+ * Ensure the device is not open and nothing further can open it.
+ */
+ 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);
- return 0;
+ return r;
+ }
+ } else {
+ /*
+ * Interposer should be suspended and detached from
+ * the interposed block device.
+ */
+ r = dm_suspend(md, DM_SUSPEND_DETACH_IP_FLAG |
+ DM_SUSPEND_LOCKFS_FLAG);
+ if (r) {
+ DMERR("%s: unable to suspend and detach interposer",
+ dm_device_name(md));
+ up_write(&_hash_lock);
+ dm_put(md);
+ return r;
}
- DMDEBUG_LIMIT("unable to remove open device %s", hc->name);
- up_write(&_hash_lock);
- dm_put(md);
- return r;
}

t = __hash_remove(hc);
@@ -1050,6 +1088,7 @@ static int do_resume(struct dm_ioctl *param)

md = hc->md;

+
new_map = hc->new_map;
hc->new_map = NULL;
param->flags &= ~DM_INACTIVE_PRESENT_FLAG;
@@ -1063,8 +1102,14 @@ static int do_resume(struct dm_ioctl *param)
suspend_flags &= ~DM_SUSPEND_LOCKFS_FLAG;
if (param->flags & DM_NOFLUSH_FLAG)
suspend_flags |= DM_SUSPEND_NOFLUSH_FLAG;
- if (!dm_suspended_md(md))
- dm_suspend(md, suspend_flags);
+
+ if (md->interpose) {
+ if (!dm_suspended_md(md) || dm_interposer_attached(md))
+ dm_suspend(md, suspend_flags | DM_SUSPEND_DETACH_IP_FLAG);
+ } else {
+ if (!dm_suspended_md(md))
+ dm_suspend(md, suspend_flags);
+ }

old_map = dm_swap_table(md, new_map);
if (IS_ERR(old_map)) {
@@ -1267,6 +1312,11 @@ static inline fmode_t get_mode(struct dm_ioctl *param)
return mode;
}

+static inline bool get_interpose_flag(struct dm_ioctl *param)
+{
+ return (param->flags & DM_INTERPOSE_FLAG);
+}
+
static int next_target(struct dm_target_spec *last, uint32_t next, void *end,
struct dm_target_spec **spec, char **target_params)
{
@@ -1289,11 +1339,6 @@ static int populate_table(struct dm_table *table,
void *end = (void *) param + param_size;
char *target_params;

- if (!param->target_count) {
- DMWARN("populate_table: no targets specified");
- return -EINVAL;
- }
-
for (i = 0; i < param->target_count; i++) {

r = next_target(spec, next, end, &spec, &target_params);
@@ -1338,6 +1383,8 @@ static int table_load(struct file *filp, struct dm_ioctl *param, size_t param_si
if (!md)
return -ENXIO;

+ md->interpose = get_interpose_flag(param);
+
r = dm_table_create(&t, get_mode(param), param->target_count, md);
if (r)
goto err;
@@ -2098,6 +2145,8 @@ int __init dm_early_create(struct dm_ioctl *dmi,
if (r)
goto err_hash_remove;

+ md->interpose = get_interpose_flag(dmi);
+
/* add targets */
for (i = 0; i < dmi->target_count; i++) {
r = dm_table_add_target(t, spec_array[i]->target_type,
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index e5f0f1703c5d..23574c727f2b 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -327,14 +327,14 @@ static int device_area_is_invalid(struct dm_target *ti, struct dm_dev *dev,
* it is accessed concurrently.
*/
static int upgrade_mode(struct dm_dev_internal *dd, fmode_t new_mode,
- struct mapped_device *md)
+ bool interpose, struct mapped_device *md)
{
int r;
struct dm_dev *old_dev, *new_dev;

old_dev = dd->dm_dev;

- r = dm_get_table_device(md, dd->dm_dev->bdev->bd_dev,
+ r = dm_get_table_device(md, dd->dm_dev->bdev->bd_dev, interpose,
dd->dm_dev->mode | new_mode, &new_dev);
if (r)
return r;
@@ -367,6 +367,8 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode,
{
int r;
dev_t dev;
+ size_t ofs = 0;
+ bool interpose = false;
unsigned int major, minor;
char dummy;
struct dm_dev_internal *dd;
@@ -374,13 +376,40 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode,

BUG_ON(!t);

- if (sscanf(path, "%u:%u%c", &major, &minor, &dummy) == 2) {
+ /*
+ * Extract extended options for device
+ */
+ if (path[0] == '[') {
+ const char *interpose_opt = "interpose";
+ size_t opt_pos = 1;
+ size_t opt_len;
+
+ /*
+ * Because only one option is supported yet, the parser
+ * can be simplest.
+ */
+ opt_len = strlen(interpose_opt);
+ if ((opt_pos + opt_len) < strlen(path) &&
+ memcmp(&path[opt_pos], interpose_opt, opt_len) == 0) {
+ interpose = true;
+
+ if (!t->md->interpose)
+ t->md->interpose = true;
+ } else {
+ DMERR("Invalid devices extended options %s", path);
+ return -EINVAL;
+ }
+
+ ofs = opt_pos + opt_len + 1;
+ }
+
+ if (sscanf(&path[ofs], "%u:%u%c", &major, &minor, &dummy) == 2) {
/* Extract the major/minor numbers */
dev = MKDEV(major, minor);
if (MAJOR(dev) != major || MINOR(dev) != minor)
return -EOVERFLOW;
} else {
- dev = dm_get_dev_t(path);
+ dev = dm_get_dev_t(&path[ofs]);
if (!dev)
return -ENODEV;
}
@@ -391,7 +420,8 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode,
if (!dd)
return -ENOMEM;

- if ((r = dm_get_table_device(t->md, dev, mode, &dd->dm_dev))) {
+ r = dm_get_table_device(t->md, dev, mode, interpose, &dd->dm_dev);
+ if (r) {
kfree(dd);
return r;
}
@@ -401,14 +431,40 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode,
goto out;

} else if (dd->dm_dev->mode != (mode | dd->dm_dev->mode)) {
- r = upgrade_mode(dd, mode, t->md);
+ r = upgrade_mode(dd, mode, interpose, t->md);
if (r)
return r;
}
refcount_inc(&dd->count);
out:
+ if (interpose) {
+ struct block_device *original = dd->dm_dev->bdev;
+ /*
+ * Interposer target should cover all underlying device
+ */
+ if (ti->begin != 0) {
+ DMERR("%s: target offset should be zero for dm interposer",
+ dm_device_name(t->md));
+ r = -EINVAL;
+ goto fail;
+ }
+ if (bdev_nr_sectors(original) != ti->len) {
+ DMERR("%s: interposer and interposed block device size should be equal",
+ dm_device_name(t->md));
+ r = -EINVAL;
+ goto fail;
+ }
+ }
+
*result = dd->dm_dev;
return 0;
+fail:
+ if (refcount_dec_and_test(&dd->count)) {
+ dm_put_table_device(t->md, dd->dm_dev);
+ list_del(&dd->list);
+ kfree(dd);
+ }
+ return r;
}
EXPORT_SYMBOL(dm_get_device);

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 3f3be9408afa..04142454c4ee 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -149,6 +149,7 @@ EXPORT_SYMBOL_GPL(dm_bio_get_target_bio_nr);
#define DMF_DEFERRED_REMOVE 6
#define DMF_SUSPENDED_INTERNALLY 7
#define DMF_POST_SUSPENDING 8
+#define DMF_INTERPOSER_ATTACHED 9

#define DM_NUMA_NODE NUMA_NO_NODE
static int dm_numa_node = DM_NUMA_NODE;
@@ -757,18 +758,24 @@ static int open_table_device(struct table_device *td, dev_t dev,
struct mapped_device *md)
{
struct block_device *bdev;
-
+ fmode_t mode = td->dm_dev.mode;
+ void *holder = NULL;
int r;

BUG_ON(td->dm_dev.bdev);

- bdev = blkdev_get_by_dev(dev, td->dm_dev.mode | FMODE_EXCL, _dm_claim_ptr);
+ if (!td->dm_dev.interpose) {
+ mode |= FMODE_EXCL;
+ holder = _dm_claim_ptr;
+ }
+
+ bdev = blkdev_get_by_dev(dev, mode, holder);
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);
+ blkdev_put(bdev, mode);
return r;
}

@@ -782,11 +789,16 @@ static int open_table_device(struct table_device *td, dev_t dev,
*/
static void close_table_device(struct table_device *td, struct mapped_device *md)
{
+ fmode_t mode = td->dm_dev.mode;
+
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);
+ if (!td->dm_dev.interpose)
+ mode |= FMODE_EXCL;
+ blkdev_put(td->dm_dev.bdev, mode);
+
put_dax(td->dm_dev.dax_dev);
td->dm_dev.bdev = NULL;
td->dm_dev.dax_dev = NULL;
@@ -805,7 +817,7 @@ static struct table_device *find_table_device(struct list_head *l, dev_t dev,
}

int dm_get_table_device(struct mapped_device *md, dev_t dev, fmode_t mode,
- struct dm_dev **result)
+ bool interpose, struct dm_dev **result)
{
int r;
struct table_device *td;
@@ -821,6 +833,7 @@ int dm_get_table_device(struct mapped_device *md, dev_t dev, fmode_t mode,

td->dm_dev.mode = mode;
td->dm_dev.bdev = NULL;
+ td->dm_dev.interpose = interpose;

if ((r = open_table_device(td, dev, md))) {
mutex_unlock(&md->table_devices_lock);
@@ -1496,13 +1509,12 @@ static int __send_empty_flush(struct clone_info *ci)
static int __clone_and_map_data_bio(struct clone_info *ci, struct dm_target *ti,
sector_t sector, unsigned *len)
{
- struct bio *bio = ci->bio;
struct dm_target_io *tio;
int r;

tio = alloc_tio(ci, ti, 0, GFP_NOIO);
tio->len_ptr = len;
- r = clone_bio(tio, bio, sector, *len);
+ r = clone_bio(tio, ci->bio, sector, *len);
if (r < 0) {
free_tio(tio);
return r;
@@ -1696,6 +1708,13 @@ static blk_qc_t dm_submit_bio(struct bio *bio)
goto out;
}

+ /*
+ * If md is an interposer, then we must set the BIO_INTERPOSE flag
+ * so that the request is not re-interposed.
+ */
+ if (md->interpose)
+ bio_set_flag(bio, BIO_INTERPOSED);
+
/* If suspended, queue this IO for later */
if (unlikely(test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags))) {
if (bio->bi_opf & REQ_NOWAIT)
@@ -2410,7 +2429,8 @@ static void dm_queue_flush(struct mapped_device *md)
*/
struct dm_table *dm_swap_table(struct mapped_device *md, struct dm_table *table)
{
- struct dm_table *live_map = NULL, *map = ERR_PTR(-EINVAL);
+ struct dm_table *live_map = NULL;
+ struct dm_table *map = ERR_PTR(-EINVAL);
struct queue_limits limits;
int r;

@@ -2453,26 +2473,50 @@ struct dm_table *dm_swap_table(struct mapped_device *md, struct dm_table *table)
* Functions to lock and unlock any filesystem running on the
* device.
*/
-static int lock_fs(struct mapped_device *md)
+static int lock_bdev_fs(struct mapped_device *md, struct block_device *bdev)
{
int r;

WARN_ON(test_bit(DMF_FROZEN, &md->flags));

- r = freeze_bdev(md->disk->part0);
+ r = freeze_bdev(bdev);
if (!r)
set_bit(DMF_FROZEN, &md->flags);
return r;
}

-static void unlock_fs(struct mapped_device *md)
+static void unlock_bdev_fs(struct mapped_device *md, struct block_device *bdev)
{
if (!test_bit(DMF_FROZEN, &md->flags))
return;
- thaw_bdev(md->disk->part0);
+ thaw_bdev(bdev);
clear_bit(DMF_FROZEN, &md->flags);
}

+static inline int lock_fs(struct mapped_device *md)
+{
+ return lock_bdev_fs(md, md->disk->part0);
+}
+
+static inline void unlock_fs(struct mapped_device *md)
+{
+ unlock_bdev_fs(md, md->disk->part0);
+}
+
+static inline struct block_device *get_interposed_bdev(struct dm_table *t)
+{
+ struct dm_dev_internal *dd;
+
+ /*
+ * For interposer should be only one device in dm table
+ */
+ list_for_each_entry(dd, dm_table_get_devices(t), list)
+ if (dd->dm_dev->interpose)
+ return bdgrab(dd->dm_dev->bdev);
+
+ return NULL;
+}
+
/*
* @suspend_flags: DM_SUSPEND_LOCKFS_FLAG and/or DM_SUSPEND_NOFLUSH_FLAG
* @task_state: e.g. TASK_INTERRUPTIBLE or TASK_UNINTERRUPTIBLE
@@ -2488,7 +2532,10 @@ static int __dm_suspend(struct mapped_device *md, struct dm_table *map,
{
bool do_lockfs = suspend_flags & DM_SUSPEND_LOCKFS_FLAG;
bool noflush = suspend_flags & DM_SUSPEND_NOFLUSH_FLAG;
- int r;
+ bool detach_ip = suspend_flags & DM_SUSPEND_DETACH_IP_FLAG
+ && md->interpose;
+ struct block_device *original_bdev = NULL;
+ int r = 0;

lockdep_assert_held(&md->suspend_lock);

@@ -2507,18 +2554,50 @@ static int __dm_suspend(struct mapped_device *md, struct dm_table *map,
*/
dm_table_presuspend_targets(map);

+ if (!md->interpose) {
+ /*
+ * Flush I/O to the device.
+ * Any I/O submitted after lock_fs() may not be flushed.
+ * noflush takes precedence over do_lockfs.
+ * (lock_fs() flushes I/Os and waits for them to complete.)
+ */
+ if (!noflush && do_lockfs)
+ r = lock_fs(md);
+ } else if (map) {
+ /*
+ * Interposer should not lock mapped device, but
+ * should freeze interposed device and lock it.
+ */
+ original_bdev = get_interposed_bdev(map);
+ if (!original_bdev) {
+ r = -EINVAL;
+ DMERR("%s: interposer cannot get interposed device from table",
+ dm_device_name(md));
+ goto presuspend_undo;
+ }
+
+ if (!noflush && do_lockfs) {
+ r = lock_bdev_fs(md, original_bdev);
+ if (r) {
+ DMERR("%s: interposer cannot freeze interposed device",
+ dm_device_name(md));
+ goto presuspend_undo;
+ }
+ }
+
+ bdev_interposer_lock(original_bdev);
+ }
/*
- * Flush I/O to the device.
- * Any I/O submitted after lock_fs() may not be flushed.
- * noflush takes precedence over do_lockfs.
- * (lock_fs() flushes I/Os and waits for them to complete.)
+ * If map is not initialized, then we cannot suspend
+ * interposed device
*/
- if (!noflush && do_lockfs) {
- r = lock_fs(md);
- if (r) {
- dm_table_presuspend_undo_targets(map);
- return r;
- }
+
+presuspend_undo:
+ if (r) {
+ if (original_bdev)
+ bdput(original_bdev);
+ dm_table_presuspend_undo_targets(map);
+ return r;
}

/*
@@ -2559,14 +2638,40 @@ static int __dm_suspend(struct mapped_device *md, struct dm_table *map,
if (map)
synchronize_srcu(&md->io_barrier);

- /* were we interrupted ? */
- if (r < 0) {
+ if (r == 0) { /* the wait ended successfully */
+ if (md->interpose && original_bdev) {
+ if (detach_ip) {
+ bdev_interposer_detach(original_bdev);
+ clear_bit(DMF_INTERPOSER_ATTACHED, &md->flags);
+ }
+
+ bdev_interposer_unlock(original_bdev);
+
+ if (detach_ip) {
+ /*
+ * If th interposer is detached, then there is
+ * no reason in keeping the queue of the
+ * interposed device stopped.
+ */
+ unlock_bdev_fs(md, original_bdev);
+ }
+
+ bdput(original_bdev);
+ }
+ } else { /* were we interrupted ? */
dm_queue_flush(md);

if (dm_request_based(md))
dm_start_queue(md->queue);

- unlock_fs(md);
+ if (md->interpose && original_bdev) {
+ bdev_interposer_unlock(original_bdev);
+ unlock_bdev_fs(md, original_bdev);
+
+ bdput(original_bdev);
+ } else
+ unlock_fs(md);
+
dm_table_presuspend_undo_targets(map);
/* pushback list is already flushed, so skip flush */
}
@@ -2574,6 +2679,88 @@ static int __dm_suspend(struct mapped_device *md, struct dm_table *map,
return r;
}

+int __dm_attach_interposer(struct mapped_device *md)
+{
+ int r;
+ struct dm_table *map;
+ struct block_device *original_bdev = NULL;
+
+ if (dm_interposer_attached(md))
+ return 0;
+
+ map = rcu_dereference_protected(md->map,
+ lockdep_is_held(&md->suspend_lock));
+ if (!map) {
+ DMERR("%s: interposers table is not initialized",
+ dm_device_name(md));
+ return -EINVAL;
+ }
+
+ original_bdev = get_interposed_bdev(map);
+ if (!original_bdev) {
+ DMERR("%s: interposer cannot get interposed device from table",
+ dm_device_name(md));
+ return -EINVAL;
+ }
+
+ bdev_interposer_lock(original_bdev);
+
+ r = bdev_interposer_attach(original_bdev, dm_disk(md)->part0);
+ if (r)
+ DMERR("%s: failed to attach interposer",
+ dm_device_name(md));
+ else
+ set_bit(DMF_INTERPOSER_ATTACHED, &md->flags);
+
+ bdev_interposer_unlock(original_bdev);
+
+ unlock_bdev_fs(md, original_bdev);
+
+ bdput(original_bdev);
+
+ return r;
+}
+
+int __dm_detach_interposer(struct mapped_device *md)
+{
+ struct dm_table *map = NULL;
+ struct block_device *original_bdev;
+
+ if (!dm_interposer_attached(md))
+ return 0;
+ /*
+ * If mapped device is suspended, but should be detached
+ * we just detach without freeze fs on interposed device.
+ */
+ map = rcu_dereference_protected(md->map,
+ lockdep_is_held(&md->suspend_lock));
+ if (!map) {
+ /*
+ * If table is not initialized then interposed device
+ * cannot be attached
+ */
+ DMERR("%s: table is not initialized for device",
+ dm_device_name(md));
+ return -EINVAL;
+ }
+
+ original_bdev = get_interposed_bdev(map);
+ if (!original_bdev) {
+ DMERR("%s: interposer cannot get interposed device from table",
+ dm_device_name(md));
+ return -EINVAL;
+ }
+
+ bdev_interposer_lock(original_bdev);
+
+ bdev_interposer_detach(original_bdev);
+ clear_bit(DMF_INTERPOSER_ATTACHED, &md->flags);
+
+ bdev_interposer_unlock(original_bdev);
+
+ bdput(original_bdev);
+ return 0;
+}
/*
* We need to be able to change a mapping table under a mounted
* filesystem. For example we might want to move some data in
@@ -2599,7 +2786,11 @@ int dm_suspend(struct mapped_device *md, unsigned suspend_flags)
mutex_lock_nested(&md->suspend_lock, SINGLE_DEPTH_NESTING);

if (dm_suspended_md(md)) {
- r = -EINVAL;
+ if (suspend_flags & DM_SUSPEND_DETACH_IP_FLAG)
+ r = __dm_detach_interposer(md);
+ else
+ r = -EINVAL;
+
goto out_unlock;
}

@@ -2645,8 +2836,10 @@ static int __dm_resume(struct mapped_device *md, struct dm_table *map)
if (dm_request_based(md))
dm_start_queue(md->queue);

- unlock_fs(md);
+ if (md->interpose)
+ return __dm_attach_interposer(md);

+ unlock_fs(md);
return 0;
}

@@ -2880,6 +3073,11 @@ int dm_suspended_md(struct mapped_device *md)
return test_bit(DMF_SUSPENDED, &md->flags);
}

+int dm_interposer_attached(struct mapped_device *md)
+{
+ return test_bit(DMF_INTERPOSER_ATTACHED, &md->flags);
+}
+
static int dm_post_suspending_md(struct mapped_device *md)
{
return test_bit(DMF_POST_SUSPENDING, &md->flags);
diff --git a/drivers/md/dm.h b/drivers/md/dm.h
index b441ad772c18..35f71e48abd1 100644
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -28,6 +28,7 @@
*/
#define DM_SUSPEND_LOCKFS_FLAG (1 << 0)
#define DM_SUSPEND_NOFLUSH_FLAG (1 << 1)
+#define DM_SUSPEND_DETACH_IP_FLAG (1 << 2)

/*
* Status feature flags
@@ -122,6 +123,11 @@ int dm_deleting_md(struct mapped_device *md);
*/
int dm_suspended_md(struct mapped_device *md);

+/*
+ * Is the interposer of this mapped_device is attached?
+ */
+int dm_interposer_attached(struct mapped_device *md);
+
/*
* Internal suspend and resume methods.
*/
@@ -180,7 +186,7 @@ int dm_lock_for_deletion(struct mapped_device *md, bool mark_deferred, bool only
int dm_cancel_deferred_remove(struct mapped_device *md);
int dm_request_based(struct mapped_device *md);
int dm_get_table_device(struct mapped_device *md, dev_t dev, fmode_t mode,
- struct dm_dev **result);
+ bool interpose, struct dm_dev **result);
void dm_put_table_device(struct mapped_device *md, struct dm_dev *d);

int dm_kobject_uevent(struct mapped_device *md, enum kobject_action action,
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 5c641f930caf..3a7abb347702 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -159,6 +159,7 @@ struct dm_dev {
struct block_device *bdev;
struct dax_device *dax_dev;
fmode_t mode;
+ bool interpose;
char name[16];
};

diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h
index fcff6669137b..73a5b712cd0d 100644
--- a/include/uapi/linux/dm-ioctl.h
+++ b/include/uapi/linux/dm-ioctl.h
@@ -362,4 +362,10 @@ enum {
*/
#define DM_INTERNAL_SUSPEND_FLAG (1 << 18) /* Out */

+/*
+ * If set, the underlying device should open without FMODE_EXCL
+ * and attach mapped device via bdev_interposer.
+ */
+#define DM_INTERPOSE_FLAG (1 << 19) /* In/Out */
+
#endif /* _LINUX_DM_IOCTL_H */
--
2.20.1