[PATCH v4 4/6] dm: new ioctl DM_DEV_REMAP_CMD

From: Sergei Shtepa
Date: Wed Feb 03 2021 - 11:05:54 EST

New ioctl DM_DEV_REMAP_CMD allow to remap bio requests
from regular block device to dm device.

Signed-off-by: Sergei Shtepa <sergei.shtepa@xxxxxxxxx>
---
drivers/md/dm-core.h | 20 ++
drivers/md/dm-ioctl.c | 39 ++++
drivers/md/dm.c | 376 +++++++++++++++++++++++++++++++++-
include/uapi/linux/dm-ioctl.h | 15 +-
4 files changed, 438 insertions(+), 12 deletions(-)

diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h
index 086d293c2b03..7ef4c44609dc 100644
--- a/drivers/md/dm-core.h
+++ b/drivers/md/dm-core.h
@@ -13,6 +13,7 @@
#include <linux/ktime.h>
#include <linux/genhd.h>
#include <linux/blk-mq.h>
+#include <linux/rbtree.h>

#include <trace/events/block.h>

@@ -109,6 +110,9 @@ struct mapped_device {
bool init_tio_pdu:1;

struct srcu_struct io_barrier;
+
+ /* interposer device for remap */
+ struct dm_interposed_dev *ip_dev;
};

void disable_discard(struct mapped_device *md);
@@ -164,6 +168,22 @@ struct dm_table {
struct dm_md_mempools *mempools;
};

+struct dm_rb_range {
+ struct rb_node node;
+ sector_t start; /* start sector of rb node */
+ sector_t last; /* end sector of rb node */
+ sector_t _subtree_last; /* highest sector in subtree of rb node */
+};
+
+void dm_rb_insert(struct dm_rb_range *node, struct rb_root_cached *root);
+void dm_rb_remove(struct dm_rb_range *node, struct rb_root_cached *root);
+
+struct dm_rb_range *dm_rb_iter_first(struct rb_root_cached *root, sector_t start, sector_t last);
+struct dm_rb_range *dm_rb_iter_next(struct dm_rb_range *node, sector_t start, sector_t last);
+
+int dm_remap_install(struct mapped_device *md, const char *donor_device_name);
+int dm_remap_uninstall(struct mapped_device *md);
+
static inline struct completion *dm_get_completion_from_kobject(struct kobject *kobj)
{
return &container_of(kobj, struct dm_kobject_holder, kobj)->completion;
diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 5e306bba4375..2944d442c256 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1649,6 +1649,44 @@ static int target_message(struct file *filp, struct dm_ioctl *param, size_t para
return r;
}

+static inline int dev_remap_start(struct mapped_device *md, uint8_t *params)
+{
+ char *donor_device_name = (char *)params;
+
+ return dm_remap_install(md, donor_device_name);
+}
+static int dev_remap_finish(struct mapped_device *md)
+{
+ return dm_remap_uninstall(md);
+}
+
+static int dev_remap(struct file *filp, struct dm_ioctl *param, size_t param_size)
+{
+ int ret = 0;
+ struct mapped_device *md;
+ void *bin_data;
+ struct dm_remap_param *remap_param;
+
+ md = find_device(param);
+ if (!md)
+ return -ENXIO;
+
+ bin_data = (void *)(param) + param->data_start;
+ remap_param = bin_data;
+
+ if (remap_param->cmd == REMAP_START_CMD)
+ ret = dev_remap_start(md, remap_param->params);
+ else if (remap_param->cmd == REMAP_FINISH_CMD)
+ ret = dev_remap_finish(md);
+ else {
+ DMWARN("Invalid remap command, %d", remap_param->cmd);
+ ret = -EINVAL;
+ }
+
+ dm_put(md);
+ return ret;
+}
+
/*
* The ioctl parameter block consists of two parts, a dm_ioctl struct
* followed by a data buffer. This flag is set if the second part,
@@ -1691,6 +1729,7 @@ static ioctl_fn lookup_ioctl(unsigned int cmd, int *ioctl_flags)
{DM_DEV_SET_GEOMETRY_CMD, 0, dev_set_geometry},
{DM_DEV_ARM_POLL, IOCTL_FLAGS_NO_PARAMS, dev_arm_poll},
{DM_GET_TARGET_VERSION, 0, get_target_version},
+ {DM_DEV_REMAP_CMD, 0, dev_remap},
};

if (unlikely(cmd >= ARRAY_SIZE(_ioctls)))
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 7bac564f3faa..0b184dfec233 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -28,6 +28,7 @@
#include <linux/refcount.h>
#include <linux/part_stat.h>
#include <linux/blk-crypto.h>
+#include <linux/interval_tree_generic.h>

#define DM_MSG_PREFIX "core"

@@ -56,6 +57,8 @@ static struct workqueue_struct *deferred_remove_workqueue;
atomic_t dm_global_event_nr = ATOMIC_INIT(0);
DECLARE_WAIT_QUEUE_HEAD(dm_global_eventq);

+static DEFINE_MUTEX(dm_interposer_attach_lock);
+
void dm_issue_global_event(void)
{
atomic_inc(&dm_global_event_nr);
@@ -162,6 +165,37 @@ struct table_device {
struct dm_dev dm_dev;
};

+/*
+ * Device mapper's interposer.
+ */
+struct dm_interposer {
+ struct blk_interposer blk_ip;
+ struct mapped_device *md;
+
+ struct kref kref;
+ struct rw_semaphore ip_devs_lock;
+ struct rb_root_cached ip_devs_root; /* dm_interposed_dev tree */
+};
+
+typedef void (*dm_interpose_bio_t) (void *context, struct dm_rb_range *node, struct bio *bio);
+
+struct dm_interposed_dev {
+ struct gendisk *disk;
+ struct dm_rb_range node;
+ void *context;
+ dm_interpose_bio_t dm_interpose_bio;
+
+ atomic64_t ip_cnt; /*for debug purpose*/
+};
+
+/*
+ * Interval tree for device mapper
+ */
+#define START(node) ((node)->start)
+#define LAST(node) ((node)->last)
+INTERVAL_TREE_DEFINE(struct dm_rb_range, node, sector_t, _subtree_last,
+ START, LAST,, dm_rb);
+
/*
* Bio-based DM's mempools' reserved IOs set by the user.
*/
@@ -733,28 +767,342 @@ static void dm_put_live_table_fast(struct mapped_device *md) __releases(RCU)
rcu_read_unlock();
}

+static void dm_submit_bio_interposer_fn(struct bio *bio)
+{
+ struct dm_interposer *ip;
+ unsigned int noio_flag = 0;
+ sector_t start;
+ sector_t last;
+ struct dm_rb_range *node;
+
+ ip = container_of(bio->bi_disk->interposer, struct dm_interposer, blk_ip);
+ start = bio->bi_iter.bi_sector;
+ last = start + dm_sector_div_up(bio->bi_iter.bi_size, SECTOR_SIZE);
+
+ noio_flag = memalloc_noio_save();
+ down_read(&ip->ip_devs_lock);
+ node = dm_rb_iter_first(&ip->ip_devs_root, start, last);
+ while (node) {
+ struct dm_interposed_dev *ip_dev =
+ container_of(node, struct dm_interposed_dev, node);
+
+ atomic64_inc(&ip_dev->ip_cnt);
+ ip_dev->dm_interpose_bio(ip_dev->context, node, bio);
+
+ node = dm_rb_iter_next(node, start, last);
+ }
+ up_read(&ip->ip_devs_lock);
+ memalloc_noio_restore(noio_flag);
+}
+
+static void dm_interposer_free(struct kref *kref)
+{
+ struct dm_interposer *ip = container_of(kref, struct dm_interposer, kref);
+
+ blk_interposer_detach(&ip->blk_ip, dm_submit_bio_interposer_fn);
+
+ kfree(ip);
+}
+
+static struct dm_interposer *dm_interposer_new(struct gendisk *disk)
+{
+ int ret = 0;
+ struct dm_interposer *ip;
+
+ ip = kzalloc(sizeof(struct dm_interposer), GFP_NOIO);
+ if (!ip)
+ return ERR_PTR(-ENOMEM);
+
+ kref_init(&ip->kref);
+ init_rwsem(&ip->ip_devs_lock);
+ ip->ip_devs_root = RB_ROOT_CACHED;
+
+ ret = blk_interposer_attach(disk, &ip->blk_ip, dm_submit_bio_interposer_fn);
+ if (ret) {
+ DMERR("Failed to attack blk_interposer");
+ kref_put(&ip->kref, dm_interposer_free);
+ return ERR_PTR(ret);
+ }
+
+ return ip;
+}
+
+static struct dm_interposer *dm_interposer_get(struct gendisk *disk)
+{
+ struct dm_interposer *ip;
+
+ if (!blk_has_interposer(disk))
+ return NULL;
+
+ if (disk->interposer->ip_submit_bio != dm_submit_bio_interposer_fn) {
+ DMERR("Disks interposer slot already occupied.");
+ return ERR_PTR(-EBUSY);
+ }
+
+ ip = container_of(disk->interposer, struct dm_interposer, blk_ip);
+
+ kref_get(&ip->kref);
+ return ip;
+}
+
+static struct dm_interposed_dev *dm_interposer_new_dev(struct gendisk *disk,
+ sector_t ofs, sector_t len,
+ void *context,
+ dm_interpose_bio_t dm_interpose_bio)
+{
+ sector_t start = ofs;
+ sector_t last = ofs + len - 1;
+ struct dm_interposed_dev *ip_dev = NULL;
+
+ /* Allocate new ip_dev */
+ ip_dev = kzalloc(sizeof(struct dm_interposed_dev), GFP_KERNEL);
+ if (!ip_dev)
+ return NULL;
+
+ ip_dev->disk = disk;
+ ip_dev->node.start = start;
+ ip_dev->node.last = last;
+
+ ip_dev->context = context;
+ ip_dev->dm_interpose_bio = dm_interpose_bio;
+
+ atomic64_set(&ip_dev->ip_cnt, 0);
+
+ return ip_dev;
+}
+
+static inline void dm_interposer_free_dev(struct dm_interposed_dev *ip_dev)
+{
+ kfree(ip_dev);
+}
+
+static inline void dm_disk_freeze(struct gendisk *disk)
+{
+ blk_mq_freeze_queue(disk->queue);
+ blk_mq_quiesce_queue(disk->queue);
+}
+
+static inline void dm_disk_unfreeze(struct gendisk *disk)
+{
+ blk_mq_unquiesce_queue(disk->queue);
+ blk_mq_unfreeze_queue(disk->queue);
+}
+
+static int dm_interposer_attach_dev(struct dm_interposed_dev *ip_dev)
+{
+ int ret = 0;
+ struct dm_interposer *ip = NULL;
+ unsigned int noio_flag = 0;
+
+ if (!ip_dev)
+ return -EINVAL;
+
+ dm_disk_freeze(ip_dev->disk);
+ mutex_lock(&dm_interposer_attach_lock);
+ noio_flag = memalloc_noio_save();
+
+ ip = dm_interposer_get(ip_dev->disk);
+ if (ip == NULL)
+ ip = dm_interposer_new(ip_dev->disk);
+ if (IS_ERR(ip)) {
+ ret = PTR_ERR(ip);
+ goto out;
+ }
+
+ /* Attach dm_interposed_dev to dm_interposer */
+ down_write(&ip->ip_devs_lock);
+ do {
+ struct dm_rb_range *node;
+
+ /* checking that ip_dev already exists for this region */
+ node = dm_rb_iter_first(&ip->ip_devs_root, ip_dev->node.start, ip_dev->node.last);
+ if (node) {
+ DMERR("Disk part form [%llu] to [%llu] already have interposer",
+ node->start, node->last);
+
+ ret = -EBUSY;
+ break;
+ }
+
+ /* insert ip_dev to ip tree */
+ dm_rb_insert(&ip_dev->node, &ip->ip_devs_root);
+ /* increment ip reference counter */
+ kref_get(&ip->kref);
+ } while (false);
+ up_write(&ip->ip_devs_lock);
+
+ kref_put(&ip->kref, dm_interposer_free);
+
+out:
+ memalloc_noio_restore(noio_flag);
+ mutex_unlock(&dm_interposer_attach_lock);
+ dm_disk_unfreeze(ip_dev->disk);
+
+ return ret;
+}
+
+static int dm_interposer_detach_dev(struct dm_interposed_dev *ip_dev)
+{
+ int ret = 0;
+ struct dm_interposer *ip = NULL;
+ unsigned int noio_flag = 0;
+
+ if (!ip_dev)
+ return -EINVAL;
+
+ dm_disk_freeze(ip_dev->disk);
+ mutex_lock(&dm_interposer_attach_lock);
+ noio_flag = memalloc_noio_save();
+
+ ip = dm_interposer_get(ip_dev->disk);
+ if (IS_ERR(ip)) {
+ ret = PTR_ERR(ip);
+ DMERR("Interposer not found");
+ goto out;
+ }
+ if (unlikely(ip == NULL)) {
+ ret = -ENXIO;
+ DMERR("Interposer not found");
+ goto out;
+ }
+
+ down_write(&ip->ip_devs_lock);
+ do {
+ dm_rb_remove(&ip_dev->node, &ip->ip_devs_root);
+ /* the reference counter here cannot be zero */
+ kref_put(&ip->kref, dm_interposer_free);
+
+ } while (false);
+ up_write(&ip->ip_devs_lock);
+
+ /* detach and free interposer if it's not needed */
+ kref_put(&ip->kref, dm_interposer_free);
+out:
+ memalloc_noio_restore(noio_flag);
+ mutex_unlock(&dm_interposer_attach_lock);
+ dm_disk_unfreeze(ip_dev->disk);
+
+ return ret;
+}
+
+static void dm_remap_fn(void *context, struct dm_rb_range *node, struct bio *bio)
+{
+ struct mapped_device *md = context;
+
+ /* Set acceptor device. */
+ bio->bi_disk = md->disk;
+
+ /* Remap disks offset */
+ bio->bi_iter.bi_sector -= node->start;
+
+ /*
+ * bio should be resubmitted.
+ * We can just add bio to bio_list of the current process.
+ * current->bio_list must be initialized when this function is called.
+ * If call submit_bio_noacct(), the bio will be checked twice.
+ */
+ BUG_ON(!current->bio_list);
+ bio_list_add(&current->bio_list[0], bio);
+}
+
+int dm_remap_install(struct mapped_device *md, const char *donor_device_name)
+{
+ int ret = 0;
+ struct block_device *donor_bdev;
+ fmode_t mode = FMODE_READ | FMODE_WRITE;
+
+ DMDEBUG("Dm remap install for mapped device %s and donor device %s",
+ md->name, donor_device_name);
+
+ donor_bdev = blkdev_get_by_path(donor_device_name, mode, "device-mapper remap");
+ if (IS_ERR(donor_bdev)) {
+ DMERR("Cannot open device [%s]", donor_device_name);
+ return PTR_ERR(donor_bdev);
+ }
+
+ do {
+ sector_t ofs = get_start_sect(donor_bdev);
+ sector_t len = bdev_nr_sectors(donor_bdev);
+
+ md->ip_dev = dm_interposer_new_dev(donor_bdev->bd_disk, ofs, len, md, dm_remap_fn);
+ if (!md->ip_dev) {
+ ret = -ENOMEM;
+ break;
+ }
+
+ DMDEBUG("New interposed device 0x%p", md->ip_dev);
+ ret = dm_interposer_attach_dev(md->ip_dev);
+ if (ret) {
+ dm_interposer_free_dev(md->ip_dev);
+
+ md->ip_dev = NULL;
+ DMERR("Failed to attach dm interposer");
+ break;
+ }
+
+ DMDEBUG("Attached successfully.");
+ } while (false);
+
+ blkdev_put(donor_bdev, mode);
+
+ return ret;
+}
+
+int dm_remap_uninstall(struct mapped_device *md)
+{
+ int ret = 0;
+
+ DMDEBUG("Dm remap uninstall for mapped device %s ip_dev=0x%p", md->name, md->ip_dev);
+
+ if (!md->ip_dev) {
+ DMERR("Cannot detach dm interposer");
+ return -EINVAL;
+ }
+
+ ret = dm_interposer_detach_dev(md->ip_dev);
+ if (ret) {
+ DMERR("Failed to detach dm interposer");
+ return ret;
+ }
+
+ DMDEBUG("Detached successfully. %llu bios was interposed",
+ atomic64_read(&md->ip_dev->ip_cnt));
+ dm_interposer_free_dev(md->ip_dev);
+ md->ip_dev = NULL;
+
+ return 0;
+}
+
static char *_dm_claim_ptr = "I belong to device-mapper";

/*
* 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)
+ struct mapped_device *md, bool non_exclusive)
{
struct block_device *bdev;
-
- int r;
+ int ret;

BUG_ON(td->dm_dev.bdev);

- bdev = blkdev_get_by_dev(dev, td->dm_dev.mode | FMODE_EXCL, _dm_claim_ptr);
- if (IS_ERR(bdev))
- return PTR_ERR(bdev);
+ if (non_exclusive)
+ bdev = blkdev_get_by_dev(dev, td->dm_dev.mode, NULL);
+ else
+ bdev = blkdev_get_by_dev(dev, td->dm_dev.mode | FMODE_EXCL, _dm_claim_ptr);

- r = bd_link_disk_holder(bdev, dm_disk(md));
- if (r) {
- blkdev_put(bdev, td->dm_dev.mode | FMODE_EXCL);
- return r;
+ if (IS_ERR(bdev)) {
+ ret = PTR_ERR(bdev);
+ if (ret != -EBUSY)
+ return ret;
+ }
+
+ if (!non_exclusive) {
+ ret = bd_link_disk_holder(bdev, dm_disk(md));
+ if (ret) {
+ blkdev_put(bdev, td->dm_dev.mode);
+ return ret;
+ }
}

td->dm_dev.bdev = bdev;
@@ -2182,6 +2530,14 @@ static void __dm_destroy(struct mapped_device *md, bool wait)

might_sleep();

+ if (md->ip_dev) {
+ if (dm_interposer_detach_dev(md->ip_dev))
+ DMERR("Failed to detach dm interposer");
+
+ dm_interposer_free_dev(md->ip_dev);
+ md->ip_dev = NULL;
+ }
+
spin_lock(&_minor_lock);
idr_replace(&_minor_idr, MINOR_ALLOCED, MINOR(disk_devt(dm_disk(md))));
set_bit(DMF_FREEING, &md->flags);
diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h
index 4933b6b67b85..08d7dbff80f4 100644
--- a/include/uapi/linux/dm-ioctl.h
+++ b/include/uapi/linux/dm-ioctl.h
@@ -214,6 +214,15 @@ struct dm_target_msg {
char message[0];
};

+enum {
+ REMAP_START_CMD = 1,
+ REMAP_FINISH_CMD,
+};
+
+struct dm_remap_param {
+ uint8_t cmd;
+ uint8_t params[0];
+};
/*
* If you change this make sure you make the corresponding change
* to dm-ioctl.c:lookup_ioctl()
@@ -244,6 +253,7 @@ enum {
DM_DEV_SET_GEOMETRY_CMD,
DM_DEV_ARM_POLL_CMD,
DM_GET_TARGET_VERSION_CMD,
+ DM_DEV_REMAP_CMD
};

#define DM_IOCTL 0xfd
@@ -259,6 +269,7 @@ enum {
#define DM_DEV_STATUS _IOWR(DM_IOCTL, DM_DEV_STATUS_CMD, struct dm_ioctl)
#define DM_DEV_WAIT _IOWR(DM_IOCTL, DM_DEV_WAIT_CMD, struct dm_ioctl)
#define DM_DEV_ARM_POLL _IOWR(DM_IOCTL, DM_DEV_ARM_POLL_CMD, struct dm_ioctl)
+#define DM_DEV_REMAP _IOWR(DM_IOCTL, DM_DEV_REMAP_CMD, struct dm_ioctl)

#define DM_TABLE_LOAD _IOWR(DM_IOCTL, DM_TABLE_LOAD_CMD, struct dm_ioctl)
#define DM_TABLE_CLEAR _IOWR(DM_IOCTL, DM_TABLE_CLEAR_CMD, struct dm_ioctl)
@@ -272,9 +283,9 @@ 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 43
+#define DM_VERSION_MINOR 44
#define DM_VERSION_PATCHLEVEL 0
-#define DM_VERSION_EXTRA "-ioctl (2020-10-01)"
+#define DM_VERSION_EXTRA "-ioctl (2020-12-25)"

/* Status bits */
#define DM_READONLY_FLAG (1 << 0) /* In/Out */
--
2.20.1