DM_INTERPOSED_FLAG allow to create dm targets on "the fly". Underlying block device opens without a flag FMODE_EXCL. Dm target receives bio from the original device via blk_interposer.
Signed-off-by: Sergei Shtepa <[email protected]> --- drivers/md/dm-core.h | 6 ++ drivers/md/dm-ioctl.c | 9 +++ drivers/md/dm-table.c | 115 +++++++++++++++++++++++++++++++--- drivers/md/dm.c | 38 +++++++---- include/linux/device-mapper.h | 1 + include/uapi/linux/dm-ioctl.h | 6 ++ 6 files changed, 154 insertions(+), 21 deletions(-) diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h index 5953ff2bd260..e5c845f9b1df 100644 --- a/drivers/md/dm-core.h +++ b/drivers/md/dm-core.h @@ -21,6 +21,8 @@ #define DM_RESERVED_MAX_IOS 1024 +struct dm_interposed_dev; + struct dm_kobject_holder { struct kobject kobj; struct completion completion; @@ -114,6 +116,10 @@ struct mapped_device { bool init_tio_pdu:1; struct srcu_struct io_barrier; + + /* for interposers logic */ + bool is_interposed; + struct dm_interposed_dev *ip_dev; }; void disable_discard(struct mapped_device *md); diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c index 5e306bba4375..2bcb316144a1 100644 --- a/drivers/md/dm-ioctl.c +++ b/drivers/md/dm-ioctl.c @@ -1267,6 +1267,11 @@ static inline fmode_t get_mode(struct dm_ioctl *param) return mode; } +static inline bool get_interposer_flag(struct dm_ioctl *param) +{ + return (param->flags & DM_INTERPOSED_FLAG); +} + static int next_target(struct dm_target_spec *last, uint32_t next, void *end, struct dm_target_spec **spec, char **target_params) { @@ -1338,6 +1343,8 @@ static int table_load(struct file *filp, struct dm_ioctl *param, size_t param_si if (!md) return -ENXIO; + md->is_interposed = get_interposer_flag(param); + r = dm_table_create(&t, get_mode(param), param->target_count, md); if (r) goto err; @@ -2098,6 +2105,8 @@ int __init dm_early_create(struct dm_ioctl *dmi, if (r) goto err_hash_remove; + md->is_interposed = get_interposer_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 95391f78b8d5..0b2f9b66ade5 100644 --- a/drivers/md/dm-table.c +++ b/drivers/md/dm-table.c @@ -6,6 +6,7 @@ */ #include "dm-core.h" +#include "dm-interposer.h" #include <linux/module.h> #include <linux/vmalloc.h> @@ -225,12 +226,13 @@ void dm_table_destroy(struct dm_table *t) /* * See if we've already got a device in the list. */ -static struct dm_dev_internal *find_device(struct list_head *l, dev_t dev) +static struct dm_dev_internal *find_device(struct list_head *l, dev_t dev, bool is_interposed) { 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) && + (dd->dm_dev->is_interposed == is_interposed)) return dd; return NULL; @@ -358,6 +360,90 @@ dev_t dm_get_dev_t(const char *path) } EXPORT_SYMBOL_GPL(dm_get_dev_t); +/* + * Redirect bio from interposed device to dm device + */ +static void dm_interpose_fn(struct dm_interposed_dev *ip_dev, struct bio *bio) +{ + struct mapped_device *md = ip_dev->private; + + if (bio_flagged(bio, BIO_REMAPPED)) { + /* + * Since bio has already been remapped, we need to subtract + * the block device offset from the beginning of the disk. + */ + bio->bi_iter.bi_sector -= get_start_sect(bio->bi_bdev); + + bio_clear_flag(bio, BIO_REMAPPED); + } + + /* + * Set acceptor device. + * It is quite convenient that device mapper creates + * one disk for one block device. + */ + bio->bi_bdev = md->disk->part0; + + /* + * Bio should be resubmitted. + * The bio will be checked again and placed in current->bio_list. + */ + submit_bio_noacct(bio); +} + +static int _interposer_dev_create(struct block_device *bdev, sector_t ofs, sector_t len, + struct mapped_device *md) +{ + int ret; + + DMDEBUG("Create dm interposer."); + + if (md->ip_dev) { + DMERR("The dm interposer device already in use."); + return -EALREADY; + } + + if ((ofs + len) > bdev_nr_sectors(bdev)) { + DMERR("The specified range of sectors exceeds of the size of the block device."); + return -ERANGE; + } + + md->ip_dev = kzalloc(sizeof(struct dm_interposed_dev), GFP_KERNEL); + if (!md->ip_dev) + return -ENOMEM; + + if ((ofs == 0) && (len == 0)) + DMDEBUG("Whole block device should be interposed."); + + dm_interposer_dev_init(md->ip_dev, + ofs, len, + md, dm_interpose_fn); + + ret = dm_interposer_dev_attach(bdev, md->ip_dev); + if (ret) { + DMERR("Cannot attach dm interposer device."); + kfree(md->ip_dev); + md->ip_dev = NULL; + } + + return ret; +} + +static void _interposer_dev_remove(struct block_device *bdev, struct mapped_device *md) +{ + if (!md->ip_dev) + return; + + DMDEBUG("Remove dm interposer. %llu bios was interposed.", + atomic64_read(&md->ip_dev->ip_cnt)); + + if (dm_interposer_detach_dev(bdev, md->ip_dev)) + DMERR("Failed to detach dm interposer."); + + kfree(md->ip_dev); + md->ip_dev = NULL; +} + /* * Add a device to the list, or just increment the usage count if * it's already present. @@ -385,7 +471,7 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode, return -ENODEV; } - dd = find_device(&t->devices, dev); + dd = find_device(&t->devices, dev, t->md->is_interposed); if (!dd) { dd = kmalloc(sizeof(*dd), GFP_KERNEL); if (!dd) @@ -398,15 +484,22 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode, refcount_set(&dd->count, 1); list_add(&dd->list, &t->devices); - goto out; - } else if (dd->dm_dev->mode != (mode | dd->dm_dev->mode)) { r = upgrade_mode(dd, mode, t->md); if (r) return r; + refcount_inc(&dd->count); } - refcount_inc(&dd->count); -out: + + if (t->md->is_interposed) { + r = _interposer_dev_create(dd->dm_dev->bdev, ti->begin, ti->len, t->md); + if (r) { + dm_put_device(ti, dd->dm_dev); + DMERR("Failed to attach dm interposer."); + return r; + } + } + *result = dd->dm_dev; return 0; } @@ -446,6 +539,7 @@ void dm_put_device(struct dm_target *ti, struct dm_dev *d) { int found = 0; struct list_head *devices = &ti->table->devices; + struct mapped_device *md = ti->table->md; struct dm_dev_internal *dd; list_for_each_entry(dd, devices, list) { @@ -456,11 +550,14 @@ void dm_put_device(struct dm_target *ti, struct dm_dev *d) } if (!found) { DMWARN("%s: device %s not in table devices list", - dm_device_name(ti->table->md), d->name); + dm_device_name(md), d->name); return; } + if (md->is_interposed) + _interposer_dev_remove(d->bdev, md); + if (refcount_dec_and_test(&dd->count)) { - dm_put_table_device(ti->table->md, d); + dm_put_table_device(md, d); list_del(&dd->list); kfree(dd); } diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 50b693d776d6..466bf70a66b0 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -762,16 +762,24 @@ static int open_table_device(struct table_device *td, dev_t dev, 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 (md->is_interposed) { - r = bd_link_disk_holder(bdev, dm_disk(md)); - if (r) { - blkdev_put(bdev, td->dm_dev.mode | FMODE_EXCL); - return r; + bdev = blkdev_get_by_dev(dev, td->dm_dev.mode, NULL); + if (IS_ERR(bdev)) + return PTR_ERR(bdev); + } else { + bdev = blkdev_get_by_dev(dev, td->dm_dev.mode | FMODE_EXCL, _dm_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.is_interposed = md->is_interposed; td->dm_dev.bdev = bdev; td->dm_dev.dax_dev = dax_get_by_host(bdev->bd_disk->disk_name); return 0; @@ -785,20 +793,26 @@ 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); + if (td->dm_dev.is_interposed) + blkdev_put(td->dm_dev.bdev, td->dm_dev.mode); + else { + bd_unlink_disk_holder(td->dm_dev.bdev, dm_disk(md)); + blkdev_put(td->dm_dev.bdev, td->dm_dev.mode | FMODE_EXCL); + } put_dax(td->dm_dev.dax_dev); td->dm_dev.bdev = NULL; td->dm_dev.dax_dev = NULL; } static struct table_device *find_table_device(struct list_head *l, dev_t dev, - fmode_t mode) + fmode_t mode, bool is_interposed) { struct table_device *td; list_for_each_entry(td, l, list) - if (td->dm_dev.bdev->bd_dev == dev && td->dm_dev.mode == mode) + if (td->dm_dev.bdev->bd_dev == dev && + td->dm_dev.mode == mode && + td->dm_dev.is_interposed == is_interposed) return td; return NULL; @@ -811,7 +825,7 @@ int dm_get_table_device(struct mapped_device *md, dev_t dev, fmode_t mode, struct table_device *td; mutex_lock(&md->table_devices_lock); - td = find_table_device(&md->table_devices, dev, mode); + td = find_table_device(&md->table_devices, dev, mode, md->is_interposed); if (!td) { td = kmalloc_node(sizeof(*td), GFP_KERNEL, md->numa_node_id); if (!td) { diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h index 7f4ac87c0b32..76a6dfb1cb29 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 is_interposed; char name[16]; }; diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h index fcff6669137b..fc4d06bb3dbb 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_INTERPOSED_FLAG (1 << 19) /* In */ + #endif /* _LINUX_DM_IOCTL_H */ -- 2.20.1 -- dm-devel mailing list [email protected] https://listman.redhat.com/mailman/listinfo/dm-devel
