From: Heinz Mauelshagen <[email protected]> This new target is similar to the linear target except that it emulates a smaller logical block size on devices with larger ones. It's main purpose is to emulate 512 byte sectors on 4K native disks (i.e. 512e).
See Documentation/admin-guide/device-mapper/dm-ebs.rst for details. Changes versus version 2 sent on 2/13/2020: - fix __nr_blocks() to return the correct number of blocks - fix __ebs_forget_bio() to process the last block of a bio - fix __ebs_process_bios() to avoid prefetching the same block twice - use op_is_flush() in the map function - comments Reviewed-by: John Dorminy <[email protected]> Signed-off-by: Heinz Mauelshagen <[email protected]> --- .../admin-guide/device-mapper/dm-ebs.rst | 49 ++ drivers/md/Kconfig | 8 + drivers/md/Makefile | 2 + drivers/md/dm-ebs-target.c | 429 ++++++++++++++++++ 4 files changed, 488 insertions(+) create mode 100644 Documentation/admin-guide/device-mapper/dm-ebs.rst create mode 100644 drivers/md/dm-ebs-target.c diff --git a/Documentation/admin-guide/device-mapper/dm-ebs.rst b/Documentation/admin-guide/device-mapper/dm-ebs.rst new file mode 100644 index 000000000000..530771dbb352 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/dm-ebs.rst @@ -0,0 +1,49 @@ +====== +dm-ebs +====== + +This target is similar to the linear target except that it emulates +smaller logical block size on devices with larger ones. It's main +purpose is to emulate 512 byte sectors on 4K native disks (i.e 512e). + +Supported emulated logical block sizes 512, 1024, 2048 and 4096. + +Underlying block size can be set to > 4K to test buffering larger units. + + +Table parameters +---------------- + <dev path> <offset> <emulated sectors> [<underlying sectors>] + +Mandatory parameters: + + <dev path>: + Full pathname to the underlying block-device, + or a "major:minor" device-number. + <offset>: + Starting sector within the device; + has to be a multiple of <emulated sectors>. + <emulated sectors>: + Number of sectors defining the logical block size to be emulated; + 1, 2, 4, 8 sectors of 512 bytes supported. + +Optional parameter: + + <underyling sectors>: + Number of sectors defining the logical block size of <dev path>. + 2^N supported, e.g. 8 = emulate 8 sectors of 512 bytes = 4KiB. + If not provided, the logical block size of <dev path> will be used. + + +Examples: + +Emulate 1 sector = 512 bytes logical block size on /dev/sda starting at +offset 1024 sectors with underlying devices block size automatically set: + +ebs /dev/sda 1024 1 + +Emulate 2 sector = 1KiB logical block size on /dev/sda starting at +offset 128 sectors, enforce 2KiB underlying device block size. +This presumes 2KiB logical blocksize on /dev/sda or less to work: + +ebs /dev/sda 128 2 4 diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig index d6d5ab23c088..392974a2999d 100644 --- a/drivers/md/Kconfig +++ b/drivers/md/Kconfig @@ -336,6 +336,14 @@ config DM_WRITECACHE The writecache target doesn't cache reads because reads are supposed to be cached in standard RAM. +config DM_EBS + tristate "Emulated block size target (EXPERIMENTAL)" + depends on BLK_DEV_DM + default n + ---help--- + dm-ebs emulates smaller logical block size on backing devices + with larger ones (e.g. 512 byte sectors on 4K native disks). + config DM_ERA tristate "Era target (EXPERIMENTAL)" depends on BLK_DEV_DM diff --git a/drivers/md/Makefile b/drivers/md/Makefile index d91a7edcd2ab..9a2d673f94bc 100644 --- a/drivers/md/Makefile +++ b/drivers/md/Makefile @@ -17,6 +17,7 @@ dm-thin-pool-y += dm-thin.o dm-thin-metadata.o dm-cache-y += dm-cache-target.o dm-cache-metadata.o dm-cache-policy.o \ dm-cache-background-tracker.o dm-cache-smq-y += dm-cache-policy-smq.o +dm-ebs-y += dm-ebs-target.o dm-era-y += dm-era-target.o dm-clone-y += dm-clone-target.o dm-clone-metadata.o dm-verity-y += dm-verity-target.o @@ -65,6 +66,7 @@ obj-$(CONFIG_DM_THIN_PROVISIONING) += dm-thin-pool.o obj-$(CONFIG_DM_VERITY) += dm-verity.o obj-$(CONFIG_DM_CACHE) += dm-cache.o obj-$(CONFIG_DM_CACHE_SMQ) += dm-cache-smq.o +obj-$(CONFIG_DM_EBS) += dm-ebs.o obj-$(CONFIG_DM_ERA) += dm-era.o obj-$(CONFIG_DM_CLONE) += dm-clone.o obj-$(CONFIG_DM_LOG_WRITES) += dm-log-writes.o diff --git a/drivers/md/dm-ebs-target.c b/drivers/md/dm-ebs-target.c new file mode 100644 index 000000000000..a241af82543a --- /dev/null +++ b/drivers/md/dm-ebs-target.c @@ -0,0 +1,429 @@ +/* + * Copyright (C) 2020 Red Hat GmbH + * + * This file is released under the GPL. + * + * Device-mapper target to emulate smaller logical block + * size on backing devices exposing (natively) larger ones. + * + * E.g. 512 byte sector emulation on 4K native disks. + */ + +#include "dm.h" +#include <linux/module.h> +#include <linux/workqueue.h> +#include <linux/dm-bufio.h> + +#define DM_MSG_PREFIX "ebs" + +static void ebs_dtr(struct dm_target *ti); + +/* Emulated block size context. */ +struct ebs_c { + struct dm_dev *dev; + struct dm_bufio_client *bufio; + struct work_struct ws; + struct workqueue_struct *wq; + struct bio_list bios_in; + spinlock_t lock; /* Guard bios_in list above */ + sector_t start; + unsigned int ebs; + unsigned int ubs; + unsigned char shift; + unsigned short ubs_set:1; +}; + +static sector_t __sector_to_block(struct ebs_c *ec, sector_t sector) +{ + return sector >> ec->shift; +} + +static sector_t __block_mod(sector_t sector, unsigned int bs) +{ + return sector & (bs - 1); +} + +/* Return number of blocks for a bio accounting for misalignement of start and end sectors. */ +static unsigned int __nr_blocks(struct ebs_c *ec, struct bio *bio) +{ + sector_t end_sector = __block_mod(bio->bi_iter.bi_sector, ec->ubs) + bio_sectors(bio); + + return __sector_to_block(ec, end_sector) + (__block_mod(end_sector, ec->ubs) ? 1 : 0); +} + +static bool __ebs_check_bs(unsigned int bs) +{ + return bs && is_power_of_2(bs); +} + +/* READ/WRITE bio vector: copy blocks between bufio blocks and bio vector's (partial/overlapping) pages. */ +static int __ebs_rw_bvec(struct ebs_c *ec, int rw, struct bio_vec *bv, struct bvec_iter *iter) +{ + int r = 0; + unsigned char *ba, *pa = page_address(bv->bv_page) + bv->bv_offset; + unsigned int cur_len; + unsigned int bv_len = bv->bv_len; + unsigned int buf_off = to_bytes(__block_mod(iter->bi_sector, ec->ubs)); + sector_t block = __sector_to_block(ec, iter->bi_sector); + struct dm_buffer *b; + + if (!bv->bv_page || !bv_len) + return -EIO; + + /* Handle overlapping page <-> blocks */ + while (bv_len) { + cur_len = min(dm_bufio_get_block_size(ec->bufio) - buf_off, bv_len); + + /* Avoid reading for writes in case bio vector's page overwrites block completely. */ + if (rw == READ || buf_off || bv_len < dm_bufio_get_block_size(ec->bufio)) + ba = dm_bufio_read(ec->bufio, block, &b); + else + ba = dm_bufio_new(ec->bufio, block, &b); + + if (unlikely(IS_ERR(ba))) + r = PTR_ERR(ba); /* Carry on with next buffer if any to I/O all possible data but return error. */ + else { + /* Copy data to/from bio to buffer if read/new was successful above. */ + ba += buf_off; + if (rw == READ) + memcpy(pa, ba, cur_len); + else { + memcpy(ba, pa, cur_len); + dm_bufio_mark_partial_buffer_dirty(b, buf_off, buf_off + cur_len); + } + + dm_bufio_release(b); + } + + pa += cur_len; + bv_len -= cur_len; + buf_off = 0; + block++; + } + + return r; +} + +/* READ/WRITE: iterate bio vector's copying between (partial) pages and bufio blocks. */ +static int __ebs_rw_bio(struct ebs_c *ec, int rw, struct bio *bio) +{ + int r = 0, rr; + struct bio_vec bv; + struct bvec_iter iter; + + bio_for_each_bvec(bv, bio, iter) { + rr = __ebs_rw_bvec(ec, rw, &bv, &iter); + if (rr) + r = rr; + } + + return r; +} + +/* 'Discard' blocks, i.e. release them from the bufio cache. */ +static int __ebs_forget_bio(struct ebs_c *ec, struct bio *bio) +{ + sector_t blocks, sector = bio->bi_iter.bi_sector;; + + blocks = __nr_blocks(ec, bio); + for (; blocks--; sector += ec->ubs) + dm_bufio_forget(ec->bufio, __sector_to_block(ec, sector)); + + return 0; +} + +/* Worker funtion to process incoming bios. */ +static void __ebs_process_bios(struct work_struct *ws) +{ + int r; + bool write = false; + sector_t block1, block2; + struct ebs_c *ec = container_of(ws, struct ebs_c, ws); + struct bio *bio; + struct bio_list bios; + + bio_list_init(&bios); + + spin_lock_irq(&ec->lock); + bios = ec->bios_in; + bio_list_init(&ec->bios_in); + spin_unlock_irq(&ec->lock); + + /* Prefetch all read and any mis-aligned write buffers */ + bio_list_for_each(bio, &bios) { + block1 = __sector_to_block(ec, bio->bi_iter.bi_sector); + if (bio_op(bio) == REQ_OP_READ) + dm_bufio_prefetch(ec->bufio, block1, __nr_blocks(ec, bio)); + else if (bio_op(bio) == REQ_OP_WRITE && !(bio->bi_opf & REQ_PREFLUSH)) { + block2 = __sector_to_block(ec, bio_end_sector(bio)); + if (__block_mod(bio->bi_iter.bi_sector, ec->ubs)) + dm_bufio_prefetch(ec->bufio, block1, 1); + if (__block_mod(bio_end_sector(bio), ec->ubs) && block2 != block1) + dm_bufio_prefetch(ec->bufio, block2, 1); + } + } + + bio_list_for_each(bio, &bios) { + r = -EIO; + + if (bio_op(bio) == REQ_OP_READ) + r = __ebs_rw_bio(ec, READ, bio); + else if (bio_op(bio) == REQ_OP_WRITE) { + write = true; + r = __ebs_rw_bio(ec, WRITE, bio); + } else if (bio_op(bio) == REQ_OP_DISCARD) + /* FIXME: (optionally) call dm_bufio_discard_buffers() once upstream. */ + r = __ebs_forget_bio(ec, bio); + + if (r) + bio->bi_status = BLK_STS_IOERR; + } + + r = write ? dm_bufio_write_dirty_buffers(ec->bufio) : 0; + + while ((bio = bio_list_pop(&bios))) { + /* FIXME: any other request is just endioed for now. */ + if (unlikely(r && bio_op(bio) == REQ_OP_WRITE)) + bio_io_error(bio); + else + bio_endio(bio); + } +} + +/* + * Construct an emulated block size mapping: <dev_path> <offset> <ebs> [<ubs>] + * + * <dev_path>: path of the underlying device + * <offset>: offset in 512 bytes sectors into <dev_path> + * <ebs>: emulated block size in units of 512 bytes exposed to the upper layer + * [<ubs>]: underlying block size in units of 512 bytes imposed on the lower layer; + * optional, if not supplied, retrieve logical block size from underlying device + */ +static int ebs_ctr(struct dm_target *ti, unsigned int argc, char **argv) +{ + int r; + unsigned short tmp1; + unsigned long long tmp; + char dummy; + struct ebs_c *ec; + + if (argc < 3 || argc > 4) { + ti->error = "Invalid argument count"; + return -EINVAL; + } + + ec = ti->private = kzalloc(sizeof(*ec), GFP_KERNEL); + if (!ec) { + ti->error = "Cannot allocate ebs context"; + return -ENOMEM; + } + + r = -EINVAL; + if (sscanf(argv[1], "%llu%c", &tmp, &dummy) != 1 || + tmp != (sector_t)tmp || + (sector_t)tmp >= ti->len) { + ti->error = "Invalid device offset sector"; + goto bad; + } + ec->start = tmp; + + if (sscanf(argv[2], "%hu%c", &tmp1, &dummy) != 1 || + !__ebs_check_bs(tmp1) || + to_bytes(tmp1) > PAGE_SIZE) { + ti->error = "Invalid emulated block size"; + goto bad; + } + ec->ebs = tmp1; + + if (argc > 3) { + if (sscanf(argv[3], "%hu%c", &tmp1, &dummy) != 1 || !__ebs_check_bs(tmp1)) { + ti->error = "Invalid underlying block size"; + goto bad; + } + ec->ubs = tmp1; + ec->ubs_set = true; + } else + ec->ubs_set = false; + + r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &ec->dev); + if (r) { + ti->error = "Device lookup failed"; + ec->dev = NULL; + goto bad; + } + + r = -EINVAL; + if (!ec->ubs_set) { + ec->ubs = to_sector(bdev_logical_block_size(ec->dev->bdev)); + if (!__ebs_check_bs(ec->ubs)) { + ti->error = "Invalid retrieved underlying block size"; + goto bad; + } + } + + if (!ec->ubs_set && ec->ebs == ec->ubs) + DMERR("Emulation superfluous: emulated equal to underlying block size"); + + if (__block_mod(ec->start, ec->ubs)) { + ti->error = "Device offset must be multiple of underlying block size"; + goto bad; + } + + ec->bufio = dm_bufio_client_create(ec->dev->bdev, to_bytes(ec->ubs), 1, 0, NULL, NULL); + if (IS_ERR(ec->bufio)) { + ti->error = "Cannot create dm bufio client"; + r = PTR_ERR(ec->bufio); + ec->bufio = NULL; + goto bad; + } + + ec->wq = alloc_ordered_workqueue("dm-" DM_MSG_PREFIX, WQ_MEM_RECLAIM); + if (!ec->wq) { + ti->error = "Cannot create dm-" DM_MSG_PREFIX " workqueue"; + r = -ENOMEM; + goto bad; + } + + ec->shift = __ffs(ec->ubs); + INIT_WORK(&ec->ws, &__ebs_process_bios); + bio_list_init(&ec->bios_in); + spin_lock_init(&ec->lock); + + ti->num_flush_bios = 1; + ti->num_discard_bios = 1; + ti->num_secure_erase_bios = 0; + ti->num_write_same_bios = 0; + ti->num_write_zeroes_bios = 0; + return 0; +bad: + ebs_dtr(ti); + return r; +} + +static void ebs_dtr(struct dm_target *ti) +{ + struct ebs_c *ec = ti->private; + + if (ec->wq) + destroy_workqueue(ec->wq); + if (ec->bufio) + dm_bufio_client_destroy(ec->bufio); + if (ec->dev) + dm_put_device(ti, ec->dev); + kfree(ec); +} + +static int ebs_map(struct dm_target *ti, struct bio *bio) +{ + struct ebs_c *ec = ti->private; + + bio_set_dev(bio, ec->dev->bdev); + bio->bi_iter.bi_sector = ec->start + dm_target_offset(ti, bio->bi_iter.bi_sector); + + if (unlikely(op_is_flush(bio->bi_opf))) + return DM_MAPIO_REMAPPED; + + /* + * Only queue for bufio processing in case of partial or overlapping buffers + * -or- + * emulation with ebs == ubs aiming for tests of dm-bufio overhead. + */ + if (likely(__block_mod(bio->bi_iter.bi_sector, ec->ubs) || + __block_mod(bio_end_sector(bio), ec->ubs) || + ec->ebs == ec->ubs)) { + spin_lock_irq(&ec->lock); + bio_list_add(&ec->bios_in, bio); + spin_unlock_irq(&ec->lock); + + queue_work(ec->wq, &ec->ws); + + return DM_MAPIO_SUBMITTED; + } + + /* Forget any buffer content relative to this direct backing device I/O. */ + __ebs_forget_bio(ec, bio); + + return DM_MAPIO_REMAPPED; +} + +static void ebs_status(struct dm_target *ti, status_type_t type, + unsigned status_flags, char *result, unsigned maxlen) +{ + struct ebs_c *ec = ti->private; + + switch (type) { + case STATUSTYPE_INFO: + *result = '\0'; + break; + case STATUSTYPE_TABLE: + snprintf(result, maxlen, ec->ubs_set ? "%s %llu %u %u" : "%s %llu %u", + ec->dev->name, (unsigned long long) ec->start, ec->ebs, ec->ubs); + break; + } +} + +static int ebs_prepare_ioctl(struct dm_target *ti, struct block_device **bdev) +{ + struct ebs_c *ec = ti->private; + struct dm_dev *dev = ec->dev; + + /* + * Only pass ioctls through if the device sizes match exactly. + */ + *bdev = dev->bdev; + return !!(ec->start || ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT); +} + +static void ebs_io_hints(struct dm_target *ti, struct queue_limits *limits) +{ + struct ebs_c *ec = ti->private; + + limits->logical_block_size = to_bytes(ec->ebs); + limits->physical_block_size = to_bytes(ec->ubs); + limits->alignment_offset = limits->physical_block_size; + blk_limits_io_min(limits, limits->logical_block_size); +} + +static int ebs_iterate_devices(struct dm_target *ti, + iterate_devices_callout_fn fn, void *data) +{ + struct ebs_c *ec = ti->private; + + return fn(ti, ec->dev, ec->start, ti->len, data); +} + +static struct target_type ebs_target = { + .name = "ebs", + .version = {1, 0, 0}, + .features = DM_TARGET_PASSES_INTEGRITY, + .module = THIS_MODULE, + .ctr = ebs_ctr, + .dtr = ebs_dtr, + .map = ebs_map, + .status = ebs_status, + .io_hints = ebs_io_hints, + .prepare_ioctl = ebs_prepare_ioctl, + .iterate_devices = ebs_iterate_devices, +}; + +int __init dm_ebs_init(void) +{ + int r = dm_register_target(&ebs_target); + + if (r < 0) + DMERR("register failed %d", r); + + return r; +} + +void dm_ebs_exit(void) +{ + dm_unregister_target(&ebs_target); +} + +module_init(dm_ebs_init); +module_exit(dm_ebs_exit); + +MODULE_AUTHOR("Heinz Mauelshagen <[email protected]>"); +MODULE_DESCRIPTION(DM_NAME " emulated block size target"); +MODULE_LICENSE("GPL"); -- 2.24.1 -- dm-devel mailing list [email protected] https://www.redhat.com/mailman/listinfo/dm-devel
