On 2020/02/20 7:12, [email protected] wrote: > 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).
512e drives have a 512B LBA, so no emulation is needed (the drive does that itself). Did you mean to say 4Kn here ? Or is the intent to bypass the drive level 512B emulation and do all 4K aligned read-modify-write accesses on the host ? > > 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). Same comment as above. Clarifying this would help users. > + > +Supported emulated logical block sizes 512, 1024, 2048 and 4096. > + > +Underlying block size can be set to > 4K to test buffering larger units. If I understand this correctly, your target can also emulate physical sector sizes larger than 4K ? Is this correct ? All this description should I think clarify the combinations of logical/physical sector size that the target can take and change into some other combination. > + > + > +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; These two should have better name to help clarifying the code. May be: ebs -> elblocksz ubs -> epblocksz And add comments to describe the struct fields. > + 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 inline sector_t ? > + > +static sector_t __block_mod(sector_t sector, unsigned int bs) > +{ > + return sector & (bs - 1); > +} inline for this one too ? > + > +/* 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. */ May be use the regular comment block for functions here: /* * READ/WRITE... */ Same for other functions below. > +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. */ Then please fix it... > + 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) { please indent to the "if (", not "sscanf(" > + 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"; The message is confusing here. The device LBA size is certainly fine, but the parameters passed cannot accomodate it right ? So stricktly speaking, it is not the backend device LBA size that is invalid. No ? > + goto bad; > + } > + } > + > + if (!ec->ubs_set && ec->ebs == ec->ubs) > + DMERR("Emulation superfluous: emulated equal to underlying > block size"); This is an error message but you do nothing about it. May be change this into a info level output since that is not a real problem. > + > + 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"); > -- Damien Le Moal Western Digital Research -- dm-devel mailing list [email protected] https://www.redhat.com/mailman/listinfo/dm-devel
