From: Nathan Huckleberry <nhuck@xxxxxxxxxx> Using tasklets for disk verification can reduce IO latency. When there are accelerated hash instructions it is often better to compute the hash immediately using a tasklet rather than deferring verification to a work-queue. This reduces time spent waiting to schedule work-queue jobs, but requires spending slightly more time in interrupt context. If the dm-bufio cache does not have the required hashes we fallback to the work-queue implementation. FEC is only possible using work-queue because code to support the FEC feature may sleep. The following shows a speed comparison of random reads on a dm-verity device. The dm-verity device uses a 1G ramdisk for data and a 1G ramdisk for hashes. One test was run using tasklets and one test was run using the existing work-queue solution. Both tests were run when the dm-bufio cache was hot. The tasklet implementation performs significantly better since there is no time spent waiting for work-queue jobs to be scheduled. READ: bw=181MiB/s (190MB/s), 181MiB/s-181MiB/s (190MB/s-190MB/s), io=512MiB (537MB), run=2827-2827msec READ: bw=23.6MiB/s (24.8MB/s), 23.6MiB/s-23.6MiB/s (24.8MB/s-24.8MB/s), io=512MiB (537MB), run=21688-21688msec Signed-off-by: Nathan Huckleberry <nhuck@xxxxxxxxxx> Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx> --- drivers/md/dm-verity-target.c | 90 ++++++++++++++++++++++++++++++----- drivers/md/dm-verity.h | 7 ++- 2 files changed, 83 insertions(+), 14 deletions(-) diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c index 95db3a7ee3c7..3b566077a74e 100644 --- a/drivers/md/dm-verity-target.c +++ b/drivers/md/dm-verity-target.c @@ -34,6 +34,7 @@ #define DM_VERITY_OPT_PANIC "panic_on_corruption" #define DM_VERITY_OPT_IGN_ZEROES "ignore_zero_blocks" #define DM_VERITY_OPT_AT_MOST_ONCE "check_at_most_once" +#define DM_VERITY_OPT_TASKLET_VERIFY "try_verify_in_tasklet" #define DM_VERITY_OPTS_MAX (3 + DM_VERITY_OPTS_FEC + \ DM_VERITY_ROOT_HASH_VERIFICATION_OPTS) @@ -220,7 +221,7 @@ static int verity_handle_err(struct dm_verity *v, enum verity_block_type type, struct mapped_device *md = dm_table_get_md(v->ti->table); /* Corruption should be visible in device status in all modes */ - v->hash_failed = 1; + v->hash_failed = true; if (v->corrupted_errs >= DM_VERITY_MAX_CORRUPTED_ERRS) goto out; @@ -286,7 +287,19 @@ static int verity_verify_level(struct dm_verity *v, struct dm_verity_io *io, verity_hash_at_level(v, block, level, &hash_block, &offset); - data = dm_bufio_read(v->bufio, hash_block, &buf); + if (io->in_tasklet) { + data = dm_bufio_get(v->bufio, hash_block, &buf); + if (data == NULL) { + /* + * In tasklet and the hash was not in the bufio cache. + * Return early and resume execution from a work-queue + * to read the hash from disk. + */ + return -EAGAIN; + } + } else + data = dm_bufio_read(v->bufio, hash_block, &buf); + if (IS_ERR(data)) return PTR_ERR(data); @@ -307,6 +320,14 @@ static int verity_verify_level(struct dm_verity *v, struct dm_verity_io *io, if (likely(memcmp(verity_io_real_digest(v, io), want_digest, v->digest_size) == 0)) aux->hash_verified = 1; + else if (io->in_tasklet) { + /* + * FEC code cannot be run in a tasklet since it may + * sleep, so fallback to using a work-queue. + */ + r = -EAGAIN; + goto release_ret_r; + } else if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_METADATA, hash_block, data, NULL) == 0) @@ -474,13 +495,12 @@ static int verity_verify_io(struct dm_verity_io *io) bool is_zero; struct dm_verity *v = io->v; struct bvec_iter start; - unsigned b; struct crypto_wait wait; struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size); - for (b = 0; b < io->n_blocks; b++) { + for (; io->block_idx < io->n_blocks; io->block_idx++) { int r; - sector_t cur_block = io->block + b; + sector_t cur_block = io->block + io->block_idx; struct ahash_request *req = verity_io_hash_req(v, io); if (v->validated_blocks && @@ -527,8 +547,14 @@ static int verity_verify_io(struct dm_verity_io *io) if (v->validated_blocks) set_bit(cur_block, v->validated_blocks); continue; + } else if (io->in_tasklet) { + /* + * FEC code cannot be run in a tasklet since it may + * sleep, so fallback to using a work-queue. + */ + return -EAGAIN; } else if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_DATA, - cur_block, NULL, &start) == 0) { + cur_block, NULL, &start) == 0) { continue; } else { if (bio->bi_status) { @@ -566,7 +592,8 @@ static void verity_finish_io(struct dm_verity_io *io, blk_status_t status) bio->bi_end_io = io->orig_bi_end_io; bio->bi_status = status; - verity_fec_finish_io(io); + if (!io->in_tasklet) + verity_fec_finish_io(io); bio_endio(bio); } @@ -578,6 +605,24 @@ static void verity_work(struct work_struct *w) verity_finish_io(io, errno_to_blk_status(verity_verify_io(io))); } +static void verity_tasklet(unsigned long data) +{ + struct dm_verity_io *io = (struct dm_verity_io *)data; + int err; + + io->in_tasklet = true; + err = verity_verify_io(io); + if (err == -EAGAIN) { + /* fallback to retrying with work-queue */ + io->in_tasklet = false; + INIT_WORK(&io->work, verity_work); + queue_work(io->v->verify_wq, &io->work); + return; + } + + verity_finish_io(io, errno_to_blk_status(err)); +} + static void verity_end_io(struct bio *bio) { struct dm_verity_io *io = bio->bi_private; @@ -588,8 +633,14 @@ static void verity_end_io(struct bio *bio) return; } - INIT_WORK(&io->work, verity_work); - queue_work(io->v->verify_wq, &io->work); + io->block_idx = 0; + if (io->v->use_tasklet) { + tasklet_init(&io->tasklet, verity_tasklet, (unsigned long)io); + tasklet_schedule(&io->tasklet); + } else { + INIT_WORK(&io->work, verity_work); + queue_work(io->v->verify_wq, &io->work); + } } /* @@ -751,6 +802,8 @@ static void verity_status(struct dm_target *ti, status_type_t type, args++; if (v->validated_blocks) args++; + if (v->use_tasklet) + args++; if (v->signature_key_desc) args += DM_VERITY_ROOT_HASH_VERIFICATION_OPTS; if (!args) @@ -776,6 +829,8 @@ static void verity_status(struct dm_target *ti, status_type_t type, DMEMIT(" " DM_VERITY_OPT_IGN_ZEROES); if (v->validated_blocks) DMEMIT(" " DM_VERITY_OPT_AT_MOST_ONCE); + if (v->use_tasklet) + DMEMIT(" " DM_VERITY_OPT_TASKLET_VERIFY); sz = verity_fec_status_table(v, sz, result, maxlen); if (v->signature_key_desc) DMEMIT(" " DM_VERITY_ROOT_HASH_VERIFICATION_OPT_SIG_KEY @@ -1011,11 +1066,16 @@ static int verity_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v, return r; continue; + } else if (!strcasecmp(arg_name, DM_VERITY_OPT_TASKLET_VERIFY)) { + v->use_tasklet = true; + continue; + } else if (verity_is_fec_opt_arg(arg_name)) { r = verity_fec_parse_opt_args(as, v, &argc, arg_name); if (r) return r; continue; + } else if (verity_verify_is_sig_opt_arg(arg_name)) { r = verity_verify_sig_parse_opt_args(as, v, verify_args, @@ -1023,7 +1083,6 @@ static int verity_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v, if (r) return r; continue; - } ti->error = "Unrecognized verity feature request"; @@ -1155,7 +1214,11 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv) goto bad; } - v->tfm = crypto_alloc_ahash(v->alg_name, 0, 0); + /* + * FIXME: CRYPTO_ALG_ASYNC should be conditional on v->use_tasklet + * but verity_parse_opt_args() happens below and has data dep on tfm. + */ + v->tfm = crypto_alloc_ahash(v->alg_name, 0, CRYPTO_ALG_ASYNC); if (IS_ERR(v->tfm)) { ti->error = "Cannot initialize hash function"; r = PTR_ERR(v->tfm); @@ -1265,7 +1328,8 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv) v->bufio = dm_bufio_client_create(v->hash_dev->bdev, 1 << v->hash_dev_block_bits, 1, sizeof(struct buffer_aux), - dm_bufio_alloc_callback, NULL, 0); + dm_bufio_alloc_callback, NULL, + v->use_tasklet ? DM_BUFIO_CLIENT_NO_SLEEP : 0); if (IS_ERR(v->bufio)) { ti->error = "Cannot initialize dm-bufio"; r = PTR_ERR(v->bufio); @@ -1312,7 +1376,7 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv) static struct target_type verity_target = { .name = "verity", .features = DM_TARGET_IMMUTABLE, - .version = {1, 8, 0}, + .version = {1, 9, 0}, .module = THIS_MODULE, .ctr = verity_ctr, .dtr = verity_dtr, diff --git a/drivers/md/dm-verity.h b/drivers/md/dm-verity.h index 4e769d13473a..e73a7972c3e9 100644 --- a/drivers/md/dm-verity.h +++ b/drivers/md/dm-verity.h @@ -13,6 +13,7 @@ #include <linux/dm-bufio.h> #include <linux/device-mapper.h> +#include <linux/interrupt.h> #include <crypto/hash.h> #define DM_VERITY_MAX_LEVELS 63 @@ -51,9 +52,10 @@ struct dm_verity { unsigned char hash_per_block_bits; /* log2(hashes in hash block) */ unsigned char levels; /* the number of tree levels */ unsigned char version; + bool hash_failed:1; /* set if hash of any block failed */ + bool use_tasklet:1; /* try to verify in tasklet before work-queue */ unsigned digest_size; /* digest size for the current hash algorithm */ unsigned int ahash_reqsize;/* the size of temporary space for crypto */ - int hash_failed; /* set to 1 if hash of any block failed */ enum verity_mode mode; /* mode for handling verification errors */ unsigned corrupted_errs;/* Number of errors for corrupted blocks */ @@ -76,10 +78,13 @@ struct dm_verity_io { sector_t block; unsigned n_blocks; + unsigned int block_idx; + bool in_tasklet; struct bvec_iter iter; struct work_struct work; + struct tasklet_struct tasklet; /* * Three variably-size fields follow this struct: -- 2.32.1 (Apple Git-133) -- dm-devel mailing list dm-devel@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/dm-devel