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block, dm: don't copy bios for request clones

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Currently dm-multipath has to clone the bios for every request sent
to the lower devices, which wastes cpu cycles and ties down memory.

This patch instead adds a new REQ_CLONE flag that instructs req_bio_endio
to not complete bios attached to a request, which we set on clone
requests similar to bios in a flush sequence.  With this change I/O
errors on a path failure only get propagated to dm-multipath, which
can then either resubmit the I/O or complete the bios on the original
request.

I've done some basic testing of this on a Linux target with ALUA support,
and it survives path failures during I/O nicely.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Christoph Hellwig 2015-05-22 09:14:04 -04:00 committed by Jens Axboe
parent 326e1dbb57
commit 5f1b670d0b
6 changed files with 73 additions and 230 deletions
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94
block/blk-core.c
View File

@ -117,7 +117,7 @@ EXPORT_SYMBOL(blk_rq_init);
static void req_bio_endio(struct request *rq, struct bio *bio,
unsigned int nbytes, int error)
{
if (error)
if (error && !(rq->cmd_flags & REQ_CLONE))
clear_bit(BIO_UPTODATE, &bio->bi_flags);
else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
error = -EIO;
@ -128,7 +128,8 @@ static void req_bio_endio(struct request *rq, struct bio *bio,
bio_advance(bio, nbytes);
/* don't actually finish bio if it's part of flush sequence */
if (bio->bi_iter.bi_size == 0 && !(rq->cmd_flags & REQ_FLUSH_SEQ))
if (bio->bi_iter.bi_size == 0 &&
!(rq->cmd_flags & (REQ_FLUSH_SEQ|REQ_CLONE)))
bio_endio(bio, error);
}
@ -2909,95 +2910,22 @@ int blk_lld_busy(struct request_queue *q)
}
EXPORT_SYMBOL_GPL(blk_lld_busy);
/**
* blk_rq_unprep_clone - Helper function to free all bios in a cloned request
* @rq: the clone request to be cleaned up
*
* Description:
* Free all bios in @rq for a cloned request.
*/
void blk_rq_unprep_clone(struct request *rq)
{
struct bio *bio;
while ((bio = rq->bio) != NULL) {
rq->bio = bio->bi_next;
bio_put(bio);
}
}
EXPORT_SYMBOL_GPL(blk_rq_unprep_clone);
/*
* Copy attributes of the original request to the clone request.
* The actual data parts (e.g. ->cmd, ->sense) are not copied.
*/
static void __blk_rq_prep_clone(struct request *dst, struct request *src)
void blk_rq_prep_clone(struct request *dst, struct request *src)
{
dst->cpu = src->cpu;
dst->cmd_flags |= (src->cmd_flags & REQ_CLONE_MASK) | REQ_NOMERGE;
dst->cmd_flags |= (src->cmd_flags & REQ_CLONE_MASK);
dst->cmd_flags |= REQ_NOMERGE | REQ_CLONE;
dst->cmd_type = src->cmd_type;
dst->__sector = blk_rq_pos(src);
dst->__data_len = blk_rq_bytes(src);
dst->nr_phys_segments = src->nr_phys_segments;
dst->ioprio = src->ioprio;
dst->extra_len = src->extra_len;
}
/**
* blk_rq_prep_clone - Helper function to setup clone request
* @rq: the request to be setup
* @rq_src: original request to be cloned
* @bs: bio_set that bios for clone are allocated from
* @gfp_mask: memory allocation mask for bio
* @bio_ctr: setup function to be called for each clone bio.
* Returns %0 for success, non %0 for failure.
* @data: private data to be passed to @bio_ctr
*
* Description:
* Clones bios in @rq_src to @rq, and copies attributes of @rq_src to @rq.
* The actual data parts of @rq_src (e.g. ->cmd, ->sense)
* are not copied, and copying such parts is the caller's responsibility.
* Also, pages which the original bios are pointing to are not copied
* and the cloned bios just point same pages.
* So cloned bios must be completed before original bios, which means
* the caller must complete @rq before @rq_src.
*/
int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
struct bio_set *bs, gfp_t gfp_mask,
int (*bio_ctr)(struct bio *, struct bio *, void *),
void *data)
{
struct bio *bio, *bio_src;
if (!bs)
bs = fs_bio_set;
__rq_for_each_bio(bio_src, rq_src) {
bio = bio_clone_fast(bio_src, gfp_mask, bs);
if (!bio)
goto free_and_out;
if (bio_ctr && bio_ctr(bio, bio_src, data))
goto free_and_out;
if (rq->bio) {
rq->biotail->bi_next = bio;
rq->biotail = bio;
} else
rq->bio = rq->biotail = bio;
}
__blk_rq_prep_clone(rq, rq_src);
return 0;
free_and_out:
if (bio)
bio_put(bio);
blk_rq_unprep_clone(rq);
return -ENOMEM;
dst->bio = src->bio;
dst->biotail = src->biotail;
dst->cmd = src->cmd;
dst->cmd_len = src->cmd_len;
dst->sense = src->sense;
}
EXPORT_SYMBOL_GPL(blk_rq_prep_clone);

25
drivers/md/dm-table.c
View File

@ -940,21 +940,28 @@ static int dm_table_alloc_md_mempools(struct dm_table *t, struct mapped_device *
{
unsigned type = dm_table_get_type(t);
unsigned per_bio_data_size = 0;
struct dm_target *tgt;
unsigned i;
if (unlikely(type == DM_TYPE_NONE)) {
switch (type) {
case DM_TYPE_BIO_BASED:
for (i = 0; i < t->num_targets; i++) {
struct dm_target *tgt = t->targets + i;
per_bio_data_size = max(per_bio_data_size,
tgt->per_bio_data_size);
}
t->mempools = dm_alloc_bio_mempools(t->integrity_supported,
per_bio_data_size);
break;
case DM_TYPE_REQUEST_BASED:
case DM_TYPE_MQ_REQUEST_BASED:
t->mempools = dm_alloc_rq_mempools(md, type);
break;
default:
DMWARN("no table type is set, can't allocate mempools");
return -EINVAL;
}
if (type == DM_TYPE_BIO_BASED)
for (i = 0; i < t->num_targets; i++) {
tgt = t->targets + i;
per_bio_data_size = max(per_bio_data_size, tgt->per_bio_data_size);
}
t->mempools = dm_alloc_md_mempools(md, type, t->integrity_supported, per_bio_data_size);
if (!t->mempools)
return -ENOMEM;

171
drivers/md/dm.c
View File

@ -990,57 +990,6 @@ static void clone_endio(struct bio *bio, int error)
dec_pending(io, error);
}
/*
* Partial completion handling for request-based dm
*/
static void end_clone_bio(struct bio *clone, int error)
{
struct dm_rq_clone_bio_info *info =
container_of(clone, struct dm_rq_clone_bio_info, clone);
struct dm_rq_target_io *tio = info->tio;
struct bio *bio = info->orig;
unsigned int nr_bytes = info->orig->bi_iter.bi_size;
bio_put(clone);
if (tio->error)
/*
* An error has already been detected on the request.
* Once error occurred, just let clone->end_io() handle
* the remainder.
*/
return;
else if (error) {
/*
* Don't notice the error to the upper layer yet.
* The error handling decision is made by the target driver,
* when the request is completed.
*/
tio->error = error;
return;
}
/*
* I/O for the bio successfully completed.
* Notice the data completion to the upper layer.
*/
/*
* bios are processed from the head of the list.
* So the completing bio should always be rq->bio.
* If it's not, something wrong is happening.
*/
if (tio->orig->bio != bio)
DMERR("bio completion is going in the middle of the request");
/*
* Update the original request.
* Do not use blk_end_request() here, because it may complete
* the original request before the clone, and break the ordering.
*/
blk_update_request(tio->orig, 0, nr_bytes);
}
static struct dm_rq_target_io *tio_from_request(struct request *rq)
{
return (rq->q->mq_ops ? blk_mq_rq_to_pdu(rq) : rq->special);
@ -1089,8 +1038,6 @@ static void free_rq_clone(struct request *clone, bool must_be_mapped)
WARN_ON_ONCE(must_be_mapped && !clone->q);
blk_rq_unprep_clone(clone);
if (md->type == DM_TYPE_MQ_REQUEST_BASED)
/* stacked on blk-mq queue(s) */
tio->ti->type->release_clone_rq(clone);
@ -1821,39 +1768,13 @@ static void dm_dispatch_clone_request(struct request *clone, struct request *rq)
dm_complete_request(rq, r);
}
static int dm_rq_bio_constructor(struct bio *bio, struct bio *bio_orig,
void *data)
static void setup_clone(struct request *clone, struct request *rq,
struct dm_rq_target_io *tio)
{
struct dm_rq_target_io *tio = data;
struct dm_rq_clone_bio_info *info =
container_of(bio, struct dm_rq_clone_bio_info, clone);
info->orig = bio_orig;
info->tio = tio;
bio->bi_end_io = end_clone_bio;
return 0;
}
static int setup_clone(struct request *clone, struct request *rq,
struct dm_rq_target_io *tio, gfp_t gfp_mask)
{
int r;
r = blk_rq_prep_clone(clone, rq, tio->md->bs, gfp_mask,
dm_rq_bio_constructor, tio);
if (r)
return r;
clone->cmd = rq->cmd;
clone->cmd_len = rq->cmd_len;
clone->sense = rq->sense;
blk_rq_prep_clone(clone, rq);
clone->end_io = end_clone_request;
clone->end_io_data = tio;
tio->clone = clone;
return 0;
}
static struct request *clone_rq(struct request *rq, struct mapped_device *md,
@ -1874,12 +1795,7 @@ static struct request *clone_rq(struct request *rq, struct mapped_device *md,
clone = tio->clone;
blk_rq_init(NULL, clone);
if (setup_clone(clone, rq, tio, gfp_mask)) {
/* -ENOMEM */
if (alloc_clone)
free_clone_request(md, clone);
return NULL;
}
setup_clone(clone, rq, tio);
return clone;
}
@ -1973,11 +1889,7 @@ static int map_request(struct dm_rq_target_io *tio, struct request *rq,
}
if (IS_ERR(clone))
return DM_MAPIO_REQUEUE;
if (setup_clone(clone, rq, tio, GFP_ATOMIC)) {
/* -ENOMEM */
ti->type->release_clone_rq(clone);
return DM_MAPIO_REQUEUE;
}
setup_clone(clone, rq, tio);
}
switch (r) {
@ -2431,8 +2343,6 @@ static void __bind_mempools(struct mapped_device *md, struct dm_table *t)
goto out;
}
BUG_ON(!p || md->io_pool || md->rq_pool || md->bs);
md->io_pool = p->io_pool;
p->io_pool = NULL;
md->rq_pool = p->rq_pool;
@ -3536,48 +3446,23 @@ int dm_noflush_suspending(struct dm_target *ti)
}
EXPORT_SYMBOL_GPL(dm_noflush_suspending);
struct dm_md_mempools *dm_alloc_md_mempools(struct mapped_device *md, unsigned type,
unsigned integrity, unsigned per_bio_data_size)
struct dm_md_mempools *dm_alloc_bio_mempools(unsigned integrity,
unsigned per_bio_data_size)
{
struct dm_md_mempools *pools = kzalloc(sizeof(*pools), GFP_KERNEL);
struct kmem_cache *cachep = NULL;
unsigned int pool_size = 0;
struct dm_md_mempools *pools;
unsigned int pool_size = dm_get_reserved_bio_based_ios();
unsigned int front_pad;
pools = kzalloc(sizeof(*pools), GFP_KERNEL);
if (!pools)
return NULL;
type = filter_md_type(type, md);
front_pad = roundup(per_bio_data_size, __alignof__(struct dm_target_io)) +
offsetof(struct dm_target_io, clone);
switch (type) {
case DM_TYPE_BIO_BASED:
cachep = _io_cache;
pool_size = dm_get_reserved_bio_based_ios();
front_pad = roundup(per_bio_data_size, __alignof__(struct dm_target_io)) + offsetof(struct dm_target_io, clone);
break;
case DM_TYPE_REQUEST_BASED:
cachep = _rq_tio_cache;
pool_size = dm_get_reserved_rq_based_ios();
pools->rq_pool = mempool_create_slab_pool(pool_size, _rq_cache);
if (!pools->rq_pool)
goto out;
/* fall through to setup remaining rq-based pools */
case DM_TYPE_MQ_REQUEST_BASED:
if (!pool_size)
pool_size = dm_get_reserved_rq_based_ios();
front_pad = offsetof(struct dm_rq_clone_bio_info, clone);
/* per_bio_data_size is not used. See __bind_mempools(). */
WARN_ON(per_bio_data_size != 0);
break;
default:
BUG();
}
if (cachep) {
pools->io_pool = mempool_create_slab_pool(pool_size, cachep);
if (!pools->io_pool)
goto out;
}
pools->io_pool = mempool_create_slab_pool(pool_size, _io_cache);
if (!pools->io_pool)
goto out;
pools->bs = bioset_create_nobvec(pool_size, front_pad);
if (!pools->bs)
@ -3587,10 +3472,34 @@ struct dm_md_mempools *dm_alloc_md_mempools(struct mapped_device *md, unsigned t
goto out;
return pools;
out:
dm_free_md_mempools(pools);
return NULL;
}
struct dm_md_mempools *dm_alloc_rq_mempools(struct mapped_device *md,
unsigned type)
{
unsigned int pool_size = dm_get_reserved_rq_based_ios();
struct dm_md_mempools *pools;
pools = kzalloc(sizeof(*pools), GFP_KERNEL);
if (!pools)
return NULL;
if (filter_md_type(type, md) == DM_TYPE_REQUEST_BASED) {
pools->rq_pool = mempool_create_slab_pool(pool_size, _rq_cache);
if (!pools->rq_pool)
goto out;
}
pools->io_pool = mempool_create_slab_pool(pool_size, _rq_tio_cache);
if (!pools->io_pool)
goto out;
return pools;
out:
dm_free_md_mempools(pools);
return NULL;
}

5
drivers/md/dm.h
View File

@ -222,8 +222,9 @@ void dm_kcopyd_exit(void);
/*
* Mempool operations
*/
struct dm_md_mempools *dm_alloc_md_mempools(struct mapped_device *md, unsigned type,
unsigned integrity, unsigned per_bio_data_size);
struct dm_md_mempools *dm_alloc_bio_mempools(unsigned integrity,
unsigned per_bio_data_size);
struct dm_md_mempools *dm_alloc_rq_mempools(struct mapped_device *md, unsigned type);
void dm_free_md_mempools(struct dm_md_mempools *pools);
/*

2
include/linux/blk_types.h
View File

@ -192,6 +192,7 @@ enum rq_flag_bits {
__REQ_HASHED, /* on IO scheduler merge hash */
__REQ_MQ_INFLIGHT, /* track inflight for MQ */
__REQ_NO_TIMEOUT, /* requests may never expire */
__REQ_CLONE, /* cloned bios */
__REQ_NR_BITS, /* stops here */
};
@ -246,5 +247,6 @@ enum rq_flag_bits {
#define REQ_HASHED (1ULL << __REQ_HASHED)
#define REQ_MQ_INFLIGHT (1ULL << __REQ_MQ_INFLIGHT)
#define REQ_NO_TIMEOUT (1ULL << __REQ_NO_TIMEOUT)
#define REQ_CLONE (1ULL << __REQ_CLONE)
#endif /* __LINUX_BLK_TYPES_H */

6
include/linux/blkdev.h
View File

@ -775,11 +775,7 @@ extern void blk_add_request_payload(struct request *rq, struct page *page,
unsigned int len);
extern int blk_rq_check_limits(struct request_queue *q, struct request *rq);
extern int blk_lld_busy(struct request_queue *q);
extern int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
struct bio_set *bs, gfp_t gfp_mask,
int (*bio_ctr)(struct bio *, struct bio *, void *),
void *data);
extern void blk_rq_unprep_clone(struct request *rq);
extern void blk_rq_prep_clone(struct request *rq, struct request *rq_src);
extern int blk_insert_cloned_request(struct request_queue *q,
struct request *rq);
extern void blk_delay_queue(struct request_queue *, unsigned long);