[PATCH 22/22] block: Don't save/copy bvec array anymore, share when cloning

Kent Overstreet
2013-08-07T21:56:23Z

Now that drivers have been converted to the bvec_iter primitives, they
shouldn't be modifying the biovec anymore and thus saving it is
unnecessary - code that was previously making a backup of the bvec array
can now just save bio->bi_iter.

Also, when cloning bios we can usually just reuse the original bio's
bvec array. For code that does need to modify the clone's biovec (the
bounce buffer code, mainly), add bio_clone_biovec().

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Alasdair Kergon <agk@redhat.com>
Cc: dm-devel@redhat.com
---
drivers/md/bcache/request.c | 2 -
drivers/md/bcache/request.h | 1 -
drivers/md/dm-bio-record.h | 25 -------
fs/bio-integrity.c | 12 +---
fs/bio.c | 154 +++++++++++++++++++-------------------------
include/linux/bio.h | 1 +
mm/bounce.c | 1 +
7 files changed, 71 insertions(+), 125 deletions(-)

diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
index 542ae36..8d0880f 100644
--- a/drivers/md/bcache/request.c
+++ b/drivers/md/bcache/request.c
@@ -681,8 +681,6 @@ static void do_bio_hook(struct search *s)
struct bio *bio = &s->bio.bio;

bio_init(bio);
- bio->bi_io_vec = s->bv;
- bio->bi_max_vecs = BIO_MAX_PAGES;
__bio_clone(bio, s->orig_bio);
bio->bi_end_io = request_endio;
bio->bi_private = &s->cl;
diff --git a/drivers/md/bcache/request.h b/drivers/md/bcache/request.h
index bee95a9..6bcdf33 100644
--- a/drivers/md/bcache/request.h
+++ b/drivers/md/bcache/request.h
@@ -26,7 +26,6 @@ struct search {

/* Anything past op->keys won't get zeroed in do_bio_hook */
struct btree_op op;
- struct bio_vec bv[BIO_MAX_PAGES];
};

void bch_cache_read_endio(struct bio *, int);
diff --git a/drivers/md/dm-bio-record.h b/drivers/md/dm-bio-record.h
index 4f46e8e..dd36461 100644
--- a/drivers/md/dm-bio-record.h
+++ b/drivers/md/dm-bio-record.h
@@ -17,49 +17,24 @@
* original bio state.
*/

-struct dm_bio_vec_details {
-#if PAGE_SIZE < 65536
- __u16 bv_len;
- __u16 bv_offset;
-#else
- unsigned bv_len;
- unsigned bv_offset;
-#endif
-};
-
struct dm_bio_details {
struct block_device *bi_bdev;
unsigned long bi_flags;
struct bvec_iter bi_iter;
- struct dm_bio_vec_details bi_io_vec[BIO_MAX_PAGES];
};

static inline void dm_bio_record(struct dm_bio_details *bd, struct bio *bio)
{
- unsigned i;
-
bd->bi_bdev = bio->bi_bdev;
bd->bi_flags = bio->bi_flags;
bd->bi_iter = bio->bi_iter;
-
- for (i = 0; i < bio->bi_vcnt; i++) {
- bd->bi_io_vec[i].bv_len = bio->bi_io_vec[i].bv_len;
- bd->bi_io_vec[i].bv_offset = bio->bi_io_vec[i].bv_offset;
- }
}

static inline void dm_bio_restore(struct dm_bio_details *bd, struct bio *bio)
{
- unsigned i;
-
bio->bi_bdev = bd->bi_bdev;
bio->bi_flags = bd->bi_flags;
bio->bi_iter = bd->bi_iter;
-
- for (i = 0; i < bio->bi_vcnt; i++) {
- bio->bi_io_vec[i].bv_len = bd->bi_io_vec[i].bv_len;
- bio->bi_io_vec[i].bv_offset = bd->bi_io_vec[i].bv_offset;
- }
}

#endif
diff --git a/fs/bio-integrity.c b/fs/bio-integrity.c
index 72fa942..0c466e6 100644
--- a/fs/bio-integrity.c
+++ b/fs/bio-integrity.c
@@ -594,17 +594,11 @@ int bio_integrity_clone(struct bio *bio, struct bio *bio_src,
struct bio_integrity_payload *bip_src = bio_src->bi_integrity;
struct bio_integrity_payload *bip;

- BUG_ON(bip_src == NULL);
-
- bip = bio_integrity_alloc(bio, gfp_mask, bip_src->bip_vcnt);
-
+ bip = bio_integrity_alloc(bio, gfp_mask, 0);
if (bip == NULL)
- return -EIO;
-
- memcpy(bip->bip_vec, bip_src->bip_vec,
- bip_src->bip_vcnt * sizeof(struct bio_vec));
+ return -ENOMEM;

- bip->bip_vcnt = bip_src->bip_vcnt;
+ bip->bip_vec = bip_src->bip_vec;
bip->bip_iter = bip_src->bip_iter;

return 0;
diff --git a/fs/bio.c b/fs/bio.c
index 7cc64c4..498ca24 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -544,8 +544,7 @@ EXPORT_SYMBOL(bio_phys_segments);
*/
void __bio_clone(struct bio *bio, struct bio *bio_src)
{
- memcpy(bio->bi_io_vec, bio_src->bi_io_vec,
- bio_src->bi_max_vecs * sizeof(struct bio_vec));
+ BUG_ON(bio->bi_pool && BIO_POOL_IDX(bio) != BIO_POOL_NONE);

/*
* most users will be overriding ->bi_bdev with a new target,
@@ -554,8 +553,8 @@ void __bio_clone(struct bio *bio, struct bio *bio_src)
bio->bi_bdev = bio_src->bi_bdev;
bio->bi_flags |= 1 << BIO_CLONED;
bio->bi_rw = bio_src->bi_rw;
- bio->bi_vcnt = bio_src->bi_vcnt;
bio->bi_iter = bio_src->bi_iter;
+ bio->bi_io_vec = bio_src->bi_io_vec;
}
EXPORT_SYMBOL(__bio_clone);

@@ -572,7 +571,7 @@ struct bio *bio_clone_bioset(struct bio *bio, gfp_t gfp_mask,
{
struct bio *b;

- b = bio_alloc_bioset(gfp_mask, bio->bi_max_vecs, bs);
+ b = bio_alloc_bioset(gfp_mask, 0, bs);
if (!b)
return NULL;

@@ -594,6 +593,50 @@ struct bio *bio_clone_bioset(struct bio *bio, gfp_t gfp_mask,
EXPORT_SYMBOL(bio_clone_bioset);

/**
+ * bio_clone_biovec: Given a cloned bio, give the clone its own copy of the
+ * biovec
+ * @bio: cloned bio
+ *
+ * @bio must have been allocated from a bioset - i.e. returned from
+ * bio_clone_bioset()
+ */
+int bio_clone_biovec(struct bio *bio, gfp_t gfp_mask)
+{
+ unsigned long idx = BIO_POOL_NONE;
+ unsigned nr_iovecs = 0;
+ struct bio_vec bv, *bvl = NULL;
+ struct bvec_iter iter;
+
+ BUG_ON(!bio->bi_pool);
+ BUG_ON(BIO_POOL_IDX(bio) != BIO_POOL_NONE);
+
+ bio_for_each_segment(bv, bio, iter)
+ nr_iovecs++;
+
+ if (nr_iovecs > BIO_INLINE_VECS) {
+ bvl = bvec_alloc(gfp_mask, nr_iovecs, &idx,
+ bio->bi_pool->bvec_pool);
+ if (!bvl)
+ return -ENOMEM;
+ } else if (nr_iovecs) {
+ bvl = bio->bi_inline_vecs;
+ }
+
+ bio_for_each_segment(bv, bio, iter)
+ bvl[bio->bi_vcnt++] = bv;
+
+ bio->bi_io_vec = bvl;
+ bio->bi_iter.bi_idx = 0;
+ bio->bi_iter.bi_bvec_done = 0;
+
+ bio->bi_flags &= BIO_POOL_MASK - 1;
+ bio->bi_flags |= idx << BIO_POOL_OFFSET;
+
+ return 0;
+}
+EXPORT_SYMBOL(bio_clone_biovec);
+
+/**
* bio_get_nr_vecs - return approx number of vecs
* @bdev: I/O target
*
@@ -918,60 +961,33 @@ void bio_copy_data(struct bio *dst, struct bio *src)
EXPORT_SYMBOL(bio_copy_data);

struct bio_map_data {
- struct bio_vec *iovecs;
- struct sg_iovec *sgvecs;
int nr_sgvecs;
int is_our_pages;
+ struct sg_iovec sgvecs[];
};

static void bio_set_map_data(struct bio_map_data *bmd, struct bio *bio,
struct sg_iovec *iov, int iov_count,
int is_our_pages)
{
- memcpy(bmd->iovecs, bio->bi_io_vec, sizeof(struct bio_vec) * bio->bi_vcnt);
memcpy(bmd->sgvecs, iov, sizeof(struct sg_iovec) * iov_count);
bmd->nr_sgvecs = iov_count;
bmd->is_our_pages = is_our_pages;
bio->bi_private = bmd;
}

-static void bio_free_map_data(struct bio_map_data *bmd)
-{
- kfree(bmd->iovecs);
- kfree(bmd->sgvecs);
- kfree(bmd);
-}
-
static struct bio_map_data *bio_alloc_map_data(int nr_segs,
unsigned int iov_count,
gfp_t gfp_mask)
{
- struct bio_map_data *bmd;
-
if (iov_count > UIO_MAXIOV)
return NULL;

- bmd = kmalloc(sizeof(*bmd), gfp_mask);
- if (!bmd)
- return NULL;
-
- bmd->iovecs = kmalloc(sizeof(struct bio_vec) * nr_segs, gfp_mask);
- if (!bmd->iovecs) {
- kfree(bmd);
- return NULL;
- }
-
- bmd->sgvecs = kmalloc(sizeof(struct sg_iovec) * iov_count, gfp_mask);
- if (bmd->sgvecs)
- return bmd;
-
- kfree(bmd->iovecs);
- kfree(bmd);
- return NULL;
+ return kmalloc(sizeof(struct bio_map_data) +
+ sizeof(struct sg_iovec) * iov_count, gfp_mask);
}

-static int __bio_copy_iov(struct bio *bio, struct bio_vec *iovecs,
- struct sg_iovec *iov, int iov_count,
+static int __bio_copy_iov(struct bio *bio, struct sg_iovec *iov, int iov_count,
int to_user, int from_user, int do_free_page)
{
int ret = 0, i;
@@ -981,7 +997,7 @@ static int __bio_copy_iov(struct bio *bio, struct bio_vec *iovecs,

bio_for_each_segment_all(bvec, bio, i) {
char *bv_addr = page_address(bvec->bv_page);
- unsigned int bv_len = iovecs[i].bv_len;
+ unsigned int bv_len = bvec->bv_len;

while (bv_len && iov_idx < iov_count) {
unsigned int bytes;
@@ -1035,10 +1051,10 @@ int bio_uncopy_user(struct bio *bio)
int ret = 0;

if (!bio_flagged(bio, BIO_NULL_MAPPED))
- ret = __bio_copy_iov(bio, bmd->iovecs, bmd->sgvecs,
- bmd->nr_sgvecs, bio_data_dir(bio) == READ,
+ ret = __bio_copy_iov(bio, bmd->sgvecs, bmd->nr_sgvecs,
+ bio_data_dir(bio) == READ,
0, bmd->is_our_pages);
- bio_free_map_data(bmd);
+ kfree(bmd);
bio_put(bio);
return ret;
}
@@ -1152,7 +1168,7 @@ struct bio *bio_copy_user_iov(struct request_queue *q,
*/
if ((!write_to_vm && (!map_data || !map_data->null_mapped)) ||
(map_data && map_data->from_user)) {
- ret = __bio_copy_iov(bio, bio->bi_io_vec, iov, iov_count, 0, 1, 0);
+ ret = __bio_copy_iov(bio, iov, iov_count, 0, 1, 0);
if (ret)
goto cleanup;
}
@@ -1166,7 +1182,7 @@ cleanup:

bio_put(bio);
out_bmd:
- bio_free_map_data(bmd);
+ kfree(bmd);
return ERR_PTR(ret);
}

@@ -1483,16 +1499,15 @@ static void bio_copy_kern_endio(struct bio *bio, int err)

bio_for_each_segment_all(bvec, bio, i) {
char *addr = page_address(bvec->bv_page);
- int len = bmd->iovecs[i].bv_len;

if (read)
- memcpy(p, addr, len);
+ memcpy(p, addr, bvec->bv_len);

__free_page(bvec->bv_page);
- p += len;
+ p += bvec->bv_len;
}

- bio_free_map_data(bmd);
+ kfree(bmd);
bio_put(bio);
}

@@ -1720,62 +1735,25 @@ EXPORT_SYMBOL(bio_endio);
* Allocates and returns a new bio which represents @sectors from the start of
* @bio, and updates @bio to represent the remaining sectors.
*
- * If bio_sectors(@bio) was less than or equal to @sectors, returns @bio
- * unchanged.
+ * The newly allocated bio will point to @bio's bi_io_vec; it is the caller's
+ * responsibility to ensure that @bio is not freed before the split.
*/
struct bio *bio_split(struct bio *bio, int sectors,
gfp_t gfp, struct bio_set *bs)
{
- unsigned vcnt = 0, nbytes = sectors << 9;
- struct bio_vec bv;
- struct bvec_iter iter;
struct bio *split = NULL;

BUG_ON(sectors <= 0);
BUG_ON(sectors >= bio_sectors(bio));

- if (bio->bi_rw & REQ_DISCARD) {
- split = bio_alloc_bioset(gfp, 1, bs);
- if (!split)
- return NULL;
- goto out;
- }
-
- bio_for_each_segment(bv, bio, iter) {
- vcnt++;
-
- if (nbytes <= bv.bv_len)
- break;
-
- nbytes -= bv.bv_len;
- }
-
- split = bio_alloc_bioset(gfp, vcnt, bs);
+ split = bio_clone_bioset(bio, gfp, bs);
if (!split)
return NULL;

- bio_for_each_segment(bv, bio, iter) {
- split->bi_io_vec[split->bi_vcnt++] = bv;
-
- if (split->bi_vcnt == vcnt)
- break;
- }
+ split->bi_iter.bi_size = sectors << 9;

- split->bi_io_vec[split->bi_vcnt - 1].bv_len = nbytes;
-out:
- split->bi_bdev = bio->bi_bdev;
- split->bi_iter.bi_sector = bio->bi_iter.bi_sector;
- split->bi_iter.bi_size = sectors << 9;
- split->bi_rw = bio->bi_rw;
-
- if (bio_integrity(bio)) {
- if (bio_integrity_clone(split, bio, gfp)) {
- bio_put(split);
- return NULL;
- }
-
- bio_integrity_trim(split, 0, bio_sectors(split));
- }
+ if (bio_integrity(split))
+ bio_integrity_trim(split, 0, sectors);

bio_advance(bio, split->bi_iter.bi_size);

diff --git a/include/linux/bio.h b/include/linux/bio.h
index c9c2bd0..d65cf85 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -310,6 +310,7 @@ extern void bio_put(struct bio *);

extern void __bio_clone(struct bio *, struct bio *);
extern struct bio *bio_clone_bioset(struct bio *, gfp_t, struct bio_set *bs);
+extern int bio_clone_biovec(struct bio *bio, gfp_t gfp_mask);

extern struct bio_set *fs_bio_set;

diff --git a/mm/bounce.c b/mm/bounce.c
index 4525e3d..985fe23 100644
--- a/mm/bounce.c
+++ b/mm/bounce.c
@@ -209,6 +209,7 @@ static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
return;
bounce:
bio = bio_clone_bioset(*bio_orig, GFP_NOIO, fs_bio_set);
+ bio_clone_biovec(bio, GFP_NOIO);

bio_for_each_segment_all(to, bio, i) {
struct page *page = to->bv_page;
--
1.8.4.rc1