Commit 3f86a82a authored by Kent Overstreet's avatar Kent Overstreet Committed by Jens Axboe
Browse files

block: Consolidate bio_alloc_bioset(), bio_kmalloc() 



Previously, bio_kmalloc() and bio_alloc_bioset() behaved slightly
different because there was some almost-duplicated code - this fixes
some of that.

The important change is that previously bio_kmalloc() always set
bi_io_vec = bi_inline_vecs, even if nr_iovecs == 0 - unlike
bio_alloc_bioset(). This would cause bio_has_data() to return true; I
don't know if this resulted in any actual bugs but it was certainly
wrong.

bio_kmalloc() and bio_alloc_bioset() also have different arbitrary
limits on nr_iovecs - 1024 (UIO_MAXIOV) for bio_kmalloc(), 256
(BIO_MAX_PAGES) for bio_alloc_bioset(). This patch doesn't fix that, but
at least they're enforced closer together and hopefully they will be
fixed in a later patch.

This'll also help with some future cleanups - there are a fair number of
functions that allocate bios (e.g. bio_clone()), and now they don't have
to be duplicated for bio_alloc(), bio_alloc_bioset(), and bio_kmalloc().

Signed-off-by: default avatarKent Overstreet <koverstreet@google.com>
CC: Jens Axboe <axboe@kernel.dk>
v7: Re-add dropped comments, improv patch description
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 4254bba1

fs/bio.c

+37 −73
Original line number Diff line number Diff line
@@ -55,6 +55,7 @@ static struct biovec_slab bvec_slabs[BIOVEC_NR_POOLS] __read_mostly = { 
 * IO code that does not need private memory pools.

 */

struct bio_set *fs_bio_set;

EXPORT_SYMBOL(fs_bio_set);



/*

 * Our slab pool management
@@ -301,39 +302,58 @@ EXPORT_SYMBOL(bio_reset); 
 * @bs:		the bio_set to allocate from.

 *

 * Description:

 *   bio_alloc_bioset will try its own mempool to satisfy the allocation.

 *   If %__GFP_WAIT is set then we will block on the internal pool waiting

 *   for a &struct bio to become free.

 **/

 *   If @bs is NULL, uses kmalloc() to allocate the bio; else the allocation is

 *   backed by the @bs's mempool.

 *

 *   When @bs is not NULL, if %__GFP_WAIT is set then bio_alloc will always be

 *   able to allocate a bio. This is due to the mempool guarantees. To make this

 *   work, callers must never allocate more than 1 bio at a time from this pool.

 *   Callers that need to allocate more than 1 bio must always submit the

 *   previously allocated bio for IO before attempting to allocate a new one.

 *   Failure to do so can cause deadlocks under memory pressure.

 *

 *   RETURNS:

 *   Pointer to new bio on success, NULL on failure.

 */

struct bio *bio_alloc_bioset(gfp_t gfp_mask, int nr_iovecs, struct bio_set *bs)

{

	unsigned front_pad;

	unsigned inline_vecs;

	unsigned long idx = BIO_POOL_NONE;

	struct bio_vec *bvl = NULL;

	struct bio *bio;

	void *p;



	if (!bs) {

		if (nr_iovecs > UIO_MAXIOV)

			return NULL;



		p = kmalloc(sizeof(struct bio) +

			    nr_iovecs * sizeof(struct bio_vec),

			    gfp_mask);

		front_pad = 0;

		inline_vecs = nr_iovecs;

	} else {

		p = mempool_alloc(bs->bio_pool, gfp_mask);

		front_pad = bs->front_pad;

		inline_vecs = BIO_INLINE_VECS;

	}



	if (unlikely(!p))

		return NULL;

	bio = p + bs->front_pad;



	bio = p + front_pad;

	bio_init(bio);

	bio->bi_pool = bs;



	if (unlikely(!nr_iovecs))

		goto out_set;



	if (nr_iovecs <= BIO_INLINE_VECS) {

		bvl = bio->bi_inline_vecs;

		nr_iovecs = BIO_INLINE_VECS;

	} else {

	if (nr_iovecs > inline_vecs) {

		bvl = bvec_alloc_bs(gfp_mask, nr_iovecs, &idx, bs);

		if (unlikely(!bvl))

			goto err_free;



		nr_iovecs = bvec_nr_vecs(idx);

	} else if (nr_iovecs) {

		bvl = bio->bi_inline_vecs;

	}

out_set:



	bio->bi_pool = bs;

	bio->bi_flags |= idx << BIO_POOL_OFFSET;

	bio->bi_max_vecs = nr_iovecs;

	bio->bi_io_vec = bvl;
@@ -345,62 +365,6 @@ err_free: 
}

EXPORT_SYMBOL(bio_alloc_bioset);



/**

 *	bio_alloc - allocate a new bio, memory pool backed

 *	@gfp_mask: allocation mask to use

 *	@nr_iovecs: number of iovecs

 *

 *	bio_alloc will allocate a bio and associated bio_vec array that can hold

 *	at least @nr_iovecs entries. Allocations will be done from the

 *	fs_bio_set. Also see @bio_alloc_bioset and @bio_kmalloc.

 *

 *	If %__GFP_WAIT is set, then bio_alloc will always be able to allocate

 *	a bio. This is due to the mempool guarantees. To make this work, callers

 *	must never allocate more than 1 bio at a time from this pool. Callers

 *	that need to allocate more than 1 bio must always submit the previously

 *	allocated bio for IO before attempting to allocate a new one. Failure to

 *	do so can cause livelocks under memory pressure.

 *

 *	RETURNS:

 *	Pointer to new bio on success, NULL on failure.

 */

struct bio *bio_alloc(gfp_t gfp_mask, unsigned int nr_iovecs)

{

	return bio_alloc_bioset(gfp_mask, nr_iovecs, fs_bio_set);

}

EXPORT_SYMBOL(bio_alloc);



/**

 * bio_kmalloc - allocate a bio for I/O using kmalloc()

 * @gfp_mask:   the GFP_ mask given to the slab allocator

 * @nr_iovecs:	number of iovecs to pre-allocate

 *

 * Description:

 *   Allocate a new bio with @nr_iovecs bvecs.  If @gfp_mask contains

 *   %__GFP_WAIT, the allocation is guaranteed to succeed.

 *

 **/

struct bio *bio_kmalloc(gfp_t gfp_mask, unsigned int nr_iovecs)

{

	struct bio *bio;



	if (nr_iovecs > UIO_MAXIOV)

		return NULL;



	bio = kmalloc(sizeof(struct bio) + nr_iovecs * sizeof(struct bio_vec),

		      gfp_mask);

	if (unlikely(!bio))

		return NULL;



	bio_init(bio);

	bio->bi_flags |= BIO_POOL_NONE << BIO_POOL_OFFSET;

	bio->bi_max_vecs = nr_iovecs;

	bio->bi_io_vec = bio->bi_inline_vecs;



	return bio;

}

EXPORT_SYMBOL(bio_kmalloc);



void zero_fill_bio(struct bio *bio)

{

	unsigned long flags;

include/linux/bio.h

+12 −4
Original line number Diff line number Diff line
@@ -212,11 +212,21 @@ extern void bio_pair_release(struct bio_pair *dbio); 
extern struct bio_set *bioset_create(unsigned int, unsigned int);

extern void bioset_free(struct bio_set *);



extern struct bio *bio_alloc(gfp_t, unsigned int);

extern struct bio *bio_kmalloc(gfp_t, unsigned int);

extern struct bio *bio_alloc_bioset(gfp_t, int, struct bio_set *);

extern void bio_put(struct bio *);



extern struct bio_set *fs_bio_set;



static inline struct bio *bio_alloc(gfp_t gfp_mask, unsigned int nr_iovecs)

{

	return bio_alloc_bioset(gfp_mask, nr_iovecs, fs_bio_set);

}



static inline struct bio *bio_kmalloc(gfp_t gfp_mask, unsigned int nr_iovecs)

{

	return bio_alloc_bioset(gfp_mask, nr_iovecs, NULL);

}



extern void bio_endio(struct bio *, int);

struct request_queue;

extern int bio_phys_segments(struct request_queue *, struct bio *);
@@ -304,8 +314,6 @@ struct biovec_slab { 
	struct kmem_cache *slab;

};



extern struct bio_set *fs_bio_set;



/*

 * a small number of entries is fine, not going to be performance critical.

 * basically we just need to survive

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