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block: split bio_kmalloc from bio_alloc_bioset

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bio_kmalloc shares almost no logic with the bio_set based fast path
in bio_alloc_bioset.  Split it into an entirely separate implementation.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Acked-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig 2021-01-26 15:52:34 +01:00 committed by Jens Axboe
parent 4eb1d68904
commit 3175199ab0
2 changed files with 85 additions and 86 deletions
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165
block/bio.c
View file

@ -396,123 +396,101 @@ static void punt_bios_to_rescuer(struct bio_set *bs)
* @nr_iovecs: number of iovecs to pre-allocate
* @bs: the bio_set to allocate from.
*
* Description:
* If @bs is NULL, uses kmalloc() to allocate the bio; else the allocation is
* backed by the @bs's mempool.
* Allocate a bio from the mempools in @bs.
*
* When @bs is not NULL, if %__GFP_DIRECT_RECLAIM 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.
* If %__GFP_DIRECT_RECLAIM 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 the general 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.
*
* Note that when running under submit_bio_noacct() (i.e. any block
* driver), bios are not submitted until after you return - see the code in
* submit_bio_noacct() that converts recursion into iteration, to prevent
* stack overflows.
* Note that when running under submit_bio_noacct() (i.e. any block driver),
* bios are not submitted until after you return - see the code in
* submit_bio_noacct() that converts recursion into iteration, to prevent
* stack overflows.
*
* This would normally mean allocating multiple bios under
* submit_bio_noacct() would be susceptible to deadlocks, but we have
* deadlock avoidance code that resubmits any blocked bios from a rescuer
* thread.
* This would normally mean allocating multiple bios under submit_bio_noacct()
* would be susceptible to deadlocks, but we have
* deadlock avoidance code that resubmits any blocked bios from a rescuer
* thread.
*
* However, we do not guarantee forward progress for allocations from other
* mempools. Doing multiple allocations from the same mempool under
* submit_bio_noacct() should be avoided - instead, use bio_set's front_pad
* for per bio allocations.
* However, we do not guarantee forward progress for allocations from other
* mempools. Doing multiple allocations from the same mempool under
* submit_bio_noacct() should be avoided - instead, use bio_set's front_pad
* for per bio allocations.
*
* RETURNS:
* Pointer to new bio on success, NULL on failure.
* Returns: Pointer to new bio on success, NULL on failure.
*/
struct bio *bio_alloc_bioset(gfp_t gfp_mask, unsigned int nr_iovecs,
struct bio_set *bs)
{
gfp_t saved_gfp = gfp_mask;
unsigned front_pad;
unsigned inline_vecs;
struct bio_vec *bvl = NULL;
struct bio *bio;
void *p;
if (!bs) {
if (nr_iovecs > UIO_MAXIOV)
return NULL;
/* should not use nobvec bioset for nr_iovecs > 0 */
if (WARN_ON_ONCE(!mempool_initialized(&bs->bvec_pool) && nr_iovecs > 0))
return NULL;
p = kmalloc(struct_size(bio, bi_inline_vecs, nr_iovecs), gfp_mask);
front_pad = 0;
inline_vecs = nr_iovecs;
} else {
/* should not use nobvec bioset for nr_iovecs > 0 */
if (WARN_ON_ONCE(!mempool_initialized(&bs->bvec_pool) &&
nr_iovecs > 0))
return NULL;
/*
* submit_bio_noacct() converts recursion to iteration; this
* means if we're running beneath it, any bios we allocate and
* submit will not be submitted (and thus freed) until after we
* return.
*
* This exposes us to a potential deadlock if we allocate
* multiple bios from the same bio_set() while running
* underneath submit_bio_noacct(). If we were to allocate
* multiple bios (say a stacking block driver that was splitting
* bios), we would deadlock if we exhausted the mempool's
* reserve.
*
* We solve this, and guarantee forward progress, with a rescuer
* workqueue per bio_set. If we go to allocate and there are
* bios on current->bio_list, we first try the allocation
* without __GFP_DIRECT_RECLAIM; if that fails, we punt those
* bios we would be blocking to the rescuer workqueue before
* we retry with the original gfp_flags.
*/
if (current->bio_list &&
(!bio_list_empty(&current->bio_list[0]) ||
!bio_list_empty(&current->bio_list[1])) &&
bs->rescue_workqueue)
gfp_mask &= ~__GFP_DIRECT_RECLAIM;
/*
* submit_bio_noacct() converts recursion to iteration; this means if
* we're running beneath it, any bios we allocate and submit will not be
* submitted (and thus freed) until after we return.
*
* This exposes us to a potential deadlock if we allocate multiple bios
* from the same bio_set() while running underneath submit_bio_noacct().
* If we were to allocate multiple bios (say a stacking block driver
* that was splitting bios), we would deadlock if we exhausted the
* mempool's reserve.
*
* We solve this, and guarantee forward progress, with a rescuer
* workqueue per bio_set. If we go to allocate and there are bios on
* current->bio_list, we first try the allocation without
* __GFP_DIRECT_RECLAIM; if that fails, we punt those bios we would be
* blocking to the rescuer workqueue before we retry with the original
* gfp_flags.
*/
if (current->bio_list &&
(!bio_list_empty(&current->bio_list[0]) ||
!bio_list_empty(&current->bio_list[1])) &&
bs->rescue_workqueue)
gfp_mask &= ~__GFP_DIRECT_RECLAIM;
p = mempool_alloc(&bs->bio_pool, gfp_mask);
if (!p && gfp_mask != saved_gfp) {
punt_bios_to_rescuer(bs);
gfp_mask = saved_gfp;
p = mempool_alloc(&bs->bio_pool, gfp_mask);
if (!p && gfp_mask != saved_gfp) {
punt_bios_to_rescuer(bs);
gfp_mask = saved_gfp;
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 + front_pad;
bio_init(bio, NULL, 0);
if (nr_iovecs > inline_vecs) {
bio = p + bs->front_pad;
if (nr_iovecs > BIO_INLINE_VECS) {
unsigned long idx = 0;
struct bio_vec *bvl = NULL;
bvl = bvec_alloc(gfp_mask, nr_iovecs, &idx, &bs->bvec_pool);
if (!bvl && gfp_mask != saved_gfp) {
punt_bios_to_rescuer(bs);
gfp_mask = saved_gfp;
bvl = bvec_alloc(gfp_mask, nr_iovecs, &idx, &bs->bvec_pool);
bvl = bvec_alloc(gfp_mask, nr_iovecs, &idx,
&bs->bvec_pool);
}
if (unlikely(!bvl))
goto err_free;
bio->bi_flags |= idx << BVEC_POOL_OFFSET;
bio->bi_max_vecs = bvec_nr_vecs(idx);
bio_init(bio, bvl, bvec_nr_vecs(idx));
} else if (nr_iovecs) {
bvl = bio->bi_inline_vecs;
bio->bi_max_vecs = inline_vecs;
bio_init(bio, bio->bi_inline_vecs, BIO_INLINE_VECS);
} else {
bio_init(bio, NULL, 0);
}
bio->bi_pool = bs;
bio->bi_io_vec = bvl;
return bio;
err_free:
@ -521,6 +499,31 @@ struct bio *bio_alloc_bioset(gfp_t gfp_mask, unsigned int nr_iovecs,
}
EXPORT_SYMBOL(bio_alloc_bioset);
/**
* bio_kmalloc - kmalloc a bio for I/O
* @gfp_mask: the GFP_* mask given to the slab allocator
* @nr_iovecs: number of iovecs to pre-allocate
*
* Use kmalloc to allocate and initialize a bio.
*
* Returns: Pointer to new bio on success, NULL on failure.
*/
struct bio *bio_kmalloc(gfp_t gfp_mask, unsigned int nr_iovecs)
{
struct bio *bio;
if (nr_iovecs > UIO_MAXIOV)
return NULL;
bio = kmalloc(struct_size(bio, bi_inline_vecs, nr_iovecs), gfp_mask);
if (unlikely(!bio))
return NULL;
bio_init(bio, nr_iovecs ? bio->bi_inline_vecs : NULL, nr_iovecs);
bio->bi_pool = NULL;
return bio;
}
EXPORT_SYMBOL(bio_kmalloc);
void zero_fill_bio_iter(struct bio *bio, struct bvec_iter start)
{
unsigned long flags;

6
include/linux/bio.h
View file

@ -408,6 +408,7 @@ extern int biovec_init_pool(mempool_t *pool, int pool_entries);
extern int bioset_init_from_src(struct bio_set *bs, struct bio_set *src);
extern struct bio *bio_alloc_bioset(gfp_t, unsigned int, struct bio_set *);
struct bio *bio_kmalloc(gfp_t gfp_mask, unsigned int nr_iovecs);
extern void bio_put(struct bio *);
extern void __bio_clone_fast(struct bio *, struct bio *);
@ -420,11 +421,6 @@ 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 blk_qc_t submit_bio(struct bio *);
extern void bio_endio(struct bio *);