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dm: enhance alloc_multiple_bios() to be more versatile

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alloc_multiple_bios() has the useful ability to try allocating bios
with GFP_NOWAIT but will fallback to using GFP_NOIO.  The callers
service both empty flush bios and abnormal bios (e.g. discard).

alloc_multiple_bios() enhancements offered in this commit:
- don't require table_devices_lock if num_bios = 1
- allow caller to pass GFP_NOWAIT to do usual GFP_NOWAIT with GFP_NOIO
  fallback
- allow caller to pass GFP_NOIO to _only_ allocate using GFP_NOIO

Flush bios with data may be issued to DM with REQ_NOWAIT, as such it
makes sense to attempt servicing them with GFP_NOWAIT allocations.

But abnormal IO should never be issued using REQ_NOWAIT (if that
changes in the future that's fine, but no sense supporting it now).

While at it, rename __send_changing_extent_only() to
__send_abnormal_io().

[Thanks to both Ming and Mikulas for help with translating known
possible IO scenarios to requirements.]

Suggested-by: Ming Lei <ming.lei@redhat.com>
Suggested-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
This commit is contained in:
Mike Snitzer 2023-10-27 11:29:36 -04:00
parent 34dbaa88ca
commit 4a2fe29608
1 changed files with 34 additions and 34 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

68
drivers/md/dm.c
View file

@ -1478,15 +1478,15 @@ static void setup_split_accounting(struct clone_info *ci, unsigned int len)
static void alloc_multiple_bios(struct bio_list *blist, struct clone_info *ci,
struct dm_target *ti, unsigned int num_bios,
unsigned *len)
unsigned *len, gfp_t gfp_flag)
{
struct bio *bio;
int try;
int try = (gfp_flag & GFP_NOWAIT) ? 0 : 1;
for (try = 0; try < 2; try++) {
for (; try < 2; try++) {
int bio_nr;
if (try)
if (try && num_bios > 1)
mutex_lock(&ci->io->md->table_devices_lock);
for (bio_nr = 0; bio_nr < num_bios; bio_nr++) {
bio = alloc_tio(ci, ti, bio_nr, len,
@ -1496,7 +1496,7 @@ static void alloc_multiple_bios(struct bio_list *blist, struct clone_info *ci,
bio_list_add(blist, bio);
}
if (try)
if (try && num_bios > 1)
mutex_unlock(&ci->io->md->table_devices_lock);
if (bio_nr == num_bios)
return;
@ -1507,33 +1507,30 @@ static void alloc_multiple_bios(struct bio_list *blist, struct clone_info *ci,
}
static unsigned int __send_duplicate_bios(struct clone_info *ci, struct dm_target *ti,
unsigned int num_bios, unsigned int *len)
unsigned int num_bios, unsigned int *len,
gfp_t gfp_flag)
{
struct bio_list blist = BIO_EMPTY_LIST;
struct bio *clone;
unsigned int ret = 0;
switch (num_bios) {
case 0:
break;
case 1:
if (len)
setup_split_accounting(ci, *len);
clone = alloc_tio(ci, ti, 0, len, GFP_NOIO);
__map_bio(clone);
ret = 1;
break;
default:
if (len)
setup_split_accounting(ci, *len);
/* dm_accept_partial_bio() is not supported with shared tio->len_ptr */
alloc_multiple_bios(&blist, ci, ti, num_bios, len);
while ((clone = bio_list_pop(&blist))) {
if (WARN_ON_ONCE(num_bios == 0)) /* num_bios = 0 is a bug in caller */
return 0;
/* dm_accept_partial_bio() is not supported with shared tio->len_ptr */
if (len)
setup_split_accounting(ci, *len);
/*
* Using alloc_multiple_bios(), even if num_bios is 1, to consistently
* support allocating using GFP_NOWAIT with GFP_NOIO fallback.
*/
alloc_multiple_bios(&blist, ci, ti, num_bios, len, gfp_flag);
while ((clone = bio_list_pop(&blist))) {
if (num_bios > 1)
dm_tio_set_flag(clone_to_tio(clone), DM_TIO_IS_DUPLICATE_BIO);
__map_bio(clone);
ret += 1;
}
break;
__map_bio(clone);
ret += 1;
}
return ret;
@ -1560,8 +1557,12 @@ static void __send_empty_flush(struct clone_info *ci)
unsigned int bios;
struct dm_target *ti = dm_table_get_target(t, i);
if (unlikely(ti->num_flush_bios == 0))
continue;
atomic_add(ti->num_flush_bios, &ci->io->io_count);
bios = __send_duplicate_bios(ci, ti, ti->num_flush_bios, NULL);
bios = __send_duplicate_bios(ci, ti, ti->num_flush_bios,
NULL, GFP_NOWAIT);
atomic_sub(ti->num_flush_bios - bios, &ci->io->io_count);
}
@ -1574,10 +1575,9 @@ static void __send_empty_flush(struct clone_info *ci)
bio_uninit(ci->bio);
}
static void __send_changing_extent_only(struct clone_info *ci, struct dm_target *ti,
unsigned int num_bios,
unsigned int max_granularity,
unsigned int max_sectors)
static void __send_abnormal_io(struct clone_info *ci, struct dm_target *ti,
unsigned int num_bios, unsigned int max_granularity,
unsigned int max_sectors)
{
unsigned int len, bios;
@ -1585,7 +1585,7 @@ static void __send_changing_extent_only(struct clone_info *ci, struct dm_target
__max_io_len(ti, ci->sector, max_granularity, max_sectors));
atomic_add(num_bios, &ci->io->io_count);
bios = __send_duplicate_bios(ci, ti, num_bios, &len);
bios = __send_duplicate_bios(ci, ti, num_bios, &len, GFP_NOIO);
/*
* alloc_io() takes one extra reference for submission, so the
* reference won't reach 0 without the following (+1) subtraction
@ -1654,8 +1654,8 @@ static blk_status_t __process_abnormal_io(struct clone_info *ci,
if (unlikely(!num_bios))
return BLK_STS_NOTSUPP;
__send_changing_extent_only(ci, ti, num_bios,
max_granularity, max_sectors);
__send_abnormal_io(ci, ti, num_bios, max_granularity, max_sectors);
return BLK_STS_OK;
}