Re: [PATCH 4.4 25/26] blk: Ensure users for current->bio_list can see the full list.

Jinpu Wang
2017-04-07T08:34:08Z

On Thu, Apr 6, 2017 at 8:17 PM, Ben Hutchings
<ben.hutchings@codethink.co.uk> wrote:
> On Thu, 2017-04-06 at 10:38 +0200, Greg Kroah-Hartman wrote:
>> 4.4-stable review patch. If anyone has any objections, please let me know.
>>
>> ------------------
>>
>> From: NeilBrown <neilb@suse.com>
>>
>> commit f5fe1b51905df7cfe4fdfd85c5fb7bc5b71a094f upstream.
>>
>> Commit 79bd99596b73 ("blk: improve order of bio handling in generic_make_request()")
>> changed current->bio_list so that it did not contain *all* of the
>> queued bios, but only those submitted by the currently running
>> make_request_fn.
>>
>> There are two places which walk the list and requeue selected bios,
>> and others that check if the list is empty. These are no longer
>> correct.
>>
>> So redefine current->bio_list to point to an array of two lists, which
>> contain all queued bios, and adjust various code to test or walk both
>> lists.
>>
>> Signed-off-by: NeilBrown <neilb@suse.com>
>> Fixes: 79bd99596b73 ("blk: improve order of bio handling in generic_make_request()")
>> Signed-off-by: Jens Axboe <axboe@fb.com>
>> [jwang: backport to 4.4]
>> Signed-off-by: Jack Wang <jinpu.wang@profitbricks.com>
>> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> ---
>> block/bio.c | 12 +++++++++---
>> block/blk-core.c | 31 +++++++++++++++++++------------
>> drivers/md/raid1.c | 3 ++-
>> drivers/md/raid10.c | 3 ++-
>> 4 files changed, 32 insertions(+), 17 deletions(-)
>
> Why did you drop the changes in drivers/md/dm.c?
>
> Ben.
>
>> --- a/block/bio.c
>> +++ b/block/bio.c
>> @@ -373,10 +373,14 @@ static void punt_bios_to_rescuer(struct
>> bio_list_init(&punt);
>> bio_list_init(&nopunt);
>>
>> - while ((bio = bio_list_pop(current->bio_list)))
>> + while ((bio = bio_list_pop(&current->bio_list[0])))
>> bio_list_add(bio->bi_pool == bs ? &punt : &nopunt, bio);
>> + current->bio_list[0] = nopunt;
>>
>> - *current->bio_list = nopunt;
>> + bio_list_init(&nopunt);
>> + while ((bio = bio_list_pop(&current->bio_list[1])))
>> + bio_list_add(bio->bi_pool == bs ? &punt : &nopunt, bio);
>> + current->bio_list[1] = nopunt;
>>
>> spin_lock(&bs->rescue_lock);
>> bio_list_merge(&bs->rescue_list, &punt);
>> @@ -464,7 +468,9 @@ struct bio *bio_alloc_bioset(gfp_t gfp_m
>> * we retry with the original gfp_flags.
>> */
>>
>> - if (current->bio_list && !bio_list_empty(current->bio_list))
>> + if (current->bio_list &&
>> + (!bio_list_empty(&current->bio_list[0]) ||
>> + !bio_list_empty(&current->bio_list[1])))
>> gfp_mask &= ~__GFP_DIRECT_RECLAIM;
>>
>> p = mempool_alloc(bs->bio_pool, gfp_mask);
>> --- a/block/blk-core.c
>> +++ b/block/blk-core.c
>> @@ -2021,7 +2021,14 @@ end_io:
>> */
>> blk_qc_t generic_make_request(struct bio *bio)
>> {
>> - struct bio_list bio_list_on_stack;
>> + /*
>> + * bio_list_on_stack[0] contains bios submitted by the current
>> + * make_request_fn.
>> + * bio_list_on_stack[1] contains bios that were submitted before
>> + * the current make_request_fn, but that haven't been processed
>> + * yet.
>> + */
>> + struct bio_list bio_list_on_stack[2];
>> blk_qc_t ret = BLK_QC_T_NONE;
>>
>> if (!generic_make_request_checks(bio))
>> @@ -2038,7 +2045,7 @@ blk_qc_t generic_make_request(struct bio
>> * should be added at the tail
>> */
>> if (current->bio_list) {
>> - bio_list_add(current->bio_list, bio);
>> + bio_list_add(&current->bio_list[0], bio);
>> goto out;
>> }
>>
>> @@ -2057,17 +2064,17 @@ blk_qc_t generic_make_request(struct bio
>> * bio_list, and call into ->make_request() again.
>> */
>> BUG_ON(bio->bi_next);
>> - bio_list_init(&bio_list_on_stack);
>> - current->bio_list = &bio_list_on_stack;
>> + bio_list_init(&bio_list_on_stack[0]);
>> + current->bio_list = bio_list_on_stack;
>> do {
>> struct request_queue *q = bdev_get_queue(bio->bi_bdev);
>>
>> if (likely(blk_queue_enter(q, __GFP_DIRECT_RECLAIM) == 0)) {
>> - struct bio_list lower, same, hold;
>> + struct bio_list lower, same;
>>
>> /* Create a fresh bio_list for all subordinate requests */
>> - hold = bio_list_on_stack;
>> - bio_list_init(&bio_list_on_stack);
>> + bio_list_on_stack[1] = bio_list_on_stack[0];
>> + bio_list_init(&bio_list_on_stack[0]);
>>
>> ret = q->make_request_fn(q, bio);
>>
>> @@ -2077,19 +2084,19 @@ blk_qc_t generic_make_request(struct bio
>> */
>> bio_list_init(&lower);
>> bio_list_init(&same);
>> - while ((bio = bio_list_pop(&bio_list_on_stack)) != NULL)
>> + while ((bio = bio_list_pop(&bio_list_on_stack[0])) != NULL)
>> if (q == bdev_get_queue(bio->bi_bdev))
>> bio_list_add(&same, bio);
>> else
>> bio_list_add(&lower, bio);
>> /* now assemble so we handle the lowest level first */
>> - bio_list_merge(&bio_list_on_stack, &lower);
>> - bio_list_merge(&bio_list_on_stack, &same);
>> - bio_list_merge(&bio_list_on_stack, &hold);
>> + bio_list_merge(&bio_list_on_stack[0], &lower);
>> + bio_list_merge(&bio_list_on_stack[0], &same);
>> + bio_list_merge(&bio_list_on_stack[0], &bio_list_on_stack[1]);
>> } else {
>> bio_io_error(bio);
>> }
>> - bio = bio_list_pop(current->bio_list);
>> + bio = bio_list_pop(&bio_list_on_stack[0]);
>> } while (bio);
>> current->bio_list = NULL; /* deactivate */
>>
>> --- a/drivers/md/raid1.c
>> +++ b/drivers/md/raid1.c
>> @@ -877,7 +877,8 @@ static sector_t wait_barrier(struct r1co
>> ((conf->start_next_window <
>> conf->next_resync + RESYNC_SECTORS) &&
>> current->bio_list &&
>> - !bio_list_empty(current->bio_list))),
>> + (!bio_list_empty(&current->bio_list[0]) ||
>> + !bio_list_empty(&current->bio_list[1])))),
>> conf->resync_lock);
>> conf->nr_waiting--;
>> }
>> --- a/drivers/md/raid10.c
>> +++ b/drivers/md/raid10.c
>> @@ -946,7 +946,8 @@ static void wait_barrier(struct r10conf
>> !conf->barrier ||
>> (conf->nr_pending &&
>> current->bio_list &&
>> - !bio_list_empty(current->bio_list)),
>> + (!bio_list_empty(&current->bio_list[0]) ||
>> + !bio_list_empty(&current->bio_list[1]))),
>> conf->resync_lock);
>> conf->nr_waiting--;
>> }
>>
>>
>>
>
> --
> Ben Hutchings
> Software Developer, Codethink Ltd.
>
>
Hi Ben,

Because the code snip doesn't exist in 4.4.

--
Jack Wang
Linux Kernel Developer