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

Greg Kroah-Hartman
2017-04-06T09:34:22Z

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(-)

--- 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--;
}