On Wed, Mar 13, 2024 at 2:25 AM Wentao Zhang <[email protected]> wrote: > > 832a4d4cdb3f612d5079aadcc67a44f18fa7b5b7 in 5.10 did the patch back from > 2112f5c1330a671fa852051d85cb9eadc05d7eb7 in upstream. > > 2112f5c1330a671fa852051d85cb9eadc05d7eb7 add BLK_MQ_F_NO_SCHED_BY_DEFAULT to > tag_set.flags in loop device in the upstream, but > > 832a4d4cdb3f612d5079aadcc67a44f18fa7b5b7 add BLK_MQ_F_NO_SCHED > to tag_set.flags in loop device in the 5.10. > > this backport cause elv_support_iosched return false, then loop device get no > scheduler. As shown in the following record: > > root@intel-x86-64:~# cat /sys/block/sda/queue/scheduler > [mq-deadline] kyber bfq none > root@intel-x86-64:~# cat /sys/block/loop2/queue/scheduler > [none] > > To solve this problem, we can backport the patch from upstream correctly, or > revert 832a4d4cdb3f612d5079aadcc67a44f18fa7b5b7. > > The loop device gets schedulers after applying the patch I submitted. > I did the test in intel-x86-64 with linux-yocto, qemux86-64 with linux-yocto > and qemux86-64 with linux-yocto-rt. > The test steps includes boot and "cat /sys/block/loop*/queue/scheduler".
Thanks! This is exactly the information I was looking for. I agree that fixing this is better than the revert, since future -stable patches may need the functionality as a building block. Bruce > > On 2024-03-13 10:59, Bruce Ashfield wrote: > > CAUTION: This email comes from a non Wind River email account! > Do not click links or open attachments unless you recognize the sender and > know the content is safe. > > Since this is requested for the common branches and > hence all BSPs (This is the right place for a patch > like this) ... can you provide some extra context > about how they were identified (and tested). > > Similar to my earlier comment, these in theory should > be nominated for -stable. > > Bruce > > In message: [linux-yocto][v5.10/standard/base && > v5.10/standard/preempt-rt/base][PATCH 1/2] blk-mq: Introduce the > BLK_MQ_F_NO_SCHED_BY_DEFAULT flag > on 12/03/2024 Wentao Zhang wrote: > > From: Bart Van Assche <[email protected]> > > commit 90b7198001f23ea37d3b46dc631bdaa2357a20b1 upstream. > > elevator_get_default() uses the following algorithm to select an I/O > scheduler from inside add_disk(): > - In case of a single hardware queue or if sharing hardware queues across > multiple request queues (BLK_MQ_F_TAG_HCTX_SHARED), use mq-deadline. > - Otherwise, use 'none'. > > This is a good choice for most but not for all block drivers. Make it > possible to override the selection of mq-deadline with a new flag, > namely BLK_MQ_F_NO_SCHED_BY_DEFAULT. > > Cc: Christoph Hellwig <[email protected]> > Cc: Ming Lei <[email protected]> > Cc: Tetsuo Handa <[email protected]> > Cc: Martijn Coenen <[email protected]> > Cc: Jaegeuk Kim <[email protected]> > Signed-off-by: Bart Van Assche <[email protected]> > Link: https://lore.kernel.org/r/[email protected] > Signed-off-by: Jens Axboe <[email protected]> > Signed-off-by: Wentao Zhang <[email protected]> > --- > block/elevator.c | 3 +++ > include/linux/blk-mq.h | 6 ++++++ > 2 files changed, 9 insertions(+) > > diff --git a/block/elevator.c b/block/elevator.c > index 2f962662c32a..f762b2af1d2a 100644 > --- a/block/elevator.c > +++ b/block/elevator.c > @@ -622,6 +622,9 @@ static inline bool elv_support_iosched(struct > request_queue *q) > */ > static struct elevator_type *elevator_get_default(struct request_queue *q) > { > + if (q->tag_set && q->tag_set->flags & BLK_MQ_F_NO_SCHED_BY_DEFAULT) > + return NULL; > + > if (q->nr_hw_queues != 1) > return NULL; > > diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h > index f8ea27423d1d..39526279fbd3 100644 > --- a/include/linux/blk-mq.h > +++ b/include/linux/blk-mq.h > @@ -398,7 +398,13 @@ enum { > BLK_MQ_F_STACKING = 1 << 2, > BLK_MQ_F_TAG_HCTX_SHARED = 1 << 3, > BLK_MQ_F_BLOCKING = 1 << 5, > + /* Do not allow an I/O scheduler to be configured. */ > BLK_MQ_F_NO_SCHED = 1 << 6, > + /* > + * Select 'none' during queue registration in case of a single hwq > + * or shared hwqs instead of 'mq-deadline'. > + */ > + BLK_MQ_F_NO_SCHED_BY_DEFAULT = 1 << 7, > BLK_MQ_F_ALLOC_POLICY_START_BIT = 8, > BLK_MQ_F_ALLOC_POLICY_BITS = 1, > > -- > 2.31.1 > > -- > ☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮ > ☮ Wentao Zhang > ☮ Wind River Linux > ☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮ -- - Thou shalt not follow the NULL pointer, for chaos and madness await thee at its end - "Use the force Harry" - Gandalf, Star Trek II
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