From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Jeff Moyer To: Jens Axboe Cc: Takashi Iwai , Paolo Valente , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [REGRESSION] bfq probe failed on 4.19-rc3 References: <8b5a7dc9-2dc1-16ee-4b05-a72eb6680c77@kernel.dk> Date: Tue, 11 Sep 2018 12:51:27 -0400 In-Reply-To: (Jens Axboe's message of "Tue, 11 Sep 2018 10:49:05 -0600") Message-ID: MIME-Version: 1.0 Content-Type: text/plain List-ID: Jens Axboe writes: > On 9/11/18 10:48 AM, Jeff Moyer wrote: >> Jens Axboe writes: >> >>> On 9/11/18 10:03 AM, Takashi Iwai wrote: >>>> Hi, >>>> >>>> I noticed that bfq doesn't appear in the I/O scheduler list on >>>> 4.19-rc3. It seems that blkcg_policy_register() at the beginning of >>>> bfq_init() returns -ENOSPC, hence the probe aborts silently. >>>> >>>> Is this already addressed? >>> >>> Haven't heard about this one before. What kernel did you last use that >>> worked? >> >> I'm guessing you just need to update the maximum number of policies: >> >> /* >> * Maximum number of blkcg policies allowed to be registered concurrently. >> * Defined here to simplify include dependency. >> */ >> #define BLKCG_MAX_POLS 3 > > That is my guess too, hence the suggestion to try and disable the > iolatency policy. Just tried here without, and it works, rebooting > with to verify that we're running out of policy slots. Functions calling this function: blkcg_policy_register File Function Line 0 block/bfq-iosched.c bfq_init 5675 ret = blkcg_policy_register(&blkcg_pol icy_bfq); 1 block/blk-iolatency.c iolatency_init 946 return blkcg_policy_register(&blkcg_pol icy_iolatency); 2 block/blk-throttle.c throtl_init 2511 return blkcg_policy_register(&blkcg_pol icy_throtl); 3 block/cfq-iosched.c cfq_init 4869 ret = blkcg_policy_register(&blkcg_pol icy_cfq); And then there were 4... -Jeff