linux-kernel - IO request merging

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20141016122740.GI6085@quack.suse.cz>
Date:	Thu, 16 Oct 2014 14:27:40 +0200
From:	Jan Kara <jack@...e.cz>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Jens Axboe <axboe@...nel.dk>
Subject: IO request merging

  Hello,

  one of our customers was complaining that elv_attempt_insert_merge()
merges two requests (via blk_attempt_req_merge()) without asking IO
scheduler for permission (->elevator_allow_merge_fn() callback). Now for
them this is a problem because of their custom IO scheduler but looking
into the code this can result in somewhat suboptimal behavior for CFQ as
well (merging two requests from different IO contexts, possibly merging
sync & async request). What do others think about this?

Regarding possible fix, we cannot really call ->elevator_allow_merge_fn()
because that assumes it is called from a context of a process submitting the
passed bio. So we would need to create a separate allow merge callback for
this.

								Honza

-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/