linux-kernel - Re: [PATCH] squashfs: Migrate from ll_rw

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-prev] [day] [month] [year] [list]

Message-ID: <20191030140144.GA14098@lst.de>
Date:   Wed, 30 Oct 2019 15:01:44 +0100
From:   Christoph Hellwig <hch@....de>
To:     Philippe Liard <pliard@...gle.com>
Cc:     phillip@...ashfs.org.uk, hch@....de, linux-kernel@...r.kernel.org,
        groeck@...omium.org
Subject: Re: [PATCH] squashfs: Migrate from ll_rw_block usage to BIO

On Wed, Oct 30, 2019 at 10:19:54AM +0900, Philippe Liard wrote:
> > What access do you need to synchronize?  If you read data into the
> > page cache the page lock provides all synchronization needed.  If
> > you just read into decrompression buffers there probably is no need
> > for synchronization at all as each buffer is only accessed by one
> > thread at a time.
> My main concern here was waiting for the BIO request to complete but
> submit_bio_wait() that you pointed out below should address that.

Note that if you are doing multiple bios for a single request using
submit_bio_wait might not be optimal.  In that case you probably want
a refcount and only complete when all of them are done, but by looking
at submit_bio_wait should get an idea how that works.  Alternatively look
at others users, e.g. __blkdev_direct_IO in fs/block_dev.c that already
support multiple bios.