linux-kernel - Re: [PATCH] xfs: Correctly invert xfs

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 for Android: free password hash cracker in your pocket

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

Message-ID: <20180305185259.GC18989@magnolia>
Date:   Mon, 5 Mar 2018 10:52:59 -0800
From:   "Darrick J. Wong" <darrick.wong@...cle.com>
To:     Vratislav Bendel <vbendel@...hat.com>
Cc:     linux-xfs@...r.kernel.org, Brian Foster <bfoster@...hat.com>,
        linux-kernel@...r.kernel.org, djwong@...nel.org
Subject: Re: [PATCH] xfs: Correctly invert xfs_buftarg LRU isolation logic

On Mon, Mar 05, 2018 at 11:19:46AM +0100, Vratislav Bendel wrote:
> (In response to Luis' comment:)
> > Can you add a respective Fixes: tag?
> 
> It was apparently present since LRU was added to xfs buffer cache via:
> commit 430cbeb86fdcbbdabea7d4aa65307de8de425350
> [xfs: add a lru to the XFS buffer cache]
> 
> But I wouldn't say this patch "fixes" that commit.
> What do you think? Should a fixes tag be added in this case?
> 
> 
> > Also what effects are observed by
> > the user when this happens on the kernel log?
> 
> I haven't spotted any differences visible to user, nor in the kernel log.
> 
> (In response to Brian's comment:)
> >> However, as per documentation, atomic_add_unless() returns _zero_
> >> if the atomic value was originally equal to the specified *unsless* value.
> >>
> > Nit:                                                         unless
> 
> Thanks very much for feedback. Since it's my very first upstream
> commit-proposal,
> I expected that some polish would be needed.
> 
> 
> > It might be worth pointing out in the commit log that currently isolated
> > buffers end up right back on the LRU once they are released, because
> > ->b_lru_ref remains elevated. Therefore, this patch essentially fixes
> > that circuitous route by leaving them on the LRU as originally intended.
> > Otherwise this looks Ok to me:
> 
> So the final commit message could be:
> ~~~
> Currently the xfs_buftarg_isolate() is causing an xfs_buffer

"Due to an inverted logic mistake in xfs_buftarg_isolate()..."?

> with zero b_lru_ref, to take another trip around LRU, while

                   ^^^^ no need for this comma

> isolating buffers with non-zero b_lru_ref.
> 
> Additionally those isolated buffers end up right back on the LRU
> once they are released, because ->b_lru_ref remains elevated.
> 
> Fix that circuitous route by leaving them on the LRU
> as originally intended.

Otherwise this seems fine to me; can you please resend the patch w/
updated change log and reviewed-by tags?

Reviewed-by: Darrick J. Wong <darrick.wong@...cle.com>

--D

> 
> >> Signed-off-by: Vratislav Bendel <vbendel@...hat.com>
> > Reviewed-by: Brian Foster <bfoster@...hat.com>
> > ---
> --
> To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> the body of a message to majordomo@...r.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html