From: "Darrick J. Wong" <djwong@kernel.org>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: David Rientjes <rientjes@google.com>,
Rustam Kovhaev <rkovhaev@gmail.com>,
Dave Chinner <david@fromorbit.com>,
linux-xfs@vger.kernel.org, cl@linux.com, penberg@kernel.org,
iamjoonsoo.kim@lge.com, akpm@linux-foundation.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
gregkh@linuxfoundation.org, Al Viro <viro@zeniv.linux.org.uk>,
dvyukov@google.com
Subject: Re: [PATCH] xfs: use kmem_cache_free() for kmem_cache objects
Date: Tue, 12 Oct 2021 16:22:55 -0700 [thread overview]
Message-ID: <20211012232255.GS24307@magnolia> (raw)
In-Reply-To: <9db5d16a-2999-07a4-c49d-7417601f834f@suse.cz>
On Tue, Oct 12, 2021 at 11:32:25PM +0200, Vlastimil Babka wrote:
> On 10/12/2021 10:43 PM, Darrick J. Wong wrote:
> > On Tue, Oct 12, 2021 at 01:43:20PM -0700, Darrick J. Wong wrote:
> >> On Sun, Oct 03, 2021 at 06:07:20PM -0700, David Rientjes wrote:
> >>> On Thu, 30 Sep 2021, Rustam Kovhaev wrote:
> >>>
> >>>>>>> I think it's fair if something like XFS (not meant for tiny systems AFAIK?)
> >>>>>>> excludes SLOB (meant for tiny systems). Clearly nobody tried to use these
> >>>>>>> two together last 5 years anyway.
> >>>>>>
> >>>>>> +1 for adding Kconfig option, it seems like some things are not meant to
> >>>>>> be together.
> >>>>>
> >>>>> But if we patch SLOB, we won't need it.
> >>>>
> >>>> OK, so we consider XFS on SLOB a supported configuration that might be
> >>>> used and should be tested.
> >>>> I'll look into maybe adding a config with CONFIG_SLOB and CONFIG_XFS_FS
> >>>> to syzbot.
> >>>>
> >>>> It seems that we need to patch SLOB anyway, because any other code can
> >>>> hit the very same issue.
> >>>>
> >>>
> >>> It's probably best to introduce both (SLOB fix and Kconfig change for
> >>> XFS), at least in the interim because the combo of XFS and SLOB could be
> >>> broken in other ways. If syzbot doesn't complain with a patched kernel to
> >>> allow SLOB to be used with XFS, then we could potentially allow them to be
> >>> used together.
> >>>
> >>> (I'm not sure that this freeing issue is the *only* thing that is broken,
> >>> nor that we have sufficient information to make that determination right
> >>> now..)
> >>
> >> I audited the entire xfs (kernel) codebase and didn't find any other
> >> usage errors. Thanks for the patch; I'll apply it to for-next.
>
> Which patch, the one that started this thread and uses kmem_cache_free() instead
> of kfree()? I thought we said it's not the best way?
It's probably better to fix slob to be able to tell that a kmem_free'd
object actually belongs to a cache and should get freed that way, just
like its larger sl[ua]b cousins.
However, even if that does come to pass, anybody /else/ who wants to
start(?) using XFS on a SLOB system will need this patch to fix the
minor papercut. Now that I've checked the rest of the codebase, I don't
find it reasonable to make XFS mutually exclusive with SLOB over two
instances of slab cache misuse. Hence the RVB. :)
--D
> > Also, the obligatory
> >
> > Reviewed-by: Darrick J. Wong <djwong@kernel.org>
> >
> > --D
> >
> >>
> >> --D
>
next prev parent reply other threads:[~2021-10-12 23:22 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-29 21:23 [PATCH] xfs: use kmem_cache_free() for kmem_cache objects Rustam Kovhaev
2021-09-30 4:42 ` Dave Chinner
2021-09-30 8:13 ` Vlastimil Babka
2021-09-30 18:48 ` Rustam Kovhaev
2021-09-30 21:10 ` Vlastimil Babka
2021-10-01 0:32 ` Rustam Kovhaev
2021-10-04 1:07 ` David Rientjes
2021-10-12 20:43 ` Darrick J. Wong
2021-10-12 20:43 ` Darrick J. Wong
2021-10-12 21:32 ` Vlastimil Babka
2021-10-12 23:22 ` Darrick J. Wong [this message]
2021-10-13 7:38 ` Vlastimil Babka
2021-10-13 16:56 ` Rustam Kovhaev
2021-10-15 0:57 ` Darrick J. Wong
2021-10-18 3:38 ` [PATCH] slob: add size header to all allocations Rustam Kovhaev
2021-10-18 9:22 ` Vlastimil Babka
2021-10-19 1:22 ` Rustam Kovhaev
2021-10-20 11:46 ` Hyeonggon Yoo
2021-10-21 17:36 ` Vlastimil Babka
2021-10-23 6:41 ` [PATCH v2] " Rustam Kovhaev
2021-10-25 9:36 ` Vlastimil Babka
2021-10-25 21:49 ` Rustam Kovhaev
2021-10-29 3:05 ` [PATCH v3] " Rustam Kovhaev
2021-11-16 11:26 ` Vlastimil Babka
2021-11-16 23:19 ` Rustam Kovhaev
2021-11-22 1:30 ` [PATCH v4] " Rustam Kovhaev
2021-11-22 9:22 ` Christoph Lameter
2021-11-22 9:40 ` Vlastimil Babka
2021-11-22 10:36 ` Christoph Lameter
2021-11-22 10:45 ` Vlastimil Babka
2021-11-22 11:40 ` Christoph Lameter
2021-11-22 11:49 ` Vlastimil Babka
2021-11-23 10:18 ` David Laight
2021-11-30 7:00 ` Rustam Kovhaev
2021-11-30 9:23 ` David Laight
2021-11-30 9:41 ` Christoph Lameter
2021-11-30 14:55 ` Vlastimil Babka
2021-11-30 15:21 ` David Laight
2021-11-30 15:39 ` Vlastimil Babka
2021-11-30 15:26 ` Christoph Lameter
2021-10-24 10:43 ` [PATCH] " Hyeonggon Yoo
2021-10-25 8:19 ` Vlastimil Babka
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