From: Matthew Wilcox <willy@infradead.org>
To: Hugh Dickins <hughd@google.com>
Cc: syzbot <syzbot+b8e0dfee3fd8c9012771@syzkaller.appspotmail.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
syzkaller-bugs@googlegroups.com
Subject: Re: kernel BUG at mm/shmem.c:LINE!
Date: Thu, 26 Jul 2018 12:32:03 -0700 [thread overview]
Message-ID: <20180726193203.GA12992@bombadil.infradead.org> (raw)
In-Reply-To: <alpine.LSU.2.11.1807260936040.1101@eggly.anvils>
On Thu, Jul 26, 2018 at 09:40:20AM -0700, Hugh Dickins wrote:
> On Thu, 26 Jul 2018, Matthew Wilcox wrote:
> > On Wed, Jul 25, 2018 at 11:53:15PM -0700, Hugh Dickins wrote:
> >
> > and fixing the bug differently ;-) But many thanks for spotting it!
>
> I thought you might :)
The xas_* functions are all _expected_ to behave the same way when
passed an XA_STATE containing an error -- do nothing. xas_create_range()
behaved that way initially, then I fixed a bug and broke that invariant.
Now the test suite checks it so I won't break it again.
> > I'll look into the next bug you reported ...
>
> No need: that idea now works a lot better when I use the initialized
> "start", instead of the uninitialized "index".
Ugh. xas_create_range() is _supposed_ to return with xas pointing to
the first index in the range. I wonder what I messed up. I've had a
go at producing a test-case for this and haven't provoked a bug yet.
Still, I don't want to keep xas_create_range() around long-term.
I want to transition all the places that currently use it to use
multi-index entries. So I'm going to put your workaround in and then
work on deleting xas_create_range() altogether.
Thanks so much for all your work on this!
prev parent reply other threads:[~2018-07-26 19:32 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-07 1:19 kernel BUG at mm/shmem.c:LINE! syzbot
2018-07-07 2:57 ` Matthew Wilcox
2018-07-09 14:36 ` Matthew Wilcox
2018-07-23 2:28 ` Hugh Dickins
2018-07-23 14:01 ` Matthew Wilcox
2018-07-23 19:14 ` Hugh Dickins
2018-07-23 20:36 ` Matthew Wilcox
2018-07-23 22:42 ` Hugh Dickins
2018-07-23 22:54 ` Matthew Wilcox
2018-07-24 9:12 ` Hugh Dickins
2018-07-26 6:53 ` Hugh Dickins
2018-07-26 14:33 ` Matthew Wilcox
2018-07-26 16:40 ` Hugh Dickins
2018-07-26 19:32 ` Matthew Wilcox [this message]
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