From: Hugh Dickins <hughd@google.com>
To: "Huang, Ying" <ying.huang@intel.com>
Cc: Jan Kara <jack@suse.cz>, Hugh Dickins <hughd@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org, Zi Yan <ziy@nvidia.com>,
Yang Shi <shy828301@gmail.com>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
Oscar Salvador <osalvador@suse.de>,
Matthew Wilcox <willy@infradead.org>,
Bharata B Rao <bharata@amd.com>,
Alistair Popple <apopple@nvidia.com>,
Xin Hao <xhao@linux.alibaba.com>,
Minchan Kim <minchan@kernel.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
Hyeonggon Yoo <42.hyeyoo@gmail.com>
Subject: Re: [PATCH -v5 0/9] migrate_pages(): batch TLB flushing
Date: Mon, 27 Feb 2023 21:59:17 -0800 (PST) [thread overview]
Message-ID: <46f82df2-c925-e3f9-b185-69b3f0b6e366@google.com> (raw)
In-Reply-To: <87pm9ubnih.fsf@yhuang6-desk2.ccr.corp.intel.com>
On Tue, 28 Feb 2023, Huang, Ying wrote:
> Jan Kara <jack@suse.cz> writes:
> > On Fri 17-02-23 13:47:48, Hugh Dickins wrote:
> >>
> >> Cc'ing Jan Kara, who knows buffer_migrate_folio_norefs() and jbd2
> >> very well, and I hope can assure us that there is an understandable
> >> deadlock here, from holding several random folio locks, then trying
> >> to lock buffers. Cc'ing fsdevel, because there's a risk that mm
> >> folk think something is safe, when it's not sufficient to cope with
> >> the diversity of filesystems. I hope nothing more than the below is
> >> needed (and I've had no other problems with the patchset: good job),
> >> but cannot be sure.
> >
> > I suspect it can indeed be caused by the presence of the loop device as
> > Huang Ying has suggested. What filesystems using buffer_heads do is a
> > pattern like:
> >
> > bh = page_buffers(loop device page cache page);
> > lock_buffer(bh);
> > submit_bh(bh);
> > - now on loop dev this ends up doing:
> > lo_write_bvec()
> > vfs_iter_write()
> > ...
> > folio_lock(backing file folio);
> >
> > So if migration code holds "backing file folio" lock and at the same time
> > waits for 'bh' lock (while trying to migrate loop device page cache page), it
> > is a deadlock.
> >
> > Proposed solution of never waiting for locks in batched mode looks like a
> > sensible one to me...
>
> Thank you very much for detail explanation!
Yes, thanks a lot, Jan, for elucidating the deadlocks.
I was running with the 1/3,2/3,3/3 series for 48 hours on two machines
at the weekend, and hit no problems with all of them on.
I did try to review them this evening, but there's too much for me to
take in there to give an Acked-by: but I'll ask a couple of questions.
Hugh
prev parent reply other threads:[~2023-02-28 5:59 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-13 12:34 [PATCH -v5 0/9] migrate_pages(): batch TLB flushing Huang Ying
2023-02-13 12:34 ` [PATCH -v5 1/9] migrate_pages: organize stats with struct migrate_pages_stats Huang Ying
2023-02-13 12:34 ` [PATCH -v5 2/9] migrate_pages: separate hugetlb folios migration Huang Ying
2023-02-13 12:34 ` [PATCH -v5 3/9] migrate_pages: restrict number of pages to migrate in batch Huang Ying
2023-02-13 12:34 ` [PATCH -v5 4/9] migrate_pages: split unmap_and_move() to _unmap() and _move() Huang Ying
2023-02-13 12:34 ` [PATCH -v5 5/9] migrate_pages: batch _unmap and _move Huang Ying
2023-02-13 12:34 ` [PATCH -v5 6/9] migrate_pages: move migrate_folio_unmap() Huang Ying
2023-02-13 12:34 ` [PATCH -v5 7/9] migrate_pages: share more code between _unmap and _move Huang Ying
2023-02-13 12:34 ` [PATCH -v5 8/9] migrate_pages: batch flushing TLB Huang Ying
2023-02-13 12:34 ` [PATCH -v5 9/9] migrate_pages: move THP/hugetlb migration support check to simplify code Huang Ying
2023-02-17 21:47 ` [PATCH -v5 0/9] migrate_pages(): batch TLB flushing Hugh Dickins
2023-02-20 9:28 ` Huang, Ying
2023-02-21 2:48 ` Hugh Dickins
2023-02-21 3:34 ` Huang, Ying
2023-02-21 22:15 ` Hugh Dickins
2023-02-21 4:30 ` Matthew Wilcox
2023-02-21 4:38 ` Huang, Ying
2023-02-21 14:04 ` Huang, Ying
2023-02-21 22:25 ` Hugh Dickins
2023-02-22 1:02 ` Huang, Ying
2023-02-27 11:06 ` Jan Kara
2023-02-28 1:13 ` Huang, Ying
2023-02-28 5:59 ` Hugh Dickins [this message]
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