From: Hugh Dickins <hughd@google.com>
To: Dave Chinner <david@fromorbit.com>
Cc: Jan Kara <jack@suse.cz>, Amir Goldstein <amir73il@gmail.com>,
Andreas Gruenbacher <agruenba@redhat.com>,
Theodore Tso <tytso@mit.edu>,
Martin Brandenburg <martin@omnibond.com>,
Mike Marshall <hubcap@omnibond.com>,
Damien Le Moal <damien.lemoal@wdc.com>,
Jaegeuk Kim <jaegeuk@kernel.org>,
Qiuyang Sun <sunqiuyang@huawei.com>,
linux-xfs <linux-xfs@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Linux MM <linux-mm@kvack.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Matthew Wilcox <willy@infradead.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Andrew Morton <akpm@linux-foundation.org>,
Al Viro <viro@zeniv.linux.org.uk>,
nborisov@suse.de
Subject: Re: More filesystem need this fix (xfs: use MMAPLOCK around filemap_map_pages())
Date: Wed, 16 Sep 2020 19:04:46 -0700 (PDT) [thread overview]
Message-ID: <alpine.LSU.2.11.2009161853220.2087@eggly.anvils> (raw)
In-Reply-To: <20200917014454.GZ12131@dread.disaster.area>
On Thu, 17 Sep 2020, Dave Chinner wrote:
>
> So....
>
> P0 p1
>
> hole punch starts
> takes XFS_MMAPLOCK_EXCL
> truncate_pagecache_range()
> unmap_mapping_range(start, end)
> <clears ptes>
> <read fault>
> do_fault_around()
> ->map_pages
> filemap_map_pages()
> page mapping valid,
> page is up to date
> maps PTEs
> <fault done>
> truncate_inode_pages_range()
> truncate_cleanup_page(page)
> invalidates page
> delete_from_page_cache_batch(page)
> frees page
> <pte now points to a freed page>
No. filemap_map_pages() checks page->mapping after trylock_page(),
before setting up the pte; and truncate_cleanup_page() does a one-page
unmap_mapping_range() if page_mapped(), while holding page lock.
(Of course, there's a different thread, in which less reliance on
page lock is being discussed, but that would be a future thing.)
Hugh
next prev parent reply other threads:[~2020-09-17 2:13 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-23 5:20 [PATCH] xfs: use MMAPLOCK around filemap_map_pages() Dave Chinner
2020-06-23 8:54 ` Amir Goldstein
2020-06-23 9:40 ` Dave Chinner
2020-06-23 19:47 ` Brian Foster
2020-06-23 21:19 ` Darrick J. Wong
2020-06-23 22:14 ` Dave Chinner
2020-06-29 17:00 ` Darrick J. Wong
2020-06-30 15:23 ` Amir Goldstein
2020-06-30 18:26 ` Darrick J. Wong
2020-06-30 22:46 ` Dave Chinner
2020-06-30 18:27 ` Darrick J. Wong
2020-09-12 6:19 ` More filesystem need this fix (xfs: use MMAPLOCK around filemap_map_pages()) Amir Goldstein
2020-09-14 11:35 ` Jan Kara
2020-09-14 12:29 ` Andreas Gruenbacher
2020-09-16 15:58 ` Jan Kara
2020-09-17 1:44 ` Dave Chinner
2020-09-17 2:04 ` Hugh Dickins [this message]
2020-09-17 6:45 ` Dave Chinner
2020-09-17 7:47 ` Hugh Dickins
2020-09-21 8:26 ` Dave Chinner
2020-09-21 9:11 ` Jan Kara
2020-09-21 16:20 ` Linus Torvalds
2020-09-21 17:59 ` Matthew Wilcox
2020-09-22 7:54 ` Jan Kara
2020-09-17 3:01 ` Matthew Wilcox
2020-09-17 5:37 ` Nikolay Borisov
2020-09-17 7:40 ` Jan Kara
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