From: Ayush Ranjan <ayushr@modal.com>
To: Jan Kara <jack@suse.cz>
Cc: Ayush Ranjan <ayushr@modal.com>, Hugh Dickins <hughd@google.com>,
Matthew Wilcox <willy@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
Pedro Falcato <pfalcato@suse.de>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
David Hildenbrand <david@kernel.org>,
Gregory Price <gourry@gourry.net>,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [BUG] shmem: FALLOC_FL_PUNCH_HOLE vs fault-around race corrupts page cache / rss counters
Date: Fri, 25 Sep 2026 05:32:10 +0000 [thread overview]
Message-ID: <20260925053211.2036445-1-ayushr@modal.com> (raw)
In-Reply-To: <uf7lys6izqrxjsp3tstqxmdok5yy3w52d3bnpkfzyjm7uiyqzr@ickbg3ocvcji>
On Thu, Sep 24, 2026 at 09:15 +0000, Jan Kara wrote:
> Can this be perhaps somehow related to the fixes in partial large folio
> truncation Zhang Yi is working on, possibly even the tmpfs bug in handling
> of folio split I've found [1]? It seems large folios are used here so that
> matches, I just don't immediately see how those bugs would lead to the
> errors reported here...
That would fit what I see, for what it's worth:
- the rss-counter imbalance from the reproducer is always exactly
one PMD-order folio (+/-512), which looks more like large-folio
split/accounting going wrong than lost or extra PTEs;
- the reproducer's punching thread deliberately mixes unaligned
sub-PMD ranges, so partial truncation of large folios is exercised
constantly, and the production "still mapped when deleted" splat
is reported from truncate_inode_partial_folio() (full stack in my
reply to Pedro).
Thanks,
Ayush
next prev parent reply other threads:[~2026-09-25 5:32 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-24 6:16 Ayush Ranjan
2026-09-24 7:12 ` David Hildenbrand (Arm)
2026-09-24 8:34 ` Pedro Falcato
2026-09-24 9:15 ` Jan Kara
2026-09-25 5:32 ` Ayush Ranjan [this message]
2026-09-24 9:30 ` Baolin Wang
2026-09-25 5:33 ` Ayush Ranjan
2026-09-25 5:30 ` Ayush Ranjan
2026-09-25 6:50 ` Ayush Ranjan
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