From: "Huang, Ying" <ying.huang@intel.com>
To: Minchan Kim <minchan@kernel.org>
Cc: Kairui Song <ryncsn@gmail.com>,
linux-mm@kvack.org, Kairui Song <kasong@tencent.com>,
Andrew Morton <akpm@linux-foundation.org>,
Chris Li <chrisl@kernel.org>, Hugh Dickins <hughd@google.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Matthew Wilcox <willy@infradead.org>,
Michal Hocko <mhocko@suse.com>,
Yosry Ahmed <yosryahmed@google.com>,
David Hildenbrand <david@redhat.com>,
linux-kernel@vger.kernel.org, Yu Zhao <yuzhao@google.com>
Subject: Whether is the race for SWP_SYNCHRONOUS_IO possible? (was Re: [PATCH v3 6/7] mm/swap, shmem: use unified swapin helper for shmem)
Date: Wed, 31 Jan 2024 10:51:38 +0800 [thread overview]
Message-ID: <87bk92gqpx.fsf_-_@yhuang6-desk2.ccr.corp.intel.com> (raw)
In-Reply-To: <20240129175423.1987-7-ryncsn@gmail.com> (Kairui Song's message of "Tue, 30 Jan 2024 01:54:21 +0800")
Hi, Minchan,
When I review the patchset from Kairui, I checked the code to skip swap
cache in do_swap_page() for swap device with SWP_SYNCHRONOUS_IO. Is the
following race possible? Where a page is swapped out to a swap device
with SWP_SYNCHRONOUS_IO and the swap count is 1. Then 2 threads of the
process runs on CPU0 and CPU1 as below. CPU0 is running do_swap_page().
CPU0 CPU1
---- ----
swap_cache_get_folio()
check sync io and swap count
alloc folio
swap_readpage()
folio_lock_or_retry()
swap in the swap entry
write page
swap out to same swap entry
pte_offset_map_lock()
check pte_same()
swap_free() <-- new content lost!
set_pte_at() <-- stale page!
folio_unlock()
pte_unmap_unlock()
Do I miss anything?
--
Best Regards,
Huang, Ying
next prev parent reply other threads:[~2024-01-31 2:53 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-29 17:54 [PATCH v3 0/7] swapin refactor for optimization and unified readahead Kairui Song
2024-01-29 17:54 ` [PATCH v3 1/7] mm/swapfile.c: add back some comment Kairui Song
2024-01-29 17:54 ` [PATCH v3 2/7] mm/swap: move no readahead swapin code to a stand-alone helper Kairui Song
2024-01-30 5:38 ` Huang, Ying
2024-01-30 5:55 ` Kairui Song
2024-01-29 17:54 ` [PATCH v3 3/7] mm/swap: always account swapped in page into current memcg Kairui Song
2024-01-30 6:12 ` Huang, Ying
2024-01-30 7:01 ` Kairui Song
2024-01-30 7:03 ` Kairui Song
2024-01-29 17:54 ` [PATCH v3 4/7] mm/swap: introduce swapin_entry for unified readahead policy Kairui Song
2024-01-30 6:29 ` Huang, Ying
2024-01-29 17:54 ` [PATCH v3 5/7] mm/swap: avoid a duplicated swap cache lookup for SWP_SYNCHRONOUS_IO Kairui Song
2024-01-30 6:51 ` Huang, Ying
2024-01-29 17:54 ` [PATCH v3 6/7] mm/swap, shmem: use unified swapin helper for shmem Kairui Song
2024-01-31 2:51 ` Huang, Ying [this message]
2024-01-31 3:58 ` Whether is the race for SWP_SYNCHRONOUS_IO possible? (was Re: [PATCH v3 6/7] mm/swap, shmem: use unified swapin helper for shmem) Kairui Song
2024-01-31 23:45 ` Chris Li
2024-02-01 0:52 ` Huang, Ying
2024-01-31 23:38 ` Chris Li
2024-01-29 17:54 ` [PATCH v3 7/7] mm/swap: refactor swap_cache_get_folio Kairui Song
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