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From: Shakeel Butt To: Baolin Wang Cc: akpm@linux-foundation.org, hughd@google.com, hannes@cmpxchg.org, nphamcs@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: shmem: fix getting incorrect lruvec when replacing a shmem folio Message-ID: References: <3c11000dd6c1df83015a8321a859e9775ebbc23e.1718266112.git.baolin.wang@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3c11000dd6c1df83015a8321a859e9775ebbc23e.1718266112.git.baolin.wang@linux.alibaba.com> X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 9DF31140015 X-Stat-Signature: oea8x63eg7y3a43himzo75rfxnjwif86 X-Rspam-User: X-HE-Tag: 1718299794-368029 X-HE-Meta: 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 vBgh3unn CWQahhmOD5m6e88Pa02yDuP6c+yNa2CLO14AQGqYX+79F7N8Go40x5VPTgqaGqnuKxI4B4ooK2K/xuyL9Qsf0GZ8Pdolz5FxOx/bw83OWBGuuijMrqqi1sF7lw6JxWaATYZGoosq4hlQszBY= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Jun 13, 2024 at 04:21:19PM GMT, Baolin Wang wrote: > When testing shmem swapin, I encountered the warning below on my machine. > The reason is that replacing an old shmem folio with a new one causes > mem_cgroup_migrate() to clear the old folio's memcg data. As a result, > the old folio cannot get the correct memcg's lruvec needed to remove itself > from the LRU list when it is being freed. This could lead to possible serious > problems, such as LRU list crashes due to holding the wrong LRU lock, and > incorrect LRU statistics. > > To fix this issue, we can fallback to use the mem_cgroup_replace_folio() > to replace the old shmem folio. > > [ 5241.100311] page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x5d9960 > [ 5241.100317] head: order:4 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 > [ 5241.100319] flags: 0x17fffe0000040068(uptodate|lru|head|swapbacked|node=0|zone=2|lastcpupid=0x3ffff) > [ 5241.100323] raw: 17fffe0000040068 fffffdffd6687948 fffffdffd69ae008 0000000000000000 > [ 5241.100325] raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 > [ 5241.100326] head: 17fffe0000040068 fffffdffd6687948 fffffdffd69ae008 0000000000000000 > [ 5241.100327] head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 > [ 5241.100328] head: 17fffe0000000204 fffffdffd6665801 ffffffffffffffff 0000000000000000 > [ 5241.100329] head: 0000000a00000010 0000000000000000 00000000ffffffff 0000000000000000 > [ 5241.100330] page dumped because: VM_WARN_ON_ONCE_FOLIO(!memcg && !mem_cgroup_disabled()) > [ 5241.100338] ------------[ cut here ]------------ > [ 5241.100339] WARNING: CPU: 19 PID: 78402 at include/linux/memcontrol.h:775 folio_lruvec_lock_irqsave+0x140/0x150 > [...] > [ 5241.100374] pc : folio_lruvec_lock_irqsave+0x140/0x150 > [ 5241.100375] lr : folio_lruvec_lock_irqsave+0x138/0x150 > [ 5241.100376] sp : ffff80008b38b930 > [...] > [ 5241.100398] Call trace: > [ 5241.100399] folio_lruvec_lock_irqsave+0x140/0x150 > [ 5241.100401] __page_cache_release+0x90/0x300 > [ 5241.100404] __folio_put+0x50/0x108 > [ 5241.100406] shmem_replace_folio+0x1b4/0x240 > [ 5241.100409] shmem_swapin_folio+0x314/0x528 > [ 5241.100411] shmem_get_folio_gfp+0x3b4/0x930 > [ 5241.100412] shmem_fault+0x74/0x160 > [ 5241.100414] __do_fault+0x40/0x218 > [ 5241.100417] do_shared_fault+0x34/0x1b0 > [ 5241.100419] do_fault+0x40/0x168 > [ 5241.100420] handle_pte_fault+0x80/0x228 > [ 5241.100422] __handle_mm_fault+0x1c4/0x440 > [ 5241.100424] handle_mm_fault+0x60/0x1f0 > [ 5241.100426] do_page_fault+0x120/0x488 > [ 5241.100429] do_translation_fault+0x4c/0x68 > [ 5241.100431] do_mem_abort+0x48/0xa0 > [ 5241.100434] el0_da+0x38/0xc0 > [ 5241.100436] el0t_64_sync_handler+0x68/0xc0 > [ 5241.100437] el0t_64_sync+0x14c/0x150 > [ 5241.100439] ---[ end trace 0000000000000000 ]--- > > Fixes: 85ce2c517ade ("memcontrol: only transfer the memcg data for migration") > Signed-off-by: Baolin Wang This is a good find. I wonder if we should put VM_BUG_ON_FOLIO(folio_test_lru(folio), folio) in mem_cgroup_migrate(). > --- > mm/shmem.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/shmem.c b/mm/shmem.c > index 99bd3c34f0fb..4acaf02bfe44 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -1908,7 +1908,7 @@ static int shmem_replace_folio(struct folio **foliop, gfp_t gfp, > xa_lock_irq(&swap_mapping->i_pages); > error = shmem_replace_entry(swap_mapping, swap_index, old, new); > if (!error) { > - mem_cgroup_migrate(old, new); > + mem_cgroup_replace_folio(old, new); > __lruvec_stat_mod_folio(new, NR_FILE_PAGES, 1); > __lruvec_stat_mod_folio(new, NR_SHMEM, 1); > __lruvec_stat_mod_folio(old, NR_FILE_PAGES, -1); > -- > 2.39.3 >