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b=O9okBel8EoCT5ZxHRSRcHiGPOMtZfD2f3KoANB76OzZiv4dRZ30cK8mbclES6xSeCYMq+fm+E25m4/pCTj2jFrPzyLKKXAkhm8KM270fIzmEZya0QncdFC26pVoi3vYY3NaI6aXuhZacn5dWh1jYX/GqDO70UkT4MWKABB++0wQ= X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R271e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033045046011;MF=hsiangkao@linux.alibaba.com;NM=1;PH=DS;RN=5;SR=0;TI=SMTPD_---0WBRR1Kv_1722181756; Received: from x31i01179.sqa.na131.tbsite.net(mailfrom:hsiangkao@linux.alibaba.com fp:SMTPD_---0WBRR1Kv_1722181756) by smtp.aliyun-inc.com; Sun, 28 Jul 2024 23:49:21 +0800 From: Gao Xiang To: Andrew Morton , Huang Ying , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Gao Xiang Subject: [PATCH] mm/migrate: fix deadlock in migrate_pages_batch() on large folios Date: Sun, 28 Jul 2024 23:49:13 +0800 Message-ID: <20240728154913.4023977-1-hsiangkao@linux.alibaba.com> X-Mailer: git-send-email 2.43.5 MIME-Version: 1.0 X-Rspamd-Queue-Id: 43AB014000B X-Stat-Signature: dxw4fgijft71n9gcc3pf7ani9bc4gcsz X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1722181765-244593 X-HE-Meta: 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 Eg9PEfQa Iv+sQzHsmUFZmjWr8CubudGo3IhydJHI/sJkFXjfO2l2YATZlQxEdagS+7UlJGnaKFFsAdmabvwNINjmt2KtdPKwLkryBy39G0yq+4WYhJmJkZMUEODuf1AxPALFxRVjAaEwN9sJR/RIBqx/YqJKkzRla2ww+g+SxvII3DO5bqHKO/6IR7saH/N3TYSZj/TImXyM6NS/WrDYLerOMfW5gXD0b0QMLV1IJalCwx2Hqvhz3Q3q64mZ2hoZQKbKfJO9AA639XCDlaYmY5kM= 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: Currently, migrate_pages_batch() can lock multiple locked folios with an arbitrary order. Although folio_trylock() is used to avoid deadlock as commit 2ef7dbb26990 ("migrate_pages: try migrate in batch asynchronously firstly") mentioned, it seems try_split_folio() is still missing. It was found by compaction stress test when I explicitly enable EROFS compressed files to use large folios, which case I cannot reproduce with the same workload if large folio support is off (current mainline). Typically, filesystem reads (with locked file-backed folios) could use another bdev/meta inode to load some other I/Os (e.g. inode extent metadata or caching compressed data), so the locking order will be: file-backed folios (A) bdev/meta folios (B) The following calltrace shows the deadlock: Thread 1 takes (B) lock and tries to take folio (A) lock Thread 2 takes (A) lock and tries to take folio (B) lock [Thread 1] INFO: task stress:1824 blocked for more than 30 seconds. Tainted: G OE 6.10.0-rc7+ #6 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:stress state:D stack:0 pid:1824 tgid:1824 ppid:1822 flags:0x0000000c Call trace: __switch_to+0xec/0x138 __schedule+0x43c/0xcb0 schedule+0x54/0x198 io_schedule+0x44/0x70 folio_wait_bit_common+0x184/0x3f8 <-- folio mapping ffff00036d69cb18 index 996 (**) __folio_lock+0x24/0x38 migrate_pages_batch+0x77c/0xea0 // try_split_folio (mm/migrate.c:1486:2) // migrate_pages_batch (mm/migrate.c:1734:16) <--- LIST_HEAD(unmap_folios) has .. folio mapping 0xffff0000d184f1d8 index 1711; (*) folio mapping 0xffff0000d184f1d8 index 1712; .. migrate_pages+0xb28/0xe90 compact_zone+0xa08/0x10f0 compact_node+0x9c/0x180 sysctl_compaction_handler+0x8c/0x118 proc_sys_call_handler+0x1a8/0x280 proc_sys_write+0x1c/0x30 vfs_write+0x240/0x380 ksys_write+0x78/0x118 __arm64_sys_write+0x24/0x38 invoke_syscall+0x78/0x108 el0_svc_common.constprop.0+0x48/0xf0 do_el0_svc+0x24/0x38 el0_svc+0x3c/0x148 el0t_64_sync_handler+0x100/0x130 el0t_64_sync+0x190/0x198 [Thread 2] INFO: task stress:1825 blocked for more than 30 seconds. Tainted: G OE 6.10.0-rc7+ #6 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:stress state:D stack:0 pid:1825 tgid:1825 ppid:1822 flags:0x0000000c Call trace: __switch_to+0xec/0x138 __schedule+0x43c/0xcb0 schedule+0x54/0x198 io_schedule+0x44/0x70 folio_wait_bit_common+0x184/0x3f8 <-- folio = 0xfffffdffc6b503c0 (mapping == 0xffff0000d184f1d8 index == 1711) (*) __folio_lock+0x24/0x38 z_erofs_runqueue+0x384/0x9c0 [erofs] z_erofs_readahead+0x21c/0x350 [erofs] <-- folio mapping 0xffff00036d69cb18 range from [992, 1024] (**) read_pages+0x74/0x328 page_cache_ra_order+0x26c/0x348 ondemand_readahead+0x1c0/0x3a0 page_cache_sync_ra+0x9c/0xc0 filemap_get_pages+0xc4/0x708 filemap_read+0x104/0x3a8 generic_file_read_iter+0x4c/0x150 vfs_read+0x27c/0x330 ksys_pread64+0x84/0xd0 __arm64_sys_pread64+0x28/0x40 invoke_syscall+0x78/0x108 el0_svc_common.constprop.0+0x48/0xf0 do_el0_svc+0x24/0x38 el0_svc+0x3c/0x148 el0t_64_sync_handler+0x100/0x130 el0t_64_sync+0x190/0x198 Fixes: 5dfab109d519 ("migrate_pages: batch _unmap and _move") Cc: "Huang, Ying" Signed-off-by: Gao Xiang Reviewed-by: "Huang, Ying" Acked-by: David Hildenbrand --- mm/migrate.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/migrate.c b/mm/migrate.c index 20cb9f5f7446..a912e4b83228 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1483,7 +1483,8 @@ static inline int try_split_folio(struct folio *folio, struct list_head *split_f { int rc; - folio_lock(folio); + if (!folio_trylock(folio)) + return -EAGAIN; rc = split_folio_to_list(folio, split_folios); folio_unlock(folio); if (!rc)