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Wed, 11 Jun 2025 03:33:06 +0000 (UTC) Received: from localhost (unknown [10.72.112.181]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 4499219560A3; Wed, 11 Jun 2025 03:33:04 +0000 (UTC) Date: Wed, 11 Jun 2025 11:33:00 +0800 From: Baoquan He To: Kairui Song Cc: linux-mm@kvack.org, Andrew Morton , Hugh Dickins , Baolin Wang , Kemeng Shi , Chris Li , Nhat Pham , Barry Song , Usama Arif , linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] mm/shmem, swap: fix softlockup with mTHP swapin Message-ID: References: <20250610181645.45922-1-ryncsn@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250610181645.45922-1-ryncsn@gmail.com> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 X-Stat-Signature: yzjwj43akiaxax561c373juurzb1zoui X-Rspamd-Queue-Id: 4EF46180002 X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1749612794-859543 X-HE-Meta: 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 YkKLrut7 XuUHeL7p3PIl5Sm0RC/C+fU32lMaASCicIg75zRm5+SWarj9cEeJgzmfnv0cJE6Yfu0Lflwpzeogt6ihbHQFCOkiVwY2e8WQern9hXtT/k4Y5R2f+YZQkN0rSwoIpeUOjrcYrfMdV8Ae4Uix2okQ39Yzc+JpoLgU42x5rpqyt5YGG7plTGUcyW8nYB2NdxwDC1+ddcTPY4EH4MshFk0GUbKeAynHNBqK4fWuCI3THgoOGr9mRqOrnkEoHSuwRfzVCQfRsB2ZikYJ2rZGkqIW0Vvv46RUeWj9vx5zBnuXT5h1f/nsF0AQ0FP/IS8UqLOm5xA3EoxFoFBh2G06jpob6dh1ZZT90utI1EHuZi24BEZ4SNFfkS48Com4jiXqy85PfnLBGE5/hkf+rsPlKBvw3/xi3m5uU/WEN9XrR3KkZez+B8+inBDGChHohWaH2pMcF8llrZErAtz2IuSM= 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 06/11/25 at 02:16am, Kairui Song wrote: > From: Kairui Song > > Following softlockup can be easily reproduced on my test machine with: > > echo always > /sys/kernel/mm/transparent_hugepage/hugepages-64kB/enabled > swapon /dev/zram0 # zram0 is a 48G swap device > mkdir -p /sys/fs/cgroup/memory/test > echo 1G > /sys/fs/cgroup/test/memory.max > echo $BASHPID > /sys/fs/cgroup/test/cgroup.procs > while true; do > dd if=/dev/zero of=/tmp/test.img bs=1M count=5120 > cat /tmp/test.img > /dev/null > rm /tmp/test.img > done > > Then after a while: > watchdog: BUG: soft lockup - CPU#0 stuck for 763s! [cat:5787] > Modules linked in: zram virtiofs > CPU: 0 UID: 0 PID: 5787 Comm: cat Kdump: loaded Tainted: G L 6.15.0.orig-gf3021d9246bc-dirty #118 PREEMPT(voluntary)· > Tainted: [L]=SOFTLOCKUP > Hardware name: Red Hat KVM/RHEL-AV, BIOS 0.0.0 02/06/2015 > RIP: 0010:mpol_shared_policy_lookup+0xd/0x70 > Code: e9 b8 b4 ff ff 31 c0 c3 cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 66 0f 1f 00 0f 1f 44 00 00 41 54 55 53 <48> 8b 1f 48 85 db 74 41 4c 8d 67 08 48 89 fb 48 89 f5 4c 89 e7 e8 > RSP: 0018:ffffc90002b1fc28 EFLAGS: 00000202 > RAX: 00000000001c20ca RBX: 0000000000724e1e RCX: 0000000000000001 > RDX: ffff888118e214c8 RSI: 0000000000057d42 RDI: ffff888118e21518 > RBP: 000000000002bec8 R08: 0000000000000001 R09: 0000000000000000 > R10: 0000000000000bf4 R11: 0000000000000000 R12: 0000000000000001 > R13: 00000000001c20ca R14: 00000000001c20ca R15: 0000000000000000 > FS: 00007f03f995c740(0000) GS:ffff88a07ad9a000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007f03f98f1000 CR3: 0000000144626004 CR4: 0000000000770eb0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > PKRU: 55555554 > Call Trace: > > shmem_alloc_folio+0x31/0xc0 > shmem_swapin_folio+0x309/0xcf0 > ? filemap_get_entry+0x117/0x1e0 > ? xas_load+0xd/0xb0 > ? filemap_get_entry+0x101/0x1e0 > shmem_get_folio_gfp+0x2ed/0x5b0 > shmem_file_read_iter+0x7f/0x2e0 > vfs_read+0x252/0x330 > ksys_read+0x68/0xf0 > do_syscall_64+0x4c/0x1c0 > entry_SYSCALL_64_after_hwframe+0x76/0x7e > RIP: 0033:0x7f03f9a46991 > Code: 00 48 8b 15 81 14 10 00 f7 d8 64 89 02 b8 ff ff ff ff eb bd e8 20 ad 01 00 f3 0f 1e fa 80 3d 35 97 10 00 00 74 13 31 c0 0f 05 <48> 3d 00 f0 ff ff 77 4f c3 66 0f 1f 44 00 00 55 48 89 e5 48 83 ec > RSP: 002b:00007fff3c52bd28 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 > RAX: ffffffffffffffda RBX: 0000000000040000 RCX: 00007f03f9a46991 > RDX: 0000000000040000 RSI: 00007f03f98ba000 RDI: 0000000000000003 > RBP: 00007fff3c52bd50 R08: 0000000000000000 R09: 00007f03f9b9a380 > R10: 0000000000000022 R11: 0000000000000246 R12: 0000000000040000 > R13: 00007f03f98ba000 R14: 0000000000000003 R15: 0000000000000000 > > > The reason is simple, readahead brought some order 0 folio in swap cache, > and the swapin mTHP folio being allocated is in confict with it, so ^^^typo, conflict > swapcache_prepare fails and causes shmem_swap_alloc_folio to return > -EEXIST, and shmem simply retries again and again causing this loop. > > Fix it by applying a similar fix for anon mTHP swapin. > ......snip...