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{ "id": 2220439, "url": "http://patchwork.ozlabs.org/api/1.1/covers/2220439/?format=api", "web_url": "http://patchwork.ozlabs.org/project/ubuntu-kernel/cover/20260407092650.1094713-1-gerald.yang@canonical.com/", "project": { "id": 15, "url": "http://patchwork.ozlabs.org/api/1.1/projects/15/?format=api", "name": "Ubuntu Kernel", "link_name": "ubuntu-kernel", "list_id": "kernel-team.lists.ubuntu.com", "list_email": "kernel-team@lists.ubuntu.com", "web_url": null, "scm_url": null, "webscm_url": null }, "msgid": "<20260407092650.1094713-1-gerald.yang@canonical.com>", "date": "2026-04-07T09:26:43", "name": "[SRU,N/Q,0/1] Remount ext4 to readonly with data=journal mode may dump call trace", "submitter": { "id": 77781, "url": "http://patchwork.ozlabs.org/api/1.1/people/77781/?format=api", "name": "Gerald Yang", "email": "gerald.yang@canonical.com" }, "mbox": "http://patchwork.ozlabs.org/project/ubuntu-kernel/cover/20260407092650.1094713-1-gerald.yang@canonical.com/mbox/", "series": [ { "id": 498950, "url": "http://patchwork.ozlabs.org/api/1.1/series/498950/?format=api", "web_url": "http://patchwork.ozlabs.org/project/ubuntu-kernel/list/?series=498950", "date": "2026-04-07T09:26:43", "name": "Remount ext4 to readonly with data=journal mode may dump call trace", "version": 1, "mbox": "http://patchwork.ozlabs.org/series/498950/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/covers/2220439/comments/", "headers": { "Return-Path": "<kernel-team-bounces@lists.ubuntu.com>", "X-Original-To": "incoming@patchwork.ozlabs.org", "Delivered-To": "patchwork-incoming@legolas.ozlabs.org", "Authentication-Results": [ "legolas.ozlabs.org;\n\tdkim=fail reason=\"signature verification failed\" (4096-bit key;\n unprotected) header.d=canonical.com header.i=@canonical.com\n header.a=rsa-sha256 header.s=20251003 header.b=Td9I1Mdn;\n\tdkim-atps=neutral", "legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.ubuntu.com\n (client-ip=185.125.189.65; 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charset=\"utf-8\"", "Content-Transfer-Encoding": "base64", "Errors-To": "kernel-team-bounces@lists.ubuntu.com", "Sender": "\"kernel-team\" <kernel-team-bounces@lists.ubuntu.com>" }, "content": "BugLink: https://bugs.launchpad.net/bugs/2147400\n\n[Impact]\n\nWhen journal is filled with some data and remount the filesystem to read-only in data=journal mode\nit may dump the following call trace:\n[ 71.629350] CPU: 0 UID: 0 PID: 177 Comm: kworker/u96:5 Tainted: G E 6.19.0-rc7 #1 PREEMPT(voluntary)\n[ 71.629352] Tainted: [E]=UNSIGNED_MODULE\n[ 71.629353] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009)/LXD, BIOS unknown 2/2/2022\n[ 71.629354] Workqueue: writeback wb_workfn (flush-7:4)\n[ 71.629359] RIP: 0010:ext4_journal_check_start+0x8b/0xd0\n[ 71.629360] Code: 31 ff 45 31 c0 45 31 c9 e9 42 ad c4 00 48 8b 5d f8 b8 fb ff ff ff c9 31 d2 31 c9 31 f6 31 ff 45 31 c0 45 31 c9 c3 cc cc cc cc <0f> 0b b8 e2 ff ff ff eb c2 0f 0b eb\n a9 44 8b 42 08 68 c7 53 ce b8\n[ 71.629361] RSP: 0018:ffffcf32c0fdf6a8 EFLAGS: 00010202\n[ 71.629364] RAX: ffff8f08c8505000 RBX: ffff8f08c67ee800 RCX: 0000000000000000\n[ 71.629366] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000\n[ 71.629367] RBP: ffffcf32c0fdf6b0 R08: 0000000000000001 R09: 0000000000000000\n[ 71.629368] R10: ffff8f08db18b3a8 R11: 0000000000000000 R12: 0000000000000000\n[ 71.629368] R13: 0000000000000002 R14: 0000000000000a48 R15: ffff8f08c67ee800\n[ 71.629369] FS: 0000000000000000(0000) GS:ffff8f0a7d273000(0000) knlGS:0000000000000000\n[ 71.629370] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n[ 71.629371] CR2: 00007b66825905cc CR3: 000000011053d004 CR4: 0000000000772ef0\n[ 71.629374] PKRU: 55555554\n[ 71.629374] Call Trace:\n[ 71.629378] <TASK>\n[ 71.629382] __ext4_journal_start_sb+0x38/0x1c0\n[ 71.629383] mpage_prepare_extent_to_map+0x4af/0x580\n[ 71.629389] ? sbitmap_get+0x73/0x180\n[ 71.629399] ext4_do_writepages+0x3cc/0x10a0\n[ 71.629400] ? kvm_sched_clock_read+0x11/0x20\n[ 71.629409] ext4_writepages+0xc8/0x1b0\n[ 71.629410] ? ext4_writepages+0xc8/0x1b0\n[ 71.629411] do_writepages+0xc4/0x180\n[ 71.629416] __writeback_single_inode+0x45/0x350\n[ 71.629419] ? _raw_spin_unlock+0xe/0x40\n[ 71.629423] writeback_sb_inodes+0x260/0x5c0\n[ 71.629425] ? __schedule+0x4d1/0x1870\n[ 71.629429] __writeback_inodes_wb+0x54/0x100\n[ 71.629431] ? queue_io+0x82/0x140\n[ 71.629433] wb_writeback+0x1ab/0x330\n[ 71.629448] wb_workfn+0x31d/0x410\n[ 71.629450] process_one_work+0x191/0x3e0\n[ 71.629455] worker_thread+0x2e3/0x420\n\n[Fix]\n\nThis upstream commit fixes the issue:\nhttps://github.com/torvalds/linux/commit/f4a2b42e78914ff15630e71289adc589c3a8eb45\n\nAll the discussions are in this thread:\nhttps://lore.kernel.org/all/20260128074515.2028982-1-gerald.yang@canonical.com/\n\n[Test Plan]\n\nThis can be easily reproduced by the following script:\nmkdir -p mnt\ndd if=/dev/zero of=ext4disk bs=1G count=2 oflag=direct\nmkfs.ext4 ext4disk\ntune2fs -o journal_data ext4disk\nmount ext4disk mnt\nfio --name=fiotest --rw=randwrite --bs=4k --runtime=3 --ioengine=libaio --iodepth=128 --numjobs=4 --filename=mnt/fiotest --filesize=1G --group_reporting\nmount -o remount,ro ext4disk mnt\nsync\n\n[Where problems could occur]\n\nWhen the call trace happens, there is no data lost, all the dirty data has been flushed to file system before remounting.\nThe fix is to make sure folio state is correct and update the xarray, so the writeback thread won't be trigger if there is no dirty data.\nSo if there is something really goes wrong, there still won't be data lost, even remount it to read-write mode again.\n\nJan Kara (1):\n ext4: fix stale xarray tags after writeback\n\n fs/ext4/page-io.c | 10 ++++++++--\n 1 file changed, 8 insertions(+), 2 deletions(-)" }