kernel.git/fs/jbd2/checkpoint.c, branch linux-5.4.y

jbd2: prevent softlockup in jbd2_log_do_checkpoint()

2025-08-28T14:21:31Z

commit 9d98cf4632258720f18265a058e62fde120c0151 upstream. Both jbd2_log_do_checkpoint() and jbd2_journal_shrink_checkpoint_list() periodically release j_list_lock after processing a batch of buffers to avoid long hold times on the j_list_lock. However, since both functions contend for j_list_lock, the combined time spent waiting and processing can be significant. jbd2_journal_shrink_checkpoint_list() explicitly calls cond_resched() when need_resched() is true to avoid softlockups during prolonged operations. But jbd2_log_do_checkpoint() only exits its loop when need_resched() is true, relying on potentially sleeping functions like __flush_batch() or wait_on_buffer() to trigger rescheduling. If those functions do not sleep, the kernel may hit a softlockup. watchdog: BUG: soft lockup - CPU#3 stuck for 156s! [kworker/u129:2:373] CPU: 3 PID: 373 Comm: kworker/u129:2 Kdump: loaded Not tainted 6.6.0+ #10 Hardware name: Huawei TaiShan 2280 /BC11SPCD, BIOS 1.27 06/13/2017 Workqueue: writeback wb_workfn (flush-7:2) pstate: 20000005 (nzCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : native_queued_spin_lock_slowpath+0x358/0x418 lr : jbd2_log_do_checkpoint+0x31c/0x438 [jbd2] Call trace: native_queued_spin_lock_slowpath+0x358/0x418 jbd2_log_do_checkpoint+0x31c/0x438 [jbd2] __jbd2_log_wait_for_space+0xfc/0x2f8 [jbd2] add_transaction_credits+0x3bc/0x418 [jbd2] start_this_handle+0xf8/0x560 [jbd2] jbd2__journal_start+0x118/0x228 [jbd2] __ext4_journal_start_sb+0x110/0x188 [ext4] ext4_do_writepages+0x3dc/0x740 [ext4] ext4_writepages+0xa4/0x190 [ext4] do_writepages+0x94/0x228 __writeback_single_inode+0x48/0x318 writeback_sb_inodes+0x204/0x590 __writeback_inodes_wb+0x54/0xf8 wb_writeback+0x2cc/0x3d8 wb_do_writeback+0x2e0/0x2f8 wb_workfn+0x80/0x2a8 process_one_work+0x178/0x3e8 worker_thread+0x234/0x3b8 kthread+0xf0/0x108 ret_from_fork+0x10/0x20 So explicitly call cond_resched() in jbd2_log_do_checkpoint() to avoid softlockup. Cc: stable@kernel.org Signed-off-by: Baokun Li Link: https://patch.msgid.link/20250812063752.912130-1-libaokun@huaweicloud.com Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman

jbd2: stop waiting for space when jbd2_cleanup_journal_tail() returns error

2024-11-08T15:20:40Z

commit f5cacdc6f2bb2a9bf214469dd7112b43dd2dd68a upstream. In __jbd2_log_wait_for_space(), we might call jbd2_cleanup_journal_tail() to recover some journal space. But if an error occurs while executing jbd2_cleanup_journal_tail() (e.g., an EIO), we don't stop waiting for free space right away, we try other branches, and if j_committing_transaction is NULL (i.e., the tid is 0), we will get the following complain: ============================================ JBD2: I/O error when updating journal superblock for sdd-8. __jbd2_log_wait_for_space: needed 256 blocks and only had 217 space available __jbd2_log_wait_for_space: no way to get more journal space in sdd-8 ------------[ cut here ]------------ WARNING: CPU: 2 PID: 139804 at fs/jbd2/checkpoint.c:109 __jbd2_log_wait_for_space+0x251/0x2e0 Modules linked in: CPU: 2 PID: 139804 Comm: kworker/u8:3 Not tainted 6.6.0+ #1 RIP: 0010:__jbd2_log_wait_for_space+0x251/0x2e0 Call Trace: add_transaction_credits+0x5d1/0x5e0 start_this_handle+0x1ef/0x6a0 jbd2__journal_start+0x18b/0x340 ext4_dirty_inode+0x5d/0xb0 __mark_inode_dirty+0xe4/0x5d0 generic_update_time+0x60/0x70 [...] ============================================ So only if jbd2_cleanup_journal_tail() returns 1, i.e., there is nothing to clean up at the moment, continue to try to reclaim free space in other ways. Note that this fix relies on commit 6f6a6fda2945 ("jbd2: fix ocfs2 corrupt when updating journal superblock fails") to make jbd2_cleanup_journal_tail return the correct error code. Fixes: 8c3f25d8950c ("jbd2: don't give up looking for space so easily in __jbd2_log_wait_for_space") Cc: stable@kernel.org Signed-off-by: Baokun Li Reviewed-by: Jan Kara Link: https://patch.msgid.link/20240718115336.2554501-1-libaokun@huaweicloud.com Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman

ext4: fix incorrect tid assumption in __jbd2_log_wait_for_space()

2024-11-08T15:20:40Z

commit 972090651ee15e51abfb2160e986fa050cfc7a40 upstream. Function __jbd2_log_wait_for_space() assumes that '0' is not a valid value for transaction IDs, which is incorrect. Don't assume that and invoke jbd2_log_wait_commit() if the journal had a committing transaction instead. Signed-off-by: Luis Henriques (SUSE) Reviewed-by: Jan Kara Link: https://patch.msgid.link/20240724161119.13448-3-luis.henriques@linux.dev Signed-off-by: Theodore Ts'o Cc: stable@kernel.org Signed-off-by: Greg Kroah-Hartman

jbd2: Fix wrongly judgement for buffer head removing while doing checkpoint

2023-08-11T09:53:43Z

[ Upstream commit e34c8dd238d0c9368b746480f313055f5bab5040 ] Following process, jbd2_journal_commit_transaction // there are several dirty buffer heads in transaction->t_checkpoint_list P1 wb_workfn jbd2_log_do_checkpoint if (buffer_locked(bh)) // false __block_write_full_page trylock_buffer(bh) test_clear_buffer_dirty(bh) if (!buffer_dirty(bh)) __jbd2_journal_remove_checkpoint(jh) if (buffer_write_io_error(bh)) // false >> bh IO error occurs << jbd2_cleanup_journal_tail __jbd2_update_log_tail jbd2_write_superblock // The bh won't be replayed in next mount. , which could corrupt the ext4 image, fetch a reproducer in [Link]. Since writeback process clears buffer dirty after locking buffer head, we can fix it by try locking buffer and check dirtiness while buffer is locked, the buffer head can be removed if it is neither dirty nor locked. Link: https://bugzilla.kernel.org/show_bug.cgi?id=217490 Fixes: 470decc613ab ("[PATCH] jbd2: initial copy of files from jbd") Signed-off-by: Zhihao Cheng Signed-off-by: Zhang Yi Reviewed-by: Jan Kara Link: https://lore.kernel.org/r/20230606135928.434610-5-yi.zhang@huaweicloud.com Signed-off-by: Theodore Ts'o Signed-off-by: Sasha Levin

jbd2: recheck chechpointing non-dirty buffer

2023-08-11T09:53:43Z

[ Upstream commit c2d6fd9d6f35079f1669f0100f05b46708c74b7f ] There is a long-standing metadata corruption issue that happens from time to time, but it's very difficult to reproduce and analyse, benefit from the JBD2_CYCLE_RECORD option, we found out that the problem is the checkpointing process miss to write out some buffers which are raced by another do_get_write_access(). Looks below for detail. jbd2_log_do_checkpoint() //transaction X //buffer A is dirty and not belones to any transaction __buffer_relink_io() //move it to the IO list __flush_batch() write_dirty_buffer() do_get_write_access() clear_buffer_dirty __jbd2_journal_file_buffer() //add buffer A to a new transaction Y lock_buffer(bh) //doesn't write out __jbd2_journal_remove_checkpoint() //finish checkpoint except buffer A //filesystem corrupt if the new transaction Y isn't fully write out. Due to the t_checkpoint_list walking loop in jbd2_log_do_checkpoint() have already handles waiting for buffers under IO and re-added new transaction to complete commit, and it also removing cleaned buffers, this makes sure the list will eventually get empty. So it's fine to leave buffers on the t_checkpoint_list while flushing out and completely stop using the t_checkpoint_io_list. Cc: stable@vger.kernel.org Suggested-by: Jan Kara Signed-off-by: Zhang Yi Tested-by: Zhihao Cheng Reviewed-by: Jan Kara Link: https://lore.kernel.org/r/20230606135928.434610-2-yi.zhang@huaweicloud.com Signed-off-by: Theodore Ts'o Stable-dep-of: e34c8dd238d0 ("jbd2: Fix wrongly judgement for buffer head removing while doing checkpoint") Signed-off-by: Sasha Levin

jbd2: remove redundant buffer io error checks

2023-08-11T09:53:43Z

[ Upstream commit 214eb5a4d8a2032fb9f0711d1b202eb88ee02920 ] Now that __jbd2_journal_remove_checkpoint() can detect buffer io error and mark journal checkpoint error, then we abort the journal later before updating log tail to ensure the filesystem works consistently. So we could remove other redundant buffer io error checkes. Signed-off-by: Zhang Yi Reviewed-by: Jan Kara Link: https://lore.kernel.org/r/20210610112440.3438139-5-yi.zhang@huawei.com Signed-off-by: Theodore Ts'o Stable-dep-of: e34c8dd238d0 ("jbd2: Fix wrongly judgement for buffer head removing while doing checkpoint") Signed-off-by: Sasha Levin

jbd2: fix up sparse warnings in checkpoint code

2020-11-18T18:20:30Z

commit 05d5233df85e9621597c5838e95235107eb624a2 upstream. Add missing __acquires() and __releases() annotations. Also, in an "this should never happen" WARN_ON check, if it *does* actually happen, we need to release j_state_lock since this function is always supposed to release that lock. Otherwise, things will quickly grind to a halt after the WARN_ON trips. Fixes: 96f1e0974575 ("jbd2: avoid long hold times of j_state_lock...") Cc: stable@kernel.org Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman

ext4, jbd2: ensure panic when aborting with zero errno

2020-02-24T07:36:30Z

[ Upstream commit 51f57b01e4a3c7d7bdceffd84de35144e8c538e7 ] JBD2_REC_ERR flag used to indicate the errno has been updated when jbd2 aborted, and then __ext4_abort() and ext4_handle_error() can invoke panic if ERRORS_PANIC is specified. But if the journal has been aborted with zero errno, jbd2_journal_abort() didn't set this flag so we can no longer panic. Fix this by always record the proper errno in the journal superblock. Fixes: 4327ba52afd03 ("ext4, jbd2: ensure entering into panic after recording an error in superblock") Signed-off-by: zhangyi (F) Reviewed-by: Jan Kara Link: https://lore.kernel.org/r/20191204124614.45424-3-yi.zhang@huawei.com Signed-off-by: Theodore Ts'o Signed-off-by: Sasha Levin

jbd2: remove repeated assignments in __jbd2_log_wait_for_space()

2019-04-06T22:14:17Z

At the beginning, nblocks has been assigned. There is no need to repeat the assignment in the while loop, and remove it. Signed-off-by: Liu Song Signed-off-by: Theodore Ts'o Reviewed-by: Jan Kara

jbd2: fix deadlock while checkpoint thread waits commit thread to finish

2019-02-01T04:42:11Z

This issue was found when I tried to put checkpoint work in a separate thread, the deadlock below happened: Thread1 | Thread2 __jbd2_log_wait_for_space | jbd2_log_do_checkpoint (hold j_checkpoint_mutex)| if (jh->b_transaction != NULL) | ... | jbd2_log_start_commit(journal, tid); |jbd2_update_log_tail | will lock j_checkpoint_mutex, | but will be blocked here. | jbd2_log_wait_commit(journal, tid); | wait_event(journal->j_wait_done_commit, | !tid_gt(tid, journal->j_commit_sequence)); | ... |wake_up(j_wait_done_commit) } | then deadlock occurs, Thread1 will never be waken up. To fix this issue, drop j_checkpoint_mutex in jbd2_log_do_checkpoint() when we are going to wait for transaction commit. Reviewed-by: Jan Kara Signed-off-by: Xiaoguang Wang Signed-off-by: Theodore Ts'o