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Message-ID: <ab380b0c-9a9b-4f16-a427-7fef8a2ef212@huaweicloud.com> Date: Tue, 3 Dec 2024 15:24:26 +0800 From: Zhang Yi <yi.zhang@...weicloud.com> To: Kemeng Shi <shikemeng@...weicloud.com>, linux-ext4@...r.kernel.org Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, tytso@....edu, adilger.kernel@...ger.ca, jack@...e.cz, yi.zhang@...wei.com, chengzhihao1@...wei.com, yukuai3@...wei.com, yangerkun@...wei.com Subject: Re: [PATCH 2/2] jbd2: flush filesystem device before updating tail sequence On 2024/12/3 14:53, Kemeng Shi wrote: > > > on 12/3/2024 9:44 AM, Zhang Yi wrote: >> From: Zhang Yi <yi.zhang@...wei.com> >> >> When committing transaction in jbd2_journal_commit_transaction(), the >> disk caches for the filesystem device should be flushed before updating >> the journal tail sequence. However, this step is missed if the journal >> is not located on the filesystem device. As a result, the filesystem may >> become inconsistent following a power failure or system crash. Fix it by >> ensuring that the filesystem device is flushed appropriately. >> >> Fixes: 3339578f0578 ("jbd2: cleanup journal tail after transaction commit") >> Signed-off-by: Zhang Yi <yi.zhang@...wei.com> >> --- >> fs/jbd2/commit.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c >> index 4305a1ac808a..f95cf272a1b5 100644 >> --- a/fs/jbd2/commit.c >> +++ b/fs/jbd2/commit.c >> @@ -776,9 +776,9 @@ void jbd2_journal_commit_transaction(journal_t *journal) >> /* >> * If the journal is not located on the file system device, >> * then we must flush the file system device before we issue >> - * the commit record >> + * the commit record and update the journal tail sequence. >> */ >> - if (commit_transaction->t_need_data_flush && >> + if ((commit_transaction->t_need_data_flush || update_tail) && >> (journal->j_fs_dev != journal->j_dev) && >> (journal->j_flags & JBD2_BARRIER)) >> blkdev_issue_flush(journal->j_fs_dev); >> > In journal_submit_commit_record(), we will submit commit block with REQ_PREFLUSH > which is supposed to ensure disk cache is flushed before writing commit block. > So I think the current code is fine. > Please correct me if I miss anything. > The commit I/O with REQ_PREFLUSH only flushes 'journal->j_dev', not 'journal->j_fs_dev'. We need to flush journal->j_fs_dev to ensure that all written metadata has been persisted to the filesystem disk, Until then, we cannot update the tail sequence. Thanks, Yi.
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