* Re: [PATCH v2] jbd2: fix the inconsistency between checksum and data in memory for journal sb
2025-11-03 1:01 [PATCH v2] jbd2: fix the inconsistency between checksum and data in memory for journal sb Ye Bin
@ 2025-11-03 12:00 ` Jan Kara
2025-11-03 21:37 ` Darrick J. Wong
2025-11-08 3:55 ` Baokun Li
2 siblings, 0 replies; 4+ messages in thread
From: Jan Kara @ 2025-11-03 12:00 UTC (permalink / raw)
To: Ye Bin; +Cc: tytso, adilger.kernel, linux-ext4, jack
On Mon 03-11-25 09:01:23, Ye Bin wrote:
> From: Ye Bin <yebin10@huawei.com>
>
> Copying the file system while it is mounted as read-only results in
> a mount failure:
> [~]# mkfs.ext4 -F /dev/sdc
> [~]# mount /dev/sdc -o ro /mnt/test
> [~]# dd if=/dev/sdc of=/dev/sda bs=1M
> [~]# mount /dev/sda /mnt/test1
> [ 1094.849826] JBD2: journal checksum error
> [ 1094.850927] EXT4-fs (sda): Could not load journal inode
> mount: mount /dev/sda on /mnt/test1 failed: Bad message
>
> The process described above is just an abstracted way I came up with to
> reproduce the issue. In the actual scenario, the file system was mounted
> read-only and then copied while it was still mounted. It was found that
> the mount operation failed. The user intended to verify the data or use
> it as a backup, and this action was performed during a version upgrade.
> Above issue may happen as follows:
> ext4_fill_super
> set_journal_csum_feature_set(sb)
> if (ext4_has_metadata_csum(sb))
> incompat = JBD2_FEATURE_INCOMPAT_CSUM_V3;
> if (test_opt(sb, JOURNAL_CHECKSUM)
> jbd2_journal_set_features(sbi->s_journal, compat, 0, incompat);
> lock_buffer(journal->j_sb_buffer);
> sb->s_feature_incompat |= cpu_to_be32(incompat);
> //The data in the journal sb was modified, but the checksum was not
> updated, so the data remaining in memory has a mismatch between the
> data and the checksum.
> unlock_buffer(journal->j_sb_buffer);
>
> In this case, the journal sb copied over is in a state where the checksum
> and data are inconsistent, so mounting fails.
> To solve the above issue, update the checksum in memory after modifying
> the journal sb.
>
> Fixes: 4fd5ea43bc11 ("jbd2: checksum journal superblock")
> Signed-off-by: Ye Bin <yebin10@huawei.com>
Looks good. Feel free to add:
Reviewed-by: Jan Kara <jack@suse.cz>
Honza
> ---
> fs/jbd2/journal.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> index d480b94117cd..bf255f8b5eeb 100644
> --- a/fs/jbd2/journal.c
> +++ b/fs/jbd2/journal.c
> @@ -2349,6 +2349,12 @@ int jbd2_journal_set_features(journal_t *journal, unsigned long compat,
> sb->s_feature_compat |= cpu_to_be32(compat);
> sb->s_feature_ro_compat |= cpu_to_be32(ro);
> sb->s_feature_incompat |= cpu_to_be32(incompat);
> + /*
> + * Update the checksum now so that it is valid even for read-only
> + * filesystems where jbd2_write_superblock() doesn't get called.
> + */
> + if (jbd2_journal_has_csum_v2or3(journal))
> + sb->s_checksum = jbd2_superblock_csum(sb);
> unlock_buffer(journal->j_sb_buffer);
> jbd2_journal_init_transaction_limits(journal);
>
> @@ -2378,9 +2384,17 @@ void jbd2_journal_clear_features(journal_t *journal, unsigned long compat,
>
> sb = journal->j_superblock;
>
> + lock_buffer(journal->j_sb_buffer);
> sb->s_feature_compat &= ~cpu_to_be32(compat);
> sb->s_feature_ro_compat &= ~cpu_to_be32(ro);
> sb->s_feature_incompat &= ~cpu_to_be32(incompat);
> + /*
> + * Update the checksum now so that it is valid even for read-only
> + * filesystems where jbd2_write_superblock() doesn't get called.
> + */
> + if (jbd2_journal_has_csum_v2or3(journal))
> + sb->s_checksum = jbd2_superblock_csum(sb);
> + unlock_buffer(journal->j_sb_buffer);
> jbd2_journal_init_transaction_limits(journal);
> }
> EXPORT_SYMBOL(jbd2_journal_clear_features);
> --
> 2.34.1
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH v2] jbd2: fix the inconsistency between checksum and data in memory for journal sb
2025-11-03 1:01 [PATCH v2] jbd2: fix the inconsistency between checksum and data in memory for journal sb Ye Bin
2025-11-03 12:00 ` Jan Kara
@ 2025-11-03 21:37 ` Darrick J. Wong
2025-11-08 3:55 ` Baokun Li
2 siblings, 0 replies; 4+ messages in thread
From: Darrick J. Wong @ 2025-11-03 21:37 UTC (permalink / raw)
To: Ye Bin; +Cc: tytso, adilger.kernel, linux-ext4, jack
On Mon, Nov 03, 2025 at 09:01:23AM +0800, Ye Bin wrote:
> From: Ye Bin <yebin10@huawei.com>
>
> Copying the file system while it is mounted as read-only results in
> a mount failure:
> [~]# mkfs.ext4 -F /dev/sdc
> [~]# mount /dev/sdc -o ro /mnt/test
> [~]# dd if=/dev/sdc of=/dev/sda bs=1M
> [~]# mount /dev/sda /mnt/test1
> [ 1094.849826] JBD2: journal checksum error
> [ 1094.850927] EXT4-fs (sda): Could not load journal inode
> mount: mount /dev/sda on /mnt/test1 failed: Bad message
>
> The process described above is just an abstracted way I came up with to
> reproduce the issue. In the actual scenario, the file system was mounted
> read-only and then copied while it was still mounted. It was found that
> the mount operation failed. The user intended to verify the data or use
> it as a backup, and this action was performed during a version upgrade.
> Above issue may happen as follows:
> ext4_fill_super
> set_journal_csum_feature_set(sb)
> if (ext4_has_metadata_csum(sb))
> incompat = JBD2_FEATURE_INCOMPAT_CSUM_V3;
> if (test_opt(sb, JOURNAL_CHECKSUM)
> jbd2_journal_set_features(sbi->s_journal, compat, 0, incompat);
> lock_buffer(journal->j_sb_buffer);
> sb->s_feature_incompat |= cpu_to_be32(incompat);
> //The data in the journal sb was modified, but the checksum was not
> updated, so the data remaining in memory has a mismatch between the
> data and the checksum.
> unlock_buffer(journal->j_sb_buffer);
>
> In this case, the journal sb copied over is in a state where the checksum
> and data are inconsistent, so mounting fails.
> To solve the above issue, update the checksum in memory after modifying
> the journal sb.
>
> Fixes: 4fd5ea43bc11 ("jbd2: checksum journal superblock")
> Signed-off-by: Ye Bin <yebin10@huawei.com>
Looks fine to me,
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
--D
> ---
> fs/jbd2/journal.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> index d480b94117cd..bf255f8b5eeb 100644
> --- a/fs/jbd2/journal.c
> +++ b/fs/jbd2/journal.c
> @@ -2349,6 +2349,12 @@ int jbd2_journal_set_features(journal_t *journal, unsigned long compat,
> sb->s_feature_compat |= cpu_to_be32(compat);
> sb->s_feature_ro_compat |= cpu_to_be32(ro);
> sb->s_feature_incompat |= cpu_to_be32(incompat);
> + /*
> + * Update the checksum now so that it is valid even for read-only
> + * filesystems where jbd2_write_superblock() doesn't get called.
> + */
> + if (jbd2_journal_has_csum_v2or3(journal))
> + sb->s_checksum = jbd2_superblock_csum(sb);
> unlock_buffer(journal->j_sb_buffer);
> jbd2_journal_init_transaction_limits(journal);
>
> @@ -2378,9 +2384,17 @@ void jbd2_journal_clear_features(journal_t *journal, unsigned long compat,
>
> sb = journal->j_superblock;
>
> + lock_buffer(journal->j_sb_buffer);
> sb->s_feature_compat &= ~cpu_to_be32(compat);
> sb->s_feature_ro_compat &= ~cpu_to_be32(ro);
> sb->s_feature_incompat &= ~cpu_to_be32(incompat);
> + /*
> + * Update the checksum now so that it is valid even for read-only
> + * filesystems where jbd2_write_superblock() doesn't get called.
> + */
> + if (jbd2_journal_has_csum_v2or3(journal))
> + sb->s_checksum = jbd2_superblock_csum(sb);
> + unlock_buffer(journal->j_sb_buffer);
> jbd2_journal_init_transaction_limits(journal);
> }
> EXPORT_SYMBOL(jbd2_journal_clear_features);
> --
> 2.34.1
>
>
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH v2] jbd2: fix the inconsistency between checksum and data in memory for journal sb
2025-11-03 1:01 [PATCH v2] jbd2: fix the inconsistency between checksum and data in memory for journal sb Ye Bin
2025-11-03 12:00 ` Jan Kara
2025-11-03 21:37 ` Darrick J. Wong
@ 2025-11-08 3:55 ` Baokun Li
2 siblings, 0 replies; 4+ messages in thread
From: Baokun Li @ 2025-11-08 3:55 UTC (permalink / raw)
To: Ye Bin; +Cc: tytso, adilger.kernel, jack, linux-ext4, Baokun Li
On 2025-11-03 09:01, Ye Bin wrote:
> From: Ye Bin <yebin10@huawei.com>
>
> Copying the file system while it is mounted as read-only results in
> a mount failure:
> [~]# mkfs.ext4 -F /dev/sdc
> [~]# mount /dev/sdc -o ro /mnt/test
> [~]# dd if=/dev/sdc of=/dev/sda bs=1M
> [~]# mount /dev/sda /mnt/test1
> [ 1094.849826] JBD2: journal checksum error
> [ 1094.850927] EXT4-fs (sda): Could not load journal inode
> mount: mount /dev/sda on /mnt/test1 failed: Bad message
>
> The process described above is just an abstracted way I came up with to
> reproduce the issue. In the actual scenario, the file system was mounted
> read-only and then copied while it was still mounted. It was found that
> the mount operation failed. The user intended to verify the data or use
> it as a backup, and this action was performed during a version upgrade.
> Above issue may happen as follows:
> ext4_fill_super
> set_journal_csum_feature_set(sb)
> if (ext4_has_metadata_csum(sb))
> incompat = JBD2_FEATURE_INCOMPAT_CSUM_V3;
> if (test_opt(sb, JOURNAL_CHECKSUM)
> jbd2_journal_set_features(sbi->s_journal, compat, 0, incompat);
> lock_buffer(journal->j_sb_buffer);
> sb->s_feature_incompat |= cpu_to_be32(incompat);
> //The data in the journal sb was modified, but the checksum was not
> updated, so the data remaining in memory has a mismatch between the
> data and the checksum.
> unlock_buffer(journal->j_sb_buffer);
>
> In this case, the journal sb copied over is in a state where the checksum
> and data are inconsistent, so mounting fails.
> To solve the above issue, update the checksum in memory after modifying
> the journal sb.
>
> Fixes: 4fd5ea43bc11 ("jbd2: checksum journal superblock")
> Signed-off-by: Ye Bin <yebin10@huawei.com>
Updating features on a read-only mount looks strange, but we still need
to update the checksum when touching the jbd2 superblock.
Reviewed-by: Baokun Li <libaokun1@huawei.com>
> ---
> fs/jbd2/journal.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> index d480b94117cd..bf255f8b5eeb 100644
> --- a/fs/jbd2/journal.c
> +++ b/fs/jbd2/journal.c
> @@ -2349,6 +2349,12 @@ int jbd2_journal_set_features(journal_t *journal, unsigned long compat,
> sb->s_feature_compat |= cpu_to_be32(compat);
> sb->s_feature_ro_compat |= cpu_to_be32(ro);
> sb->s_feature_incompat |= cpu_to_be32(incompat);
> + /*
> + * Update the checksum now so that it is valid even for read-only
> + * filesystems where jbd2_write_superblock() doesn't get called.
> + */
> + if (jbd2_journal_has_csum_v2or3(journal))
> + sb->s_checksum = jbd2_superblock_csum(sb);
> unlock_buffer(journal->j_sb_buffer);
> jbd2_journal_init_transaction_limits(journal);
>
> @@ -2378,9 +2384,17 @@ void jbd2_journal_clear_features(journal_t *journal, unsigned long compat,
>
> sb = journal->j_superblock;
>
> + lock_buffer(journal->j_sb_buffer);
> sb->s_feature_compat &= ~cpu_to_be32(compat);
> sb->s_feature_ro_compat &= ~cpu_to_be32(ro);
> sb->s_feature_incompat &= ~cpu_to_be32(incompat);
> + /*
> + * Update the checksum now so that it is valid even for read-only
> + * filesystems where jbd2_write_superblock() doesn't get called.
> + */
> + if (jbd2_journal_has_csum_v2or3(journal))
> + sb->s_checksum = jbd2_superblock_csum(sb);
> + unlock_buffer(journal->j_sb_buffer);
> jbd2_journal_init_transaction_limits(journal);
> }
> EXPORT_SYMBOL(jbd2_journal_clear_features);
^ permalink raw reply [flat|nested] 4+ messages in thread