From: Ye Bin 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 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 --- fs/jbd2/journal.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c index d480b94117cd..5b6e8c1a5e6a 100644 --- a/fs/jbd2/journal.c +++ b/fs/jbd2/journal.c @@ -2349,6 +2349,8 @@ 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); + 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 +2380,13 @@ 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); + 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