From: Zhihao Cheng chengzhihao1@huawei.com
commit 26fb5290240dc31cae99b8b4dd2af7f46dfcba6b upstream.
Following process makes ext4 load stale buffer heads from last failed mounting in a new mounting operation: mount_bdev ext4_fill_super | ext4_load_and_init_journal | ext4_load_journal | jbd2_journal_load | load_superblock | journal_get_superblock | set_buffer_verified(bh) // buffer head is verified | jbd2_journal_recover // failed caused by EIO | goto failed_mount3a // skip 'sb->s_root' initialization deactivate_locked_super kill_block_super generic_shutdown_super if (sb->s_root) // false, skip ext4_put_super->invalidate_bdev-> // invalidate_mapping_pages->mapping_evict_folio-> // filemap_release_folio->try_to_free_buffers, which // cannot drop buffer head. blkdev_put blkdev_put_whole if (atomic_dec_and_test(&bdev->bd_openers)) // false, systemd-udev happens to open the device. Then // blkdev_flush_mapping->kill_bdev->truncate_inode_pages-> // truncate_inode_folio->truncate_cleanup_folio-> // folio_invalidate->block_invalidate_folio-> // filemap_release_folio->try_to_free_buffers will be skipped, // dropping buffer head is missed again.
Second mount: ext4_fill_super ext4_load_and_init_journal ext4_load_journal ext4_get_journal jbd2_journal_init_inode journal_init_common bh = getblk_unmovable bh = __find_get_block // Found stale bh in last failed mounting journal->j_sb_buffer = bh jbd2_journal_load load_superblock journal_get_superblock if (buffer_verified(bh)) // true, skip journal->j_format_version = 2, value is 0 jbd2_journal_recover do_one_pass next_log_block += count_tags(journal, bh) // According to journal_tag_bytes(), 'tag_bytes' calculating is // affected by jbd2_has_feature_csum3(), jbd2_has_feature_csum3() // returns false because 'j->j_format_version >= 2' is not true, // then we get wrong next_log_block. The do_one_pass may exit // early whenoccuring non JBD2_MAGIC_NUMBER in 'next_log_block'.
The filesystem is corrupted here, journal is partially replayed, and new journal sequence number actually is already used by last mounting.
The invalidate_bdev() can drop all buffer heads even racing with bare reading block device(eg. systemd-udev), so we can fix it by invalidating bdev in error handling path in __ext4_fill_super().
Fetch a reproducer in [Link].
Link: https://bugzilla.kernel.org/show_bug.cgi?id=217171 Fixes: 25ed6e8a54df ("jbd2: enable journal clients to enable v2 checksumming") Cc: stable@vger.kernel.org # v3.5 Signed-off-by: Zhihao Cheng chengzhihao1@huawei.com Reviewed-by: Jan Kara jack@suse.cz Link: https://lore.kernel.org/r/20230315013128.3911115-2-chengzhihao1@huawei.com Signed-off-by: Theodore Ts'o tytso@mit.edu Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/ext4/super.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-)
--- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -1129,6 +1129,12 @@ static void ext4_blkdev_remove(struct ex struct block_device *bdev; bdev = sbi->s_journal_bdev; if (bdev) { + /* + * Invalidate the journal device's buffers. We don't want them + * floating about in memory - the physical journal device may + * hotswapped, and it breaks the `ro-after' testing code. + */ + invalidate_bdev(bdev); ext4_blkdev_put(bdev); sbi->s_journal_bdev = NULL; } @@ -1274,13 +1280,7 @@ static void ext4_put_super(struct super_ sync_blockdev(sb->s_bdev); invalidate_bdev(sb->s_bdev); if (sbi->s_journal_bdev && sbi->s_journal_bdev != sb->s_bdev) { - /* - * Invalidate the journal device's buffers. We don't want them - * floating about in memory - the physical journal device may - * hotswapped, and it breaks the `ro-after' testing code. - */ sync_blockdev(sbi->s_journal_bdev); - invalidate_bdev(sbi->s_journal_bdev); ext4_blkdev_remove(sbi); }
@@ -5634,6 +5634,7 @@ failed_mount: brelse(sbi->s_sbh); ext4_blkdev_remove(sbi); out_fail: + invalidate_bdev(sb->s_bdev); sb->s_fs_info = NULL; return err ? err : ret; }