diff mbox series

[v3,1/6] ext4: Fix reusing stale buffer heads from last failed mounting

Message ID 20230315013128.3911115-2-chengzhihao1@huawei.com
State New
Headers
Series ext4: Fix stale buffer loading from last failed |

Commit Message

Zhihao Cheng March 15, 2023, 1:31 a.m. UTC 
  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>
---
 fs/ext4/super.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

Comments

Jan Kara March 15, 2023, 8:43 a.m. UTC | #1 
On Wed 15-03-23 09:31:23, Zhihao Cheng wrote:
> 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>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/ext4/super.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index f43e526112ae..61511b7ba017 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -1126,6 +1126,12 @@ static void ext4_blkdev_remove(struct ext4_sb_info *sbi)
>  	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;
>  	}
> @@ -1272,13 +1278,7 @@ static void ext4_put_super(struct super_block *sb)
>  	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);
>  	}
>  
> @@ -5610,6 +5610,7 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
>  	brelse(sbi->s_sbh);
>  	ext4_blkdev_remove(sbi);
>  out_fail:
> +	invalidate_bdev(sb->s_bdev);
>  	sb->s_fs_info = NULL;
>  	return err ? err : ret;
>  }
> -- 
> 2.31.1
>
diff mbox series

Patch

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index f43e526112ae..61511b7ba017 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1126,6 +1126,12 @@  static void ext4_blkdev_remove(struct ext4_sb_info *sbi)
 	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;
 	}
@@ -1272,13 +1278,7 @@  static void ext4_put_super(struct super_block *sb)
 	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);
 	}
 
@@ -5610,6 +5610,7 @@  static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
 	brelse(sbi->s_sbh);
 	ext4_blkdev_remove(sbi);
 out_fail:
+	invalidate_bdev(sb->s_bdev);
 	sb->s_fs_info = NULL;
 	return err ? err : ret;
 }