On Sat, 5 Jul 2014, Theodore Ts'o wrote:
> Date: Sat, 5 Jul 2014 16:28:51 -0400
> From: Theodore Ts'o <tytso@xxxxxxx>
> To: Ext4 Developers List <linux-ext4@xxxxxxxxxxxxxxx>
> Cc: Theodore Ts'o <tytso@xxxxxxx>, stable@xxxxxxxxxxxxxxx
> Subject: [PATCH] ext4: fix unjournalled bg descriptor while initializing inode
> bitmap
>
> The first time that we allocate from an uninitialized inode allocation
> bitmap, if the block allocation bitmap is also uninitalized, we need
> to get write access to the block group descriptor before we start
> modifying the block group descriptor flags and updating the free block
> count, etc. Otherwise, there is the potential of a bad journal
> checksum (if journal checksums are enabled), and of the file system
> becoming inconsistent if we crash at exactly the wrong time.
Looks good.
Reviewed-by: Lukas Czerner <lczerner@xxxxxxxxxx>
>
> Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
> fs/ext4/ialloc.c | 14 +++++++-------
> 1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
> index a87455d..0840bf3 100644
> --- a/fs/ext4/ialloc.c
> +++ b/fs/ext4/ialloc.c
> @@ -874,6 +874,13 @@ got:
> goto out;
> }
>
> + BUFFER_TRACE(group_desc_bh, "get_write_access");
> + err = ext4_journal_get_write_access(handle, group_desc_bh);
> + if (err) {
> + ext4_std_error(sb, err);
> + goto out;
> + }
> +
> /* We may have to initialize the block bitmap if it isn't already */
> if (ext4_has_group_desc_csum(sb) &&
> gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
> @@ -910,13 +917,6 @@ got:
> }
> }
>
> - BUFFER_TRACE(group_desc_bh, "get_write_access");
> - err = ext4_journal_get_write_access(handle, group_desc_bh);
> - if (err) {
> - ext4_std_error(sb, err);
> - goto out;
> - }
> -
> /* Update the relevant bg descriptor fields */
> if (ext4_has_group_desc_csum(sb)) {
> int free;
>
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