On Wed, 2008-02-13 at 17:26 +0100, Valerie Clement wrote:
> Modify the block allocation algorithm for the last group
>
> From: Valerie Clement <valerie.clement@xxxxxxxx>
>
> When a directory inode is allocated in the last group and the last group
> contains less than s_blocks_per_group blocks, the initial block allocated
> for the directory is not always allocated in the same group as the
> directory inode, but in one of the first groups of the filesystem (group 1
> for example).
> Depending on the current process's pid, ext4_find_near() and
> ext4_ext_find_goal() can return a block number greater than the maximum
> blocks count in the filesystem and in that case the block will be not
> allocated in the same group as the inode.
>
> The following patch fixes the problem.
>
> Comments?
Looks sane to me.
> Should the modification also be done in ext2/3 code?
>
I think so.
Mingming
> Signed-off-by: Valerie Clement <valerie.clement@xxxxxxxx>
> ---
>
> fs/ext4/extents.c | 8 +++++++-
> fs/ext4/inode.c | 8 +++++++-
> 2 files changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 5c4af51..1391ded 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -148,6 +148,7 @@ ext4_fsblk_t ext4_ext_find_goal(struct inode *inode,
> {
> struct ext4_inode_info *ei = EXT4_I(inode);
> ext4_fsblk_t bg_start;
> + ext4_fsblk_t last_block;
> ext4_grpblk_t colour;
> int depth;
>
> @@ -169,8 +170,13 @@ ext4_fsblk_t ext4_ext_find_goal(struct inode *inode,
> /* OK. use inode's group */
> bg_start = (ei->i_block_group * EXT4_BLOCKS_PER_GROUP(inode->i_sb)) +
> le32_to_cpu(EXT4_SB(inode->i_sb)->s_es->s_first_data_block);
> - colour = (current->pid % 16) *
> + last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1;
> +
> + if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block)
> + colour = (current->pid % 16) *
> (EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
> + else
> + colour = (current->pid % 16) * ((last_block - bg_start) / 16);
> return bg_start + colour + block;
> }
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 51bf3b5..c4f8ace 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -405,6 +405,7 @@ static ext4_fsblk_t ext4_find_near(struct inode *inode, Indirect *ind)
> __le32 *start = ind->bh ? (__le32*) ind->bh->b_data : ei->i_data;
> __le32 *p;
> ext4_fsblk_t bg_start;
> + ext4_fsblk_t last_block;
> ext4_grpblk_t colour;
>
> /* Try to find previous block */
> @@ -422,8 +423,13 @@ static ext4_fsblk_t ext4_find_near(struct inode *inode, Indirect *ind)
> * into the same cylinder group then.
> */
> bg_start = ext4_group_first_block_no(inode->i_sb, ei->i_block_group);
> - colour = (current->pid % 16) *
> + last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1;
> +
> + if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block)
> + colour = (current->pid % 16) *
> (EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
> + else
> + colour = (current->pid % 16) * ((last_block - bg_start) / 16);
> return bg_start + colour;
> }
>
>
>
> -
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