Re: [PATCH v2 8/9] ext4: make ext4_insert_delayed_block() insert multi-blocks

Jan Kara
2024-04-29T10:07:11Z

On Wed 10-04-24 11:42:02, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@huawei.com>
>
> Rename ext4_insert_delayed_block() to ext4_insert_delayed_blocks(),
> pass length parameter to make it insert multi delalloc blocks once a
> time. For non-bigalloc case, just reserve len blocks and insert delalloc
> extent. For bigalloc case, we can ensure the middle clusters are not
> allocated, but need to check whether the start and end clusters are
> delayed/allocated, if not, we should reserve more space for the start
> and/or end block(s).
>
> Signed-off-by: Zhang Yi <yi.zhang@huawei.com>

Thanks for the patch. Some comments below.

> ---
> fs/ext4/inode.c | 51 ++++++++++++++++++++++++++++++++++---------------
> 1 file changed, 36 insertions(+), 15 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 46c34baa848a..08e2692b7286 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -1678,24 +1678,28 @@ static int ext4_da_check_clu_allocated(struct inode *inode, ext4_lblk_t lblk,
> }
>
> /*
> - * ext4_insert_delayed_block - adds a delayed block to the extents status
> - * tree, incrementing the reserved cluster/block
> - * count or making a pending reservation
> - * where needed
> + * ext4_insert_delayed_blocks - adds a multiple delayed blocks to the extents
> + * status tree, incrementing the reserved
> + * cluster/block count or making pending
> + * reservations where needed
> *
> * @inode - file containing the newly added block
> - * @lblk - logical block to be added
> + * @lblk - start logical block to be added
> + * @len - length of blocks to be added
> *
> * Returns 0 on success, negative error code on failure.
> */
> -static int ext4_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk)
> +static int ext4_insert_delayed_blocks(struct inode *inode, ext4_lblk_t lblk,
> + ext4_lblk_t len)
> {
> struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
> - int ret;
> - bool allocated = false;
> + int resv_clu, ret;
^^^ this variable is in prinple the length of the extent. Thus
it should be ext4_lblk_t type.

> + bool lclu_allocated = false;
> + bool end_allocated = false;
> + ext4_lblk_t end = lblk + len - 1;
>
> /*
> - * If the cluster containing lblk is shared with a delayed,
> + * If the cluster containing lblk or end is shared with a delayed,
> * written, or unwritten extent in a bigalloc file system, it's
> * already been accounted for and does not need to be reserved.
> * A pending reservation must be made for the cluster if it's
> @@ -1706,21 +1710,38 @@ static int ext4_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk)
> * extents status tree doesn't get a match.
> */
> if (sbi->s_cluster_ratio == 1) {
> - ret = ext4_da_reserve_space(inode, 1);
> + ret = ext4_da_reserve_space(inode, len);
> if (ret != 0) /* ENOSPC */
> return ret;
> } else { /* bigalloc */
> - ret = ext4_da_check_clu_allocated(inode, lblk, &allocated);
> + resv_clu = EXT4_B2C(sbi, end) - EXT4_B2C(sbi, lblk) - 1;
> + if (resv_clu < 0)
> + resv_clu = 0;

Here resv_clu going negative is strange I'm not sure the math is 100%
correct in all the cases. I think it would be more logical as:

resv_clu = EXT4_B2C(sbi, end) - EXT4_B2C(sbi, lblk) + 1;

and then update resv_clu below as:

> +
> + ret = ext4_da_check_clu_allocated(inode, lblk, &lclu_allocated);
> if (ret < 0)
> return ret;
> - if (ret > 0) {
> - ret = ext4_da_reserve_space(inode, 1);
> + if (ret > 0)
> + resv_clu++;

Here we would do:
if (ret == 0)
resv_clu--;

> +
> + if (EXT4_B2C(sbi, lblk) != EXT4_B2C(sbi, end)) {
> + ret = ext4_da_check_clu_allocated(inode, end,
> + &end_allocated);
> + if (ret < 0)
> + return ret;
> + if (ret > 0)
> + resv_clu++;

And similarly here:
if (ret == 0)
resv_clu--;

Honza

> + }
> +
> + if (resv_clu) {
> + ret = ext4_da_reserve_space(inode, resv_clu);
> if (ret != 0) /* ENOSPC */
> return ret;
> }
> }
>
> - ext4_es_insert_delayed_extent(inode, lblk, 1, allocated, false);
> + ext4_es_insert_delayed_extent(inode, lblk, len, lclu_allocated,
> + end_allocated);
> return 0;
> }
>
> @@ -1823,7 +1844,7 @@ static int ext4_da_map_blocks(struct inode *inode, struct ext4_map_blocks *map,
> }
> }
>
> - retval = ext4_insert_delayed_block(inode, map->m_lblk);
> + retval = ext4_insert_delayed_blocks(inode, map->m_lblk, map->m_len);
> up_write(&EXT4_I(inode)->i_data_sem);
> if (retval)
> return retval;
> --
> 2.39.2
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR