Re: [RFC v3 2/8] ext4: Refactor code related to freeing PAs

Jan Kara
2022-09-29T11:26:21Z

On Tue 27-09-22 14:46:42, Ojaswin Mujoo wrote:
> This patch makes the following changes:
>
> * Rename ext4_mb_pa_free to ext4_mb_pa_put_free
> to better reflect its purpose
>
> * Add new ext4_mb_pa_free() which only handles freeing
>
> * Refactor ext4_mb_pa_callback() to use ext4_mb_pa_free()
>
> There are no functional changes in this patch
>
> Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
> Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>

Looks good. Feel free to add:

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

Honza

> ---
> fs/ext4/mballoc.c | 29 ++++++++++++++++++++---------
> 1 file changed, 20 insertions(+), 9 deletions(-)
>
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 2e3eb632a216..8be6f8765a6f 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -4531,16 +4531,21 @@ static void ext4_mb_mark_pa_deleted(struct super_block *sb,
> }
> }
>
> -static void ext4_mb_pa_callback(struct rcu_head *head)
> +static void inline ext4_mb_pa_free(struct ext4_prealloc_space *pa)
> {
> - struct ext4_prealloc_space *pa;
> - pa = container_of(head, struct ext4_prealloc_space, u.pa_rcu);
> -
> + BUG_ON(!pa);
> BUG_ON(atomic_read(&pa->pa_count));
> BUG_ON(pa->pa_deleted == 0);
> kmem_cache_free(ext4_pspace_cachep, pa);
> }
>
> +static void ext4_mb_pa_callback(struct rcu_head *head)
> +{
> + struct ext4_prealloc_space *pa;
> + pa = container_of(head, struct ext4_prealloc_space, u.pa_rcu);
> + ext4_mb_pa_free(pa);
> +}
> +
> /*
> * drops a reference to preallocated space descriptor
> * if this was the last reference and the space is consumed
> @@ -5067,14 +5072,20 @@ static int ext4_mb_pa_alloc(struct ext4_allocation_context *ac)
> return 0;
> }
>
> -static void ext4_mb_pa_free(struct ext4_allocation_context *ac)
> +static void ext4_mb_pa_put_free(struct ext4_allocation_context *ac)
> {
> struct ext4_prealloc_space *pa = ac->ac_pa;
>
> BUG_ON(!pa);
> ac->ac_pa = NULL;
> WARN_ON(!atomic_dec_and_test(&pa->pa_count));
> - kmem_cache_free(ext4_pspace_cachep, pa);
> + /*
> + * current function is only called due to an error or due to
> + * len of found blocks < len of requested blocks hence the PA has not
> + * been added to grp->bb_prealloc_list. So we don't need to lock it
> + */
> + pa->pa_deleted = 1;
> + ext4_mb_pa_free(pa);
> }
>
> #ifdef CONFIG_EXT4_DEBUG
> @@ -5623,13 +5634,13 @@ ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle,
> * So we have to free this pa here itself.
> */
> if (*errp) {
> - ext4_mb_pa_free(ac);
> + ext4_mb_pa_put_free(ac);
> ext4_discard_allocated_blocks(ac);
> goto errout;
> }
> if (ac->ac_status == AC_STATUS_FOUND &&
> ac->ac_o_ex.fe_len >= ac->ac_f_ex.fe_len)
> - ext4_mb_pa_free(ac);
> + ext4_mb_pa_put_free(ac);
> }
> if (likely(ac->ac_status == AC_STATUS_FOUND)) {
> *errp = ext4_mb_mark_diskspace_used(ac, handle, reserv_clstrs);
> @@ -5648,7 +5659,7 @@ ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle,
> * If block allocation fails then the pa allocated above
> * needs to be freed here itself.
> */
> - ext4_mb_pa_free(ac);
> + ext4_mb_pa_put_free(ac);
> *errp = -ENOSPC;
> }
>
> --
> 2.31.1
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR