Re: [PATCH v2 1/3] erofs: get rid of erofs_{find,insert}_workgroup

[Chao Yu <chao@kernel.org>]

On 2024/10/21 11:53, Gao Xiang wrote:
> Just fold them into the only two callers since
> they are simple enough.
> 
> Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
> ---
> v1: https://lore.kernel.org/r/20241017115705.877515-1-hsiangkao@linux.alibaba.com
> change since v1:
>   - !grp case should be handled properly mentioned by Chunhai;
> 
>   fs/erofs/internal.h |  5 +----
>   fs/erofs/zdata.c    | 38 +++++++++++++++++++++++++---------
>   fs/erofs/zutil.c    | 50 +--------------------------------------------
>   3 files changed, 30 insertions(+), 63 deletions(-)
> 
> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index 4efd578d7c62..8081ee43cd83 100644
> --- a/fs/erofs/internal.h
> +++ b/fs/erofs/internal.h
> @@ -457,10 +457,7 @@ void erofs_release_pages(struct page **pagepool);
>   
>   #ifdef CONFIG_EROFS_FS_ZIP
>   void erofs_workgroup_put(struct erofs_workgroup *grp);
> -struct erofs_workgroup *erofs_find_workgroup(struct super_block *sb,
> -					     pgoff_t index);
> -struct erofs_workgroup *erofs_insert_workgroup(struct super_block *sb,
> -					       struct erofs_workgroup *grp);
> +bool erofs_workgroup_get(struct erofs_workgroup *grp);
>   void erofs_workgroup_free_rcu(struct erofs_workgroup *grp);
>   void erofs_shrinker_register(struct super_block *sb);
>   void erofs_shrinker_unregister(struct super_block *sb);
> diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
> index a569ff9dfd04..bb1b73d99d07 100644
> --- a/fs/erofs/zdata.c
> +++ b/fs/erofs/zdata.c
> @@ -714,9 +714,10 @@ static int z_erofs_register_pcluster(struct z_erofs_decompress_frontend *fe)
>   {
>   	struct erofs_map_blocks *map = &fe->map;
>   	struct super_block *sb = fe->inode->i_sb;
> +	struct erofs_sb_info *sbi = EROFS_SB(sb);
>   	bool ztailpacking = map->m_flags & EROFS_MAP_META;
>   	struct z_erofs_pcluster *pcl;
> -	struct erofs_workgroup *grp;
> +	struct erofs_workgroup *grp, *pre;
>   	int err;
>   
>   	if (!(map->m_flags & EROFS_MAP_ENCODED) ||
> @@ -752,15 +753,23 @@ static int z_erofs_register_pcluster(struct z_erofs_decompress_frontend *fe)
>   		pcl->obj.index = 0;	/* which indicates ztailpacking */
>   	} else {
>   		pcl->obj.index = erofs_blknr(sb, map->m_pa);
> -
> -		grp = erofs_insert_workgroup(fe->inode->i_sb, &pcl->obj);
> -		if (IS_ERR(grp)) {
> -			err = PTR_ERR(grp);
> -			goto err_out;
> +		while (1) {
> +			xa_lock(&sbi->managed_pslots);
> +			pre = __xa_cmpxchg(&sbi->managed_pslots, grp->index,
> +					   NULL, grp, GFP_KERNEL);
> +			if (!pre || xa_is_err(pre) || erofs_workgroup_get(pre)) {
> +				xa_unlock(&sbi->managed_pslots);
> +				break;
> +			}
> +			/* try to legitimize the current in-tree one */
> +			xa_unlock(&sbi->managed_pslots);
> +			cond_resched();
>   		}
> -
> -		if (grp != &pcl->obj) {

Do we need to keep this logic?

Thanks,

> -			fe->pcl = container_of(grp,
> +		if (xa_is_err(pre)) {
> +			err = xa_err(pre);
> +			goto err_out;
> +		} else if (pre) {
> +			fe->pcl = container_of(pre,
>   					struct z_erofs_pcluster, obj);
>   			err = -EEXIST;
>   			goto err_out;
> @@ -789,7 +798,16 @@ static int z_erofs_pcluster_begin(struct z_erofs_decompress_frontend *fe)
>   	DBG_BUGON(fe->owned_head == Z_EROFS_PCLUSTER_NIL);
>   
>   	if (!(map->m_flags & EROFS_MAP_META)) {
> -		grp = erofs_find_workgroup(sb, blknr);
> +		while (1) {
> +			rcu_read_lock();
> +			grp = xa_load(&EROFS_SB(sb)->managed_pslots, blknr);
> +			if (!grp || erofs_workgroup_get(grp)) {
> +				DBG_BUGON(grp && blknr != grp->index);
> +				rcu_read_unlock();
> +				break;
> +			}
> +			rcu_read_unlock();
> +		}
>   	} else if ((map->m_pa & ~PAGE_MASK) + map->m_plen > PAGE_SIZE) {
>   		DBG_BUGON(1);
>   		return -EFSCORRUPTED;
> diff --git a/fs/erofs/zutil.c b/fs/erofs/zutil.c
> index 37afe2024840..218b0249a482 100644
> --- a/fs/erofs/zutil.c
> +++ b/fs/erofs/zutil.c
> @@ -214,7 +214,7 @@ void erofs_release_pages(struct page **pagepool)
>   	}
>   }
>   
> -static bool erofs_workgroup_get(struct erofs_workgroup *grp)
> +bool erofs_workgroup_get(struct erofs_workgroup *grp)
>   {
>   	if (lockref_get_not_zero(&grp->lockref))
>   		return true;
> @@ -231,54 +231,6 @@ static bool erofs_workgroup_get(struct erofs_workgroup *grp)
>   	return true;
>   }
>   
> -struct erofs_workgroup *erofs_find_workgroup(struct super_block *sb,
> -					     pgoff_t index)
> -{
> -	struct erofs_sb_info *sbi = EROFS_SB(sb);
> -	struct erofs_workgroup *grp;
> -
> -repeat:
> -	rcu_read_lock();
> -	grp = xa_load(&sbi->managed_pslots, index);
> -	if (grp) {
> -		if (!erofs_workgroup_get(grp)) {
> -			/* prefer to relax rcu read side */
> -			rcu_read_unlock();
> -			goto repeat;
> -		}
> -
> -		DBG_BUGON(index != grp->index);
> -	}
> -	rcu_read_unlock();
> -	return grp;
> -}
> -
> -struct erofs_workgroup *erofs_insert_workgroup(struct super_block *sb,
> -					       struct erofs_workgroup *grp)
> -{
> -	struct erofs_sb_info *const sbi = EROFS_SB(sb);
> -	struct erofs_workgroup *pre;
> -
> -	DBG_BUGON(grp->lockref.count < 1);
> -repeat:
> -	xa_lock(&sbi->managed_pslots);
> -	pre = __xa_cmpxchg(&sbi->managed_pslots, grp->index,
> -			   NULL, grp, GFP_KERNEL);
> -	if (pre) {
> -		if (xa_is_err(pre)) {
> -			pre = ERR_PTR(xa_err(pre));
> -		} else if (!erofs_workgroup_get(pre)) {
> -			/* try to legitimize the current in-tree one */
> -			xa_unlock(&sbi->managed_pslots);
> -			cond_resched();
> -			goto repeat;
> -		}
> -		grp = pre;
> -	}
> -	xa_unlock(&sbi->managed_pslots);
> -	return grp;
> -}
> -
>   static void  __erofs_workgroup_free(struct erofs_workgroup *grp)
>   {
>   	atomic_long_dec(&erofs_global_shrink_cnt);