[PATCH] mm: zsmalloc: return -ENOSPC rather than -EINVAL in zs_malloc while size is too large

[PATCH] mm: zsmalloc: return -ENOSPC rather than -EINVAL in zs_malloc while size is too large

[Barry Song]

This is the case the "compressed" data is larger than the original data,
it is better to return -ENOSPC which can help zswap record a poor compr
rather than an invalid request. Then we get more friendly counting for
reject_compress_poor in debugfs.

 bool zswap_store(struct folio *folio)
 {
 	...
 	ret = zpool_malloc(zpool, dlen, gfp, &handle);
 	if (ret == -ENOSPC) {
 		zswap_reject_compress_poor++;
 		goto put_dstmem;
 	}
 	if (ret) {
 		zswap_reject_alloc_fail++;
 		goto put_dstmem;
 	}
 	...
 }

Also, zbud_alloc() and z3fold_alloc() are returning ENOSPC in the same
case, eg
 static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
 			unsigned long *handle)
 {
 	...
 	if (!size || (gfp & __GFP_HIGHMEM))
 		return -EINVAL;

 	if (size > PAGE_SIZE)
 		return -ENOSPC;
 	...
 }

Signed-off-by: Barry Song <v-songbaohua@oppo.com>
---
 mm/zsmalloc.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index b1c0dad7f4cf..c937635e0ad1 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -1364,9 +1364,12 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t gfp)
 	int newfg;
 	struct zspage *zspage;
 
-	if (unlikely(!size || size > ZS_MAX_ALLOC_SIZE))
+	if (unlikely(!size))
 		return (unsigned long)ERR_PTR(-EINVAL);
 
+	if (unlikely(size > ZS_MAX_ALLOC_SIZE))
+		return (unsigned long)ERR_PTR(-ENOSPC);
+
 	handle = cache_alloc_handle(pool, gfp);
 	if (!handle)
 		return (unsigned long)ERR_PTR(-ENOMEM);
-- 
2.34.1

Re: [PATCH] mm: zsmalloc: return -ENOSPC rather than -EINVAL in zs_malloc while size is too large

[Chengming Zhou]

On 2023/12/28 14:18, Barry Song wrote:
> This is the case the "compressed" data is larger than the original data,
> it is better to return -ENOSPC which can help zswap record a poor compr
> rather than an invalid request. Then we get more friendly counting for
> reject_compress_poor in debugfs.
> 
>  bool zswap_store(struct folio *folio)
>  {
>  	...
>  	ret = zpool_malloc(zpool, dlen, gfp, &handle);
>  	if (ret == -ENOSPC) {
>  		zswap_reject_compress_poor++;
>  		goto put_dstmem;
>  	}
>  	if (ret) {
>  		zswap_reject_alloc_fail++;
>  		goto put_dstmem;
>  	}
>  	...
>  }
> 
> Also, zbud_alloc() and z3fold_alloc() are returning ENOSPC in the same
> case, eg
>  static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
>  			unsigned long *handle)
>  {
>  	...
>  	if (!size || (gfp & __GFP_HIGHMEM))
>  		return -EINVAL;
> 
>  	if (size > PAGE_SIZE)
>  		return -ENOSPC;
>  	...
>  }
> 
> Signed-off-by: Barry Song <v-songbaohua@oppo.com>

Looks good to me.

Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>

Thanks.

> ---
>  mm/zsmalloc.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index b1c0dad7f4cf..c937635e0ad1 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -1364,9 +1364,12 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t gfp)
>  	int newfg;
>  	struct zspage *zspage;
>  
> -	if (unlikely(!size || size > ZS_MAX_ALLOC_SIZE))
> +	if (unlikely(!size))
>  		return (unsigned long)ERR_PTR(-EINVAL);
>  
> +	if (unlikely(size > ZS_MAX_ALLOC_SIZE))
> +		return (unsigned long)ERR_PTR(-ENOSPC);
> +
>  	handle = cache_alloc_handle(pool, gfp);
>  	if (!handle)
>  		return (unsigned long)ERR_PTR(-ENOMEM);

Re: [PATCH] mm: zsmalloc: return -ENOSPC rather than -EINVAL in zs_malloc while size is too large

[Nhat Pham]

On Wed, Dec 27, 2023 at 10:18 PM Barry Song <21cnbao@gmail.com> wrote:
>
> This is the case the "compressed" data is larger than the original data,
> it is better to return -ENOSPC which can help zswap record a poor compr
> rather than an invalid request. Then we get more friendly counting for
> reject_compress_poor in debugfs.
>
>  bool zswap_store(struct folio *folio)
>  {
>         ...
>         ret = zpool_malloc(zpool, dlen, gfp, &handle);
>         if (ret == -ENOSPC) {
>                 zswap_reject_compress_poor++;
>                 goto put_dstmem;
>         }
>         if (ret) {
>                 zswap_reject_alloc_fail++;
>                 goto put_dstmem;
>         }
>         ...
>  }
>
> Also, zbud_alloc() and z3fold_alloc() are returning ENOSPC in the same
> case, eg
>  static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
>                         unsigned long *handle)
>  {
>         ...
>         if (!size || (gfp & __GFP_HIGHMEM))
>                 return -EINVAL;
>
>         if (size > PAGE_SIZE)
>                 return -ENOSPC;
>         ...
>  }
>
> Signed-off-by: Barry Song <v-songbaohua@oppo.com>
> ---
>  mm/zsmalloc.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index b1c0dad7f4cf..c937635e0ad1 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -1364,9 +1364,12 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t gfp)
>         int newfg;
>         struct zspage *zspage;
>
> -       if (unlikely(!size || size > ZS_MAX_ALLOC_SIZE))
> +       if (unlikely(!size))
>                 return (unsigned long)ERR_PTR(-EINVAL);
>
> +       if (unlikely(size > ZS_MAX_ALLOC_SIZE))
> +               return (unsigned long)ERR_PTR(-ENOSPC);
> +
>         handle = cache_alloc_handle(pool, gfp);
>         if (!handle)
>                 return (unsigned long)ERR_PTR(-ENOMEM);
> --
> 2.34.1
>

LGTM.
Reviewed-by: Nhat Pham <nphamcs@gmail.com>