+ mm-zsmalloc-return-enospc-rather-than-einval-in-zs_malloc-while-size-is-too-large.patch added to mm-unstable branch

+ mm-zsmalloc-return-enospc-rather-than-einval-in-zs_malloc-while-size-is-too-large.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm: zsmalloc: return -ENOSPC rather than -EINVAL in zs_malloc while size is too large
has been added to the -mm mm-unstable branch.  Its filename is
     mm-zsmalloc-return-enospc-rather-than-einval-in-zs_malloc-while-size-is-too-large.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-zsmalloc-return-enospc-rather-than-einval-in-zs_malloc-while-size-is-too-large.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Barry Song <21cnbao@gmail.com>
Subject: mm: zsmalloc: return -ENOSPC rather than -EINVAL in zs_malloc while size is too large
Date: Thu, 28 Dec 2023 19:18:02 +1300

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;
 	...
 }

Link: https://lkml.kernel.org/r/20231228061802.25280-1-v-songbaohua@oppo.com
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/zsmalloc.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/mm/zsmalloc.c~mm-zsmalloc-return-enospc-rather-than-einval-in-zs_malloc-while-size-is-too-large
+++ a/mm/zsmalloc.c
@@ -1364,9 +1364,12 @@ unsigned long zs_malloc(struct zs_pool *
 	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);
_

Patches currently in -mm which might be from 21cnbao@gmail.com are

mm-zsmalloc-return-enospc-rather-than-einval-in-zs_malloc-while-size-is-too-large.patch

Re: + mm-zsmalloc-return-enospc-rather-than-einval-in-zs_malloc-while-size-is-too-large.patch added to mm-unstable branch

[Sergey Senozhatsky]

On (23/12/28 11:12), Andrew Morton 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;
>  	...
>  }
> 
> Link: https://lkml.kernel.org/r/20231228061802.25280-1-v-songbaohua@oppo.com
> Signed-off-by: Barry Song <v-songbaohua@oppo.com>
> Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
> Cc: Chris Li <chrisl@kernel.org>
> Cc: Dan Streetman <ddstreet@ieee.org>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Minchan Kim <minchan@kernel.org>
> Cc: Nhat Pham <nphamcs@gmail.com>
> Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
> Cc: Seth Jennings <sjenning@redhat.com>
> Cc: Vitaly Wool <vitaly.wool@konsulko.com>
> Cc: Yosry Ahmed <yosryahmed@google.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Acked-by: Sergey Senozhatsky <senozhatsky@chromium.org>