Date: Thu, 22 Oct 2026 16:14:02 +0800
From: Herbert Xu <herbert@gondor.apana.org.au>
To: Suseendran Bhaskaran <suseendranb@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	"David S . Miller" <davem@davemloft.net>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Yosry Ahmed <yosry@kernel.org>, Nhat Pham <nphamcs@gmail.com>,
	Chengming Zhou <chengming.zhou@linux.dev>,
	Nick Terrell <terrelln@fb.com>, David Sterba <dsterba@suse.com>,
	SJ Park <sj@kernel.org>, Chris Li <chrisl@kernel.org>,
	Giovanni Cabiddu <giovanni.cabiddu@intel.com>,
	Suman Kumar Chakraborty <suman.kumar.chakraborty@intel.com>,
	linux-crypto@vger.kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] crypto: return -ENOSPC on compression destination
 overflow
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References: <20261021205626.3286270-1-suseendranb@google.com>
 <20261021205626.3286270-2-suseendranb@google.com>
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On Wed, Oct 21, 2026 at 08:56:25PM +0000, Suseendran Bhaskaran wrote:
> In the acomp/scomp compression interface, callers pass a bounded
> destination buffer and rely on the return code to distinguish a
> destination buffer overflow (incompressible input) from genuine
> compressor failures (such as invalid parameters, uninitialized state, or
> hardware errors).
> 
> While the multi-segment streaming path in zstd_compress(),
> crypto/deflate.c, and lib/842/842_compress.c returns -ENOSPC when the
> destination buffer runs out of space, the single-buffer path
> zstd_compress_one() (taken when input and output are contiguous single
> pages, such as in zswap) as well as lz4, lz4hc, lzo, and lzo-rle return
> -EINVAL instead of -ENOSPC on destination buffer overflow.
> 
> For users such as zswap, which reduced its per-CPU compression buffer to
> a single page in commit 0b1bf60c324a ("mm/zswap: reduce the size of the
> compression buffer to a single page"), incompressible pages typically
> overflow the PAGE_SIZE destination buffer due to compressor header/token
> overhead. Because these compressors return -EINVAL rather than -ENOSPC,
> zswap cannot distinguish a destination buffer overflow from a compressor
> failure, causing broken debugfs error accounting (reject_compress_fail
> vs. reject_compress_poor) or masking real compressor errors.
> 
> Update zstd_compress_one(), lz4, lz4hc, lzo, and lzo-rle to return
> -ENOSPC when the compressed output overflows the destination buffer,
> matching the streaming path in zstd_compress(), deflate, and 842.
> 
> Fixes: f5ad93ffb541 ("crypto: zstd - convert to acomp")
> Signed-off-by: Suseendran Bhaskaran <suseendranb@google.com>
> ---
>  crypto/lz4.c     | 2 +-
>  crypto/lz4hc.c   | 2 +-
>  crypto/lzo-rle.c | 2 +-
>  crypto/lzo.c     | 2 +-
>  crypto/zstd.c    | 5 ++++-
>  5 files changed, 8 insertions(+), 5 deletions(-)

I can take this patch through the cryptodev tree.  Is that OK with
you Yosry?

Thanks,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt