From: Nhat Pham <nphamcs@gmail.com>
To: SeongJae Park <sj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Chengming Zhou <chengming.zhou@linux.dev>,
Johannes Weiner <hannes@cmpxchg.org>,
Takero Funaki <flintglass@gmail.com>,
Yosry Ahmed <yosry.ahmed@linux.dev>,
kernel-team@meta.com, linux-kernel@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: [RFC PATCH] mm/zswap: store compression failed page as-is
Date: Wed, 30 Jul 2025 17:22:51 -0700 [thread overview]
Message-ID: <CAKEwX=Py+yvxtR5zt-1DtskhGWWHkRP_h8kneEHSrcQ947=m9Q@mail.gmail.com> (raw)
In-Reply-To: <CAKEwX=NC65XCkmX1YzivEJtPc+sEJ3pLHUsYhF60QJnk_OtpVw@mail.gmail.com>
On Wed, Jul 30, 2025 at 5:21 PM Nhat Pham <nphamcs@gmail.com> wrote:
>
> On Wed, Jul 30, 2025 at 4:41 PM SeongJae Park <sj@kernel.org> wrote:
>
> This might not be safe.
>
> It's conceivable that in zswap_compress(), some compression algorithm
> "successfully" compresses a page to the same size (comp_ret == 0). We
> hand that to zsmalloc, which happily stores the page.
>
> When we "decompress" the page again, we will attempt to
> memcpy_to_folio from a bogus address (the handle from zsmalloc).
>
> So, in zswap_compress, you have to treat both comp_ret == 0 and dlen
> == PAGE_SIZE as "compression failure".
Meant to say comp_ret != 0 here... sorry for the confusion...
next prev parent reply other threads:[~2025-07-31 0:23 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-30 23:40 SeongJae Park
2025-07-31 0:21 ` Nhat Pham
2025-07-31 0:22 ` Nhat Pham [this message]
2025-07-31 16:43 ` SeongJae Park
2025-07-31 16:43 ` SeongJae Park
2025-07-31 0:48 ` Nhat Pham
2025-07-31 16:56 ` SeongJae Park
2025-07-31 15:27 ` Johannes Weiner
2025-07-31 17:09 ` SeongJae Park
2025-07-31 18:16 ` Johannes Weiner
2025-07-31 17:20 ` Joshua Hahn
2025-08-01 19:57 ` SeongJae Park
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