From: Sergey Senozhatsky <senozhatsky@chromium.org>
To: Nhat Pham <nphamcs@gmail.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>,
Andrew Morton <akpm@linux-foundation.org>,
Yosry Ahmed <yosry.ahmed@linux.dev>,
Johannes Weiner <hannes@cmpxchg.org>,
Brian Geffon <bgeffon@google.com>,
Minchan Kim <minchan@kernel.org>,
Richard Chang <richardycc@google.com>,
linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: [PATCH v2 08/11] zsmalloc: encode 1-based obj_idx so valid obj is never 0
Date: Wed, 11 Nov 2026 13:45:51 +0900 [thread overview]
Message-ID: <avPy0QUkvtzNy8aA@google.com> (raw)
In-Reply-To: <CAKEwX=OhvH80f-6emK0fBhbm2d4Er0rQ8oXX=FmfG0vrTdvZdA@mail.gmail.com>
On (26/11/10 10:57), Nhat Pham wrote:
> > The next patch embeds struct zs_handle into zram and zswap entries,
> > and a handle is considered allocated when its obj is not 0. But obj
> > can be 0: object 0 of a zspage whose first page is PFN 0 encodes to
> > 0, and some platforms do give PFN 0 to the page allocator.
> >
> > Store obj_idx + 1 in obj, so that a valid obj is never 0, and adjust
> > ZS_MIN_ALLOC_SIZE so that the largest index still fits. Unlike a
> > separate tag bit, this doesn't take any bits from obj. zsmalloc did
> > the same before handles moved to handle_cachep, see
> > commit 67296874eb1c ("staging: zsmalloc: Ensure handle is never 0 on
> > success").
> >
> > Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
>
> Bit convoluted, I assume the this is so that we can use obj's 0 value
> to mark unallocated state?
Correct, 0 is for zs_handle_is_allocated().
next prev parent reply other threads:[~2026-11-11 4:45 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-10 5:48 [PATCH v2 00/11] zsmalloc: redesign object alloc API Sergey Senozhatsky
2026-11-10 5:48 ` [PATCH v2 01/11] zram: drop stale comment in write_incompressible_page() Sergey Senozhatsky
2026-11-10 5:48 ` [PATCH v2 02/11] zram: drop get_slot_handle() and set_slot_handle() Sergey Senozhatsky
2026-11-10 5:48 ` [PATCH v2 03/11] zsmalloc: return handle from obj_allocated() Sergey Senozhatsky
2026-11-10 16:28 ` Yosry Ahmed
2026-11-10 17:37 ` Nhat Pham
2026-11-10 5:48 ` [PATCH v2 04/11] zsmalloc: switch handle type to struct zs_handle Sergey Senozhatsky
2026-11-10 16:35 ` Yosry Ahmed
2026-11-11 4:15 ` Sergey Senozhatsky
2026-11-10 17:40 ` Nhat Pham
2026-11-10 5:48 ` [PATCH v2 05/11] zram: check mem_limit before allocating zsmalloc object Sergey Senozhatsky
2026-11-10 18:37 ` sashiko-bot
2026-11-11 4:20 ` Sergey Senozhatsky
2026-11-10 5:48 ` [PATCH v2 06/11] zram: allocate zsmalloc object under slot lock Sergey Senozhatsky
2026-11-10 5:48 ` [PATCH v2 07/11] zswap: do not free the entry if its pool is NULL Sergey Senozhatsky
2026-11-10 16:37 ` Yosry Ahmed
2026-11-10 17:42 ` Nhat Pham
2026-11-10 5:48 ` [PATCH v2 08/11] zsmalloc: encode 1-based obj_idx so valid obj is never 0 Sergey Senozhatsky
2026-11-10 16:44 ` Yosry Ahmed
2026-11-11 4:44 ` Sergey Senozhatsky
2026-11-10 17:57 ` Nhat Pham
2026-11-11 4:45 ` Sergey Senozhatsky [this message]
2026-11-10 18:37 ` sashiko-bot
2026-11-11 4:24 ` Sergey Senozhatsky
2026-11-10 5:48 ` [PATCH v2 09/11] zsmalloc: embed struct zs_handle into zram and zswap entries Sergey Senozhatsky
2026-11-10 16:57 ` Yosry Ahmed
2026-11-10 17:55 ` Nhat Pham
2026-11-10 5:48 ` [PATCH v2 10/11] zsmalloc: fold zs_obj_write() into zs_store() Sergey Senozhatsky
2026-11-10 17:00 ` Yosry Ahmed
2026-11-10 18:01 ` Nhat Pham
2026-11-11 6:05 ` Sergey Senozhatsky
2026-11-10 5:48 ` [PATCH v2 11/11] zsmalloc: populate new zspage outside class->lock in zs_store() Sergey Senozhatsky
2026-11-10 17:03 ` Yosry Ahmed
2026-11-10 18:06 ` Nhat Pham
2026-11-10 16:16 ` [PATCH v2 00/11] zsmalloc: redesign object alloc API Yosry Ahmed
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