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Mon, 24 Feb 2025 20:43:01 -0800 (PST) Received: from google.com ([2401:fa00:8f:203:e27d:842a:e0d1:29c4]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2230a00a970sm4651855ad.69.2025.02.24.20.42.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Feb 2025 20:43:00 -0800 (PST) Date: Tue, 25 Feb 2025 13:42:55 +0900 From: Sergey Senozhatsky To: Sebastian Andrzej Siewior Cc: Sergey Senozhatsky , Andrew Morton , Yosry Ahmed , Hillf Danton , Kairui Song , Minchan Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v8 14/17] zram: permit reclaim in zstd custom allocator Message-ID: References: <20250221222958.2225035-1-senozhatsky@chromium.org> <20250221222958.2225035-15-senozhatsky@chromium.org> <20250224091036.Y9fHrKr-@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250224091036.Y9fHrKr-@linutronix.de> X-Rspamd-Queue-Id: 3C74D120005 X-Stat-Signature: 9gs8exqrchor3rjrpdczm6ihb1qhp3ae X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1740458582-481375 X-HE-Meta: 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 3WhAg5q3 m0R2B6mRJ5S+DdwoDB2pMUuqVF/fRL7Pjo7Hq6ZpQelsw2p5XDPVUog5H2CaZv9PXTiCixSFgrg9izg9kOmVmy2gD6OxJ+ZMxe5aURH9n7xJnGUxlcjYShrHL1PWeHC9zd73p/d+OSjkwGEgNmM8n/TP1vs5txgwM1FraGpQ4IsS2zv0fguYz2qLy7igIBqMcALZYByg6GgniaDzjlLLYA/gHgVH1k2MWPwOzEqZJN5Uy0d9PX/cSoovo5pqCdYJ208S731D1bk8l2xVnB8IhK2x8ZxCg26pmPAecOz+dw0B2pxpPPUYGc3ycV1oUyqJJgmIMytHk+PDVpnMS+OIyVAO/PyBiRv06ZSx34GwLbSBWV64= X-Bogosity: Ham, tests=bogofilter, spamicity=0.006258, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On (25/02/24 10:10), Sebastian Andrzej Siewior wrote: > On 2025-02-22 07:25:45 [+0900], Sergey Senozhatsky wrote: > > static void *zstd_custom_alloc(void *opaque, size_t size) > > { > > - if (!preemptible()) > > + /* Technically this should not happen */ > > + if (WARN_ON_ONCE(!preemptible())) > > return kvzalloc(size, GFP_ATOMIC); > > This check works only on preemptible kernels. I'm not sure this is true. > If you run this on !PREEMPTIBLE kernels, preemptible() reports always 0 > so that WARNING will always trigger there. I thought that preemptible() depends on PREEMPT_COUNT, not on PREEMPTIBLE, because even on !PREEMPTIBLE preempt-count still holds hard/soft irq counts, etc. I ran CONFIG_PREEMPT_NONE=y zram-zstd tests and didn't see any warnings.