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Mon, 10 Aug 2026 19:06:45 -0700 (PDT) Received: from google.com ([2a00:79e0:2031:6:ddfb:e755:8f7f:81af]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-392d4050827sm1513560a91.2.2026.08.10.19.06.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 Aug 2026 19:06:45 -0700 (PDT) Date: Tue, 11 Aug 2026 11:06:41 +0900 From: Sergey Senozhatsky To: David Carlier Cc: Minchan Kim , Sergey Senozhatsky , Andrew Morton , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] zram: fix slot lock bit position on big-endian 64-bit Message-ID: References: <20260810202241.2436603-1-devnexen@gmail.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260810202241.2436603-1-devnexen@gmail.com> On (26/08/10 21:22), David Carlier wrote: > The slot lock is a bit operation on the whole __lock word, which > flags and ac_time alias as two u32s. On little-endian the lock bit > lands in the position ZRAM_ENTRY_LOCK reserves in flags, so the > aliasing works out. On 64-bit big-endian it lands in ac_time > instead: with ZRAM_TRACK_ENTRY_ACTIME enabled, storing the access > time from mark_slot_accessed() or slot_free() wipes out the held > lock bit, letting another CPU take the same slot lock; an access > time value with that bit set makes the slot look locked forever. > > Shift the lock bit into the flags half of the word on big-endian > 64-bit. > > Fixes: 2e8ff2f51dde ("zram: use u32 for entry ac_time tracking") > Cc: stable@vger.kernel.org > Signed-off-by: David Carlier Reviewed-by: Sergey Senozhatsky