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Wed, 18 Mar 2026 21:05:59 -0700 (PDT) Received: from google.com ([2a00:79e0:2031:6:13e1:7517:52f3:cfc8]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-35bc6017492sm1281973a91.5.2026.03.18.21.05.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Mar 2026 21:05:59 -0700 (PDT) Date: Thu, 19 Mar 2026 13:05:55 +0900 From: Sergey Senozhatsky To: Sergey Senozhatsky Cc: Andrew Morton , Minchan Kim , Brian Geffon , Richard Chang , linux-block@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] zram: do not slot_free() written-back slots Message-ID: References: <20260319034912.1894770-1-senozhatsky@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260319034912.1894770-1-senozhatsky@chromium.org> X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: C93D4100010 X-Stat-Signature: 4udjn71jwujhf6fjis86u65sn1izq4s4 X-Rspam-User: X-HE-Tag: 1773893160-318549 X-HE-Meta: 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 wTMgxsVJ gLBhcPo6dOVgrrI0GkjMDmNaxog== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: As a side note: On (26/03/19 12:44), Sergey Senozhatsky wrote: > - slot_free(zram, index); [..] > - if (huge) > - set_slot_flag(zram, index, ZRAM_HUGE); Original code had a bug. slot_free() would decrement ->huge_pages, then writeback completion would restore the HUGE flag, so when slot would get freed for real slot_free() would decrement ->huge_pages again, leading to underflow.