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Thu, 27 Aug 2026 21:30:48 -0700 (PDT) Received: from google.com ([2a00:79e0:2031:6:ff0:ad84:24b0:9e52]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2d7594fc0c9sm1794885ad.2.2026.08.27.21.30.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Aug 2026 21:30:48 -0700 (PDT) Date: Fri, 28 Aug 2026 13:30:43 +0900 From: Sergey Senozhatsky To: Sergey Senozhatsky Cc: Hao Jia , Brian Geffon , minchan@kernel.org, axboe@kernel.dk, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, Hao Jia Subject: Re: [PATCH] zram: fix idle age_sec underflow in idle_store() Message-ID: References: <20260825092316.69658-1-jiahao.kernel@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@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: On (26/08/28 13:23), Sergey Senozhatsky wrote: > Can we instead just reject such cases? It should be an error to > request writeback of pages that are 2y old on a system that has > uptime of 2d. > > Maybe something like this: > > + time64_t uptime; > > - if (IS_ENABLED(CONFIG_ZRAM_TRACK_ENTRY_ACTIME) && > - !kstrtouint(buf, 0, &age_sec)) > - cutoff = ktime_sub((u32)ktime_get_boottime_seconds(), > - age_sec); > - else > + if (!IS_ENABLED(CONFIG_ZRAM_TRACK_ENTRY_ACTIME) || > + kstrtouint(buf, 0, &age_sec)) > return -EINVAL; > + > + /* No slot can be older than the system uptime */ > + uptime = ktime_get_boottime_seconds(); > + if (age_sec >= uptime) > + return -ERANGE; > + > + cutoff = uptime - age_sec; > } > > We are probably fine doing just basic arithmetics operations on those two. > One is u32 the other one is s64: we should be fine just doing >= and sub. > I guess we also can use plain comparison > cutoff > zram->table[index].attr.ac_time > in mark_idle(). Or am I hallucinating? That implies that cutoff becomes time64_t both in idle_store() and in mark_idle().