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[75.158.111.22]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2adfb6c4dd0sm204135445ad.70.2026.03.04.10.17.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Mar 2026 10:17:53 -0800 (PST) Sender: Paul Tarjan From: Paul Tarjan X-Google-Original-From: Paul Tarjan To: git@vger.kernel.org Cc: ps@pks.im, paul@paultarjan.com Subject: Re: [PATCH v7 08/10] fsmonitor: add tests for Linux Date: Wed, 4 Mar 2026 11:17:52 -0700 Message-ID: <20260304181752.25768-1-github@paulisageek.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: git@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Tue, Mar 4, 2026, Patrick Steinhardt wrote: > Hm. So the fsmonitor listener for Linux is not reliable? Wouldn't the > end user see the same issue then? I'm not sure whether just ignoring > that issue and adding a timeout to our tests is the proper way to fix > it. > > Before we jump to such solutions I'd rather want to know what the root > cause of this. We had similar issues in the past on macOS, where we > eventually figured out that we were missing events due to the buffers > not being big enough. So did you investigate what the conditions are to > trigger this? This isn't a buffer issue or a bug in our code, it's a kernel limitation in overlayfs. On older kernels, overlayfs doesn't implement the fsnotify hooks that inotify depends on, so inotify_add_watch succeeds but events are silently never delivered. Newer kernels have partially fixed this but it still affects some configurations. An end user on overlayfs would hit the same thing: the cookie wait times out and they get a full-scan fallback. Correct results, just no incremental speedup. The smoke test catches this early so we can skip instead of timing out on every subsequent test.