On Tue, Dec 19, 2017 at 16:59:39 -0700, Chris Murphy wrote: >> Sth like this? I got such problem a few months ago, my solution was >> accepted upstream: >> https://github.com/systemd/systemd/commit/0e8856d25ab71764a279c2377ae593c0f2460d8f > > I can't parse this commit. In particular I can't tell how long it > waits, or what triggers the end to waiting.
The point is - it doesn't wait at all. Instead, every 'ready' btrfs device triggers event on all the pending devices. Consider 3-device filesystem consisting of /dev/sd[abd] with /dev/sdc being different, standalone btrfs: /dev/sda -> 'not ready' /dev/sdb -> 'not ready' /dev/sdc -> 'ready', triggers /dev/sda -> 'not ready' and /dev/sdb - still 'not ready' /dev/sdc -> kernel says 'ready', triggers /dev/sda - 'ready' and /dev/sdb -> 'ready' This way all the parts of a volume are marked as ready, so systemd won't refuse mounting using legacy device nodes like /dev/sda. This particular solution depends on kernel returning 'btrfs ready', which would obviously not work for degraded arrays unless the btrfs.ko handles some 'missing' or 'mount_degraded' kernel cmdline options _before_ actually _trying_ to mount it with -o degraded. And there is a logical problem with this - _which_ array components should be ignored? Consider: volume1: /dev/sda /dev/sdb volume2: /dev/sdc /dev/sdd-broken If /dev/sdd is missing from the system, it would never be scanned, so /dev/sdc would be pending. It cannot be assembled just in time of scanning alone, because the same would happen with /dev/sda and there would be desync with /dev/sdb, which IS available - a few moments later. This is the place for the timeout you've mentioned - there should be *some* decent timeout allowing all the devices to show up (udev waits for 90 seconds by default or x-systemd.device-timeout=N from fstab). After such timeout, I'd like to tell the kernel: "no more devices, give me all the remaining btrfs volumes in degraded mode if possible". By "give me btrfs vulumes" I mean "mark them as 'ready'" so the udev could fire it's rules. And if there would be anything for udev to distinguish 'ready' from 'ready-degraded' one could easily compose some notification scripting on top of it, including sending e-mail to sysadmin. Is there anything that would make the kernel do the above? -- Tomasz Pala <go...@pld-linux.org> -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
