Date: Wed, 29 Sep 2021 16:17:01 +0300 From: Andriy Gapon <avg@freebsd.org> To: Alan Somers <asomers@freebsd.org> Cc: freebsd-fs <fs@freebsd.org> Subject: Re: vfs.zfs.vol.recursive completely broken, time to remove? Message-ID: <b94786f0-8e37-89b6-2c28-47d4b92f6447@FreeBSD.org> In-Reply-To: <CAOtMX2guaaAUsyi0BSxdBL9qRrS%2BXC6bGNhpqXf6F9JJXA973w@mail.gmail.com> References: <10583cba-c2f5-ffbe-5a1b-8dfcd8114b4d@FreeBSD.org> <CAOtMX2guaaAUsyi0BSxdBL9qRrS%2BXC6bGNhpqXf6F9JJXA973w@mail.gmail.com>
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On 29/09/2021 16:05, Alan Somers wrote: > On Wed, Sep 29, 2021 at 12:10 AM Andriy Gapon <avg@freebsd.org> wrote: >> >> >> It seems that while previously there could sometimes be a deadlock with >> vfs.zfs.vol.recursive=1, now it is guaranteed. >> >> There was an OpenZFS change to use a pool of threads for vdev opening (to >> parallelize / speed up). When such a thread opens a zvol it needs to acquire >> spa_namespace_lock. But the lock is already held by a thread requesting the >> operation such as a thread doing zpool import (spa_load). >> So, it's an obvious deadlock: the main thread is waiting for the workers while >> holding the namespace lock, at least one of the workers is blocked on the same lock. > > The last time I tried that there was pushback from a lot of different > people. I think we need to fix it instead. Here's the beginning of > that flame war. > https://docs.freebsd.org/cgi/getmsg.cgi?fetch=1031189+0+archive/2016/svn-src-all/20160124.svn-src-all > Back then it probably had a chance of working. At least, I have been using it for a long time without much problems. Now (for the past half a year or so) it's completely unusable. -- Andriy Gaponhelp
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