From: Beata Michalska Subject: Re: [RFC 1/4] fs: Add generic file system event notifications Date: Fri, 17 Apr 2015 18:25:37 +0200 Message-ID: <55313401.5080008@samsung.com> References: <1429082147-4151-1-git-send-email-b.michalska@samsung.com> <1429082147-4151-2-git-send-email-b.michalska@samsung.com> <20150417113110.GD3116@quack.suse.cz> <553104E5.2040704@samsung.com> <55310957.3070101@gmail.com> <55311DE2.9000901@redhat.com> <20150417154351.GA26736@quack.suse.cz> <55312FEA.3030905@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: Jan Kara , Austin S Hemmelgarn , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, tytso-3s7WtUTddSA@public.gmane.org, adilger.kernel-m1MBpc4rdrD3fQ9qLvQP4Q@public.gmane.org, hughd-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, lczerner-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, kyungmin.park-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org, kmpark-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, Linux Filesystem Mailing List , linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: John Spray Return-path: In-reply-to: <55312FEA.3030905-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-ext4.vger.kernel.org On 04/17/2015 06:08 PM, John Spray wrote: > > On 17/04/2015 16:43, Jan Kara wrote: >> On Fri 17-04-15 15:51:14, John Spray wrote: >>> On 17/04/2015 14:23, Austin S Hemmelgarn wrote: >>> >>>> For some filesystems, it may make sense to differentiate between a >>>> generic warning and an error. For BTRFS and ZFS for example, if >>>> there is a csum error on a block, this will get automatically >>>> corrected in many configurations, and won't require anything like >>>> fsck to be run, but monitoring applications will still probably >>>> want to be notified. >>> Another key differentiation IMHO is between transient errors (like >>> server is unavailable in a distributed filesystem) that will block >>> the filesystem but might clear on their own, vs. permanent errors >>> like unreadable drives that definitely will not clear until the >>> administrator takes some action. It's usually a reasonable >>> approximation to call transient issues warnings, and permanent >>> issues errors. >> So you can have events like FS_UNAVAILABLE and FS_AVAILABLE but what use >> would this have? I wouldn't like the interface to be dumping ground for >> random crap - we have dmesg for that :). > In that case I'm confused -- why would ENOSPC be an appropriate use of this interface if the mount being entirely blocked would be inappropriate? Isn't being unable to service any I/O a more fundamental and severe thing than being up and healthy but full? > > Were you intending the interface to be exclusively for data integrity issues like checksum failures, rather than more general events about a mount that userspace would probably like to know about? > > John > I think we should support both and leave the decision on what is to be reported or not to particular file systems keeping it to a reasonable extent, of course. The interface should hand it over to user space - acting as a go-between. I would though avoid any filesystem specific events (when it comes to specifying those), keeping it as generic as possible. BR Beata