From mboxrd@z Thu Jan 1 00:00:00 1970 From: Theodore Ts'o Subject: Re: [RFC] ext4: Add pollable sysfs entry for block threshold events Date: Fri, 13 Mar 2015 11:05:22 -0400 Message-ID: <20150313150522.GA21922@thunk.org> References: <1426068993-1051-1-git-send-email-b.michalska@samsung.com> <1426068993-1051-2-git-send-email-b.michalska@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Beata Michalska , adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, kyungmin.park@samsung.com, linux-fsdevel@vger.kernel.org To: =?utf-8?B?THVrw6HFoQ==?= Czerner Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Wed, Mar 11, 2015 at 03:12:25PM +0100, Luk=C3=A1=C5=A1 Czerner wrote= : >=20 > I though you were advocating for a solution independent on the file > system. This is ext4 only solution, but I do not really have > anything against this. It would be nice if we could have a fs-independent solution so that we don't have to support the ext4-specific interface forever. If we had the thresholds set in struct super, and the file system were to call a function defined in struct super_operations when the file system has gotten too full, this wouldn't be all that hard. The main issue is what is the proper generic way of notifying userspace. Using a pollable sysfs file is one way, although problem with that is we don't yet have a standardized place to locate where, given a particular mounted file system / block device, where to find its hierarchy in the sysfs tree. Right now we have /sys/fs//... but that's owned by the file system and so it get's = a bit tricky to do something generic. Other solutions might be to report file system full (and file system corruption issues, etc.) via a netlink socket, or if we want to do things in a systemd-complaint way, we could use the kernel-level dbus approach which Greg K-H and company are pushing. :-) - Ted