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Date: Tue, 3 Oct 2017 22:06:14 +0200 (CEST) From: Jiri Kosina <jikos@...nel.org> To: "Luis R. Rodriguez" <mcgrof@...nel.org> cc: viro@...iv.linux.org.uk, bart.vanassche@....com, ming.lei@...hat.com, tytso@....edu, darrick.wong@...cle.com, rjw@...ysocki.net, pavel@....cz, len.brown@...el.com, linux-fsdevel@...r.kernel.org, boris.ostrovsky@...cle.com, jgross@...e.com, todd.e.brandt@...ux.intel.com, nborisov@...e.com, jack@...e.cz, martin.petersen@...cle.com, ONeukum@...e.com, oleksandr@...alenko.name, oleg.b.antonyan@...il.com, linux-pm@...r.kernel.org, linux-block@...r.kernel.org, linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [RFC 2/5] fs: freeze on suspend and thaw on resume On Tue, 3 Oct 2017, Luis R. Rodriguez wrote: > This uses the existing filesystem freeze and thaw callbacks to > freeze each filesystem on suspend/hibernation and thaw upon resume. > > This is needed so that we properly really stop IO in flight without > races after userspace has been frozen. Without this we rely on > kthread freezing and its semantics are loose and error prone. > For instance, even though a kthread may use try_to_freeze() and end > up being frozen we have no way of being sure that everything that > has been spawned asynchronously from it (such as timers) have also > been stopped as well. > > A long term advantage of also adding filesystem freeze / thawing > supporting durign suspend / hibernation is that long term we may > be able to eventually drop the kernel's thread freezing completely > as it was originally added to stop disk IO in flight as we hibernate > or suspend. > > This also implies that many kthread users exist which have been > adding freezer semantics onto its kthreads without need. These also > will need to be reviewed later. > > This is based on prior work originally by Rafael Wysocki and later by > Jiri Kosina. > > Signed-off-by: Luis R. Rodriguez <mcgrof@...nel.org> Thanks a lot for picking this up; I never found time to actually finalize it. Acked-by: Jiri Kosina <jkosina@...e.cz> for patches 2 and 5 (the fs agnostic code), which were in the core of my original work. -- Jiri Kosina SUSE Labs
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