On Thu, Apr 12, 2018 at 10:07:13PM +0200, Martin Wilck wrote: > On Thu, 2018-04-12 at 13:33 -0500, Benjamin Marzinski wrote: > > On Wed, Apr 04, 2018 at 06:16:16PM +0200, Martin Wilck wrote: > > > Create a simple API that indicates failure to create a map for a > > > certain WWID. This will allow multipathd to indicate to other tools > > > (in particular, "multipath -u" during udev processing) that > > > an attempt to create a map for a certain wwid failed. > > > > > > The indicator is simply the existence of a file under > > > /dev/shm/multipath/failed_wwids. > > > > I'm a little confused about the necessity of a lock file here. What > > it > > the race that you are worried about? If two processes try to create a > > file at the same time, surely one of them will succeed. If two > > processes > > try to delete a file at the same time, it will get deleted. If one > > process is trying to create a file and one is trying to remove it, > > the > > outcome depends on the who wins the race. But this is true whether > > you > > add a lock file to make those actions atomic or not. The same goes > > with > > stating a file that's being created or removed. As far a I can tell, > > this should work if you simply create an empty file without any > > locking. > > Are you worried about some odd errno due to a race? > > My thinking was that it's generally a good thing to make file system > operations like this atomic, and the well-tested and mature open_file() > API was there ready to be used, thus I did. > > You're probably right that the locking not strictly necessary. I don't > think it hurts, performance-wise the impact is quite low. > Do you require me to change this, or can we change it later? That's fine. I don't see how it can hurt. Reviewed-by: Benjamin Marzinski <bmarzins@xxxxxxxxxx> > > Martin > > -- > Dr. Martin Wilck <mwilck@xxxxxxxx>, Tel. +49 (0)911 74053 2107 > SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton > HRB 21284 (AG Nürnberg) -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
