On Tue, May 25, 2010 at 08:26:31PM +0200, Albert Herranz wrote: > Hi, > > On 05/25/2010 06:01 PM, Nick Piggin wrote: > > Hi, > > > > I couldn't find where this patch (49bbd815fd8) was discussed, so I'll > > make my own thread. Adding a few lists to cc because it might be of > > interest to driver and filesystem writers. > > > > The original thread can be found here: > http://marc.info/?l=linux-fbdev&m=127369791432181 Thanks. > > The old ->page_mkwrite calling convention was causing problems exactly > > because of this race, and we solved it by allowing page_mkwrite to > > return with the page locked, and the lock will be held until the > > pte is marked dirty. See commit b827e496c893de0c0f142abfaeb8730a2fd6b37f. > > > > Ah, didn't know about that. Thanks for the pointer. > > > I hope that should provide a more elegant solution to your problem. I > > would really like you to take a look at that, because we already have > > filesystem code (NFS) relying on it, and more code we have relying on > > this synchronization, the more chance we would find a subtle problem > > with it (also it should be just nicer). > > > > So if I undestand it correctly, using the "new" calling convention I should just lock the page on fb_deferred_io_mkwrite() and return VM_FAULT_LOCKED to fix the described race for fb_defio. As far as I can see from quick reading of the fb_defio code, yes that should solve it (provided you lock the page inside the mutex, of course). -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>