On Tue, 2019-07-23 at 10:08 -0700, Christoph Hellwig wrote: > On Tue, Jul 23, 2019 at 01:07:00PM -0400, Jeff Layton wrote: > > Note that those places are already broken. AIUI, the basic issue is that > > vmalloc/vfree have to fix up page tables and that requires being able to > > sleep. This patch just makes this situation more evident. If that patch > > gets merged, I imagine we'll have a lot of places to clean up (not just > > in xfs). > > > > Anyway, in the case of being in an interrupt, we currently queue the > > freeing to a workqueue. Al mentioned that we could create a new > > kvfree_atomic that we could use from atomic contexts like this. That may > > be another option (though Carlos' patch looked reasonable to me and > > would probably be more efficient). > > The point is for XFS we generally only use kmem_free for pure kmalloc > allocations under spinlocks. But yes, the interfac is a little > suboptimal and a kmem_free_large would be nicer and then warnings like > this that might be pretty useful could be added. Ahh ok, I get it now. You're using it as a generic "free this, no matter what it is" wrapper, and relying on the caller to ensure that it will never try to free a vmalloc'ed addr from an atomic context. I wonder how many other places are doing that? I count 858 call sites for kvfree. If significant portion of those are doing this, then we may have to re-think my patch. It seems like the right thing to do, but we there may be more fallout than I expected. -- Jeff Layton <jlayton@xxxxxxxxxx>
