On Tue, 12 Aug 2008 12:00:36 -0700 Daniel Phillips <phillips@xxxxxxxxx> wrote: > On Tuesday 12 August 2008 06:14, FUJITA Tomonori wrote: > > > You just want to use getblk for alloc_chunk_buffer, > > > not vmalloc. > > > > I think that it means that we cache all the chunks, both btree chunks > > and the data chunks (which are passed to the upper layer such as file > > systems). I think that we don't want cache the latter in dm. > > That is true. However your code should not be reading data chunks into > memory at all. The only time the snapshot code has to read a data > chunk is when performing the copy from origin to snapshot store in > make_unique. Your code does not directly perform this task as far as I > can see. That would be done in a part of the dm snapshot code your > patch does not touch, which I seem to recall uses the kcopyd mechanism. Yes, dm-snapshot doesn't access to data chunks. However, dm does for dm-snapshot (by using submit_bio friends). So if dm-snapshot uses __getblk, we use both __getblk and submit_bio with a single device at the same time. I think that it's the right thing. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
