On Mon, Aug 19, 2019 at 07:46:00PM +0200, David Sterba wrote: > Another thing that is lost is the slub debugging support for all > architectures, because get_zeroed_pages lacking the red zones and sanity > checks. > > I find working with raw pages in this code a bit inconsistent with the > rest of btrfs code, but that's rather minor compared to the above. > > Summing it up, I think that the proper fix should go to copy_page > implementation on architectures that require it or make it clear what > are the copy_page constraints. The whole point of copy_page is to copy exactly one page and it makes sense to assume that is aligned. A sane memcpy would use the same underlying primitives as well after checking they fit. So I think the prime issue here is btrfs' use of copy_page instead of memcpy. The secondary issue is slub fucking up alignments for no good reason. We just got bitten by that crap again in XFS as well :(
