[PATCH] btrfs: fix allocation of bitmap pages.

[Christoph Hellwig]

On Tue, Aug 20, 2019 at 01:06:25PM +0200, Vlastimil Babka wrote:
> > 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 :(
> 
> Meh, I should finally get back to https://lwn.net/Articles/787740/ right

Yes.  For now Dave came up with an idea for a workaround that will
be forward-compatible with that:

https://www.spinics.net/lists/linux-xfs/msg30521.html