Re: [PATCH] btrfs: fix allocation of bitmap pages.

On Tue, Aug 20, 2019 at 01:06:25PM +0200, Vlastimil Babka wrote:

quoted

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