[PATCH 00/23] arch: allow pte_offset_map[_lock]() to fail

Mike Rapoport rppt at kernel.org
Fri May 12 13:38:24 AEST 2023


On Thu, May 11, 2023 at 03:02:55PM +0100, Matthew Wilcox wrote:
> On Wed, May 10, 2023 at 09:35:44PM -0700, Hugh Dickins wrote:
> > On Wed, 10 May 2023, Matthew Wilcox wrote:
> > 
> > I don't really understand why you're going down a remove-CONFIG_HIGHPTE
> > route: I thought you were motivated by the awkardness of kmap on large
> > folios; but I don't see how removing HIGHPTE helps with that at all
> > (unless you have a "large page tables" effort in mind, but I doubt it).
> Quite right, my primary concern is filesystem metadata; primarily
> directories as I don't think anybody has ever supported symlinks or
> superblocks larger than 4kB.
> I was thinking that removing CONFIG_HIGHPTE might simplify the page
> fault handling path a little, but now I've looked at it some more, and
> I'm not sure there's any simplification to be had.  It should probably
> use kmap_local instead of kmap_atomic(), though.
Removing CONFIG_HIGHPTE will drop several lines and will allow to get rid
of custom __pte_alloc_one on x86.

Sincerely yours,

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