[PATCH v2 0/1] mm/gup: avoid an unnecessary allocation call for FOLL_LONGTERM cases

[John Hubbard]

This applies to today's mm-hotfixes-unstable (only). In order to test
this, my earlier patch is a prequisite: commit 255231c75dcd ("mm/gup:
stop leaking pinned pages in low memory conditions").

Changes since v1 [1]:

1) Completely different implementation: instead of changing the
allocator from kmalloc() to kvmalloc(), just avoid allocations entirely.

Note that David's original suggestion [2] included something that I've
left out for now, mostly because it's a pre-existing question and
deserves its own patch. But also, I don't understand it yet, either.


[1] https://lore.kernel.org/20241030030116.670307-1-jhubbard@xxxxxxxxxx

[2] https://lore.kernel.org/8d9dc103-47c5-4719-971a-31efb091432a@xxxxxxxxxx


thanks,
John Hubbard

Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Vivek Kasireddy <vivek.kasireddy@xxxxxxxxx>
Cc: Dave Airlie <airlied@xxxxxxxxxx>
Cc: Gerd Hoffmann <kraxel@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Dongwon Kim <dongwon.kim@xxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Junxiao Chang <junxiao.chang@xxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: linux-stable@xxxxxxxxxxxxxxx

John Hubbard (1):
  mm/gup: avoid an unnecessary allocation call for FOLL_LONGTERM cases

 mm/gup.c | 116 ++++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 77 insertions(+), 39 deletions(-)


base-commit: 0012ab094cad019afcd07bdfc28e2946537e715c
-- 
2.47.0