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gup: Introduce FOLL_NOFAULT flag to disable page faults

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commit 55b8fe703bc51200d4698596c90813453b35ae63 upstream

Introduce a new FOLL_NOFAULT flag that causes get_user_pages to return
-EFAULT when it would otherwise trigger a page fault.  This is roughly
similar to FOLL_FAST_ONLY but available on all architectures, and less
fragile.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Andreas Gruenbacher
2022-04-15 06:28:51 +08:00
committed by Greg Kroah-Hartman
parent d3b744791b
commit 6e213bc614
2 changed files with 5 additions and 2 deletions
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3
include/linux/mm.h
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@@ -2858,7 +2858,8 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
#define FOLL_FORCE 0x10 /* get_user_pages read/write w/o permission */
#define FOLL_NOWAIT 0x20 /* if a disk transfer is needed, start the IO
* and return without waiting upon it */
#define FOLL_POPULATE 0x40 /* fault in page */
#define FOLL_POPULATE 0x40 /* fault in pages (with FOLL_MLOCK) */
#define FOLL_NOFAULT 0x80 /* do not fault in pages */
#define FOLL_HWPOISON 0x100 /* check page is hwpoisoned */
#define FOLL_NUMA 0x200 /* force NUMA hinting page fault */
#define FOLL_MIGRATION 0x400 /* wait for page to replace migration entry */