diff options
| author | Andreas Gruenbacher <agruenba@redhat.com> | 2021-08-17 22:52:08 +0200 |
|---|---|---|
| committer | Andreas Gruenbacher <agruenba@redhat.com> | 2021-10-24 15:26:05 +0200 |
| commit | 55b8fe703bc51200d4698596c90813453b35ae63 (patch) | |
| tree | 9a7f9a0bcf98aea2fe8f3c7dcf483c75ffd6f6ea | |
| parent | 4fdccaa0d184c202f98d73b24e3ec8eeee88ab8d (diff) | |
gup: Introduce FOLL_NOFAULT flag to disable page faults
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>
| -rw-r--r-- | include/linux/mm.h | 3 | ||||
| -rw-r--r-- | mm/gup.c | 4 |
2 files changed, 5 insertions, 2 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 73a52aba448f..2f0e6b9f8f3b 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2851,7 +2851,8 @@ 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 */ @@ -918,6 +918,8 @@ static int faultin_page(struct vm_area_struct *vma, /* mlock all present pages, but do not fault in new pages */ if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK) return -ENOENT; + if (*flags & FOLL_NOFAULT) + return -EFAULT; if (*flags & FOLL_WRITE) fault_flags |= FAULT_FLAG_WRITE; if (*flags & FOLL_REMOTE) @@ -2843,7 +2845,7 @@ static int internal_get_user_pages_fast(unsigned long start, if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM | FOLL_FORCE | FOLL_PIN | FOLL_GET | - FOLL_FAST_ONLY))) + FOLL_FAST_ONLY | FOLL_NOFAULT))) return -EINVAL; if (gup_flags & FOLL_PIN) |