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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>
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4fdccaa0d1
commit
55b8fe703b
2 changed files with 5 additions and 2 deletions
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@ -2851,7 +2851,8 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
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#define FOLL_FORCE 0x10 /* get_user_pages read/write w/o permission */
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#define FOLL_NOWAIT 0x20 /* if a disk transfer is needed, start the IO
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* and return without waiting upon it */
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#define FOLL_POPULATE 0x40 /* fault in page */
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#define FOLL_POPULATE 0x40 /* fault in pages (with FOLL_MLOCK) */
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#define FOLL_NOFAULT 0x80 /* do not fault in pages */
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#define FOLL_HWPOISON 0x100 /* check page is hwpoisoned */
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#define FOLL_NUMA 0x200 /* force NUMA hinting page fault */
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#define FOLL_MIGRATION 0x400 /* wait for page to replace migration entry */
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4
mm/gup.c
4
mm/gup.c
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@ -918,6 +918,8 @@ static int faultin_page(struct vm_area_struct *vma,
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/* mlock all present pages, but do not fault in new pages */
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if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
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return -ENOENT;
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if (*flags & FOLL_NOFAULT)
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return -EFAULT;
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if (*flags & FOLL_WRITE)
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fault_flags |= FAULT_FLAG_WRITE;
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if (*flags & FOLL_REMOTE)
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@ -2843,7 +2845,7 @@ static int internal_get_user_pages_fast(unsigned long start,
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if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM |
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FOLL_FORCE | FOLL_PIN | FOLL_GET |
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FOLL_FAST_ONLY)))
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FOLL_FAST_ONLY | FOLL_NOFAULT)))
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return -EINVAL;
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if (gup_flags & FOLL_PIN)
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