mm/gup: require FOLL_GET for get_user_pages_fast()
Internal to mm/gup.c, require that get_user_pages_fast() and __get_user_pages_fast() identify themselves, by setting FOLL_GET. This is required in order to be able to make decisions based on "FOLL_PIN, or FOLL_GET, or both or neither are set", in upcoming patches. Signed-off-by: John Hubbard <jhubbard@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Jan Kara <jack@suse.cz> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Ira Weiny <ira.weiny@intel.com> Cc: Jérôme Glisse <jglisse@redhat.com> Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@infradead.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Vlastimil Babka <vbabka@suse.cz> Link: http://lkml.kernel.org/r/20200211001536.1027652-6-jhubbard@nvidia.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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mm/gup.c
19
mm/gup.c
@ -2390,6 +2390,14 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
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unsigned long len, end;
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unsigned long flags;
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int nr = 0;
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/*
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* Internally (within mm/gup.c), gup fast variants must set FOLL_GET,
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* because gup fast is always a "pin with a +1 page refcount" request.
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*/
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unsigned int gup_flags = FOLL_GET;
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if (write)
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gup_flags |= FOLL_WRITE;
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start = untagged_addr(start) & PAGE_MASK;
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len = (unsigned long) nr_pages << PAGE_SHIFT;
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@ -2415,7 +2423,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
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if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) &&
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gup_fast_permitted(start, end)) {
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local_irq_save(flags);
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gup_pgd_range(start, end, write ? FOLL_WRITE : 0, pages, &nr);
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gup_pgd_range(start, end, gup_flags, pages, &nr);
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local_irq_restore(flags);
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}
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@ -2454,7 +2462,7 @@ static int internal_get_user_pages_fast(unsigned long start, int nr_pages,
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int nr = 0, ret = 0;
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if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM |
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FOLL_FORCE | FOLL_PIN)))
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FOLL_FORCE | FOLL_PIN | FOLL_GET)))
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return -EINVAL;
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start = untagged_addr(start) & PAGE_MASK;
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@ -2521,6 +2529,13 @@ int get_user_pages_fast(unsigned long start, int nr_pages,
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if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
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return -EINVAL;
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/*
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* The caller may or may not have explicitly set FOLL_GET; either way is
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* OK. However, internally (within mm/gup.c), gup fast variants must set
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* FOLL_GET, because gup fast is always a "pin with a +1 page refcount"
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* request.
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*/
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gup_flags |= FOLL_GET;
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return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
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}
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EXPORT_SYMBOL_GPL(get_user_pages_fast);
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