mm/gup: require FOLL_GET for get_user_pages_fast() (94202f12) · Commits · 戴 / test

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>

mm/gup.c

+17 −2

Original line number	Diff line number	Diff line
		@@ -2390,6 +2390,14 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
		unsigned long len, end;
		unsigned long flags;
		int nr = 0;
		/*
		* Internally (within mm/gup.c), gup fast variants must set FOLL_GET,
		* because gup fast is always a "pin with a +1 page refcount" request.
		*/
		unsigned int gup_flags = FOLL_GET;

		if (write)
		gup_flags \|= FOLL_WRITE;

		start = untagged_addr(start) & PAGE_MASK;
		len = (unsigned long) nr_pages << PAGE_SHIFT;
		@@ -2415,7 +2423,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
		if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) &&
		gup_fast_permitted(start, end)) {
		local_irq_save(flags);
		gup_pgd_range(start, end, write ? FOLL_WRITE : 0, pages, &nr);
		gup_pgd_range(start, end, gup_flags, pages, &nr);
		local_irq_restore(flags);
		}

		@@ -2454,7 +2462,7 @@ static int internal_get_user_pages_fast(unsigned long start, int nr_pages,
		int nr = 0, ret = 0;

		if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE \| FOLL_LONGTERM \|
		FOLL_FORCE \| FOLL_PIN)))
		FOLL_FORCE \| FOLL_PIN \| FOLL_GET)))
		return -EINVAL;

		start = untagged_addr(start) & PAGE_MASK;
		@@ -2521,6 +2529,13 @@ int get_user_pages_fast(unsigned long start, int nr_pages,
		if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
		return -EINVAL;

		/*
		* The caller may or may not have explicitly set FOLL_GET; either way is
		* OK. However, internally (within mm/gup.c), gup fast variants must set
		* FOLL_GET, because gup fast is always a "pin with a +1 page refcount"
		* request.
		*/
		gup_flags \|= FOLL_GET;
		return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
		}
		EXPORT_SYMBOL_GPL(get_user_pages_fast);

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