Commit 9c4b2142 authored by Lorenzo Stoakes's avatar Lorenzo Stoakes Committed by Andrew Morton
Browse files

mm/gup: make failure to pin an error if FOLL_NOWAIT not specified 

There really should be no circumstances under which a non-FOLL_NOWAIT GUP
operation fails to return any pages, so make this an error and warn on it.

To catch the trivial case, simply exit early if nr_pages == 0.

This brings __get_user_pages_locked() in line with the behaviour of its
nommu variant.

Link: https://lkml.kernel.org/r/2a42d96dd1e37163f90a0019a541163dafb7e4c3.1696288092.git.lstoakes@gmail.com


Signed-off-by: default avatarLorenzo Stoakes <lstoakes@gmail.com>
Reviewed-by: default avatarArnd Bergmann <arnd@arndb.de>
Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 0f20bba1

mm/gup.c

+11 −0
Original line number Diff line number Diff line
@@ -1471,6 +1471,9 @@ static __always_inline long __get_user_pages_locked(struct mm_struct *mm, 
	long ret, pages_done;

	bool must_unlock = false;



	if (!nr_pages)

		return 0;



	/*

	 * The internal caller expects GUP to manage the lock internally and the

	 * lock must be released when this returns.
@@ -1595,6 +1598,14 @@ static __always_inline long __get_user_pages_locked(struct mm_struct *mm, 
		mmap_read_unlock(mm);

		*locked = 0;

	}



	/*

	 * Failing to pin anything implies something has gone wrong (except when

	 * FOLL_NOWAIT is specified).

	 */

	if (WARN_ON_ONCE(pages_done == 0 && !(flags & FOLL_NOWAIT)))

		return -EFAULT;



	return pages_done;

}