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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: Lorenzo Stoakes <lstoakes@gmail.com> Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: David 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: Andrew Morton <akpm@linux-foundation.org>
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mm/gup.c
11
mm/gup.c
@ -1471,6 +1471,9 @@ static __always_inline long __get_user_pages_locked(struct mm_struct *mm,
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long ret, pages_done;
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bool must_unlock = false;
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if (!nr_pages)
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return 0;
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/*
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* The internal caller expects GUP to manage the lock internally and the
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* lock must be released when this returns.
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@ -1595,6 +1598,14 @@ retry:
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mmap_read_unlock(mm);
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*locked = 0;
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}
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/*
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* Failing to pin anything implies something has gone wrong (except when
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* FOLL_NOWAIT is specified).
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*/
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if (WARN_ON_ONCE(pages_done == 0 && !(flags & FOLL_NOWAIT)))
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return -EFAULT;
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return pages_done;
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}
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