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Message-ID: <c7bfaf30cb682b92766e35ec85d93a84798b37f4.1696174961.git.lstoakes@gmail.com>
Date: Sun, 1 Oct 2023 17:00:04 +0100
From: Lorenzo Stoakes <lstoakes@...il.com>
To: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Ian Rogers <irogers@...gle.com>,
Adrian Hunter <adrian.hunter@...el.com>,
Oleg Nesterov <oleg@...hat.com>,
Richard Cochran <richardcochran@...il.com>,
Jason Gunthorpe <jgg@...dia.com>,
John Hubbard <jhubbard@...dia.com>,
Arnd Bergmann <arnd@...db.de>,
Lorenzo Stoakes <lstoakes@...il.com>
Subject: [PATCH 3/4] 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.
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.
Signed-off-by: Lorenzo Stoakes <lstoakes@...il.com>
---
mm/gup.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/mm/gup.c b/mm/gup.c
index b21b33d1787e..fb2218d74ca5 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -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, so explicitly make this an error.
+ */
+ if (pages_done == 0 && !(flags & FOLL_NOWAIT))
+ return -EFAULT;
+
return pages_done;
}
--
2.42.0
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