The patch titled
Subject: mm/gup: require FOLL_GET for get_user_pages_fast()
has been added to the -mm tree. Its filename is
mm-gup-require-foll_get-for-get_user_pages_fast.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-gup-require-foll_get-for-get_user_pages_fast.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-gup-require-foll_get-for-get_user_pages_fast.patch
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------------------------------------------------------
From: John Hubbard <jhubbard@xxxxxxxxxx>
Subject: 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.
Link: http://lkml.kernel.org/r/20200211001536.1027652-6-jhubbard@xxxxxxxxxx
Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: Jérôme Glisse <jglisse@xxxxxxxxxx>
Cc: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/gup.c | 19 +++++++++++++++++--
1 file changed, 17 insertions(+), 2 deletions(-)
--- a/mm/gup.c~mm-gup-require-foll_get-for-get_user_pages_fast
+++ a/mm/gup.c
@@ -2390,6 +2390,14 @@ int __get_user_pages_fast(unsigned long
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
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(
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 st
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);
_
Patches currently in -mm which might be from jhubbard@xxxxxxxxxx are
mm-gup-split-get_user_pages_remote-into-two-routines.patch
mm-gup-pass-a-flags-arg-to-__gup_device_-functions.patch
mm-introduce-page_ref_sub_return.patch
mm-gup-pass-gup-flags-to-two-more-routines.patch
mm-gup-require-foll_get-for-get_user_pages_fast.patch
mm-gup-track-foll_pin-pages.patch
mm-gup-page-hpage_pinned_refcount-exact-pin-counts-for-huge-pages.patch
mm-gup-proc-vmstat-pin_user_pages-foll_pin-reporting.patch
mm-gup_benchmark-support-pin_user_pages-and-related-calls.patch
selftests-vm-run_vmtests-invoke-gup_benchmark-with-basic-foll_pin-coverage.patch
mm-dump_page-additional-diagnostics-for-huge-pinned-pages.patch
