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authorDavid Hildenbrand <david@redhat.com>2022-08-25 19:46:58 +0300
committerAndrew Morton <akpm@linux-foundation.org>2022-09-27 05:46:28 +0300
commit0cf459866a91c741eb14a92f3633638d1dd9db59 (patch)
tree6b3a3ea4d88bb9617a69fbe1bbb68a83f003d728 /mm/gup.c
parent474098edac262ae26bfab1c48445877075a31cbd (diff)
downloadlinux-0cf459866a91c741eb14a92f3633638d1dd9db59.tar.xz
mm/gup: use gup_can_follow_protnone() also in GUP-fast
There seems to be no reason why FOLL_FORCE during GUP-fast would have to fallback to the slow path when stumbling over a PROT_NONE mapped page. We only have to trigger hinting faults in case FOLL_FORCE is not set, and any kind of fault handling naturally happens from the slow path -- where NUMA hinting accounting/handling would be performed. Note that the comment regarding THP migration is outdated: commit 2b4847e73004 ("mm: numa: serialise parallel get_user_page against THP migration") described that this was required for THP due to lack of PMD migration entries. Nowadays, we do have proper PMD migration entries in place -- see set_pmd_migration_entry(), which does a proper pmdp_invalidate() when placing the migration entry. So let's just reuse gup_can_follow_protnone() here to make it consistent and drop the somewhat outdated comments. Link: https://lkml.kernel.org/r/20220825164659.89824-3-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Peter Xu <peterx@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/gup.c')
-rw-r--r--mm/gup.c14
1 files changed, 3 insertions, 11 deletions
diff --git a/mm/gup.c b/mm/gup.c
index f06770e03549..ce00a4c40da8 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2420,11 +2420,7 @@ static int gup_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr,
struct page *page;
struct folio *folio;
- /*
- * Similar to the PMD case below, NUMA hinting must take slow
- * path using the pte_protnone check.
- */
- if (pte_protnone(pte))
+ if (pte_protnone(pte) && !gup_can_follow_protnone(flags))
goto pte_unmap;
if (!pte_access_permitted(pte, flags & FOLL_WRITE))
@@ -2808,12 +2804,8 @@ static int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr, unsigned lo
if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd) ||
pmd_devmap(pmd))) {
- /*
- * NUMA hinting faults need to be handled in the GUP
- * slowpath for accounting purposes and so that they
- * can be serialised against THP migration.
- */
- if (pmd_protnone(pmd))
+ if (pmd_protnone(pmd) &&
+ !gup_can_follow_protnone(flags))
return 0;
if (!gup_huge_pmd(pmd, pmdp, addr, next, flags,