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charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Patrick Roy =0A= =0A= This drops an optimization in gup_fast_folio_allowed() where=0A= secretmem_mapping() was only called if CONFIG_SECRETMEM=3Dy. secretmem is= =0A= enabled by default since commit b758fe6df50d ("mm/secretmem: make it on=0A= by default"), so the secretmem check did not actually end up elided in=0A= most cases anymore anyway.=0A= =0A= To make sure the fast path for ZONE_DEVICE pages (like Device DAX and=0A= PCI P2PDMA) is still allowed, check for folio_is_zone_device() if=0A= mapping is NULL.=0A= =0A= This is in preparation of the generalization of handling mappings where=0A= direct map entries of folios are set to not present. Currently,=0A= mappings that match this description are secretmem mappings=0A= (memfd_secret()). Later, some guest_memfd configurations will also fall=0A= into this category.=0A= =0A= Signed-off-by: Patrick Roy =0A= Acked-by: Vlastimil Babka =0A= Acked-by: David Hildenbrand (Red Hat) =0A= Signed-off-by: Nikita Kalyazin =0A= ---=0A= mm/gup.c | 17 ++++++-----------=0A= 1 file changed, 6 insertions(+), 11 deletions(-)=0A= =0A= diff --git a/mm/gup.c b/mm/gup.c=0A= index 8e7dc2c6ee73..e8367564d636 100644=0A= --- a/mm/gup.c=0A= +++ b/mm/gup.c=0A= @@ -2739,7 +2739,6 @@ static bool gup_fast_folio_allowed(struct folio *foli= o, unsigned int flags)=0A= {=0A= bool reject_file_backed =3D false;=0A= struct address_space *mapping;=0A= - bool check_secretmem =3D false;=0A= unsigned long mapping_flags;=0A= =0A= /*=0A= @@ -2751,14 +2750,6 @@ static bool gup_fast_folio_allowed(struct folio *fol= io, unsigned int flags)=0A= reject_file_backed =3D true;=0A= =0A= /* We hold a folio reference, so we can safely access folio fields. */=0A= -=0A= - /* secretmem folios are always order-0 folios. */=0A= - if (IS_ENABLED(CONFIG_SECRETMEM) && !folio_test_large(folio))=0A= - check_secretmem =3D true;=0A= -=0A= - if (!reject_file_backed && !check_secretmem)=0A= - return true;=0A= -=0A= if (WARN_ON_ONCE(folio_test_slab(folio)))=0A= return false;=0A= =0A= @@ -2787,9 +2778,13 @@ static bool gup_fast_folio_allowed(struct folio *fol= io, unsigned int flags)=0A= * The mapping may have been truncated, in any case we cannot determine= =0A= * if this mapping is safe - fall back to slow path to determine how to= =0A= * proceed.=0A= + *=0A= + * ZONE_DEVICE folios (e.g. Device DAX, PCI P2PDMA) may legitimately=0A= + * have a NULL mapping. They are never secretmem/no-direct-map folios,=0A= + * so let them through.=0A= */=0A= if (!mapping)=0A= - return false;=0A= + return folio_is_zone_device(folio);=0A= =0A= /* Anonymous folios pose no problem. */=0A= mapping_flags =3D (unsigned long)mapping & FOLIO_MAPPING_FLAGS;=0A= @@ -2800,7 +2795,7 @@ static bool gup_fast_folio_allowed(struct folio *foli= o, unsigned int flags)=0A= * At this point, we know the mapping is non-null and points to an=0A= * address_space object.=0A= */=0A= - if (check_secretmem && secretmem_mapping(mapping))=0A= + if (secretmem_mapping(mapping))=0A= return false;=0A= /* The only remaining allowed file system is shmem. */=0A= return !reject_file_backed || shmem_mapping(mapping);=0A= -- =0A= 2.50.1=0A= =0A=