On 1/24/23 12:34, Jason Gunthorpe wrote:
This function is only used in gup.c and closely related. It touches
FOLL_PIN so it must be moved before the next patch.
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
---
include/linux/mm.h | 65 ----------------------------------------------
mm/internal.h | 65 ++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 65 insertions(+), 65 deletions(-)
Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>
thanks,
--
John Hubbard
NVIDIA
diff --git a/include/linux/mm.h b/include/linux/mm.h
index a47a6e8a9c78be..e0bacf9f2c5ebe 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3087,71 +3087,6 @@ static inline int vm_fault_to_errno(vm_fault_t vm_fault, int foll_flags)
return 0;
}
-/*
- * Indicates for which pages that are write-protected in the page table,
- * whether GUP has to trigger unsharing via FAULT_FLAG_UNSHARE such that the
- * GUP pin will remain consistent with the pages mapped into the page tables
- * of the MM.
- *
- * Temporary unmapping of PageAnonExclusive() pages or clearing of
- * PageAnonExclusive() has to protect against concurrent GUP:
- * * Ordinary GUP: Using the PT lock
- * * GUP-fast and fork(): mm->write_protect_seq
- * * GUP-fast and KSM or temporary unmapping (swap, migration): see
- * page_try_share_anon_rmap()
- *
- * Must be called with the (sub)page that's actually referenced via the
- * page table entry, which might not necessarily be the head page for a
- * PTE-mapped THP.
- *
- * If the vma is NULL, we're coming from the GUP-fast path and might have
- * to fallback to the slow path just to lookup the vma.
- */
-static inline bool gup_must_unshare(struct vm_area_struct *vma,
- unsigned int flags, struct page *page)
-{
- /*
- * FOLL_WRITE is implicitly handled correctly as the page table entry
- * has to be writable -- and if it references (part of) an anonymous
- * folio, that part is required to be marked exclusive.
- */
- if ((flags & (FOLL_WRITE | FOLL_PIN)) != FOLL_PIN)
- return false;
- /*
- * Note: PageAnon(page) is stable until the page is actually getting
- * freed.
- */
- if (!PageAnon(page)) {
- /*
- * We only care about R/O long-term pining: R/O short-term
- * pinning does not have the semantics to observe successive
- * changes through the process page tables.
- */
- if (!(flags & FOLL_LONGTERM))
- return false;
-
- /* We really need the vma ... */
- if (!vma)
- return true;
-
- /*
- * ... because we only care about writable private ("COW")
- * mappings where we have to break COW early.
- */
- return is_cow_mapping(vma->vm_flags);
- }
-
- /* Paired with a memory barrier in page_try_share_anon_rmap(). */
- if (IS_ENABLED(CONFIG_HAVE_FAST_GUP))
- smp_rmb();
-
- /*
- * Note that PageKsm() pages cannot be exclusive, and consequently,
- * cannot get pinned.
- */
- return !PageAnonExclusive(page);
-}
-
/*
* Indicates whether GUP can follow a PROT_NONE mapped page, or whether
* a (NUMA hinting) fault is required.
diff --git a/mm/internal.h b/mm/internal.h
index 0f035bcaf133f5..5c1310b98db64d 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -854,6 +854,71 @@ int migrate_device_coherent_page(struct page *page);
struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags);
int __must_check try_grab_page(struct page *page, unsigned int flags);
+/*
+ * Indicates for which pages that are write-protected in the page table,
+ * whether GUP has to trigger unsharing via FAULT_FLAG_UNSHARE such that the
+ * GUP pin will remain consistent with the pages mapped into the page tables
+ * of the MM.
+ *
+ * Temporary unmapping of PageAnonExclusive() pages or clearing of
+ * PageAnonExclusive() has to protect against concurrent GUP:
+ * * Ordinary GUP: Using the PT lock
+ * * GUP-fast and fork(): mm->write_protect_seq
+ * * GUP-fast and KSM or temporary unmapping (swap, migration): see
+ * page_try_share_anon_rmap()
+ *
+ * Must be called with the (sub)page that's actually referenced via the
+ * page table entry, which might not necessarily be the head page for a
+ * PTE-mapped THP.
+ *
+ * If the vma is NULL, we're coming from the GUP-fast path and might have
+ * to fallback to the slow path just to lookup the vma.
+ */
+static inline bool gup_must_unshare(struct vm_area_struct *vma,
+ unsigned int flags, struct page *page)
+{
+ /*
+ * FOLL_WRITE is implicitly handled correctly as the page table entry
+ * has to be writable -- and if it references (part of) an anonymous
+ * folio, that part is required to be marked exclusive.
+ */
+ if ((flags & (FOLL_WRITE | FOLL_PIN)) != FOLL_PIN)
+ return false;
+ /*
+ * Note: PageAnon(page) is stable until the page is actually getting
+ * freed.
+ */
+ if (!PageAnon(page)) {
+ /*
+ * We only care about R/O long-term pining: R/O short-term
+ * pinning does not have the semantics to observe successive
+ * changes through the process page tables.
+ */
+ if (!(flags & FOLL_LONGTERM))
+ return false;
+
+ /* We really need the vma ... */
+ if (!vma)
+ return true;
+
+ /*
+ * ... because we only care about writable private ("COW")
+ * mappings where we have to break COW early.
+ */
+ return is_cow_mapping(vma->vm_flags);
+ }
+
+ /* Paired with a memory barrier in page_try_share_anon_rmap(). */
+ if (IS_ENABLED(CONFIG_HAVE_FAST_GUP))
+ smp_rmb();
+
+ /*
+ * Note that PageKsm() pages cannot be exclusive, and consequently,
+ * cannot get pinned.
+ */
+ return !PageAnonExclusive(page);
+}
+
extern bool mirrored_kernelcore;
static inline bool vma_soft_dirty_enabled(struct vm_area_struct *vma)
