The patch titled
Subject: mm/gup: move gup_must_unshare() to mm/internal.h
has been added to the -mm mm-unstable branch. Its filename is
mm-gup-move-gup_must_unshare-to-mm-internalh.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-gup-move-gup_must_unshare-to-mm-internalh.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Jason Gunthorpe <jgg@xxxxxxxxxx>
Subject: mm/gup: move gup_must_unshare() to mm/internal.h
Date: Tue, 24 Jan 2023 16:34:33 -0400
This function is only used in gup.c and closely related. It touches
FOLL_PIN so it must be moved before the next patch.
Link: https://lkml.kernel.org/r/12-v2-987e91b59705+36b-gup_tidy_jgg@xxxxxxxxxx
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/include/linux/mm.h~mm-gup-move-gup_must_unshare-to-mm-internalh
+++ a/include/linux/mm.h
@@ -3206,71 +3206,6 @@ static inline int vm_fault_to_errno(vm_f
}
/*
- * 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.
*/
--- a/mm/internal.h~mm-gup-move-gup_must_unshare-to-mm-internalh
+++ a/mm/internal.h
@@ -858,6 +858,71 @@ int migrate_device_coherent_page(struct
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)
_
Patches currently in -mm which might be from jgg@xxxxxxxxxx are
mm-gup-have-internal-functions-get-the-mmap_read_lock.patch
mm-gup-remove-obsolete-foll_longterm-comment.patch
mm-gup-dont-call-__gup_longterm_locked-if-foll_longterm-cannot-be-set.patch
mm-gup-move-try_grab_page-to-mm-internalh.patch
mm-gup-simplify-the-external-interface-functions-and-consolidate-invariants.patch
mm-gup-add-an-assertion-that-the-mmap-lock-is-locked.patch
mm-gup-remove-locked-being-null-from-faultin_vma_page_range.patch
mm-gup-add-foll_unlockable.patch
mm-gup-make-locked-never-null-in-the-internal-gup-functions.patch
mm-gup-remove-pin_user_pages_fast_only.patch
mm-gup-make-get_user_pages_fast_only-return-the-common-return-value.patch
mm-gup-move-gup_must_unshare-to-mm-internalh.patch
mm-gup-move-private-gup-foll_-flags-to-internalh.patch
