diff options
Diffstat (limited to 'include/linux/mm.h')
| -rw-r--r-- | include/linux/mm.h | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index e98ef2cb1176..8a5ad9d050bf 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2999,8 +2999,8 @@ static inline int vm_fault_to_errno(vm_fault_t vm_fault, int foll_flags) * 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): - * clear/invalidate+flush of the page table entry + * * 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 @@ -3021,6 +3021,11 @@ static inline bool gup_must_unshare(unsigned int flags, struct page *page) */ if (!PageAnon(page)) return false; + + /* 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. |