From: "Mike Rapoport (Microsoft)" <[email protected]> When a VMA is registered with userfaulfd in minor mode, its ->fault() method should check if a folio exists in the page cache and if yes ->fault() should call handle_userfault(VM_UFFD_MISSING).
Instead of calling handle_userfault() directly from a specific ->fault() implementation introduce new fault reason VM_FAULT_UFFD_MINOR that will notify the core page fault handler that it should call handle_userfaultfd(VM_UFFD_MISSING) to complete a page fault. Replace a call to handle_userfault(VM_UFFD_MISSING) in shmem and use the new VM_FAULT_UFFD_MINOR there instead. Suggested-by: David Hildenbrand (Red Hat) <[email protected]> Signed-off-by: Mike Rapoport (Microsoft) <[email protected]> --- include/linux/mm_types.h | 3 +++ mm/memory.c | 2 ++ mm/shmem.c | 2 +- 3 files changed, 6 insertions(+), 1 deletion(-) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 90e5790c318f..eb135369940f 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -1523,6 +1523,8 @@ typedef __bitwise unsigned int vm_fault_t; * fsync() to complete (for synchronous page faults * in DAX) * @VM_FAULT_COMPLETED: ->fault completed, meanwhile mmap lock released + * @VM_FAULT_UFFD_MINOR: ->fault did not modify page tables and needs + * handle_userfault(VM_UFFD_MINOR) to complete * @VM_FAULT_HINDEX_MASK: mask HINDEX value * */ @@ -1540,6 +1542,7 @@ enum vm_fault_reason { VM_FAULT_DONE_COW = (__force vm_fault_t)0x001000, VM_FAULT_NEEDDSYNC = (__force vm_fault_t)0x002000, VM_FAULT_COMPLETED = (__force vm_fault_t)0x004000, + VM_FAULT_UFFD_MINOR = (__force vm_fault_t)0x008000, VM_FAULT_HINDEX_MASK = (__force vm_fault_t)0x0f0000, }; diff --git a/mm/memory.c b/mm/memory.c index b59ae7ce42eb..94acbac8cefb 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -5279,6 +5279,8 @@ static vm_fault_t __do_fault(struct vm_fault *vmf) } ret = vma->vm_ops->fault(vmf); + if (unlikely(ret & VM_FAULT_UFFD_MINOR)) + return handle_userfault(vmf, VM_UFFD_MINOR); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY | VM_FAULT_DONE_COW))) return ret; diff --git a/mm/shmem.c b/mm/shmem.c index aaa21bb60f51..6dcb73b52bcc 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2461,7 +2461,7 @@ static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index, if (folio && vma && userfaultfd_minor(vma)) { if (!xa_is_value(folio)) folio_put(folio); - *fault_type = handle_userfault(vmf, VM_UFFD_MINOR); + *fault_type = VM_FAULT_UFFD_MINOR; return 0; } -- 2.50.1
