From: Nikita Kalyazin <[email protected]> When a VMA is registered with userfaulfd in missing mode, its ->fault() method should check if a folio exists in the page cache and if no ->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_MISSING 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_MISSING there instead. For configurations that don't enable CONFIG_USERFAULTFD, VM_FAULT_UFFD_MISSING is set to 0. Signed-off-by: Nikita Kalyazin <[email protected]> Signed-off-by: Mike Rapoport (Microsoft) <[email protected]> --- include/linux/mm_types.h | 7 ++++++- mm/memory.c | 5 ++++- mm/shmem.c | 2 +- 3 files changed, 11 insertions(+), 3 deletions(-) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index b25ac322bfbf..a061c43e835b 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -1557,6 +1557,8 @@ typedef __bitwise unsigned int vm_fault_t; * @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_UFFD_MISSING: ->fault did not modify page tables and needs + * handle_userfault(VM_UFFD_MISSING) to complete * @VM_FAULT_HINDEX_MASK: mask HINDEX value * */ @@ -1576,8 +1578,10 @@ enum vm_fault_reason { VM_FAULT_COMPLETED = (__force vm_fault_t)0x004000, #ifdef CONFIG_USERFAULTFD VM_FAULT_UFFD_MINOR = (__force vm_fault_t)0x008000, + VM_FAULT_UFFD_MISSING = (__force vm_fault_t)0x010000, #else VM_FAULT_UFFD_MINOR = (__force vm_fault_t)0x000000, + VM_FAULT_UFFD_MISSING = (__force vm_fault_t)0x000000, #endif VM_FAULT_HINDEX_MASK = (__force vm_fault_t)0x0f0000, }; @@ -1604,7 +1608,8 @@ enum vm_fault_reason { { VM_FAULT_DONE_COW, "DONE_COW" }, \ { VM_FAULT_NEEDDSYNC, "NEEDDSYNC" }, \ { VM_FAULT_COMPLETED, "COMPLETED" }, \ - { VM_FAULT_UFFD_MINOR, "UFFD_MINOR" } + { VM_FAULT_UFFD_MINOR, "UFFD_MINOR" }, \ + { VM_FAULT_UFFD_MISSING, "UFFD_MISSING" } struct vm_special_mapping { const char *name; /* The name, e.g. "[vdso]". */ diff --git a/mm/memory.c b/mm/memory.c index fcb3e0c3113e..f72e69a43b68 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -5319,9 +5319,12 @@ static vm_fault_t __do_fault(struct vm_fault *vmf) ret = vma->vm_ops->fault(vmf); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY | - VM_FAULT_DONE_COW | VM_FAULT_UFFD_MINOR))) { + VM_FAULT_DONE_COW | VM_FAULT_UFFD_MINOR | + VM_FAULT_UFFD_MISSING))) { if (ret & VM_FAULT_UFFD_MINOR) return handle_userfault(vmf, VM_UFFD_MINOR); + if (ret & VM_FAULT_UFFD_MISSING) + return handle_userfault(vmf, VM_UFFD_MISSING); return ret; } diff --git a/mm/shmem.c b/mm/shmem.c index 6aa905147c0c..1bc544cab2a8 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2530,7 +2530,7 @@ static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index, */ if (vma && userfaultfd_missing(vma)) { - *fault_type = handle_userfault(vmf, VM_UFFD_MISSING); + *fault_type = VM_FAULT_UFFD_MISSING; return 0; } -- 2.51.0
