Suren Baghdasaryan <surenb@xxxxxxxxxx> writes:
[...]
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 306a3d1a0fa6..b3b57c6da0e1 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -1030,6 +1030,7 @@ 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_VMA_UNLOCKED: VMA lock was released
A note here saying vmf->vma should no longer be accessed would be nice.
> * @VM_FAULT_HINDEX_MASK: mask HINDEX value
> *
> */
> @@ -1047,6 +1048,7 @@ 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_VMA_UNLOCKED = (__force vm_fault_t)0x008000,
> VM_FAULT_HINDEX_MASK = (__force vm_fault_t)0x0f0000,
> };
>
> @@ -1070,7 +1072,9 @@ enum vm_fault_reason {
> { VM_FAULT_RETRY, "RETRY" }, \
> { VM_FAULT_FALLBACK, "FALLBACK" }, \
> { VM_FAULT_DONE_COW, "DONE_COW" }, \
> - { VM_FAULT_NEEDDSYNC, "NEEDDSYNC" }
> + { VM_FAULT_NEEDDSYNC, "NEEDDSYNC" }, \
> + { VM_FAULT_COMPLETED, "COMPLETED" }, \
VM_FAULT_COMPLETED isn't used in this patch, guessing that's snuck in
from one of the other patches in the series?
> + { VM_FAULT_VMA_UNLOCKED, "VMA_UNLOCKED" }
>
> struct vm_special_mapping {
> const char *name; /* The name, e.g. "[vdso]". */
> diff --git a/mm/memory.c b/mm/memory.c
> index 41f45819a923..8222acf74fd3 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3714,8 +3714,16 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> entry = pte_to_swp_entry(vmf->orig_pte);
> if (unlikely(non_swap_entry(entry))) {
> if (is_migration_entry(entry)) {
> - migration_entry_wait(vma->vm_mm, vmf->pmd,
> - vmf->address);
> + /* Save mm in case VMA lock is dropped */
> + struct mm_struct *mm = vma->vm_mm;
> +
> + if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
> + /* No need to hold VMA lock for migration */
> + vma_end_read(vma);
> + /* CAUTION! VMA can't be used after this */
> + ret |= VM_FAULT_VMA_UNLOCKED;
> + }
> + migration_entry_wait(mm, vmf->pmd, vmf->address);
> } else if (is_device_exclusive_entry(entry)) {
> vmf->page = pfn_swap_entry_to_page(entry);
> ret = remove_device_exclusive_entry(vmf);
