On Tue, May 2, 2023 at 6:26 AM 'Alistair Popple' via kernel-team
<kernel-team@xxxxxxxxxxx> wrote:
>
>
> 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.
Good idea. Will add in the next version. Thanks!
>
> > * @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?
I noticed that an entry for VM_FAULT_COMPLETED was missing and wanted
to fix that... Should I drop that?
>
> > + { 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);
>
> --
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