Re: [PATCH 2/4] mm: rename __mlock_vma_pages_range() to populate_vma_page_range()

David Rientjes
2015-02-12T21:59:25Z

On Thu, 12 Feb 2015, Kirill A. Shutemov wrote:

> > I think it makes sense to drop the references about "downgrading"
> > mm->mmap_sem in the documentation since populate_vma_page_range() can be
> > called with it held either for read or write depending on the context.
>
> I'm not sure what references you're talking about.
>
> Is it about this part:
>
> * If @nonblocking is non-NULL, it must held for read only and may be
> * released. If it's released, *@nonblocking will be set to 0.
>
> ?
>

No, I was agreeing with your removal from the documentation:

@@ -463,21 +463,11 @@ populate the page table.

To mlock a range of memory under the unevictable/mlock infrastructure, the
mmap() handler and task address space expansion functions call
-mlock_vma_pages_range() specifying the vma and the address range to mlock.
-mlock_vma_pages_range() filters VMAs like mlock_fixup(), as described above in
-"Filtering Special VMAs". It will clear the VM_LOCKED flag, which will have
-already been set by the caller, in filtered VMAs. Thus these VMA's need not be
-visited for munlock when the region is unmapped.
-
-For "normal" VMAs, mlock_vma_pages_range() calls __mlock_vma_pages_range() to
-fault/allocate the pages and mlock them. Again, like mlock_fixup(),
-mlock_vma_pages_range() downgrades the mmap semaphore to read mode before
-attempting to fault/allocate and mlock the pages and "upgrades" the semaphore
-back to write mode before returning.
-
-The callers of mlock_vma_pages_range() will have already added the memory range
+populate_vma_page_range() specifying the vma and the address range to mlock.
+
+The callers of populate_vma_page_range() will have already added the memory range
to be mlocked to the task's "locked_vm". To account for filtered VMAs,
-mlock_vma_pages_range() returns the number of pages NOT mlocked. All of the
+populate_vma_page_range() returns the number of pages NOT mlocked. All of the
callers then subtract a non-negative return value from the task's locked_vm. A
negative return value represent an error - for example, from get_user_pages()
attempting to fault in a VMA with PROT_NONE access. In this case, we leave the