On Tue, Dec 7, 2021 at 2:47 PM Suren Baghdasaryan [off-list ref] wrote:

On Tue, Dec 7, 2021 at 2:07 PM Matthew Wilcox [off-list ref] wrote:

quoted

On Tue, Dec 07, 2021 at 01:50:30PM -0800, Suren Baghdasaryan wrote:

quoted

- Added a comment for vm_operations_struct::close, documenting restriction for
taking mmap_lock in the callback, per Michal Hocko and Matthew Wilcox

This should be a separate patch because it stands alone, but ...

I thought about it and since it was relevant to the change in
remove_vma locking, I thought it would fit here. However, if you
insist on splitting it, I'll post it as a separate patch. Please let
me know.

quoted

quoted

 struct vm_operations_struct {
      void (*open)(struct vm_area_struct * area);
+    /*
+     * Called with mmap_lock lock held for write from __split_vma and
+     * remove_vma, therefore should never take that lock.
+     */

Your whitespace indentation is weird.  And it'd be nice to make this a
kernel-doc comment (I know none of the others are, but that should be
fixed too).  And naming the functions that call it is wrong too.

        /**
         * @close: Called when the VMA is being removed from the MM.
         * Context: Caller holds mmap_lock.

BTW, is the caller always required to hold mmap_lock for write or it
*might* hold it?

quoted

         */

Ack. Will change and include in the next respin once I hear from you
on the preference for a separate patch.
Thanks!