linux-kernel - Re: [PATCH] ipc/shm.c add ->pagesize function to shm_vm

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Date:   Mon, 30 Jul 2018 20:06:40 -0700
From:   Jane Chu <jane.chu@...cle.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     akpm@...ux-foundation.org, dan.j.williams@...el.com,
        mhocko@...e.com, jack@...e.cz, jglisse@...hat.com,
        mike.kravetz@...cle.com, dave@...olabs.net, linux-mm@...ck.org,
        linux-nvdimm@...ts.01.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ipc/shm.c add ->pagesize function to shm_vm_ops

Hi, Mathew,


On 7/28/2018 12:02 PM, Matthew Wilcox wrote:
> On Fri, Jul 27, 2018 at 03:17:27PM -0600, Jane Chu wrote:
>> +++ b/include/linux/mm.h
>> @@ -387,6 +387,13 @@ enum page_entry_size {
>>    * These are the virtual MM functions - opening of an area, closing and
>>    * unmapping it (needed to keep files on disk up-to-date etc), pointer
>>    * to the functions called when a no-page or a wp-page exception occurs.
>> + *
>> + * Note, when a new function is introduced to vm_operations_struct and
>> + * added to hugetlb_vm_ops, please consider adding the function to
>> + * shm_vm_ops. This is because under System V memory model, though
>> + * mappings created via shmget/shmat with "huge page" specified are
>> + * backed by hugetlbfs files, their original vm_ops are overwritten with
>> + * shm_vm_ops.
>>    */
>>   struct vm_operations_struct {
> I don't think this header file is the right place for this comment.
> I'd think a better place for it would be at the definition of hugetlb_vm_ops.

Agreed, will make the change.
Thanks for reviewing!

-jane