Re: [PATCH 0/5] export __clear_page_buffers to cleanup code

[Gao Xiang <hsiangkao@aol.com>]

On Sat, Apr 18, 2020 at 08:14:43PM -0700, Matthew Wilcox wrote:
> On Sun, Apr 19, 2020 at 12:51:18AM +0200, Guoqing Jiang wrote:
> > When reading md code, I find md-bitmap.c copies __clear_page_buffers from
> > buffer.c, and after more search, seems there are some places in fs could
> > use this function directly. So this patchset tries to export the function
> > and use it to cleanup code.
> 
> OK, I see why you did this, but there are a couple of problems with it.
> 
> One is just a sequencing problem; between exporting __clear_page_buffers()
> and removing it from the md code, the md code won't build.
> 
> More seriously, most of this code has nothing to do with buffers.  It
> uses page->private for its own purposes.
> 
> What I would do instead is add:
> 
> clear_page_private(struct page *page)
> {
> 	ClearPagePrivate(page);
> 	set_page_private(page, 0);
> 	put_page(page);
> }
> 
> to include/linux/mm.h, then convert all callers of __clear_page_buffers()
> to call that instead.

Agreed with the new naming (__clear_page_buffers is confusing), that is not
only for initial use buffer head, but a generic convention for all unlocked
PagePrivate pages (such migration & reclaim paths indicate that).

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/mm.h?h=v5.7-rc1#n990

Thanks,
Gao Xiang


>