linux-kernel - Re: [PATCH 1/2] ext4/xfs: add page refcount helper

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Message-ID: <20200926063539.GA3540@lst.de>
Date:   Sat, 26 Sep 2020 08:35:39 +0200
From:   Christoph Hellwig <hch@....de>
To:     Ralph Campbell <rcampbell@...dia.com>
Cc:     linux-mm@...ck.org, kvm-ppc@...r.kernel.org,
        nouveau@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Dan Williams <dan.j.williams@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Matthew Wilcox <willy@...radead.org>,
        Jerome Glisse <jglisse@...hat.com>,
        John Hubbard <jhubbard@...dia.com>,
        Alistair Popple <apopple@...dia.com>,
        Christoph Hellwig <hch@....de>,
        Jason Gunthorpe <jgg@...dia.com>,
        Bharata B Rao <bharata@...ux.ibm.com>,
        Zi Yan <ziy@...dia.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Yang Shi <yang.shi@...ux.alibaba.com>,
        Paul Mackerras <paulus@...abs.org>,
        Ben Skeggs <bskeggs@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/2] ext4/xfs: add page refcount helper

On Fri, Sep 25, 2020 at 01:44:41PM -0700, Ralph Campbell wrote:
>  		error = ___wait_var_event(&page->_refcount,
> -				atomic_read(&page->_refcount) == 1,
> +				dax_layout_is_idle_page(page),
>  				TASK_INTERRUPTIBLE, 0, 0,
>  				ext4_wait_dax_page(ei));

> +++ b/fs/xfs/xfs_file.c
> @@ -750,7 +750,7 @@ xfs_break_dax_layouts(
>  
>  	*retry = true;
>  	return ___wait_var_event(&page->_refcount,
> -			atomic_read(&page->_refcount) == 1, TASK_INTERRUPTIBLE,
> +			dax_layout_is_idle_page(page), TASK_INTERRUPTIBLE,
>  			0, 0, xfs_wait_dax_page(inode));
>  }

I still think a litte helper macro would be nice here:

#define dax_wait_page(_inode, _page, _wait_cb)				\
  	___wait_var_event(&(_page)->_refcount,				\
		atomic_read(&(_page)->_refcount) == 1,			\
		TASK_INTERRUPTIBLE, dax_layout_is_idle_page(_page),	\
		TASK_INTERRUPTIBLE, 0, 0, _wait_cb(_inode));