linux-kernel - Re: [PATCH v2 2/2] dax: use PG_PMD

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Date:   Wed, 23 Aug 2017 11:58:25 +0200
From:   Jan Kara <jack@...e.cz>
To:     Ross Zwisler <ross.zwisler@...ux.intel.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@....de>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Chinner <david@...morbit.com>, Jan Kara <jack@...e.cz>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        linux-fsdevel@...r.kernel.org, linux-nvdimm@...ts.01.org,
        "Slusarz, Marcin" <marcin.slusarz@...el.com>
Subject: Re: [PATCH v2 2/2] dax: use PG_PMD_COLOUR instead of open coding

On Tue 22-08-17 16:24:36, Ross Zwisler wrote:
> Use ~PG_PMD_COLOUR in dax_entry_waitqueue() instead of open coding an
> equivalent page offset mask.
> 
> Signed-off-by: Ross Zwisler <ross.zwisler@...ux.intel.com>

Looks good. You can add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/dax.c | 11 ++++-------
>  1 file changed, 4 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/dax.c b/fs/dax.c
> index 865d42c..0e2a1fd 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -42,6 +42,9 @@
>  #define DAX_WAIT_TABLE_BITS 12
>  #define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS)
>  
> +/* The 'colour' (ie low bits) within a PMD of a page offset.  */
> +#define PG_PMD_COLOUR	((PMD_SIZE >> PAGE_SHIFT) - 1)
> +
>  static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
>  
>  static int __init init_dax_wait_table(void)
> @@ -98,7 +101,7 @@ static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
>  	 * the range covered by the PMD map to the same bit lock.
>  	 */
>  	if (dax_is_pmd_entry(entry))
> -		index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1);
> +		index &= ~PG_PMD_COLOUR;
>  
>  	key->mapping = mapping;
>  	key->entry_start = index;
> @@ -1262,12 +1265,6 @@ static int dax_iomap_pte_fault(struct vm_fault *vmf,
>  }
>  
>  #ifdef CONFIG_FS_DAX_PMD
> -/*
> - * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
> - * more often than one might expect in the below functions.
> - */
> -#define PG_PMD_COLOUR	((PMD_SIZE >> PAGE_SHIFT) - 1)
> -
>  static int dax_pmd_insert_mapping(struct vm_fault *vmf, struct iomap *iomap,
>  		loff_t pos, void **entryp)
>  {
> -- 
> 2.9.5
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR