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Date: Wed, 21 Dec 2016 09:53:47 +0100
From: Jan Kara <jack@suse.cz>
To: Dan Williams <dan.j.williams@intel.com>
Cc: akpm@linux-foundation.org, Jan Kara <jack@suse.cz>,
        Matthew Wilcox <mawilcox@microsoft.com>,
        Dave Chinner <david@fromorbit.com>,
        linux-kernel@vger.kernel.org, Dave Hansen <dave.hansen@intel.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        linux-fsdevel@vger.kernel.org,
        Ross Zwisler <ross.zwisler@linux.intel.com>,
        Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH] dax: kill uml support
Message-ID: <20161221085347.GB4756@quack2.suse.cz>
References: <148228426023.2477.2662330241414304847.stgit@dwillia2-desk3.amr.corp.intel.com>
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On Tue 20-12-16 17:37:40, Dan Williams wrote:
> The lack of common transparent-huge-page helpers for UML is becoming
> increasingly painful for fs/dax.c now that it is growing more pmd
> functionality. Add UML to the list of unsupported architectures, and
> clean up no-longer-necessary ifdef as a result.
...
> diff --git a/fs/dax.c b/fs/dax.c
> index ddcddfeaa03b..86df835783ea 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -710,8 +710,7 @@ static void dax_mapping_entry_mkclean(struct address_space *mapping,
>  		if (follow_pte_pmd(vma->vm_mm, address, &ptep, &pmdp, &ptl))
>  			continue;
>  
> -		if (pmdp) {
> -#ifdef CONFIG_FS_DAX_PMD
> +		if (pmdp && IS_ENABLED(CONFIG_FS_DAX_PMD)) {
>  			pmd_t pmd;

So I was under the impression that pmdp can never be != NULL when
CONFIG_FS_DAX_PMD is disabled. Otherwise Ross' patch would leave ptl locked
in that case... Did I miss something or we can just remove IS_ENABLED()
check?

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR