linux-kernel - Re: [PATCH v12 07/20] dax,ext2: Replace ext2_clear_xip_target with dax_clear

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Date:	Tue, 13 Jan 2015 16:39:03 -0500
From:	Matthew Wilcox <willy@...ux.intel.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Matthew Wilcox <matthew.r.wilcox@...el.com>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, willy@...ux.intel.com
Subject: Re: [PATCH v12 07/20] dax,ext2: Replace ext2_clear_xip_target with
 dax_clear_blocks

On Mon, Jan 12, 2015 at 03:09:47PM -0800, Andrew Morton wrote:
> > +int dax_clear_blocks(struct inode *inode, sector_t block, long size)
> > +{
...
> > +			if (pgsz < PAGE_SIZE)
> > +				memset(addr, 0, pgsz);
> > +			else
> > +				clear_page(addr);
> 
> Are there any cache issues in all this code? flush_dcache_page(addr)?

Here, no.  This is only called to initialise a newly allocated block.

Elsewhere, maybe.  When i was originally working on this, I think I had
code that forced mmaps of DAX files to be aligned to SHMLBA, because I
remember noticing a bug in sparc64's remap_file_range().  Unfortunately,
in the various rewrites, that got lost.  So it needs to be put back in.

flush_dcache_page() in particular won't work because it needs a struct
page.

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