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Re: [PATCH] remap_file_pages needs to check for cache coherency

To: Matthew Wilcox <>
Subject: Re: [PATCH] remap_file_pages needs to check for cache coherency
From: John David Anglin <>
Date: Fri, 27 Dec 2013 14:13:16 -0500
Cc:, "David S. Miller" <>,,,
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On 27-Dec-13, at 1:00 PM, Matthew Wilcox wrote:

+       /* Is the mapping cache-coherent? */
+       if ((pgoff ^ linear_page_index(vma, start)) &
+           ((SHMLBA-1) >> PAGE_SHIFT))
+               goto out;

I think this will cause problems on PA-RISC. The reason is we have an additional offset
for mappings.  See get_offset() in sys_parisc.c.

SHMLBA is 4 MB on PA-RISC. If we limit ourselves to aligned mappings, we run out of memory very quickly. Even with our current implementation, we fail the perl locales test
with locales-all installed.

John David Anglin

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