From: catalin.marinas@arm•com (Catalin Marinas)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH V4] ARM: handle user space mapped pages in flush_kernel_dcache_page
Date: Wed, 29 May 2013 12:05:09 +0100 [thread overview]
Message-ID: <20130529110508.GH17767@MacBook-Pro.local> (raw)
In-Reply-To: <1368336956-6693-1-git-send-email-gmbnomis@gmail.com>
On Sun, May 12, 2013 at 06:35:56AM +0100, Simon Baatz wrote:
> Commit f8b63c1 made flush_kernel_dcache_page a no-op assuming that the pages
> it needs to handle are kernel mapped only. However, for example when doing
> direct I/O, pages with user space mappings may occur.
After Nico's clarification, I think the original commit introducing this
function was also incomplete (commit 73be1591 - [ARM] 5545/2: add
flush_kernel_dcache_page() for ARM) since it ignores highmem pages and
their flushing could be deferred for a long time.
For my understanding (if I re-read this tread) - basically code like
this should not leave the user mapping inconsistent:
kmap()
...
flush_kernel_dcache_page()
kunmap()
If we use the atomic variants, we get the cache flushing automatically
but the kunmap_high() does not flush the cache immediately, so we need
to handle it in flush_kernel_dcache_page().
> Thus, continue to do lazy flushing if there are no user space mappings.
> Otherwise, flush the kernel cache lines directly.
...
> /*
> + * Ensure cache coherency for kernel mapping of this page.
> + *
> + * If the page only exists in the page cache and there are no user
> + * space mappings, this is a no-op since the page was already marked
> + * dirty at creation. Otherwise, we need to flush the dirty kernel
> + * cache lines directly.
> + */
> +void flush_kernel_dcache_page(struct page *page)
> +{
> + if (cache_is_vivt() || cache_is_vipt_aliasing()) {
> + struct address_space *mapping;
> +
> + mapping = page_mapping(page);
> +
> + if (!mapping || mapping_mapped(mapping))
> + __flush_kernel_dcache_page(page);
> + }
> +}
BTW, does the mapping check optimise anything for the
flush_kernel_dcache_page() uses? Would we have a mapping anyway (or
anonymous page) in most cases?
Otherwise the patch looks good.
--
Catalin
next prev parent reply other threads:[~2013-05-29 11:05 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-12 5:35 [PATCH V4] ARM: handle user space mapped pages in flush_kernel_dcache_page Simon Baatz
2013-05-23 10:43 ` Catalin Marinas
2013-05-25 3:53 ` Nicolas Pitre
2013-05-28 9:55 ` Catalin Marinas
2013-05-28 17:52 ` Nicolas Pitre
2013-05-29 10:37 ` Catalin Marinas
2013-05-29 14:39 ` Nicolas Pitre
2013-05-29 16:32 ` Nicolas Pitre
2013-05-29 17:33 ` Catalin Marinas
2013-05-27 21:42 ` Simon Baatz
2013-05-28 10:20 ` Catalin Marinas
2013-05-28 18:50 ` Nicolas Pitre
2013-05-29 11:05 ` Catalin Marinas [this message]
2013-05-29 19:16 ` Simon Baatz
2013-05-30 16:43 ` Catalin Marinas
2013-05-31 12:05 ` Jason Cooper
2013-05-31 14:15 ` Catalin Marinas
2013-05-31 14:20 ` Jason Cooper
2013-06-03 17:38 ` Simon Baatz
2013-06-03 18:03 ` Jason Cooper
2013-06-03 19:11 ` Simon Baatz
2013-06-03 19:22 ` Jason Cooper
2013-06-03 20:38 ` Greg KH
2013-06-05 13:58 ` Catalin Marinas
2013-06-05 19:55 ` Simon Baatz
2013-05-31 9:07 ` Ming Lei
2013-05-31 18:54 ` Simon Baatz
2013-06-01 10:27 ` Ming Lei
2013-06-03 9:33 ` Catalin Marinas
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20130529110508.GH17767@MacBook-Pro.local \
--to=catalin.marinas@arm$(echo .)com \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox