From: Linus Torvalds <torvalds@linux-foundation.org>
To: Matthew Wilcox <mawilcox@linuxonhyperv.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Konstantin Khlebnikov <koct9i@gmail.com>,
Ross Zwisler <ross.zwisler@linux.intel.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Matthew Wilcox <mawilcox@microsoft.com>
Subject: Re: [PATCH 2/2] radix-tree: Fix optimisation problem
Date: Thu, 22 Sep 2016 11:09:16 -0700 [thread overview]
Message-ID: <CA+55aFwNYAFc4KePvx50kwZ3A+8yvCCK_6nYYxG9fqTPhFzQoQ@mail.gmail.com> (raw)
In-Reply-To: <1474570415-14938-3-git-send-email-mawilcox@linuxonhyperv.com>
On Thu, Sep 22, 2016 at 11:53 AM, Matthew Wilcox
<mawilcox@linuxonhyperv.com> wrote:
>
> Change the test suite to compile with -O2, and
> fix the optimisation problem by passing 'entry' through entry_to_node()
> so gcc knows this isn't a plain pointer.
Ugh. I really don't like this patch very much.
Wouldn't it be cleaner to just fix "get_slot_offset()" instead? As it
is, looking at the code, I suspect that it's really hard to convince
people that there isn't some other place this might happen. Because
the "pointer subtraction followed by pointer addition" pattern is all
hidden in these inline functions.
Or at least add a big comment about why this is the only such case.
Because without that, the code now looks very bad.
Linus
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next prev parent reply other threads:[~2016-09-22 18:09 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-22 18:53 [PATCH 0/2] Fix radix_tree_lookup_slot() Matthew Wilcox
2016-09-22 18:53 ` [PATCH 1/2] radix tree test suite: Test radix_tree_replace_slot() for multiorder entries Matthew Wilcox
2016-09-22 18:53 ` [PATCH 2/2] radix-tree: Fix optimisation problem Matthew Wilcox
2016-09-22 18:09 ` Linus Torvalds [this message]
2016-09-23 20:16 ` Matthew Wilcox
2016-09-24 20:21 ` Linus Torvalds
2016-09-24 20:47 ` Linus Torvalds
2016-09-24 21:04 ` Kirill A. Shutemov
2016-09-24 22:54 ` Linus Torvalds
2016-09-26 4:26 ` Ross Zwisler
2016-09-24 8:36 ` Konstantin Khlebnikov
2016-09-24 23:35 ` Cedric Blancher
2016-09-25 0:18 ` Linus Torvalds
2016-09-25 17:59 ` Cedric Blancher
2016-09-25 18:04 ` Linus Torvalds
2016-09-25 19:04 ` Linus Torvalds
2016-09-25 19:40 ` Cedric Blancher
2016-09-25 19:56 ` Linus Torvalds
2016-09-26 21:28 ` Matthew Wilcox
2016-09-26 21:48 ` Cedric Blancher
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