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Message-ID: <CAPcyv4i2naLJjWzm+q0ORRfyHkT0f5dFBFKutuaXE3OgPcHX5g@mail.gmail.com>
Date: Sun, 17 Dec 2017 09:34:11 -0800
From: Dan Williams <dan.j.williams@...el.com>
To: Christoph Hellwig <hch@....de>
Cc: Jérôme Glisse <jglisse@...hat.com>,
Logan Gunthorpe <logang@...tatee.com>,
"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
X86 ML <x86@...nel.org>, Linux MM <linux-mm@...ck.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 14/17] memremap: simplify duplicate region handling in devm_memremap_pages
On Fri, Dec 15, 2017 at 6:09 AM, Christoph Hellwig <hch@....de> wrote:
> __radix_tree_insert already checks for duplicates and returns -EEXIST in
> that case, so remove the duplicate (and racy) duplicates check.
>
> Signed-off-by: Christoph Hellwig <hch@....de>
> Reviewed-by: Logan Gunthorpe <logang@...tatee.com>
> ---
> kernel/memremap.c | 11 -----------
> 1 file changed, 11 deletions(-)
>
> diff --git a/kernel/memremap.c b/kernel/memremap.c
> index 891491ddccdb..901404094df1 100644
> --- a/kernel/memremap.c
> +++ b/kernel/memremap.c
> @@ -395,17 +395,6 @@ void *devm_memremap_pages(struct device *dev, struct resource *res,
> align_end = align_start + align_size - 1;
>
> foreach_order_pgoff(res, order, pgoff) {
> - struct dev_pagemap *dup;
> -
> - rcu_read_lock();
> - dup = find_dev_pagemap(res->start + PFN_PHYS(pgoff));
> - rcu_read_unlock();
> - if (dup) {
> - dev_err(dev, "%s: %pr collides with mapping for %s\n",
> - __func__, res, dev_name(dup->dev));
> - error = -EBUSY;
> - break;
> - }
> error = __radix_tree_insert(&pgmap_radix,
> PHYS_PFN(res->start) + pgoff, order, page_map);
> if (error) {
This is not racy, we'll catch the error on insert, and I think the
extra debug information is useful for debugging a broken memory map or
alignment math.
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