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SubjectRe: [PATCH 14/17] memremap: simplify duplicate region handling in devm_memremap_pages
On Fri, Dec 15, 2017 at 6:09 AM, Christoph Hellwig <hch@lst.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@lst.de>
> Reviewed-by: Logan Gunthorpe <logang@deltatee.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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