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From: Joao Martins <joao.m.martins@oracle.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: linux-mm@kvack.org, dave.hansen@linux.intel.com, hch@lst.de,
	linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 11/12] device-dax: Add dis-contiguous resource support
Date: Mon, 6 Apr 2020 11:43:51 +0100	[thread overview]
Message-ID: <23742bb8-831f-29ff-1463-75427eec57c7@oracle.com> (raw)
In-Reply-To: <158500773552.2088294.8756587190550753100.stgit@dwillia2-desk3.amr.corp.intel.com>

On 3/23/20 11:55 PM, Dan Williams wrote:

[...]

>  static ssize_t dev_dax_resize(struct dax_region *dax_region,
>  		struct dev_dax *dev_dax, resource_size_t size)
>  {
>  	resource_size_t avail = dax_region_avail_size(dax_region), to_alloc;
> -	resource_size_t dev_size = range_len(&dev_dax->range);
> +	resource_size_t dev_size = dev_dax_size(dev_dax);
>  	struct resource *region_res = &dax_region->res;
>  	struct device *dev = &dev_dax->dev;
> -	const char *name = dev_name(dev);
>  	struct resource *res, *first;
> +	resource_size_t alloc = 0;
> +	int rc;
>  
>  	if (dev->driver)
>  		return -EBUSY;
> @@ -684,38 +766,47 @@ static ssize_t dev_dax_resize(struct dax_region *dax_region,
>  	 * allocating a new resource.
>  	 */
>  	first = region_res->child;
> -	if (!first)
> -		return __alloc_dev_dax_range(dev_dax, dax_region->res.start,
> -				to_alloc);
> -	for (res = first; to_alloc && res; res = res->sibling) {
> +retry:
> +	rc = -ENOSPC;
> +	for (res = first; res; res = res->sibling) {
>  		struct resource *next = res->sibling;
> -		resource_size_t free;
>  
>  		/* space at the beginning of the region */
> -		free = 0;
> -		if (res == first && res->start > dax_region->res.start)
> -			free = res->start - dax_region->res.start;
> -		if (free >= to_alloc && dev_size == 0)
> -			return __alloc_dev_dax_range(dev_dax,
> -					dax_region->res.start, to_alloc);
> -
> -		free = 0;
> +		if (res == first && res->start > dax_region->res.start) {
> +			alloc = min(res->start - dax_region->res.start,
> +					to_alloc);
> +			rc = __alloc_dev_dax_range(dev_dax,
> +					dax_region->res.start, alloc);

You might be missing:

	first = region_res->child;

(...) right after returning from __alloc_dev_dax_range(). Alternatively, perhaps
even moving the 'retry' label to right before the @first initialization.

In the case that you pick space from the beginning, the child resource of the
dax region will point to first occupied region, and that changes after you pick
this space. So, IIUC, you want to adjust where you start searching free space
otherwise you end up wrongly picking that same space twice.

If it helps, the bug can be reproduced in this unit test below, see
daxctl_test3() test:

https://lore.kernel.org/linux-nvdimm/20200403205900.18035-11-joao.m.martins@oracle.com/

> +			break;
> +		}
> +

[...]
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  parent reply	other threads:[~2020-04-06 10:46 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-23 23:54 [PATCH 00/12] device-dax: Support sub-dividing soft-reserved ranges Dan Williams
2020-03-23 23:54 ` [PATCH 01/12] device-dax: Drop the dax_region.pfn_flags attribute Dan Williams
2020-03-23 23:54 ` [PATCH 02/12] device-dax: Move instance creation parameters to 'struct dev_dax_data' Dan Williams
2020-03-23 23:54 ` [PATCH 03/12] device-dax: Make pgmap optional for instance creation Dan Williams
2020-03-23 23:54 ` [PATCH 04/12] device-dax: Kill dax_kmem_res Dan Williams
2020-03-23 23:55 ` [PATCH 05/12] device-dax: Add an allocation interface for device-dax instances Dan Williams
2020-03-23 23:55 ` [PATCH 06/12] device-dax: Introduce seed devices Dan Williams
2020-03-23 23:55 ` [PATCH 07/12] drivers/base: Make device_find_child_by_name() compatible with sysfs inputs Dan Williams
2020-03-23 23:55 ` [PATCH 08/12] device-dax: Add resize support Dan Williams
2020-03-23 23:55 ` [PATCH 09/12] mm/memremap_pages: Convert to 'struct range' Dan Williams
2020-03-23 23:55 ` [PATCH 10/12] mm/memremap_pages: Support multiple ranges per invocation Dan Williams
2020-03-23 23:55 ` [PATCH 11/12] device-dax: Add dis-contiguous resource support Dan Williams
2020-03-24 16:12   ` Joao Martins
2020-03-25 10:35     ` Joao Martins
2020-03-25 17:48       ` Dan Williams
2020-03-26 17:49         ` Joao Martins
2020-07-11  0:44     ` Dan Williams
2020-04-06 10:43   ` Joao Martins [this message]
2020-04-06 20:22     ` Dan Williams
2020-07-11  0:47       ` Dan Williams
2020-05-12 14:36   ` Joao Martins
2020-07-11  0:52     ` Dan Williams
2020-03-23 23:55 ` [PATCH 12/12] device-dax: Introduce 'mapping' devices Dan Williams
2020-03-24 16:27   ` Joao Martins
2020-03-24 23:51     ` Dan Williams

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