Re: [PATCH v1 3/3] kernel/resource: remove first_lvl / siblings_only logic

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Mon, Mar 22, 2021 at 05:02:00PM +0100, David Hildenbrand wrote:
> All IORESOURCE_SYSTEM_RAM and IORESOURCE_MEM now properly consider the
> whole resource tree, not just the first level. Let's drop the unused
> first_lvl / siblings_only logic.
> 
> All functions properly search the whole tree, so remove documentation
> that indicates that some functions behave differently.


Like this clean up!
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

Although a few nit-picks below.

> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
> Cc: Signed-off-by: David Hildenbrand <david@redhat.com>
> Cc: Dave Young <dyoung@redhat.com>
> Cc: Baoquan He <bhe@redhat.com>
> Cc: Vivek Goyal <vgoyal@redhat.com>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Keith Busch <keith.busch@intel.com>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Qian Cai <cai@lca.pw>
> Cc: Oscar Salvador <osalvador@suse.de>
> Cc: Eric Biederman <ebiederm@xmission.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Cc: x86@kernel.org
> Cc: kexec@lists.infradead.org
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  kernel/resource.c | 45 ++++++++++++---------------------------------
>  1 file changed, 12 insertions(+), 33 deletions(-)
> 
> diff --git a/kernel/resource.c b/kernel/resource.c
> index 16e0c7e8ed24..7e00239a023a 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -64,12 +64,8 @@ static DEFINE_RWLOCK(resource_lock);
>  static struct resource *bootmem_resource_free;
>  static DEFINE_SPINLOCK(bootmem_resource_lock);
>  
> -static struct resource *next_resource(struct resource *p, bool sibling_only)
> +static struct resource *next_resource(struct resource *p)
>  {
> -	/* Caller wants to traverse through siblings only */
> -	if (sibling_only)
> -		return p->sibling;
> -
>  	if (p->child)
>  		return p->child;
>  	while (!p->sibling && p->parent)
> @@ -81,7 +77,7 @@ static void *r_next(struct seq_file *m, void *v, loff_t *pos)
>  {
>  	struct resource *p = v;
>  	(*pos)++;
> -	return (void *)next_resource(p, false);
> +	return (void *)next_resource(p);
>  }
>  
>  #ifdef CONFIG_PROC_FS
> @@ -330,14 +326,10 @@ EXPORT_SYMBOL(release_resource);
>   * of the resource that's within [@start..@end]; if none is found, returns
>   * -ENODEV.  Returns -EINVAL for invalid parameters.
>   *
> - * This function walks the whole tree and not just first level children
> - * unless @first_lvl is true.
> - *
>   * @start:	start address of the resource searched for
>   * @end:	end address of same resource
>   * @flags:	flags which the resource must have
>   * @desc:	descriptor the resource must have
> - * @first_lvl:	walk only the first level children, if set
>   * @res:	return ptr, if resource found
>   *
>   * The caller must specify @start, @end, @flags, and @desc
> @@ -345,9 +337,8 @@ EXPORT_SYMBOL(release_resource);
>   */
>  static int find_next_iomem_res(resource_size_t start, resource_size_t end,
>  			       unsigned long flags, unsigned long desc,
> -			       bool first_lvl, struct resource *res)
> +			       struct resource *res)
>  {
> -	bool siblings_only = true;
>  	struct resource *p;
>  
>  	if (!res)
> @@ -358,7 +349,7 @@ static int find_next_iomem_res(resource_size_t start, resource_size_t end,
>  
>  	read_lock(&resource_lock);
>  
> -	for (p = iomem_resource.child; p; p = next_resource(p, siblings_only)) {
> +	for (p = iomem_resource.child; p; p = next_resource(p)) {
>  		/* If we passed the resource we are looking for, stop */
>  		if (p->start > end) {
>  			p = NULL;
> @@ -369,13 +360,6 @@ static int find_next_iomem_res(resource_size_t start, resource_size_t end,
>  		if (p->end < start)
>  			continue;
>  
> -		/*
> -		 * Now that we found a range that matches what we look for,
> -		 * check the flags and the descriptor. If we were not asked to
> -		 * use only the first level, start looking at children as well.
> -		 */
> -		siblings_only = first_lvl;
> -
>  		if ((p->flags & flags) != flags)
>  			continue;
>  		if ((desc != IORES_DESC_NONE) && (desc != p->desc))
> @@ -402,14 +386,14 @@ static int find_next_iomem_res(resource_size_t start, resource_size_t end,
>  
>  static int __walk_iomem_res_desc(resource_size_t start, resource_size_t end,
>  				 unsigned long flags, unsigned long desc,
> -				 bool first_lvl, void *arg,

> +				 void *arg,
>  				 int (*func)(struct resource *, void *))

Can it be one line?

>  {
>  	struct resource res;
>  	int ret = -EINVAL;
>  
>  	while (start < end &&
> -	       !find_next_iomem_res(start, end, flags, desc, first_lvl, &res)) {
> +	       !find_next_iomem_res(start, end, flags, desc, &res)) {
>  		ret = (*func)(&res, arg);
>  		if (ret)
>  			break;
> @@ -431,7 +415,6 @@ static int __walk_iomem_res_desc(resource_size_t start, resource_size_t end,
>   * @arg: function argument for the callback @func
>   * @func: callback function that is called for each qualifying resource area
>   *
> - * This walks through whole tree and not just first level children.
>   * All the memory ranges which overlap start,end and also match flags and
>   * desc are valid candidates.
>   *
> @@ -441,7 +424,7 @@ static int __walk_iomem_res_desc(resource_size_t start, resource_size_t end,
>  int walk_iomem_res_desc(unsigned long desc, unsigned long flags, u64 start,
>  		u64 end, void *arg, int (*func)(struct resource *, void *))
>  {
> -	return __walk_iomem_res_desc(start, end, flags, desc, false, arg, func);
> +	return __walk_iomem_res_desc(start, end, flags, desc, arg, func);
>  }
>  EXPORT_SYMBOL_GPL(walk_iomem_res_desc);
>  
> @@ -457,8 +440,8 @@ int walk_system_ram_res(u64 start, u64 end, void *arg,
>  {
>  	unsigned long flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
>  
> -	return __walk_iomem_res_desc(start, end, flags, IORES_DESC_NONE, false,
> -				     arg, func);

> +	return __walk_iomem_res_desc(start, end, flags, IORES_DESC_NONE, arg,
> +				     func);

I guess you may do it on one line.

>  }
>  
>  /*
> @@ -470,17 +453,14 @@ int walk_mem_res(u64 start, u64 end, void *arg,
>  {
>  	unsigned long flags = IORESOURCE_MEM | IORESOURCE_BUSY;
>  
> -	return __walk_iomem_res_desc(start, end, flags, IORES_DESC_NONE, false,
> -				     arg, func);
> +	return __walk_iomem_res_desc(start, end, flags, IORES_DESC_NONE, arg,
> +				     func);

Ditto.

>  }
>  
>  /*
>   * This function calls the @func callback against all memory ranges of type
>   * System RAM which are marked as IORESOURCE_SYSTEM_RAM and IORESOUCE_BUSY.
>   * It is to be used only for System RAM.
> - *
> - * This will find System RAM ranges that are children of top-level resources
> - * in addition to top-level System RAM resources.
>   */
>  int walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages,
>  			  void *arg, int (*func)(unsigned long, unsigned long, void *))
> @@ -495,8 +475,7 @@ int walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages,
>  	end = ((u64)(start_pfn + nr_pages) << PAGE_SHIFT) - 1;
>  	flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
>  	while (start < end &&
> -	       !find_next_iomem_res(start, end, flags, IORES_DESC_NONE,
> -				    false, &res)) {
> +	       !find_next_iomem_res(start, end, flags, IORES_DESC_NONE, &res)) {
>  		pfn = PFN_UP(res.start);
>  		end_pfn = PFN_DOWN(res.end + 1);
>  		if (end_pfn > pfn)
> -- 
> 2.29.2
> 

-- 
With Best Regards,
Andy Shevchenko