Messages in this thread | | | Date | Mon, 18 Jul 2022 12:48:08 +0200 | From | David Hildenbrand <> | Subject | Re: [PATCH] resource: re-factor page_is_ram() |
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On 01.06.22 18:32, Vaibhav Jain wrote: > Presently page_is_ram() relies on walk_system_ram_range() that performs a walk > on kernel iomem resources hierarchy with a dummy callback __is_ram(). Before > calling find_next_iomem_res(), walk_system_ram_range() does some book-keeping > which can be avoided for page_is_ram() use-case. > > Hence this patch proposes to update page_is_ram() to directly call > find_next_iomem_res() with minimal book-keeping needed. > > To avoid allocating a 'struct resource' the patch also updates > find_next_iomem_res() to not return -EINVAL in case 'res == NULL'. Instead > out 'struct resource *res' is only populated when its not NULL. > > Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com> > --- > kernel/resource.c | 19 ++++++++----------- > 1 file changed, 8 insertions(+), 11 deletions(-) > > diff --git a/kernel/resource.c b/kernel/resource.c > index 34eaee179689..ecf6b9a50adc 100644 > --- a/kernel/resource.c > +++ b/kernel/resource.c > @@ -311,7 +311,7 @@ EXPORT_SYMBOL(release_resource); > * > * If a resource is found, returns 0 and @*res is overwritten with the part > * of the resource that's within [@start..@end]; if none is found, returns > - * -ENODEV. Returns -EINVAL for invalid parameters. > + * -ENODEV. > *
There is still another -EINVAL in that function ...
> * @start: start address of the resource searched for > * @end: end address of same resource > @@ -328,9 +328,6 @@ static int find_next_iomem_res(resource_size_t start, resource_size_t end, > { > struct resource *p; > > - if (!res) > - return -EINVAL; > - > if (start >= end) > return -EINVAL;
As all callers guarantee that, we might just remove it.
> > @@ -356,7 +353,7 @@ static int find_next_iomem_res(resource_size_t start, resource_size_t end, > break; > } > > - if (p) { > + if (p && res) { > /* copy data */ > *res = (struct resource) { > .start = max(start, p->start), > @@ -474,18 +471,18 @@ int walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages, > return ret; > } > > -static int __is_ram(unsigned long pfn, unsigned long nr_pages, void *arg) > -{ > - return 1; > -} > - > /* > * This generic page_is_ram() returns true if specified address is > * registered as System RAM in iomem_resource list. > */ > int __weak page_is_ram(unsigned long pfn) > { > - return walk_system_ram_range(pfn, 1, NULL, __is_ram) == 1; > + const resource_size_t pfn_res = PFN_PHYS(pfn); > + > + return find_next_iomem_res(pfn_res, > + pfn_res + 1, > + IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY, > + IORES_DESC_NONE, NULL) == 0; > } > EXPORT_SYMBOL_GPL(page_is_ram); >
What about
a) A cleanup patch upfront that removes both -EINVAL cases from find_next_iomem_res() followed by
b) The actual change to page_is_ram()
?
-- Thanks,
David / dhildenb
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