Messages in this thread | | | Date | Tue, 1 Dec 2015 18:13:22 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH v3 1/3] resource: Add @flags to region_intersects() |
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On Tue, Dec 01, 2015 at 08:54:23AM -0800, Dan Williams wrote: > On Tue, Dec 1, 2015 at 5:50 AM, Borislav Petkov <bp@alien8.de> wrote: > > On Tue, Nov 24, 2015 at 03:33:36PM -0700, Toshi Kani wrote: > >> region_intersects() checks if a specified region partially overlaps > >> or fully eclipses a resource identified by @name. It currently sets > >> resource flags statically, which prevents the caller from specifying > >> a non-RAM region, such as persistent memory. Add @flags so that > >> any region can be specified to the function. > >> > >> A helper function, region_intersects_ram(), is added so that the > >> callers that check a RAM region do not have to specify its iomem > >> resource name and flags. This interface is exported for modules, > >> such as the EINJ driver. > >> > >> Signed-off-by: Toshi Kani <toshi.kani@hpe.com> > >> Reviewed-by: Dan Williams <dan.j.williams@intel.com> > >> Cc: Andrew Morton <akpm@linux-foundation.org> > >> Cc: Vishal Verma <vishal.l.verma@intel.com> > >> --- > >> include/linux/mm.h | 4 +++- > >> kernel/memremap.c | 5 ++--- > >> kernel/resource.c | 23 ++++++++++++++++------- > >> 3 files changed, 21 insertions(+), 11 deletions(-) > >> > >> diff --git a/include/linux/mm.h b/include/linux/mm.h > >> index 00bad77..c776af3 100644 > >> --- a/include/linux/mm.h > >> +++ b/include/linux/mm.h > >> @@ -362,7 +362,9 @@ enum { > >> REGION_MIXED, > >> }; > >> > >> -int region_intersects(resource_size_t offset, size_t size, const char *type); > >> +int region_intersects(resource_size_t offset, size_t size, const char *type, > >> + unsigned long flags); > >> +int region_intersects_ram(resource_size_t offset, size_t size); > >> > >> /* Support for virtually mapped pages */ > >> struct page *vmalloc_to_page(const void *addr); > >> diff --git a/kernel/memremap.c b/kernel/memremap.c > >> index 7658d32..98f52f1 100644 > >> --- a/kernel/memremap.c > >> +++ b/kernel/memremap.c > >> @@ -57,7 +57,7 @@ static void *try_ram_remap(resource_size_t offset, size_t size) > >> */ > >> void *memremap(resource_size_t offset, size_t size, unsigned long flags) > >> { > >> - int is_ram = region_intersects(offset, size, "System RAM"); > > > > Ok, question: why do those resource things types gets identified with > > a string?! We have here "System RAM" and next patch adds "Persistent > > Memory". > > > > And "persistent memory" or "System RaM" won't work and this is just > > silly. > > > > Couldn't struct resource have gained some typedef flags instead which we > > can much easily test? Using the strings looks really yucky. > > > > At least in the case of region_intersects() I was just following > existing strcmp() convention from walk_system_ram_range.
Oh sure, I didn't mean you. I was simply questioning that whole identify-resource-by-its-name approach. And that came with:
67cf13ceed89 ("x86: optimize resource lookups for ioremap")
I just think it is silly and that we should be identifying resource things in a more robust way.
Btw, the ->name thing in struct resource has been there since a *long* time, added by:
commit 40f6b7cc623f95d2a08b9adae7a6793055af4768 Author: linus1 <torvalds@linuxfoundation.org> Date: Wed Jun 30 11:00:00 1999 -0600
Import 2.3.11pre1
I'm not sure what it was used for, perhaps for human-readable output in /proc/iomem.
Let me CC Linus, he would know, most likely. akpm is already on CC.
> We could define 'const char *system_ram = "System RAM"' somewhere and > then do pointer comparisons to cut down on the thrash of adding new > flags to 'struct resource'?
See above. I think flags or type_flags or so should be cleaner/better...
I could be missing some aspect though, according to which, the name is the proper way to ident those but I can't think of one...
-- Regards/Gruss, Boris.
ECO tip #101: Trim your mails when you reply.
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