Messages in this thread | | | From | Dan Williams <> | Date | Wed, 17 Apr 2019 14:54:36 -0700 | Subject | Re: [PATCH v1 00/15] Keep track of GUPed pages in fs and block |
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On Tue, Apr 16, 2019 at 12:28 PM Boaz Harrosh <boaz@plexistor.com> wrote: > > On 16/04/19 22:12, Dan Williams wrote: > > On Tue, Apr 16, 2019 at 11:59 AM Kent Overstreet > > <kent.overstreet@gmail.com> wrote: > <> > > This all reminds of the failed attempt to teach the block layer to > > operate without pages: > > > > https://lore.kernel.org/lkml/20150316201640.33102.33761.stgit@dwillia2-desk3.amr.corp.intel.com/ > > > > Exactly why I want to make sure it is just a [pointer | flag] and not any kind of pfn > type. Let us please not go there again? > > >> > >> Question though - why do we need a flag for whether a page is a GUP page or not? > >> Couldn't the needed information just be determined by what range the pfn is not > >> (i.e. whether or not it has a struct page associated with it)? > > > > That amounts to a pfn_valid() check which is a bit heavier than if we > > can store a flag in the bv_pfn entry directly. > > > > I'd say create a new PFN_* flag, and make bv_pfn a 'pfn_t' rather than > > an 'unsigned long'. > > > > No, please please not. This is not a pfn and not a pfn_t. It is a page-ptr > and a flag that says where/how to put_page it. IE I did a GUP on this page > please do a PUP on this page instead of regular put_page. So no where do I mean > pfn or pfn_t in this code. Then why?
If it's not a pfn then it shouldn't be an unsigned long named "bv_pfn".
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