Date: Tue, 2 Mar 1999 16:40:03 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: "AARON MARKS" <amarks@sarnoff.com> Cc: hackers@FreeBSD.ORG Subject: Re: getpages() for a memory-based fs Message-ID: <199903030040.QAA59228@apollo.backplane.com> References: <36DC669B.707C33C7@sarnoff.com>
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:I'm working on the getpages() routine for a memory-based fs and I don't
:quite understand how to map my page(s) to kernel vm via the vm_page
:struct. What's the formal method of copying data to a vm page?
:
:Thanks,
:-A.
:
:--
:Aaron J. Marks Communications and Computing Systems Lab
:Assoc. Member Tech Staff Advanced Networks and Computation Group
:amarks@sarnoff.com Sarnoff Corporation
A vm_page_t is not mapped. Typically you map it by allocating a
physical buffer with getpbuf() and mapping up to MAXBSIZE bytes worth
of pages into it's reserved KVM space using pmap_qenter(). You must,
of course, undo the mappings when finished with them.
For an eample if how to do this, look at swap_pager_getpages() in
vm/swap_pager.c from FreeBSD-current ( i.e. the -4.x tree, not the -3.x
tree. The -3.x version of the function is not very readable ).
There are kernel support routines to zero pages, copy pages ( see
uiomove, uiomoveco ), and so forth but I think you will be happier using
a pbuf.
-Matt
Matthew Dillon
<dillon@backplane.com>
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