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author | alc <alc@FreeBSD.org> | 2012-06-16 18:56:19 +0000 |
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committer | alc <alc@FreeBSD.org> | 2012-06-16 18:56:19 +0000 |
commit | 6eeaee04e4175a3faa0ce3f7778a3abce0d8d9a2 (patch) | |
tree | ebf0376a21131a0f41835773afe0ddda56d3efbe /sys/vm/vm_page.h | |
parent | ca31dfb2b475f8026e45a8b10673993068ebc000 (diff) | |
download | FreeBSD-src-6eeaee04e4175a3faa0ce3f7778a3abce0d8d9a2.zip FreeBSD-src-6eeaee04e4175a3faa0ce3f7778a3abce0d8d9a2.tar.gz |
The page flag PGA_WRITEABLE is set and cleared exclusively by the pmap
layer, but it is read directly by the MI VM layer. This change introduces
pmap_page_is_write_mapped() in order to completely encapsulate all direct
access to PGA_WRITEABLE in the pmap layer.
Aesthetics aside, I am making this change because amd64 will likely begin
using an alternative method to track write mappings, and having
pmap_page_is_write_mapped() in place allows me to make such a change
without further modification to the MI VM layer.
As an added bonus, tidy up some nearby comments concerning page flags.
Reviewed by: kib
MFC after: 6 weeks
Diffstat (limited to 'sys/vm/vm_page.h')
-rw-r--r-- | sys/vm/vm_page.h | 14 |
1 files changed, 8 insertions, 6 deletions
diff --git a/sys/vm/vm_page.h b/sys/vm/vm_page.h index 479c5bf..44fe235 100644 --- a/sys/vm/vm_page.h +++ b/sys/vm/vm_page.h @@ -237,20 +237,22 @@ extern struct vpglocks pa_lock[]; #endif #define vm_page_queue_free_mtx vm_page_queue_free_lock.data + /* * These are the flags defined for vm_page. * - * aflags are updated by atomic accesses. Use the vm_page_aflag_set() + * aflags are updated by atomic accesses. Use the vm_page_aflag_set() * and vm_page_aflag_clear() functions to set and clear the flags. * * PGA_REFERENCED may be cleared only if the object containing the page is - * locked. + * locked. It is set by both the MI and MD VM layers. * * PGA_WRITEABLE is set exclusively on managed pages by pmap_enter(). When it - * does so, the page must be VPO_BUSY. + * does so, the page must be VPO_BUSY. The MI VM layer must never access this + * flag directly. Instead, it should call pmap_page_is_write_mapped(). * * PGA_EXECUTABLE may be set by pmap routines, and indicates that a page has - * at least one executable mapping. It is not consumed by the VM layer. + * at least one executable mapping. It is not consumed by the MI VM layer. */ #define PGA_WRITEABLE 0x01 /* page may be mapped writeable */ #define PGA_REFERENCED 0x02 /* page has been referenced */ @@ -262,12 +264,12 @@ extern struct vpglocks pa_lock[]; */ #define PG_CACHED 0x01 /* page is cached */ #define PG_FREE 0x02 /* page is free */ -#define PG_FICTITIOUS 0x04 /* physical page doesn't exist (O) */ +#define PG_FICTITIOUS 0x04 /* physical page doesn't exist */ #define PG_ZERO 0x08 /* page is zeroed */ #define PG_MARKER 0x10 /* special queue marker page */ #define PG_SLAB 0x20 /* object pointer is actually a slab */ #define PG_WINATCFLS 0x40 /* flush dirty page on inactive q */ -#define PG_NODUMP 0x80 /* don't include this page in the dump */ +#define PG_NODUMP 0x80 /* don't include this page in a dump */ /* * Misc constants. |