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Require that the page lock is held, instead of the object lock, when

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clearing the page's PGA_REFERENCED flag.  Since we are typically
manipulating the page's act_count field when we are clearing its
PGA_REFERENCED flag, the page lock is already held everywhere that we clear
the PGA_REFERENCED flag.  So, in fact, this revision only changes some
comments and an assertion.  Nonetheless, it will enable later changes to
object locking in the pageout code.

Introduce vm_page_assert_locked(), which completely hides the implementation
details of the page lock from the caller, and use it in
vm_page_aflag_clear().  (The existing vm_page_lock_assert() could not be
used in vm_page_aflag_clear().)  Over the coming weeks, I expect that we'll
either eliminate or replace the various uses of vm_page_lock_assert() with
vm_page_assert_locked().

Reviewed by:	attilio
Sponsored by:	EMC / Isilon Storage Division
This commit is contained in:
Alan Cox 2013-06-03 01:22:54 +00:00
parent 6a3193a773
commit b417181250
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=251280
2 changed files with 16 additions and 7 deletions
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7
sys/vm/vm_page.c
View File

@ -2724,6 +2724,13 @@ vm_page_trylock_KBI(vm_page_t m, const char *file, int line)
}
#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
void
vm_page_assert_locked_KBI(vm_page_t m, const char *file, int line)
{
vm_page_lock_assert_KBI(m, MA_OWNED, file, line);
}
void
vm_page_lock_assert_KBI(vm_page_t m, int a, const char *file, int line)
{

16
sys/vm/vm_page.h
View File

@ -229,9 +229,12 @@ extern struct mtx_padalign pa_lock[];
#define vm_page_trylock(m) mtx_trylock(vm_page_lockptr((m)))
#endif
#if defined(INVARIANTS)
#define vm_page_assert_locked(m) \
vm_page_assert_locked_KBI((m), __FILE__, __LINE__)
#define vm_page_lock_assert(m, a) \
vm_page_lock_assert_KBI((m), (a), __FILE__, __LINE__)
#else
#define vm_page_assert_locked(m)
#define vm_page_lock_assert(m, a)
#endif
@ -240,10 +243,9 @@ extern struct mtx_padalign pa_lock[];
* these flags, the functions vm_page_aflag_set() and vm_page_aflag_clear()
* must be used. Neither these flags nor these functions are part of the KBI.
*
* PGA_REFERENCED may be cleared only if the object containing the page is
* locked. It is set by both the MI and MD VM layers. However, kernel
* loadable modules should not directly set this flag. They should call
* vm_page_reference() instead.
* PGA_REFERENCED may be cleared only if the page is locked. It is set by
* both the MI and MD VM layers. However, kernel loadable modules should not
* directly set this flag. They should call vm_page_reference() instead.
*
* PGA_WRITEABLE is set exclusively on managed pages by pmap_enter(). When it
* does so, the page must be VPO_BUSY. The MI VM layer must never access this
@ -424,6 +426,7 @@ void vm_page_lock_KBI(vm_page_t m, const char *file, int line);
void vm_page_unlock_KBI(vm_page_t m, const char *file, int line);
int vm_page_trylock_KBI(vm_page_t m, const char *file, int line);
#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
void vm_page_assert_locked_KBI(vm_page_t m, const char *file, int line);
void vm_page_lock_assert_KBI(vm_page_t m, int a, const char *file, int line);
#endif
@ -451,11 +454,10 @@ vm_page_aflag_clear(vm_page_t m, uint8_t bits)
uint32_t *addr, val;
/*
* The PGA_REFERENCED flag can only be cleared if the object
* containing the page is locked.
* The PGA_REFERENCED flag can only be cleared if the page is locked.
*/
if ((bits & PGA_REFERENCED) != 0)
VM_PAGE_OBJECT_LOCK_ASSERT(m);
vm_page_assert_locked(m);
/*
* Access the whole 32-bit word containing the aflags field with an