svn commit: r363295 - head/sys/vm

Chuck Silvers chs at FreeBSD.org
Fri Jul 17 23:09:38 UTC 2020


Author: chs
Date: Fri Jul 17 23:09:36 2020
New Revision: 363295
URL: https://svnweb.freebsd.org/changeset/base/363295

Log:
  Add a new function vm_page_free_invalid() for freeing invalid pages
  that might be wired.  If the page is wired then it cannot be freed now,
  but the thread that eventually unwires it will free it at that point.
  
  Reviewed by:	markj, kib
  Sponsored by:	Netflix
  Differential Revision:	https://reviews.freebsd.org/D25430

Modified:
  head/sys/vm/vm_page.c
  head/sys/vm/vm_page.h

Modified: head/sys/vm/vm_page.c
==============================================================================
--- head/sys/vm/vm_page.c	Fri Jul 17 23:08:01 2020	(r363294)
+++ head/sys/vm/vm_page.c	Fri Jul 17 23:09:36 2020	(r363295)
@@ -1362,6 +1362,31 @@ vm_page_readahead_finish(vm_page_t m)
 }
 
 /*
+ * Destroy the identity of an invalid page and free it if possible.
+ * This is intended to be used when reading a page from backing store fails.
+ */
+void
+vm_page_free_invalid(vm_page_t m)
+{
+
+	KASSERT(vm_page_none_valid(m), ("page %p is valid", m));
+	KASSERT(!pmap_page_is_mapped(m), ("page %p is mapped", m));
+	vm_page_assert_xbusied(m);
+	KASSERT(m->object != NULL, ("page %p has no object", m));
+	VM_OBJECT_ASSERT_WLOCKED(m->object);
+
+	/*
+	 * If someone has wired this page while the object lock
+	 * was not held, then the thread that unwires is responsible
+	 * for freeing the page.  Otherwise just free the page now.
+	 * The wire count of this unmapped page cannot change while
+	 * we have the page xbusy and the page's object wlocked.
+	 */
+	if (vm_page_remove(m))
+		vm_page_free(m);
+}
+
+/*
  *	vm_page_sleep_if_busy:
  *
  *	Sleep and release the object lock if the page is busied.

Modified: head/sys/vm/vm_page.h
==============================================================================
--- head/sys/vm/vm_page.h	Fri Jul 17 23:08:01 2020	(r363294)
+++ head/sys/vm/vm_page.h	Fri Jul 17 23:09:36 2020	(r363295)
@@ -629,6 +629,7 @@ void vm_page_deactivate_noreuse(vm_page_t);
 void vm_page_dequeue(vm_page_t m);
 void vm_page_dequeue_deferred(vm_page_t m);
 vm_page_t vm_page_find_least(vm_object_t, vm_pindex_t);
+void vm_page_free_invalid(vm_page_t);
 vm_page_t vm_page_getfake(vm_paddr_t paddr, vm_memattr_t memattr);
 void vm_page_initfake(vm_page_t m, vm_paddr_t paddr, vm_memattr_t memattr);
 int vm_page_insert (vm_page_t, vm_object_t, vm_pindex_t);


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