svn commit: r276056 - head/sys/vm

[Gleb Smirnoff]

Author: glebius
Date: Mon Dec 22 09:02:21 2014
New Revision: 276056
URL: https://svnweb.freebsd.org/changeset/base/276056

Log:
  Add flag VM_ALLOC_NOWAIT for vm_page_grab() that prevents sleeping and
  allows the function to fail.
  
  Reviewed by:	kib, alc
  Sponsored by:	Nginx, Inc.

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	Mon Dec 22 09:00:47 2014	(r276055)
+++ head/sys/vm/vm_page.c	Mon Dec 22 09:02:21 2014	(r276056)
@@ -2711,6 +2711,8 @@ retrylookup:
 		sleep = (allocflags & VM_ALLOC_IGN_SBUSY) != 0 ?
 		    vm_page_xbusied(m) : vm_page_busied(m);
 		if (sleep) {
+			if ((allocflags & VM_ALLOC_NOWAIT) != 0)
+				return (NULL); 
 			/*
 			 * Reference the page before unlocking and
 			 * sleeping so that the page daemon is less
@@ -2738,6 +2740,8 @@ retrylookup:
 	}
 	m = vm_page_alloc(object, pindex, allocflags);
 	if (m == NULL) {
+		if ((allocflags & VM_ALLOC_NOWAIT) != 0)
+			return (NULL);
 		VM_OBJECT_WUNLOCK(object);
 		VM_WAIT;
 		VM_OBJECT_WLOCK(object);

Modified: head/sys/vm/vm_page.h
==============================================================================
--- head/sys/vm/vm_page.h	Mon Dec 22 09:00:47 2014	(r276055)
+++ head/sys/vm/vm_page.h	Mon Dec 22 09:02:21 2014	(r276056)
@@ -405,6 +405,7 @@ vm_page_t PHYS_TO_VM_PAGE(vm_paddr_t pa)
 #define	VM_ALLOC_IGN_SBUSY	0x1000	/* (g) Ignore shared busy flag */
 #define	VM_ALLOC_NODUMP		0x2000	/* (ag) don't include in dump */
 #define	VM_ALLOC_SBUSY		0x4000	/* (acg) Shared busy the page */
+#define	VM_ALLOC_NOWAIT		0x8000	/* (g) Do not sleep, return NULL */
 #define	VM_ALLOC_COUNT_SHIFT	16
 #define	VM_ALLOC_COUNT(count)	((count) << VM_ALLOC_COUNT_SHIFT)