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Subject: PERFORCE change 200534 for review
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http://p4web.freebsd.org/@@200534?ac=10

Change 200534 by jhb@jhb_jhbbsd on 2011/10/21 17:47:20

	- A nit from mdf.
	- Rework FADV_DONTNEED.  vm_object_sync() did not work because
	  the buffer cache still had buffers holding onto the pages, so
	  vm_object_page_remove() did not actually remove any pages.
	  vinvalbuf() will flush all the open buffers (though it is a bit
	  heavy-handed as it does all of the buffers and not just buffers
	  for the requested range).

Affected files ...

.. //depot/projects/fadvise/sys/kern/vfs_syscalls.c#7 edit

Differences ...

==== //depot/projects/fadvise/sys/kern/vfs_syscalls.c#7 (text+ko) ====

@@ -61,6 +61,7 @@
 #include <sys/filio.h>
 #include <sys/limits.h>
 #include <sys/linker.h>
+#include <sys/mman.h>
 #include <sys/sdt.h>
 #include <sys/stat.h>
 #include <sys/sx.h>
@@ -4861,7 +4862,7 @@
 	int error, vfslocked;
 
 	if (uap->offset < 0 || uap->len < 0 ||
-	    uap->offset + uap->len < uap->offset)
+	    uap->offset > OFF_MAX - uap->len)
 		return (EINVAL);
 	switch (uap->advice) {
 	case FADV_NORMAL:
@@ -4959,12 +4960,24 @@
 		break;
 	case FADV_DONTNEED:
 		/*
-		 * Invalidate pages from the backing VM object similar
-		 * to msync(MS_INVALIDATE).
+		 * Flush any open FS buffers and then remove pages
+		 * from the backing VM object.
 		 */
-		if (vp->v_object != NULL)
-			vm_object_sync(vp->v_object, uap->offset, end - uap->offset,
-			    FALSE, TRUE);
+		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
+		if (vp->v_iflag & VI_DOOMED) {
+			VOP_UNLOCK(vp, 0);
+			break;
+		}
+		vinvalbuf(vp, V_NORMAL, 0, 0);
+		if (vp->v_object != NULL) {
+			start = trunc_page(uap->offset);
+			end = round_page(end);
+			VM_OBJECT_LOCK(vp->v_object);
+			vm_object_page_remove(vp->v_object, OFF_TO_IDX(start),
+			    OFF_TO_IDX(end), OBJPR_CLEANONLY | OBJPR_DEBUG);
+			VM_OBJECT_UNLOCK(vp->v_object);
+		}
+		VOP_UNLOCK(vp, 0);
 		break;
 	}
 out: