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From: Alan Cox <alc@FreeBSD.org>
Date: Sun, 2 May 2010 19:10:27 +0000 (UTC)
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Subject: svn commit: r207534 - head/sys/kern
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Author: alc
Date: Sun May  2 19:10:27 2010
New Revision: 207534
URL: http://svn.freebsd.org/changeset/base/207534

Log:
  Properly synchronize access to the page's hold_count in vfs_vmio_release().
  
  Reviewed by:	kib

Modified:
  head/sys/kern/vfs_bio.c

Modified: head/sys/kern/vfs_bio.c
==============================================================================
--- head/sys/kern/vfs_bio.c	Sun May  2 19:07:19 2010	(r207533)
+++ head/sys/kern/vfs_bio.c	Sun May  2 19:10:27 2010	(r207534)
@@ -1563,7 +1563,6 @@ vfs_vmio_release(struct buf *bp)
 	vm_page_t m;
 
 	VM_OBJECT_LOCK(bp->b_bufobj->bo_object);
-	vm_page_lock_queues();
 	for (i = 0; i < bp->b_npages; i++) {
 		m = bp->b_pages[i];
 		bp->b_pages[i] = NULL;
@@ -1571,16 +1570,16 @@ vfs_vmio_release(struct buf *bp)
 		 * In order to keep page LRU ordering consistent, put
 		 * everything on the inactive queue.
 		 */
+		vm_page_lock(m);
+		vm_page_lock_queues();
 		vm_page_unwire(m, 0);
 		/*
 		 * We don't mess with busy pages, it is
 		 * the responsibility of the process that
 		 * busied the pages to deal with them.
 		 */
-		if ((m->oflags & VPO_BUSY) || (m->busy != 0))
-			continue;
-			
-		if (m->wire_count == 0) {
+		if ((m->oflags & VPO_BUSY) == 0 && m->busy == 0 &&
+		    m->wire_count == 0) {
 			/*
 			 * Might as well free the page if we can and it has
 			 * no valid data.  We also free the page if the
@@ -1595,8 +1594,9 @@ vfs_vmio_release(struct buf *bp)
 				vm_page_try_to_cache(m);
 			}
 		}
+		vm_page_unlock_queues();
+		vm_page_unlock(m);
 	}
-	vm_page_unlock_queues();
 	VM_OBJECT_UNLOCK(bp->b_bufobj->bo_object);
 	pmap_qremove(trunc_page((vm_offset_t) bp->b_data), bp->b_npages);