Remove a racy checks on resident and cached pages for

tmpfs_mapped{read, write}() functions:
- tmpfs_mapped{read, write}() are only called within VOP_{READ, WRITE}(),
  which check before-hand to work only on valid VREG vnodes.  Also the
  vnode is locked for the duration of the work, making vnode reclaiming
  impossible, during the operation. Hence, vobj can never be NULL.
- Currently check on resident pages and cached pages without vm object
  lock held is racy and can do even more harm than good, as a page could
  be transitioning between these 2 pools and then be skipped entirely.
  Skip the checks as lookups on empty splay trees are very cheap.

Discussed with:	alc
Tested by:	flo
MFC after:	2 weeks

1 files changed, 0 insertions, 12 deletions

diff --git a/sys/fs/tmpfs/tmpfs_vnops.c b/sys/fs/tmpfs/tmpfs_vnops.c
index 5e2ea65..bddcf24 100644
--- a/sys/fs/tmpfs/tmpfs_vnops.c
+++ b/sys/fs/tmpfs/tmpfs_vnops.c
@@ -511,10 +511,6 @@ tmpfs_mappedread(vm_object_t vobj, vm_object_t tobj, size_t len, struct uio *uio
 	offset = addr & PAGE_MASK;
 	tlen = MIN(PAGE_SIZE - offset, len);
 
-	if ((vobj == NULL) ||
-	    (vobj->resident_page_count == 0 && vobj->cache == NULL))
-		goto nocache;
-
 	VM_OBJECT_LOCK(vobj);
 lookupvpg:
 	if (((m = vm_page_lookup(vobj, idx)) != NULL) &&
@@ -569,7 +565,6 @@ lookupvpg:
 		return	(error);
 	}
 	VM_OBJECT_UNLOCK(vobj);
-nocache:
 	error = tmpfs_nocacheread(tobj, idx, offset, tlen, uio);
 
 	return	(error);
@@ -639,12 +634,6 @@ tmpfs_mappedwrite(vm_object_t vobj, vm_object_t tobj, size_t len, struct uio *ui
 	offset = addr & PAGE_MASK;
 	tlen = MIN(PAGE_SIZE - offset, len);
 
-	if ((vobj == NULL) ||
-	    (vobj->resident_page_count == 0 && vobj->cache == NULL)) {
-		vpg = NULL;
-		goto nocache;
-	}
-
 	VM_OBJECT_LOCK(vobj);
 lookupvpg:
 	if (((vpg = vm_page_lookup(vobj, idx)) != NULL) &&
@@ -668,7 +657,6 @@ lookupvpg:
 		VM_OBJECT_UNLOCK(vobj);
 		vpg = NULL;
 	}
-nocache:
 	VM_OBJECT_LOCK(tobj);
 	tpg = vm_page_grab(tobj, idx, VM_ALLOC_WIRED |
 	    VM_ALLOC_NORMAL | VM_ALLOC_RETRY);