The OBJ_TMPFS flag of vm_object means that there is unreclaimed tmpfs

vnode for the tmpfs node owning this object.  The flag is currently
used for two purposes.  First, it allows to correctly handle VV_TEXT
for tmpfs vnode when the ref count on the object is decremented to 1,
similar to vnode_pager_dealloc() for regular filesystems.  Second, it
prevents some operations, which are done on OBJT_SWAP vm objects
backing user anonymous memory, but are incorrect for the object owned
by tmpfs node.

The second kind of use of the OBJ_TMPFS flag is incorrect, since the
vnode might be reclaimed, which clears the flag, but vm object
operations must still be disallowed.

Introduce one more flag, OBJ_TMPFS_NODE, which is permanently set on
the object for VREG tmpfs node, and used instead of OBJ_TMPFS to test
whether vm object collapse and similar actions should be disabled.

Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks

2 files changed, 5 insertions, 4 deletions

diff --git a/sys/vm/vm_object.c b/sys/vm/vm_object.c
index b428219..1b97bdf 100644
--- a/sys/vm/vm_object.c
+++ b/sys/vm/vm_object.c
@@ -553,13 +553,13 @@ vm_object_deallocate(vm_object_t object)
 			    object->handle == NULL &&
 			    (object->type == OBJT_DEFAULT ||
 			    (object->type == OBJT_SWAP &&
-			    (object->flags & OBJ_TMPFS) == 0))) {
+			    (object->flags & OBJ_TMPFS_NODE) == 0))) {
 				vm_object_set_flag(object, OBJ_ONEMAPPING);
 			} else if ((object->shadow_count == 1) &&
 			    (object->handle == NULL) &&
 			    (object->type == OBJT_DEFAULT ||
 			     object->type == OBJT_SWAP)) {
-				KASSERT((object->flags & OBJ_TMPFS) == 0,
+				KASSERT((object->flags & OBJ_TMPFS_NODE) == 0,
 				    ("shadowed tmpfs v_object %p", object));
 				vm_object_t robject;
 
@@ -2103,7 +2103,7 @@ vm_object_coalesce(vm_object_t prev_object, vm_ooffset_t prev_offset,
 	VM_OBJECT_WLOCK(prev_object);
 	if ((prev_object->type != OBJT_DEFAULT &&
 	    prev_object->type != OBJT_SWAP) ||
-	    (prev_object->flags & OBJ_TMPFS) != 0) {
+	    (prev_object->flags & OBJ_TMPFS_NODE) != 0) {
 		VM_OBJECT_WUNLOCK(prev_object);
 		return (FALSE);
 	}
diff --git a/sys/vm/vm_object.h b/sys/vm/vm_object.h
index d59a9e6..8381992 100644
--- a/sys/vm/vm_object.h
+++ b/sys/vm/vm_object.h
@@ -186,10 +186,11 @@ struct vm_object {
 #define	OBJ_NOSPLIT	0x0010		/* dont split this object */
 #define OBJ_PIPWNT	0x0040		/* paging in progress wanted */
 #define OBJ_MIGHTBEDIRTY 0x0100		/* object might be dirty, only for vnode */
+#define	OBJ_TMPFS_NODE	0x0200		/* object belongs to tmpfs VREG node */
 #define	OBJ_COLORED	0x1000		/* pg_color is defined */
 #define	OBJ_ONEMAPPING	0x2000		/* One USE (a single, non-forked) mapping flag */
 #define	OBJ_DISCONNECTWNT 0x4000	/* disconnect from vnode wanted */
-#define	OBJ_TMPFS	0x8000
+#define	OBJ_TMPFS	0x8000		/* has tmpfs vnode allocated */
 
 #define IDX_TO_OFF(idx) (((vm_ooffset_t)(idx)) << PAGE_SHIFT)
 #define OFF_TO_IDX(off) ((vm_pindex_t)(((vm_ooffset_t)(off)) >> PAGE_SHIFT))