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The OBJ_TMPFS flag of vm_object means that there is unreclaimed tmpfs

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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
This commit is contained in:
Konstantin Belousov 2014-07-14 09:30:37 +00:00
parent eb2c06b63a
commit f08f7dca40
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=268615
2 changed files with 5 additions and 4 deletions
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6
sys/vm/vm_object.c
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@ -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);
}

3
sys/vm/vm_object.h
View File

@ -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))