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Move the comment about resident pages preventing vnode from leaving

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active list, into the header comment for vdrop(), which is the
function that decides whether to leave the vnode on the list.  Note
that dirty page write-out in vinactive() is asynchronous.

Discussed with:	alc
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
This commit is contained in:
Konstantin Belousov 2015-11-27 01:16:35 +00:00
parent 1b4e36949a
commit b3162b45e1
1 changed files with 11 additions and 5 deletions
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16
sys/kern/vfs_subr.c
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@ -2618,6 +2618,10 @@ _vhold(struct vnode *vp, bool locked)
* Drop the hold count of the vnode. If this is the last reference to
* the vnode we place it on the free list unless it has been vgone'd
* (marked VI_DOOMED) in which case we will free it.
*
* Because the vnode vm object keeps a hold reference on the vnode if
* there is at least one resident non-cached page, the vnode cannot
* leave the active list without the page cleanup done.
*/
void
_vdrop(struct vnode *vp, bool locked)
@ -2744,11 +2748,13 @@ vinactive(struct vnode *vp, struct thread *td)
VI_UNLOCK(vp);
/*
* Before moving off the active list, we must be sure that any
* modified pages are on the vnode's dirty list since these will
* no longer be checked once the vnode is on the inactive list.
* Because the vnode vm object keeps a hold reference on the vnode
* if there is at least one resident non-cached page, the vnode
* cannot leave the active list without the page cleanup done.
* modified pages are converted into the vnode's dirty
* buffers, since these will no longer be checked once the
* vnode is on the inactive list.
*
* The write-out of the dirty pages is asynchronous. At the
* point that VOP_INACTIVE() is called, there could still be
* pending I/O and dirty pages in the object.
*/
obj = vp->v_object;
if (obj != NULL && (obj->flags & OBJ_MIGHTBEDIRTY) != 0) {