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vfs: [1/2] fix stalls in vnode reclaim by not requeieing from vnlru

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Reported by:	pho
This commit is contained in:
Mateusz Guzik committed 2022-03-10 09:41:50 +00:00
1 parent 7b45ad3f89
commit c35ec1efdc
1 file changed
+45 -10
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sys/kern/vfs_subr.c
+45 -10
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@@ -113,6 +113,8 @@ static void vn_seqc_init(struct vnode *);
static void vn_seqc_write_end_free(struct vnode *vp);
static void vgonel(struct vnode *);
static bool vhold_recycle_free(struct vnode *);
static void vdropl_recycle(struct vnode *vp);
static void vdrop_recycle(struct vnode *vp);
static void vfs_knllock(void *arg);
static void vfs_knlunlock(void *arg);
static void vfs_knl_assert_lock(void *arg, int what);
@@ -1207,11 +1209,11 @@ restart:
mtx_unlock(&vnode_list_mtx);
if (vn_start_write(vp, &mp, V_NOWAIT) != 0) {
vdrop(vp);
vdrop_recycle(vp);
goto next_iter_unlocked;
}
if (VOP_LOCK(vp, LK_EXCLUSIVE|LK_NOWAIT) != 0) {
vdrop(vp);
vdrop_recycle(vp);
vn_finished_write(mp);
goto next_iter_unlocked;
}
@@ -1222,14 +1224,14 @@ restart:
(vp->v_object != NULL && vp->v_object->handle == vp &&
vp->v_object->resident_page_count > trigger)) {
VOP_UNLOCK(vp);
vdropl(vp);
vdropl_recycle(vp);
vn_finished_write(mp);
goto next_iter_unlocked;
}
counter_u64_add(recycles_count, 1);
vgonel(vp);
VOP_UNLOCK(vp);
vdropl(vp);
vdropl_recycle(vp);
vn_finished_write(mp);
done++;
next_iter_unlocked:
@@ -1613,7 +1615,7 @@ vtryrecycle(struct vnode *vp)
CTR2(KTR_VFS,
"%s: impossible to recycle, vp %p lock is already held",
__func__, vp);
vdrop(vp);
vdrop_recycle(vp);
return (EWOULDBLOCK);
}
/*
@@ -1624,7 +1626,7 @@ vtryrecycle(struct vnode *vp)
CTR2(KTR_VFS,
"%s: impossible to recycle, cannot start the write for %p",
__func__, vp);
vdrop(vp);
vdrop_recycle(vp);
return (EBUSY);
}
/*
@@ -1636,7 +1638,7 @@ vtryrecycle(struct vnode *vp)
VI_LOCK(vp);
if (vp->v_usecount) {
VOP_UNLOCK(vp);
vdropl(vp);
vdropl_recycle(vp);
vn_finished_write(vnmp);
CTR2(KTR_VFS,
"%s: impossible to recycle, %p is already referenced",
@@ -1648,7 +1650,7 @@ vtryrecycle(struct vnode *vp)
vgonel(vp);
}
VOP_UNLOCK(vp);
vdropl(vp);
vdropl_recycle(vp);
vn_finished_write(vnmp);
return (0);
}
@@ -3598,8 +3600,8 @@ vdrop(struct vnode *vp)
vdropl(vp);
}
void
vdropl(struct vnode *vp)
static void __always_inline
vdropl_impl(struct vnode *vp, bool enqueue)
{
ASSERT_VI_LOCKED(vp, __func__);
@@ -3627,6 +3629,39 @@ vdropl(struct vnode *vp)
vdbatch_enqueue(vp);
}
void
vdropl(struct vnode *vp)
{
vdropl_impl(vp, true);
}
/*
* vdrop a vnode when recycling
*
* This is a special case routine only to be used when recycling, differs from
* regular vdrop by not requeieing the vnode on LRU.
*
* Consider a case where vtryrecycle continuously fails with all vnodes (due to
* e.g., frozen writes on the filesystem), filling the batch and causing it to
* be requeued. Then vnlru will end up revisiting the same vnodes. This is a
* loop which can last for as long as writes are frozen.
*/
static void
vdropl_recycle(struct vnode *vp)
{
vdropl_impl(vp, false);
}
static void
vdrop_recycle(struct vnode *vp)
{
VI_LOCK(vp);
vdropl_recycle(vp);
}
/*
* Call VOP_INACTIVE on the vnode and manage the DOINGINACT and OWEINACT
* flags. DOINGINACT prevents us from recursing in calls to vinactive.