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tmpfs: reimplement the mtime scan to use the lazy list

Browse Source 
Tested by:	pho
Reviewed by:	kib, markj
Differential Revision:	https://reviews.freebsd.org/D30065
This commit is contained in:
Mateusz Guzik 2021-05-07 14:43:43 +00:00
parent 128e25842e
commit eec2e4ef7f
3 changed files with 143 additions and 32 deletions
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1
sys/fs/tmpfs/tmpfs.h
View File

@ -46,6 +46,7 @@ MALLOC_DECLARE(M_TMPFSNAME);
#endif
#define OBJ_TMPFS OBJ_PAGERPRIV1 /* has tmpfs vnode allocated */
#define OBJ_TMPFS_VREF OBJ_PAGERPRIV2 /* vnode is referenced */
/*
* Internal representation of a tmpfs directory entry.

107
sys/fs/tmpfs/tmpfs_subr.c
View File

@ -99,6 +99,92 @@ tmpfs_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
return (object);
}
/*
* Make sure tmpfs vnodes with writable mappings can be found on the lazy list.
*
* This allows for periodic mtime updates while only scanning vnodes which are
* plausibly dirty, see tmpfs_update_mtime_lazy.
*/
static void
tmpfs_pager_writecount_recalc(vm_object_t object, vm_offset_t old,
vm_offset_t new)
{
struct vnode *vp;
VM_OBJECT_ASSERT_WLOCKED(object);
vp = object->un_pager.swp.swp_tmpfs;
/*
* Forced unmount?
*/
if (vp == NULL) {
KASSERT((object->flags & OBJ_TMPFS_VREF) == 0,
("object %p with OBJ_TMPFS_VREF but without vnode", object));
VM_OBJECT_WUNLOCK(object);
return;
}
if (old == 0) {
VNASSERT((object->flags & OBJ_TMPFS_VREF) == 0, vp,
("object without writable mappings has a reference"));
VNPASS(vp->v_usecount > 0, vp);
} else {
VNASSERT((object->flags & OBJ_TMPFS_VREF) != 0, vp,
("object with writable mappings does not have a reference"));
}
if (old == new) {
VM_OBJECT_WUNLOCK(object);
return;
}
if (new == 0) {
vm_object_clear_flag(object, OBJ_TMPFS_VREF);
VM_OBJECT_WUNLOCK(object);
vrele(vp);
} else {
if ((object->flags & OBJ_TMPFS_VREF) == 0) {
vref(vp);
vlazy(vp);
vm_object_set_flag(object, OBJ_TMPFS_VREF);
}
VM_OBJECT_WUNLOCK(object);
}
}
static void
tmpfs_pager_update_writecount(vm_object_t object, vm_offset_t start,
vm_offset_t end)
{
vm_offset_t new, old;
VM_OBJECT_WLOCK(object);
KASSERT((object->flags & OBJ_ANON) == 0,
("%s: object %p with OBJ_ANON", __func__, object));
old = object->un_pager.swp.writemappings;
object->un_pager.swp.writemappings += (vm_ooffset_t)end - start;
new = object->un_pager.swp.writemappings;
tmpfs_pager_writecount_recalc(object, old, new);
VM_OBJECT_ASSERT_UNLOCKED(object);
}
static void
tmpfs_pager_release_writecount(vm_object_t object, vm_offset_t start,
vm_offset_t end)
{
vm_offset_t new, old;
VM_OBJECT_WLOCK(object);
KASSERT((object->flags & OBJ_ANON) == 0,
("%s: object %p with OBJ_ANON", __func__, object));
old = object->un_pager.swp.writemappings;
object->un_pager.swp.writemappings -= (vm_ooffset_t)end - start;
new = object->un_pager.swp.writemappings;
tmpfs_pager_writecount_recalc(object, old, new);
VM_OBJECT_ASSERT_UNLOCKED(object);
}
static void
tmpfs_pager_getvp(vm_object_t object, struct vnode **vpp, bool *vp_heldp)
{
@ -131,6 +217,8 @@ struct pagerops tmpfs_pager_ops = {
.pgo_kvme_type = KVME_TYPE_VNODE,
.pgo_alloc = tmpfs_pager_alloc,
.pgo_set_writeable_dirty = vm_object_set_writeable_dirty_,
.pgo_update_writecount = tmpfs_pager_update_writecount,
.pgo_release_writecount = tmpfs_pager_release_writecount,
.pgo_mightbedirty = vm_object_mightbedirty_,
.pgo_getvp = tmpfs_pager_getvp,
};
@ -643,6 +731,7 @@ tmpfs_free_dirent(struct tmpfs_mount *tmp, struct tmpfs_dirent *de)
void
tmpfs_destroy_vobject(struct vnode *vp, vm_object_t obj)
{
bool want_vrele;
ASSERT_VOP_ELOCKED(vp, "tmpfs_destroy_vobject");
if (vp->v_type != VREG || obj == NULL)
@ -650,12 +739,24 @@ tmpfs_destroy_vobject(struct vnode *vp, vm_object_t obj)
VM_OBJECT_WLOCK(obj);
VI_LOCK(vp);
/*
* May be going through forced unmount.
*/
want_vrele = false;
if ((obj->flags & OBJ_TMPFS_VREF) != 0) {
vm_object_clear_flag(obj, OBJ_TMPFS_VREF);
want_vrele = true;
}
vm_object_clear_flag(obj, OBJ_TMPFS);
obj->un_pager.swp.swp_tmpfs = NULL;
if (vp->v_writecount < 0)
vp->v_writecount = 0;
VI_UNLOCK(vp);
VM_OBJECT_WUNLOCK(obj);
if (want_vrele) {
vrele(vp);
}
}
/*
@ -792,6 +893,12 @@ tmpfs_alloc_vp(struct mount *mp, struct tmpfs_node *node, int lkflag,
case VREG:
object = node->tn_reg.tn_aobj;
VM_OBJECT_WLOCK(object);
KASSERT((object->flags & OBJ_TMPFS_VREF) == 0,
("%s: object %p with OBJ_TMPFS_VREF but without vnode",
__func__, object));
KASSERT(object->un_pager.swp.writemappings == 0,
("%s: object %p has writemappings",
__func__, object));
VI_LOCK(vp);
KASSERT(vp->v_object == NULL, ("Not NULL v_object in tmpfs"));
vp->v_object = object;

67
sys/fs/tmpfs/tmpfs_vfsops.c
View File

@ -99,18 +99,38 @@ static const char *tmpfs_updateopts[] = {
"from", "export", "nomtime", "size", NULL
};
/*
* Handle updates of time from writes to mmaped regions, if allowed.
* Use MNT_VNODE_FOREACH_ALL instead of MNT_VNODE_FOREACH_LAZY, since
* unmap of the tmpfs-backed vnode does not call vinactive(), due to
* vm object type is basically OBJT_SWAP. If lazy, only handle
* delayed update of mtime due to the writes to mapped files.
*/
static int
tmpfs_update_mtime_lazy_filter(struct vnode *vp, void *arg)
{
struct vm_object *obj;
if (vp->v_type != VREG)
return (0);
obj = atomic_load_ptr(&vp->v_object);
if (obj == NULL)
return (0);
return (vm_object_mightbedirty_(obj));
}
static void
tmpfs_update_mtime(struct mount *mp, bool lazy)
tmpfs_update_mtime_lazy(struct mount *mp)
{
struct vnode *vp, *mvp;
MNT_VNODE_FOREACH_LAZY(vp, mp, mvp, tmpfs_update_mtime_lazy_filter, NULL) {
if (vget(vp, LK_EXCLUSIVE | LK_INTERLOCK) != 0)
continue;
tmpfs_check_mtime(vp);
vput(vp);
}
}
static void
tmpfs_update_mtime_all(struct mount *mp)
{
struct vnode *vp, *mvp;
struct vm_object *obj;
if (VFS_TO_TMPFS(mp)->tm_nomtime)
return;
@ -119,28 +139,11 @@ tmpfs_update_mtime(struct mount *mp, bool lazy)
VI_UNLOCK(vp);
continue;
}
obj = vp->v_object;
MPASS(obj->type == tmpfs_pager_type);
MPASS((obj->flags & OBJ_TMPFS) != 0);
/*
* In lazy case, do unlocked read, avoid taking vnode
* lock if not needed. Lost update will be handled on
* the next call.
* For non-lazy case, we must flush all pending
* metadata changes now.
*/
if (!lazy || obj->generation != obj->cleangeneration) {
if (vget(vp, LK_EXCLUSIVE | LK_INTERLOCK) != 0)
continue;
tmpfs_check_mtime(vp);
if (!lazy)
tmpfs_update(vp);
vput(vp);
} else {
VI_UNLOCK(vp);
if (vget(vp, LK_EXCLUSIVE | LK_INTERLOCK) != 0)
continue;
}
tmpfs_check_mtime(vp);
tmpfs_update(vp);
vput(vp);
}
}
@ -300,7 +303,7 @@ tmpfs_rw_to_ro(struct mount *mp)
MNT_IUNLOCK(mp);
for (;;) {
tmpfs_all_rw_maps(mp, tmpfs_revoke_rw_maps_cb, NULL);
tmpfs_update_mtime(mp, false);
tmpfs_update_mtime_all(mp);
error = vflush(mp, 0, flags, curthread);
if (error != 0) {
VFS_TO_TMPFS(mp)->tm_ronly = 0;
@ -653,7 +656,7 @@ tmpfs_sync(struct mount *mp, int waitfor)
mp->mnt_kern_flag |= MNTK_SUSPEND2 | MNTK_SUSPENDED;
MNT_IUNLOCK(mp);
} else if (waitfor == MNT_LAZY) {
tmpfs_update_mtime(mp, true);
tmpfs_update_mtime_lazy(mp);
}
return (0);
}