svn commit: r315318 - in head/sys: kern vm

[Benjamin Kaduk]

Should __FreeBSD_version be bumped, e.g., for out-of-tree filesystems that
have custom vop_advise?

-Ben

On Wed, Mar 15, 2017 at 12:43 PM, Alan Cox <alc at freebsd.org> wrote:

> Author: alc
> Date: Wed Mar 15 17:43:45 2017
> New Revision: 315318
> URL: https://svnweb.freebsd.org/changeset/base/315318
>
> Log:
>   Relax the locking requirements for vm_object_page_noreuse().  While
>   reviewing all uses of OFF_TO_IDX(), I observed that
>   vm_object_page_noreuse() is requiring an exclusive lock on the object
>   when, in fact, a shared lock suffices.
>
>   Reviewed by:  kib, markj
>   MFC after:    3 days
>   Differential Revision:        https://reviews.freebsd.org/D10011
>
> Modified:
>   head/sys/kern/vfs_default.c
>   head/sys/vm/vm_object.c
>
> Modified: head/sys/kern/vfs_default.c
> ============================================================
> ==================
> --- head/sys/kern/vfs_default.c Wed Mar 15 17:26:19 2017        (r315317)
> +++ head/sys/kern/vfs_default.c Wed Mar 15 17:43:45 2017        (r315318)
> @@ -1100,10 +1100,10 @@ vop_stdadvise(struct vop_advise_args *ap
>                 if (vp->v_object != NULL) {
>                         start = trunc_page(ap->a_start);
>                         end = round_page(ap->a_end);
> -                       VM_OBJECT_WLOCK(vp->v_object);
> +                       VM_OBJECT_RLOCK(vp->v_object);
>                         vm_object_page_noreuse(vp->v_object,
> OFF_TO_IDX(start),
>                             OFF_TO_IDX(end));
> -                       VM_OBJECT_WUNLOCK(vp->v_object);
> +                       VM_OBJECT_RUNLOCK(vp->v_object);
>                 }
>
>                 bo = &vp->v_bufobj;
>
> Modified: head/sys/vm/vm_object.c
> ============================================================
> ==================
> --- head/sys/vm/vm_object.c     Wed Mar 15 17:26:19 2017        (r315317)
> +++ head/sys/vm/vm_object.c     Wed Mar 15 17:43:45 2017        (r315318)
> @@ -1978,7 +1978,7 @@ vm_object_page_noreuse(vm_object_t objec
>         struct mtx *mtx, *new_mtx;
>         vm_page_t p, next;
>
> -       VM_OBJECT_ASSERT_WLOCKED(object);
> +       VM_OBJECT_ASSERT_LOCKED(object);
>         KASSERT((object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0,
>             ("vm_object_page_noreuse: illegal object %p", object));
>         if (object->resident_page_count == 0)
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