On Mon, May 07, 2018 at 06:11:32PM +0200, Martin Pieuchot wrote:
> I'm going to protect `f_count' with a global lock soon. That implies
> that multiple FREF(9)s will be inlined. So here's a diff moving the
> vfs_stall hack to a proper function. This will help when looking for
> history and it reduces my upcoming locking diff.
>
> Better name? Ok?
OK bluhm@
> Index: kern/vfs_subr.c
> ===================================================================
> RCS file: /cvs/src/sys/kern/vfs_subr.c,v
> retrieving revision 1.269
> diff -u -p -r1.269 vfs_subr.c
> --- kern/vfs_subr.c 2 May 2018 02:24:56 -0000 1.269
> +++ kern/vfs_subr.c 7 May 2018 16:07:11 -0000
> @@ -1627,6 +1627,13 @@ vfs_stall(struct proc *p, int stall)
> return (allerror);
> }
>
> +void
> +vfs_stall_barrier(void)
> +{
> + rw_enter_read(&vfs_stall_lock);
> + rw_exit_read(&vfs_stall_lock);
> +}
> +
> /*
> * Unmount all file systems.
> * We traverse the list in reverse order under the assumption that doing so
> Index: sys/file.h
> ===================================================================
> RCS file: /cvs/src/sys/sys/file.h,v
> retrieving revision 1.41
> diff -u -p -r1.41 file.h
> --- sys/file.h 25 Apr 2018 10:29:16 -0000 1.41
> +++ sys/file.h 7 May 2018 16:08:31 -0000
> @@ -37,6 +37,7 @@
>
> #else /* _KERNEL */
> #include <sys/queue.h>
> +#include <sys/mount.h> /* vfs_stall_barrier() */
>
> struct proc;
> struct uio;
> @@ -91,9 +92,7 @@ struct file {
>
> #define FREF(fp) \
> do { \
> - extern struct rwlock vfs_stall_lock; \
> - rw_enter_read(&vfs_stall_lock); \
> - rw_exit_read(&vfs_stall_lock); \
> + vfs_stall_barrier(); \
> (fp)->f_count++; \
> } while (0)
> #define FRELE(fp,p) (--(fp)->f_count == 0 ? fdrop(fp, p) : 0)
> Index: sys/mount.h
> ===================================================================
> RCS file: /cvs/src/sys/sys/mount.h,v
> retrieving revision 1.135
> diff -u -p -r1.135 mount.h
> --- sys/mount.h 10 Feb 2018 05:24:23 -0000 1.135
> +++ sys/mount.h 7 May 2018 16:07:11 -0000
> @@ -575,6 +575,7 @@ int vfs_rootmountalloc(char *, char *, s
> void vfs_unbusy(struct mount *);
> extern TAILQ_HEAD(mntlist, mount) mountlist;
> int vfs_stall(struct proc *, int);
> +void vfs_stall_barrier(void);
>
> struct mount *getvfs(fsid_t *); /* return vfs given fsid */
> /* process mount export info */
