Author: kib
Date: Wed May 27 09:21:47 2015
New Revision: 283601
URL: https://svnweb.freebsd.org/changeset/base/283601
Log:
Add V_MNTREF flag to the vn_start_write(9) and
vn_start_secondary_write(9) functions. The flag indicates that the
caller already owns a reference on the mount point, and the functions
can consume it. The reference is released by vn_finished_write(9) and
vn_finished_secondary_write(9) in due course.
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
Modified:
head/sys/kern/vfs_vnops.c
head/sys/sys/vnode.h
Modified: head/sys/kern/vfs_vnops.c
==============================================================================
--- head/sys/kern/vfs_vnops.c Wed May 27 09:20:42 2015 (r283600)
+++ head/sys/kern/vfs_vnops.c Wed May 27 09:21:47 2015 (r283601)
@@ -1646,16 +1646,18 @@ unlock:
}
int
-vn_start_write(vp, mpp, flags)
- struct vnode *vp;
- struct mount **mpp;
- int flags;
+vn_start_write(struct vnode *vp, struct mount **mpp, int flags)
{
struct mount *mp;
int error;
- if (!vn_suspendable(vp, mpp))
+ KASSERT((flags & V_MNTREF) == 0 || (*mpp != NULL && vp == NULL),
+ ("V_MNTREF requires mp"));
+ if (!vn_suspendable(vp, mpp)) {
+ if ((flags & V_MNTREF) != 0)
+ vfs_rel(*mpp);
return (0);
+ }
error = 0;
/*
@@ -1681,7 +1683,7 @@ vn_start_write(vp, mpp, flags)
* emulate a vfs_ref().
*/
MNT_ILOCK(mp);
- if (vp == NULL)
+ if (vp == NULL && (flags & V_MNTREF) == 0)
MNT_REF(mp);
return (vn_start_write_locked(mp, flags));
@@ -1695,16 +1697,18 @@ vn_start_write(vp, mpp, flags)
* time, these operations are halted until the suspension is over.
*/
int
-vn_start_secondary_write(vp, mpp, flags)
- struct vnode *vp;
- struct mount **mpp;
- int flags;
+vn_start_secondary_write(struct vnode *vp, struct mount **mpp, int flags)
{
struct mount *mp;
int error;
- if (!vn_suspendable(vp, mpp))
+ KASSERT((flags & V_MNTREF) == 0 || (*mpp != NULL && vp == NULL),
+ ("V_MNTREF requires mp"));
+ if (!vn_suspendable(vp, mpp)) {
+ if ((flags & V_MNTREF) != 0)
+ vfs_rel(*mpp);
return (0);
+ }
retry:
if (vp != NULL) {
@@ -1730,7 +1734,7 @@ vn_start_secondary_write(vp, mpp, flags)
* emulate a vfs_ref().
*/
MNT_ILOCK(mp);
- if (vp == NULL)
+ if (vp == NULL && (flags & V_MNTREF) == 0)
MNT_REF(mp);
if ((mp->mnt_kern_flag & (MNTK_SUSPENDED | MNTK_SUSPEND2)) == 0) {
mp->mnt_secondary_writes++;
Modified: head/sys/sys/vnode.h
==============================================================================
--- head/sys/sys/vnode.h Wed May 27 09:20:42 2015 (r283600)
+++ head/sys/sys/vnode.h Wed May 27 09:21:47 2015 (r283601)
@@ -397,6 +397,7 @@ extern int vttoif_tab[];
#define V_WAIT 0x0001 /* vn_start_write: sleep for suspend */
#define V_NOWAIT 0x0002 /* vn_start_write: don't sleep for
suspend */
#define V_XSLEEP 0x0004 /* vn_start_write: just return after
sleep */
+#define V_MNTREF 0x0010 /* vn_start_write: mp is already ref-ed
*/
#define VR_START_WRITE 0x0001 /* vfs_write_resume: start write
atomically */
#define VR_NO_SUSPCLR 0x0002 /* vfs_write_resume: do not clear
suspension */
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