Author: kib
Date: Sat May 21 09:49:35 2016
New Revision: 300364
URL: https://svnweb.freebsd.org/changeset/base/300364
Log:
Improve handling of rdev->si_mountpt on mount and unmount of FFS
volumes. Treat the field as a semaphore protecting availability of
the device for mounting. Do no access devvp->v_rdev without the vnode
lock owned.
Protect change of the devvp->v_bufobj bo_ops vector with the vnode
lock.
Reviewed by: bde
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
Modified:
head/sys/ufs/ffs/ffs_vfsops.c
Modified: head/sys/ufs/ffs/ffs_vfsops.c
==============================================================================
--- head/sys/ufs/ffs/ffs_vfsops.c Sat May 21 09:27:30 2016
(r300363)
+++ head/sys/ufs/ffs/ffs_vfsops.c Sat May 21 09:49:35 2016
(r300364)
@@ -764,25 +764,31 @@ ffs_mountfs(devvp, mp, td)
cred = td ? td->td_ucred : NOCRED;
ronly = (mp->mnt_flag & MNT_RDONLY) != 0;
+ KASSERT(devvp->v_type == VCHR, ("reclaimed devvp"));
dev = devvp->v_rdev;
- dev_ref(dev);
+ if (atomic_cmpset_acq_ptr((uintptr_t *)&dev->si_mountpt, 0,
+ (uintptr_t)mp) == 0) {
+ VOP_UNLOCK(devvp, 0);
+ return (EBUSY);
+ }
DROP_GIANT();
g_topology_lock();
error = g_vfs_open(devvp, &cp, "ffs", ronly ? 0 : 1);
g_topology_unlock();
PICKUP_GIANT();
+ if (error != 0) {
+ atomic_store_rel_ptr((uintptr_t *)&dev->si_mountpt, 0);
+ VOP_UNLOCK(devvp, 0);
+ return (error);
+ }
+ dev_ref(dev);
+ devvp->v_bufobj.bo_ops = &ffs_ops;
VOP_UNLOCK(devvp, 0);
- if (error)
- goto out;
- if (devvp->v_rdev->si_iosize_max != 0)
- mp->mnt_iosize_max = devvp->v_rdev->si_iosize_max;
+ if (dev->si_iosize_max != 0)
+ mp->mnt_iosize_max = dev->si_iosize_max;
if (mp->mnt_iosize_max > MAXPHYS)
mp->mnt_iosize_max = MAXPHYS;
- devvp->v_bufobj.bo_ops = &ffs_ops;
- if (devvp->v_type == VCHR)
- devvp->v_rdev->si_mountpt = mp;
-
fs = NULL;
sblockloc = 0;
/*
@@ -1083,8 +1089,6 @@ ffs_mountfs(devvp, mp, td)
out:
if (bp)
brelse(bp);
- if (devvp->v_type == VCHR && devvp->v_rdev != NULL)
- devvp->v_rdev->si_mountpt = NULL;
if (cp != NULL) {
DROP_GIANT();
g_topology_lock();
@@ -1102,6 +1106,7 @@ out:
free(ump, M_UFSMNT);
mp->mnt_data = NULL;
}
+ atomic_store_rel_ptr((uintptr_t *)&dev->si_mountpt, 0);
dev_rel(dev);
return (error);
}
@@ -1287,8 +1292,7 @@ ffs_unmount(mp, mntflags)
g_vfs_close(ump->um_cp);
g_topology_unlock();
PICKUP_GIANT();
- if (ump->um_devvp->v_type == VCHR && ump->um_devvp->v_rdev != NULL)
- ump->um_devvp->v_rdev->si_mountpt = NULL;
+ atomic_store_rel_ptr((uintptr_t *)&ump->um_dev->si_mountpt, 0);
vrele(ump->um_devvp);
dev_rel(ump->um_dev);
mtx_destroy(UFS_MTX(ump));
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