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Improve handling of rdev->si_mountpt on mount and unmount of FFS

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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
This commit is contained in:
Konstantin Belousov 2016-05-21 09:49:35 +00:00
parent f26a190f65
commit c70b3cd28d
1 changed files with 17 additions and 13 deletions
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30
sys/ufs/ffs/ffs_vfsops.c
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@ -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 @@ ffs_mountfs(devvp, mp, td)
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));