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36 * @(#)null_vfsops.c 8.2 (Berkeley) 1/21/94
38 * @(#)lofs_vfsops.c 1.2 (Berkeley) 6/18/92
39 * $FreeBSD: src/sys/miscfs/nullfs/null_vfsops.c,v 1.35.2.3 2001/07/26 20:37:11 iedowse Exp $
40 * $DragonFly: src/sys/vfs/nullfs/null_vfsops.c,v 1.30 2008/09/05 23:27:12 dillon Exp $
45 * (See null_vnops.c for a description of what this does.)
48 #include <sys/param.h>
49 #include <sys/systm.h>
50 #include <sys/kernel.h>
52 #include <sys/malloc.h>
53 #include <sys/vnode.h>
54 #include <sys/mount.h>
55 #include <sys/nlookup.h>
58 extern struct vop_ops null_vnode_vops;
60 static MALLOC_DEFINE(M_NULLFSMNT, "NULLFS mount", "NULLFS mount structure");
62 static int nullfs_root(struct mount *mp, struct vnode **vpp);
63 static int nullfs_statfs(struct mount *mp, struct statfs *sbp,
70 nullfs_mount(struct mount *mp, char *path, caddr_t data, struct ucred *cred)
73 struct null_args args;
75 struct null_mount *xmp;
77 struct nlookupdata nd;
79 NULLFSDEBUG("nullfs_mount(mp = %p)\n", (void *)mp);
84 if (mp->mnt_flag & MNT_UPDATE) {
91 error = copyin(data, (caddr_t)&args, sizeof(struct null_args));
99 error = nlookup_init(&nd, args.target, UIO_USERSPACE, NLC_FOLLOW);
102 error = nlookup(&nd);
105 error = cache_vget(&nd.nl_nch, nd.nl_cred, LK_EXCLUSIVE, &rootvp);
109 xmp = (struct null_mount *) kmalloc(sizeof(struct null_mount),
110 M_NULLFSMNT, M_WAITOK); /* XXX */
113 * Save reference to underlying FS
115 * As lite stacking enters the scene, the old way of doing this
116 * -- via the vnode -- is not good enough anymore. Use the
117 * underlying filesystem's namecache handle as our mount point
118 * root, adjusting the mount to point to us.
120 * NCF_ISMOUNTPT is normally set on the mount point, but we also
121 * want to set it on the base directory being mounted to prevent
122 * that directory from being destroyed out from under the nullfs
125 * The forwarding mount pointer (xmp->nullm_vfs) must be set to
126 * the actual target filesystem. If the target filesystem was
127 * resolved via a nullfs mount nd.nl_nch.mount will be pointing
128 * to the nullfs mount structure instead of the target filesystem,
129 * which would otherwise cause the mount VOPS and VFSOPS to recurse
130 * endlessly. If we are mounting via a nullfs mount we inherit
131 * its read-only state, if set.
133 xmp->nullm_vfs = nd.nl_nch.mount;
134 if (xmp->nullm_vfs != rootvp->v_mount) {
135 if (xmp->nullm_vfs->mnt_flag & MNT_RDONLY)
136 mp->mnt_flag |= MNT_RDONLY;
137 xmp->nullm_vfs = rootvp->v_mount;
141 * ncmountpt is the parent glue. When mounting a nullfs via a nullfs
142 * we retain the parent nullfs to create a unique chain tuple.
144 mp->mnt_ncmountpt = nd.nl_nch;
145 cache_changemount(&mp->mnt_ncmountpt, mp);
146 mp->mnt_ncmountpt.ncp->nc_flag |= NCF_ISMOUNTPT;
147 cache_unlock(&mp->mnt_ncmountpt);
148 cache_zero(&nd.nl_nch);
151 vfs_add_vnodeops(mp, &null_vnode_vops, &mp->mnt_vn_norm_ops);
153 vn_unlock(rootvp); /* leave reference intact */
156 * Keep a held reference to the root vnode.
157 * It is vrele'd in nullfs_unmount.
159 xmp->nullm_rootvp = rootvp;
161 * XXX What's the proper safety condition for querying
162 * the underlying mount? Is this flag tuning necessary
165 if (xmp->nullm_vfs->mnt_flag & MNT_LOCAL)
166 mp->mnt_flag |= MNT_LOCAL;
167 mp->mnt_data = (qaddr_t) xmp;
170 (void) copyinstr(args.target, mp->mnt_stat.f_mntfromname, MNAMELEN - 1,
172 bzero(mp->mnt_stat.f_mntfromname + size, MNAMELEN - size);
173 (void)nullfs_statfs(mp, &mp->mnt_stat, cred);
174 NULLFSDEBUG("nullfs_mount: lower %s, alias at %s\n",
175 mp->mnt_stat.f_mntfromname, mp->mnt_stat.f_mntfromname);
178 * So unmount won't complain about namecache refs still existing
180 mp->mnt_kern_flag |= MNTK_NCALIASED;
189 * Free reference to null layer
192 nullfs_unmount(struct mount *mp, int mntflags)
194 struct null_mount *xmp;
197 NULLFSDEBUG("nullfs_unmount: mp = %p\n", (void *)mp);
199 if (mntflags & MNT_FORCE)
203 * Finally, throw away the null_mount structure
205 xmp = (void *)mp->mnt_data;
207 if (xmp->nullm_rootvp) {
208 vrele(xmp->nullm_rootvp);
209 xmp->nullm_rootvp = NULL;
211 kfree(xmp, M_NULLFSMNT);
216 nullfs_root(struct mount *mp, struct vnode **vpp)
221 NULLFSDEBUG("nullfs_root(mp = %p, vp = %p)\n", (void *)mp,
222 (void *)MOUNTTONULLMOUNT(mp)->nullm_rootvp);
225 * Return locked reference to root.
227 vp = MOUNTTONULLMOUNT(mp)->nullm_rootvp;
228 error = vget(vp, LK_EXCLUSIVE | LK_RETRY);
235 nullfs_quotactl(struct mount *mp, int cmd, uid_t uid, caddr_t arg,
238 return VFS_QUOTACTL(MOUNTTONULLMOUNT(mp)->nullm_vfs, cmd, uid, arg, cred);
242 nullfs_statfs(struct mount *mp, struct statfs *sbp, struct ucred *cred)
247 NULLFSDEBUG("nullfs_statfs(mp = %p, vp = %p)\n", (void *)mp,
248 (void *)MOUNTTONULLMOUNT(mp)->nullm_rootvp);
250 bzero(&mstat, sizeof(mstat));
252 error = VFS_STATFS(MOUNTTONULLMOUNT(mp)->nullm_vfs, &mstat, cred);
256 /* now copy across the "interesting" information and fake the rest */
257 sbp->f_type = mstat.f_type;
258 sbp->f_flags = mstat.f_flags;
259 sbp->f_bsize = mstat.f_bsize;
260 sbp->f_iosize = mstat.f_iosize;
261 sbp->f_blocks = mstat.f_blocks;
262 sbp->f_bfree = mstat.f_bfree;
263 sbp->f_bavail = mstat.f_bavail;
264 sbp->f_files = mstat.f_files;
265 sbp->f_ffree = mstat.f_ffree;
266 if (sbp != &mp->mnt_stat) {
267 bcopy(&mp->mnt_stat.f_fsid, &sbp->f_fsid, sizeof(sbp->f_fsid));
268 bcopy(mp->mnt_stat.f_mntfromname, sbp->f_mntfromname, MNAMELEN);
274 nullfs_checkexp(struct mount *mp, struct sockaddr *nam, int *extflagsp,
275 struct ucred **credanonp)
278 return VFS_CHECKEXP(MOUNTTONULLMOUNT(mp)->nullm_vfs, nam,
279 extflagsp, credanonp);
283 nullfs_extattrctl(struct mount *mp, int cmd, const char *attrname, caddr_t arg,
286 return VFS_EXTATTRCTL(MOUNTTONULLMOUNT(mp)->nullm_vfs, cmd, attrname,
291 static struct vfsops null_vfsops = {
292 .vfs_mount = nullfs_mount,
293 .vfs_unmount = nullfs_unmount,
294 .vfs_root = nullfs_root,
295 .vfs_quotactl = nullfs_quotactl,
296 .vfs_statfs = nullfs_statfs,
297 .vfs_sync = vfs_stdsync,
298 .vfs_checkexp = nullfs_checkexp,
299 .vfs_extattrctl = nullfs_extattrctl
302 VFS_SET(null_vfsops, null, VFCF_LOOPBACK);