fdesc_vfsops.c revision 277985 
1/*-
2 * Copyright (c) 1992, 1993, 1995
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * This code is derived from software donated to Berkeley by
6 * Jan-Simon Pendry.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 4. Neither the name of the University nor the names of its contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 *
32 *	@(#)fdesc_vfsops.c	8.4 (Berkeley) 1/21/94
33 *
34 * $FreeBSD: stable/10/sys/fs/fdescfs/fdesc_vfsops.c 277985 2015-01-31 17:35:53Z jamie $
35 */
36
37/*
38 * /dev/fd Filesystem
39 */
40
41#include <sys/param.h>
42#include <sys/systm.h>
43#include <sys/filedesc.h>
44#include <sys/kernel.h>
45#include <sys/jail.h>
46#include <sys/lock.h>
47#include <sys/mutex.h>
48#include <sys/malloc.h>
49#include <sys/mount.h>
50#include <sys/proc.h>
51#include <sys/racct.h>
52#include <sys/resourcevar.h>
53#include <sys/vnode.h>
54
55#include <fs/fdescfs/fdesc.h>
56
57static MALLOC_DEFINE(M_FDESCMNT, "fdesc_mount", "FDESC mount structure");
58
59static vfs_cmount_t	fdesc_cmount;
60static vfs_mount_t	fdesc_mount;
61static vfs_unmount_t	fdesc_unmount;
62static vfs_statfs_t	fdesc_statfs;
63static vfs_root_t	fdesc_root;
64
65/*
66 * Compatibility shim for old mount(2) system call.
67 */
68int
69fdesc_cmount(struct mntarg *ma, void *data, uint64_t flags)
70{
71	return kernel_mount(ma, flags);
72}
73
74/*
75 * Mount the per-process file descriptors (/dev/fd)
76 */
77static int
78fdesc_mount(struct mount *mp)
79{
80	int error = 0;
81	struct fdescmount *fmp;
82	struct thread *td = curthread;
83	struct vnode *rvp;
84
85	if (!prison_allow(td->td_ucred, PR_ALLOW_MOUNT_FDESCFS))
86		return (EPERM);
87
88	/*
89	 * Update is a no-op
90	 */
91	if (mp->mnt_flag & (MNT_UPDATE | MNT_ROOTFS))
92		return (EOPNOTSUPP);
93
94	fmp = malloc(sizeof(struct fdescmount),
95				M_FDESCMNT, M_WAITOK);	/* XXX */
96
97	/*
98	 * We need to initialize a few bits of our local mount point struct to
99	 * avoid confusion in allocvp.
100	 */
101	mp->mnt_data = (qaddr_t) fmp;
102	fmp->flags = 0;
103	error = fdesc_allocvp(Froot, -1, FD_ROOT, mp, &rvp);
104	if (error) {
105		free(fmp, M_FDESCMNT);
106		mp->mnt_data = NULL;
107		return (error);
108	}
109	rvp->v_type = VDIR;
110	rvp->v_vflag |= VV_ROOT;
111	fmp->f_root = rvp;
112	VOP_UNLOCK(rvp, 0);
113	/* XXX -- don't mark as local to work around fts() problems */
114	/*mp->mnt_flag |= MNT_LOCAL;*/
115	vfs_getnewfsid(mp);
116
117	vfs_mountedfrom(mp, "fdescfs");
118	return (0);
119}
120
121static int
122fdesc_unmount(mp, mntflags)
123	struct mount *mp;
124	int mntflags;
125{
126	struct fdescmount *fmp;
127	caddr_t data;
128	int error;
129	int flags = 0;
130
131	fmp = (struct fdescmount *)mp->mnt_data;
132	if (mntflags & MNT_FORCE) {
133		/* The hash mutex protects the private mount flags. */
134		mtx_lock(&fdesc_hashmtx);
135		fmp->flags |= FMNT_UNMOUNTF;
136		mtx_unlock(&fdesc_hashmtx);
137		flags |= FORCECLOSE;
138	}
139
140	/*
141	 * Clear out buffer cache.  I don't think we
142	 * ever get anything cached at this level at the
143	 * moment, but who knows...
144	 *
145	 * There is 1 extra root vnode reference corresponding
146	 * to f_root.
147	 */
148	if ((error = vflush(mp, 1, flags, curthread)) != 0)
149		return (error);
150
151	/*
152	 * Finally, throw away the fdescmount structure. Hold the hashmtx to
153	 * protect the fdescmount structure.
154	 */
155	mtx_lock(&fdesc_hashmtx);
156	data = mp->mnt_data;
157	mp->mnt_data = NULL;
158	mtx_unlock(&fdesc_hashmtx);
159	free(data, M_FDESCMNT);	/* XXX */
160
161	return (0);
162}
163
164static int
165fdesc_root(mp, flags, vpp)
166	struct mount *mp;
167	int flags;
168	struct vnode **vpp;
169{
170	struct vnode *vp;
171
172	/*
173	 * Return locked reference to root.
174	 */
175	vp = VFSTOFDESC(mp)->f_root;
176	vget(vp, LK_EXCLUSIVE | LK_RETRY, curthread);
177	*vpp = vp;
178	return (0);
179}
180
181static int
182fdesc_statfs(mp, sbp)
183	struct mount *mp;
184	struct statfs *sbp;
185{
186	struct thread *td;
187	struct filedesc *fdp;
188	int lim;
189	int i;
190	int last;
191	int freefd;
192	uint64_t limit;
193
194	td = curthread;
195
196	/*
197	 * Compute number of free file descriptors.
198	 * [ Strange results will ensue if the open file
199	 * limit is ever reduced below the current number
200	 * of open files... ]
201	 */
202	PROC_LOCK(td->td_proc);
203	lim = lim_cur(td->td_proc, RLIMIT_NOFILE);
204	PROC_UNLOCK(td->td_proc);
205	fdp = td->td_proc->p_fd;
206	FILEDESC_SLOCK(fdp);
207	limit = racct_get_limit(td->td_proc, RACCT_NOFILE);
208	if (lim > limit)
209		lim = limit;
210	last = min(fdp->fd_nfiles, lim);
211	freefd = 0;
212	for (i = fdp->fd_freefile; i < last; i++)
213		if (fdp->fd_ofiles[i].fde_file == NULL)
214			freefd++;
215
216	/*
217	 * Adjust for the fact that the fdesc array may not
218	 * have been fully allocated yet.
219	 */
220	if (fdp->fd_nfiles < lim)
221		freefd += (lim - fdp->fd_nfiles);
222	FILEDESC_SUNLOCK(fdp);
223
224	sbp->f_flags = 0;
225	sbp->f_bsize = DEV_BSIZE;
226	sbp->f_iosize = DEV_BSIZE;
227	sbp->f_blocks = 2;		/* 1K to keep df happy */
228	sbp->f_bfree = 0;
229	sbp->f_bavail = 0;
230	sbp->f_files = lim + 1;		/* Allow for "." */
231	sbp->f_ffree = freefd;		/* See comments above */
232	return (0);
233}
234
235static struct vfsops fdesc_vfsops = {
236	.vfs_cmount =		fdesc_cmount,
237	.vfs_init =		fdesc_init,
238	.vfs_mount =		fdesc_mount,
239	.vfs_root =		fdesc_root,
240	.vfs_statfs =		fdesc_statfs,
241	.vfs_uninit =		fdesc_uninit,
242	.vfs_unmount =		fdesc_unmount,
243};
244
245VFS_SET(fdesc_vfsops, fdescfs, VFCF_SYNTHETIC | VFCF_JAIL);
246