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