xref: /freebsd/sys/fs/fdescfs/fdesc_vfsops.c (revision d93a896ef95946b0bf1219866fcb324b78543444)
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  * 3. 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  * $FreeBSD$
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 
57 static MALLOC_DEFINE(M_FDESCMNT, "fdesc_mount", "FDESC mount structure");
58 
59 static vfs_cmount_t	fdesc_cmount;
60 static vfs_mount_t	fdesc_mount;
61 static vfs_unmount_t	fdesc_unmount;
62 static vfs_statfs_t	fdesc_statfs;
63 static vfs_root_t	fdesc_root;
64 
65 /*
66  * Compatibility shim for old mount(2) system call.
67  */
68 int
69 fdesc_cmount(struct mntarg *ma, void *data, uint64_t flags)
70 {
71 
72 	return kernel_mount(ma, flags);
73 }
74 
75 /*
76  * Mount the per-process file descriptors (/dev/fd)
77  */
78 static int
79 fdesc_mount(struct mount *mp)
80 {
81 	struct fdescmount *fmp;
82 	struct thread *td = curthread;
83 	struct vnode *rvp;
84 	int error;
85 
86 	if (!prison_allow(td->td_ucred, PR_ALLOW_MOUNT_FDESCFS))
87 		return (EPERM);
88 
89 	/*
90 	 * Update is a no-op
91 	 */
92 	if (mp->mnt_flag & (MNT_UPDATE | MNT_ROOTFS))
93 		return (EOPNOTSUPP);
94 
95 	fmp = malloc(sizeof(struct fdescmount),
96 				M_FDESCMNT, M_WAITOK);	/* XXX */
97 
98 	/*
99 	 * We need to initialize a few bits of our local mount point struct to
100 	 * avoid confusion in allocvp.
101 	 */
102 	mp->mnt_data = fmp;
103 	fmp->flags = 0;
104 	if (vfs_getopt(mp->mnt_optnew, "linrdlnk", NULL, NULL) == 0)
105 		fmp->flags |= FMNT_LINRDLNKF;
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 	rvp->v_type = VDIR;
113 	rvp->v_vflag |= VV_ROOT;
114 	fmp->f_root = rvp;
115 	VOP_UNLOCK(rvp, 0);
116 	/* XXX -- don't mark as local to work around fts() problems */
117 	/*mp->mnt_flag |= MNT_LOCAL;*/
118 	vfs_getnewfsid(mp);
119 
120 	vfs_mountedfrom(mp, "fdescfs");
121 	return (0);
122 }
123 
124 static int
125 fdesc_unmount(struct mount *mp, int mntflags)
126 {
127 	struct fdescmount *fmp;
128 	int error, flags;
129 
130 	flags = 0;
131 	fmp = 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.
153 	 */
154 	mp->mnt_data = NULL;
155 	free(fmp, M_FDESCMNT);
156 	return (0);
157 }
158 
159 static int
160 fdesc_root(struct mount *mp, int flags, struct vnode **vpp)
161 {
162 	struct vnode *vp;
163 
164 	/*
165 	 * Return locked reference to root.
166 	 */
167 	vp = VFSTOFDESC(mp)->f_root;
168 	vget(vp, LK_EXCLUSIVE | LK_RETRY, curthread);
169 	*vpp = vp;
170 	return (0);
171 }
172 
173 static int
174 fdesc_statfs(struct mount *mp, struct statfs *sbp)
175 {
176 	struct thread *td;
177 	struct filedesc *fdp;
178 	int lim;
179 	int i;
180 	int last;
181 	int freefd;
182 	uint64_t limit;
183 
184 	td = curthread;
185 
186 	/*
187 	 * Compute number of free file descriptors.
188 	 * [ Strange results will ensue if the open file
189 	 * limit is ever reduced below the current number
190 	 * of open files... ]
191 	 */
192 	lim = lim_cur(td, RLIMIT_NOFILE);
193 	fdp = td->td_proc->p_fd;
194 	FILEDESC_SLOCK(fdp);
195 	limit = racct_get_limit(td->td_proc, RACCT_NOFILE);
196 	if (lim > limit)
197 		lim = limit;
198 	last = min(fdp->fd_nfiles, lim);
199 	freefd = 0;
200 	for (i = fdp->fd_freefile; i < last; i++)
201 		if (fdp->fd_ofiles[i].fde_file == NULL)
202 			freefd++;
203 
204 	/*
205 	 * Adjust for the fact that the fdesc array may not
206 	 * have been fully allocated yet.
207 	 */
208 	if (fdp->fd_nfiles < lim)
209 		freefd += (lim - fdp->fd_nfiles);
210 	FILEDESC_SUNLOCK(fdp);
211 
212 	sbp->f_flags = 0;
213 	sbp->f_bsize = DEV_BSIZE;
214 	sbp->f_iosize = DEV_BSIZE;
215 	sbp->f_blocks = 2;		/* 1K to keep df happy */
216 	sbp->f_bfree = 0;
217 	sbp->f_bavail = 0;
218 	sbp->f_files = lim + 1;		/* Allow for "." */
219 	sbp->f_ffree = freefd;		/* See comments above */
220 	return (0);
221 }
222 
223 static struct vfsops fdesc_vfsops = {
224 	.vfs_cmount =		fdesc_cmount,
225 	.vfs_init =		fdesc_init,
226 	.vfs_mount =		fdesc_mount,
227 	.vfs_root =		fdesc_root,
228 	.vfs_statfs =		fdesc_statfs,
229 	.vfs_uninit =		fdesc_uninit,
230 	.vfs_unmount =		fdesc_unmount,
231 };
232 
233 VFS_SET(fdesc_vfsops, fdescfs, VFCF_SYNTHETIC | VFCF_JAIL);
234