source: branches/minix3-book/servers/fs/mount.c@ 12

Last change on this file since 12 was 4, checked in by Mattia Monga, 14 years ago

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File size: 6.3 KB
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[4]1/* This file performs the MOUNT and UMOUNT system calls.
2 *
3 * The entry points into this file are
4 * do_mount: perform the MOUNT system call
5 * do_umount: perform the UMOUNT system call
6 */
7
8#include "fs.h"
9#include <fcntl.h>
10#include <minix/com.h>
11#include <sys/stat.h>
12#include "buf.h"
13#include "file.h"
14#include "fproc.h"
15#include "inode.h"
16#include "param.h"
17#include "super.h"
18
19FORWARD _PROTOTYPE( dev_t name_to_dev, (char *path) );
20
21/*===========================================================================*
22 * do_mount *
23 *===========================================================================*/
24PUBLIC int do_mount()
25{
26/* Perform the mount(name, mfile, rd_only) system call. */
27
28 register struct inode *rip, *root_ip;
29 struct super_block *xp, *sp;
30 dev_t dev;
31 mode_t bits;
32 int rdir, mdir; /* TRUE iff {root|mount} file is dir */
33 int r, found;
34
35 /* Only the super-user may do MOUNT. */
36 if (!super_user) return(EPERM);
37
38 /* If 'name' is not for a block special file, return error. */
39 if (fetch_name(m_in.name1, m_in.name1_length, M1) != OK) return(err_code);
40 if ( (dev = name_to_dev(user_path)) == NO_DEV) return(err_code);
41
42 /* Scan super block table to see if dev already mounted & find a free slot.*/
43 sp = NIL_SUPER;
44 found = FALSE;
45 for (xp = &super_block[0]; xp < &super_block[NR_SUPERS]; xp++) {
46 if (xp->s_dev == dev) found = TRUE; /* is it mounted already? */
47 if (xp->s_dev == NO_DEV) sp = xp; /* record free slot */
48 }
49 if (found) return(EBUSY); /* already mounted */
50 if (sp == NIL_SUPER) return(ENFILE); /* no super block available */
51
52 /* Open the device the file system lives on. */
53 if (dev_open(dev, who, m_in.rd_only ? R_BIT : (R_BIT|W_BIT)) != OK)
54 return(EINVAL);
55
56 /* Make the cache forget about blocks it has open on the filesystem */
57 (void) do_sync();
58 invalidate(dev);
59
60 /* Fill in the super block. */
61 sp->s_dev = dev; /* read_super() needs to know which dev */
62 r = read_super(sp);
63
64 /* Is it recognized as a Minix filesystem? */
65 if (r != OK) {
66 dev_close(dev);
67 sp->s_dev = NO_DEV;
68 return(r);
69 }
70
71 /* Now get the inode of the file to be mounted on. */
72 if (fetch_name(m_in.name2, m_in.name2_length, M1) != OK) {
73 dev_close(dev);
74 sp->s_dev = NO_DEV;
75 return(err_code);
76 }
77 if ( (rip = eat_path(user_path)) == NIL_INODE) {
78 dev_close(dev);
79 sp->s_dev = NO_DEV;
80 return(err_code);
81 }
82
83 /* It may not be busy. */
84 r = OK;
85 if (rip->i_count > 1) r = EBUSY;
86
87 /* It may not be special. */
88 bits = rip->i_mode & I_TYPE;
89 if (bits == I_BLOCK_SPECIAL || bits == I_CHAR_SPECIAL) r = ENOTDIR;
90
91 /* Get the root inode of the mounted file system. */
92 root_ip = NIL_INODE; /* if 'r' not OK, make sure this is defined */
93 if (r == OK) {
94 if ( (root_ip = get_inode(dev, ROOT_INODE)) == NIL_INODE) r = err_code;
95 }
96 if (root_ip != NIL_INODE && root_ip->i_mode == 0) {
97 r = EINVAL;
98 }
99
100 /* File types of 'rip' and 'root_ip' may not conflict. */
101 if (r == OK) {
102 mdir = ((rip->i_mode & I_TYPE) == I_DIRECTORY); /* TRUE iff dir */
103 rdir = ((root_ip->i_mode & I_TYPE) == I_DIRECTORY);
104 if (!mdir && rdir) r = EISDIR;
105 }
106
107 /* If error, return the super block and both inodes; release the maps. */
108 if (r != OK) {
109 put_inode(rip);
110 put_inode(root_ip);
111 (void) do_sync();
112 invalidate(dev);
113 dev_close(dev);
114 sp->s_dev = NO_DEV;
115 return(r);
116 }
117
118 /* Nothing else can go wrong. Perform the mount. */
119 rip->i_mount = I_MOUNT; /* this bit says the inode is mounted on */
120 sp->s_imount = rip;
121 sp->s_isup = root_ip;
122 sp->s_rd_only = m_in.rd_only;
123 return(OK);
124}
125
126/*===========================================================================*
127 * do_umount *
128 *===========================================================================*/
129PUBLIC int do_umount()
130{
131/* Perform the umount(name) system call. */
132 dev_t dev;
133
134 /* Only the super-user may do UMOUNT. */
135 if (!super_user) return(EPERM);
136
137 /* If 'name' is not for a block special file, return error. */
138 if (fetch_name(m_in.name, m_in.name_length, M3) != OK) return(err_code);
139 if ( (dev = name_to_dev(user_path)) == NO_DEV) return(err_code);
140
141 return(unmount(dev));
142}
143
144/*===========================================================================*
145 * unmount *
146 *===========================================================================*/
147PUBLIC int unmount(dev)
148Dev_t dev;
149{
150/* Unmount a file system by device number. */
151 register struct inode *rip;
152 struct super_block *sp, *sp1;
153 int count;
154
155 /* See if the mounted device is busy. Only 1 inode using it should be
156 * open -- the root inode -- and that inode only 1 time.
157 */
158 count = 0;
159 for (rip = &inode[0]; rip< &inode[NR_INODES]; rip++)
160 if (rip->i_count > 0 && rip->i_dev == dev) count += rip->i_count;
161 if (count > 1) return(EBUSY); /* can't umount a busy file system */
162
163 /* Find the super block. */
164 sp = NIL_SUPER;
165 for (sp1 = &super_block[0]; sp1 < &super_block[NR_SUPERS]; sp1++) {
166 if (sp1->s_dev == dev) {
167 sp = sp1;
168 break;
169 }
170 }
171
172 /* Sync the disk, and invalidate cache. */
173 (void) do_sync(); /* force any cached blocks out of memory */
174 invalidate(dev); /* invalidate cache entries for this dev */
175 if (sp == NIL_SUPER) {
176 return(EINVAL);
177 }
178
179 /* Close the device the file system lives on. */
180 dev_close(dev);
181
182 /* Finish off the unmount. */
183 sp->s_imount->i_mount = NO_MOUNT; /* inode returns to normal */
184 put_inode(sp->s_imount); /* release the inode mounted on */
185 put_inode(sp->s_isup); /* release the root inode of the mounted fs */
186 sp->s_imount = NIL_INODE;
187 sp->s_dev = NO_DEV;
188 return(OK);
189}
190
191/*===========================================================================*
192 * name_to_dev *
193 *===========================================================================*/
194PRIVATE dev_t name_to_dev(path)
195char *path; /* pointer to path name */
196{
197/* Convert the block special file 'path' to a device number. If 'path'
198 * is not a block special file, return error code in 'err_code'.
199 */
200
201 register struct inode *rip;
202 register dev_t dev;
203
204 /* If 'path' can't be opened, give up immediately. */
205 if ( (rip = eat_path(path)) == NIL_INODE) return(NO_DEV);
206
207 /* If 'path' is not a block special file, return error. */
208 if ( (rip->i_mode & I_TYPE) != I_BLOCK_SPECIAL) {
209 err_code = ENOTBLK;
210 put_inode(rip);
211 return(NO_DEV);
212 }
213
214 /* Extract the device number. */
215 dev = (dev_t) rip->i_zone[0];
216 put_inode(rip);
217 return(dev);
218}
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