fs/autofs4/expire.c

   1 /* -*- c -*- --------------------------------------------------------------- *
   2  *
   3  * linux/fs/autofs/expire.c
   4  *
   5  *  Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
   6  *  Copyright 1999-2000 Jeremy Fitzhardinge <jeremy@goop.org>
   7  *  Copyright 2001-2003 Ian Kent <raven@themaw.net>
   8  *
   9  * This file is part of the Linux kernel and is made available under
  10  * the terms of the GNU General Public License, version 2, or at your
  11  * option, any later version, incorporated herein by reference.
  12  *
  13  * ------------------------------------------------------------------------- */
  14
  15 #include "autofs_i.h"
  16
  17 static unsigned long now;
  18
  19 /* Check if a dentry can be expired return 1 if it can else return 0 */
  20 static inline int autofs4_can_expire(struct dentry *dentry,
  21                                         unsigned long timeout, int do_now)
  22 {
  23         struct autofs_info *ino = autofs4_dentry_ino(dentry);
  24
  25         /* dentry in the process of being deleted */
  26         if (ino == NULL)
  27                 return 0;
  28
  29         /* No point expiring a pending mount */
  30         if (dentry->d_flags & DCACHE_AUTOFS_PENDING)
  31                 return 0;
  32
  33         if (!do_now) {
  34                 /* Too young to die */
  35                 if (time_after(ino->last_used + timeout, now))
  36                         return 0;
  37
  38                 /* update last_used here :-
  39                    - obviously makes sense if it is in use now
  40                    - less obviously, prevents rapid-fire expire
  41                      attempts if expire fails the first time */
  42                 ino->last_used = now;
  43         }
  44
  45         return 1;
  46 }
  47
  48 /* Check a mount point for busyness return 1 if not busy, otherwise */
  49 static int autofs4_check_mount(struct vfsmount *mnt, struct dentry *dentry)
  50 {
  51         int status = 0;
  52
  53         DPRINTK("dentry %p %.*s",
  54                 dentry, (int)dentry->d_name.len, dentry->d_name.name);
  55
  56         mntget(mnt);
  57         dget(dentry);
  58
  59         if (!autofs4_follow_mount(&mnt, &dentry))
  60                 goto done;
  61
  62         /* This is an autofs submount, we can't expire it */
  63         if (is_autofs4_dentry(dentry))
  64                 goto done;
  65
  66         /* The big question */
  67         if (may_umount_tree(mnt) == 0)
  68                 status = 1;
  69 done:
  70         DPRINTK("returning = %d", status);
  71         mntput(mnt);
  72         dput(dentry);
  73         return status;
  74 }
  75
  76 /* Check a directory tree of mount points for busyness
  77  * The tree is not busy iff no mountpoints are busy
  78  * Return 1 if the tree is busy or 0 otherwise
  79  */
  80 static int autofs4_check_tree(struct vfsmount *mnt,
  81                               struct dentry *top,
  82                               unsigned long timeout,
  83                               int do_now)
  84 {
  85         struct dentry *this_parent = top;
  86         struct list_head *next;
  87
  88         DPRINTK("parent %p %.*s",
  89                 top, (int)top->d_name.len, top->d_name.name);
  90
  91         /* Negative dentry - give up */
  92         if (!simple_positive(top))
  93                 return 0;
  94
  95         /* Timeout of a tree mount is determined by its top dentry */
  96         if (!autofs4_can_expire(top, timeout, do_now))
  97                 return 0;
  98
  99         /* Is someone visiting anywhere in the tree ? */
 100         if (may_umount_tree(mnt))
 101                 return 0;
 102
 103         spin_lock(&dcache_lock);
 104 repeat:
 105         next = this_parent->d_subdirs.next;
 106 resume:
 107         while (next != &this_parent->d_subdirs) {
 108                 struct dentry *dentry = list_entry(next, struct dentry, d_u.d_child);
 109
 110                 /* Negative dentry - give up */
 111                 if (!simple_positive(dentry)) {
 112                         next = next->next;
 113                         continue;
 114                 }
 115
 116                 DPRINTK("dentry %p %.*s",
 117                         dentry, (int)dentry->d_name.len, dentry->d_name.name);
 118
 119                 if (!simple_empty_nolock(dentry)) {
 120                         this_parent = dentry;
 121                         goto repeat;
 122                 }
 123
 124                 dentry = dget(dentry);
 125                 spin_unlock(&dcache_lock);
 126
 127                 if (d_mountpoint(dentry)) {
 128                         /* First busy => tree busy */
 129                         if (!autofs4_check_mount(mnt, dentry)) {
 130                                 dput(dentry);
 131                                 return 0;
 132                         }
 133                 }
 134
 135                 dput(dentry);
 136                 spin_lock(&dcache_lock);
 137                 next = next->next;
 138         }
 139
 140         if (this_parent != top) {
 141                 next = this_parent->d_u.d_child.next;
 142                 this_parent = this_parent->d_parent;
 143                 goto resume;
 144         }
 145         spin_unlock(&dcache_lock);
 146
 147         return 1;
 148 }
 149
 150 static struct dentry *autofs4_check_leaves(struct vfsmount *mnt,
 151                                            struct dentry *parent,
 152                                            unsigned long timeout,
 153                                            int do_now)
 154 {
 155         struct dentry *this_parent = parent;
 156         struct list_head *next;
 157
 158         DPRINTK("parent %p %.*s",
 159                 parent, (int)parent->d_name.len, parent->d_name.name);
 160
 161         spin_lock(&dcache_lock);
 162 repeat:
 163         next = this_parent->d_subdirs.next;
 164 resume:
 165         while (next != &this_parent->d_subdirs) {
 166                 struct dentry *dentry = list_entry(next, struct dentry, d_u.d_child);
 167
 168                 /* Negative dentry - give up */
 169                 if (!simple_positive(dentry)) {
 170                         next = next->next;
 171                         continue;
 172                 }
 173
 174                 DPRINTK("dentry %p %.*s",
 175                         dentry, (int)dentry->d_name.len, dentry->d_name.name);
 176
 177                 if (!list_empty(&dentry->d_subdirs)) {
 178                         this_parent = dentry;
 179                         goto repeat;
 180                 }
 181
 182                 dentry = dget(dentry);
 183                 spin_unlock(&dcache_lock);
 184
 185                 if (d_mountpoint(dentry)) {
 186                         /* Can we expire this guy */
 187                         if (!autofs4_can_expire(dentry, timeout, do_now))
 188                                 goto cont;
 189
 190                         /* Can we umount this guy */
 191                         if (autofs4_check_mount(mnt, dentry))
 192                                 return dentry;
 193
 194                 }
 195 cont:
 196                 dput(dentry);
 197                 spin_lock(&dcache_lock);
 198                 next = next->next;
 199         }
 200
 201         if (this_parent != parent) {
 202                 next = this_parent->d_u.d_child.next;
 203                 this_parent = this_parent->d_parent;
 204                 goto resume;
 205         }
 206         spin_unlock(&dcache_lock);
 207
 208         return NULL;
 209 }
 210
 211 /*
 212  * Find an eligible tree to time-out
 213  * A tree is eligible if :-
 214  *  - it is unused by any user process
 215  *  - it has been unused for exp_timeout time
 216  */
 217 static struct dentry *autofs4_expire(struct super_block *sb,
 218                                      struct vfsmount *mnt,
 219                                      struct autofs_sb_info *sbi,
 220                                      int how)
 221 {
 222         unsigned long timeout;
 223         struct dentry *root = sb->s_root;
 224         struct dentry *expired = NULL;
 225         struct list_head *next;
 226         int do_now = how & AUTOFS_EXP_IMMEDIATE;
 227         int exp_leaves = how & AUTOFS_EXP_LEAVES;
 228
 229         if ( !sbi->exp_timeout || !root )
 230                 return NULL;
 231
 232         now = jiffies;
 233         timeout = sbi->exp_timeout;
 234
 235         spin_lock(&dcache_lock);
 236         next = root->d_subdirs.next;
 237
 238         /* On exit from the loop expire is set to a dgot dentry
 239          * to expire or it's NULL */
 240         while ( next != &root->d_subdirs ) {
 241                 struct dentry *dentry = list_entry(next, struct dentry, d_u.d_child);
 242
 243                 /* Negative dentry - give up */
 244                 if ( !simple_positive(dentry) ) {
 245                         next = next->next;
 246                         continue;
 247                 }
 248
 249                 dentry = dget(dentry);
 250                 spin_unlock(&dcache_lock);
 251
 252                 /* Case 1: indirect mount or top level direct mount */
 253                 if (d_mountpoint(dentry)) {
 254                         DPRINTK("checking mountpoint %p %.*s",
 255                                 dentry, (int)dentry->d_name.len, dentry->d_name.name);
 256
 257                         /* Can we expire this guy */
 258                         if (!autofs4_can_expire(dentry, timeout, do_now))
 259                                 goto next;
 260
 261                         /* Can we umount this guy */
 262                         if (autofs4_check_mount(mnt, dentry)) {
 263                                 expired = dentry;
 264                                 break;
 265                         }
 266                         goto next;
 267                 }
 268
 269                 if ( simple_empty(dentry) )
 270                         goto next;
 271
 272                 /* Case 2: tree mount, expire iff entire tree is not busy */
 273                 if (!exp_leaves) {
 274                         /* Lock the tree as we must expire as a whole */
 275                         spin_lock(&sbi->fs_lock);
 276                         if (autofs4_check_tree(mnt, dentry, timeout, do_now)) {
 277                                 struct autofs_info *inf = autofs4_dentry_ino(dentry);
 278
 279                                 /* Set this flag early to catch sys_chdir and the like */
 280                                 inf->flags |= AUTOFS_INF_EXPIRING;
 281                                 spin_unlock(&sbi->fs_lock);
 282                                 expired = dentry;
 283                                 break;
 284                         }
 285                         spin_unlock(&sbi->fs_lock);
 286                 /* Case 3: direct mount, expire individual leaves */
 287                 } else {
 288                         expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
 289                         if (expired) {
 290                                 dput(dentry);
 291                                 break;
 292                         }
 293                 }
 294 next:
 295                 dput(dentry);
 296                 spin_lock(&dcache_lock);
 297                 next = next->next;
 298         }
 299
 300         if ( expired ) {
 301                 DPRINTK("returning %p %.*s",
 302                         expired, (int)expired->d_name.len, expired->d_name.name);
 303                 spin_lock(&dcache_lock);
 304                 list_del(&expired->d_parent->d_subdirs);
 305                 list_add(&expired->d_parent->d_subdirs, &expired->d_u.d_child);
 306                 spin_unlock(&dcache_lock);
 307                 return expired;
 308         }
 309         spin_unlock(&dcache_lock);
 310
 311         return NULL;
 312 }
 313
 314 /* Perform an expiry operation */
 315 int autofs4_expire_run(struct super_block *sb,
 316                       struct vfsmount *mnt,
 317                       struct autofs_sb_info *sbi,
 318                       struct autofs_packet_expire __user *pkt_p)
 319 {
 320         struct autofs_packet_expire pkt;
 321         struct dentry *dentry;
 322
 323         memset(&pkt,0,sizeof pkt);
 324
 325         pkt.hdr.proto_version = sbi->version;
 326         pkt.hdr.type = autofs_ptype_expire;
 327
 328         if ((dentry = autofs4_expire(sb, mnt, sbi, 0)) == NULL)
 329                 return -EAGAIN;
 330
 331         pkt.len = dentry->d_name.len;
 332         memcpy(pkt.name, dentry->d_name.name, pkt.len);
 333         pkt.name[pkt.len] = '\0';
 334         dput(dentry);
 335
 336         if ( copy_to_user(pkt_p, &pkt, sizeof(struct autofs_packet_expire)) )
 337                 return -EFAULT;
 338
 339         return 0;
 340 }
 341
 342 /* Call repeatedly until it returns -EAGAIN, meaning there's nothing
 343    more to be done */
 344 int autofs4_expire_multi(struct super_block *sb, struct vfsmount *mnt,
 345                         struct autofs_sb_info *sbi, int __user *arg)
 346 {
 347         struct dentry *dentry;
 348         int ret = -EAGAIN;
 349         int do_now = 0;
 350
 351         if (arg && get_user(do_now, arg))
 352                 return -EFAULT;
 353
 354         if ((dentry = autofs4_expire(sb, mnt, sbi, do_now)) != NULL) {
 355                 struct autofs_info *de_info = autofs4_dentry_ino(dentry);
 356
 357                 /* This is synchronous because it makes the daemon a
 358                    little easier */
 359                 de_info->flags |= AUTOFS_INF_EXPIRING;
 360                 ret = autofs4_wait(sbi, dentry, NFY_EXPIRE);
 361                 de_info->flags &= ~AUTOFS_INF_EXPIRING;
 362                 dput(dentry);
 363         }
 364
 365         return ret;
 366 }
 367