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 (!follow_down(&mnt, &dentry))
  60                 goto done;
  61
  62         while (d_mountpoint(dentry) && follow_down(&mnt, &dentry))
  63                 ;
  64
  65         /* This is an autofs submount, we can't expire it */
  66         if (is_autofs4_dentry(dentry))
  67                 goto done;
  68
  69         /* The big question */
  70         if (may_umount_tree(mnt) == 0)
  71                 status = 1;
  72 done:
  73         DPRINTK("returning = %d", status);
  74         mntput(mnt);
  75         dput(dentry);
  76         return status;
  77 }
  78
  79 /* Check a directory tree of mount points for busyness
  80  * The tree is not busy iff no mountpoints are busy
  81  * Return 1 if the tree is busy or 0 otherwise
  82  */
  83 static int autofs4_check_tree(struct vfsmount *mnt,
  84                               struct dentry *top,
  85                               unsigned long timeout,
  86                               int do_now)
  87 {
  88         struct dentry *this_parent = top;
  89         struct list_head *next;
  90
  91         DPRINTK("parent %p %.*s",
  92                 top, (int)top->d_name.len, top->d_name.name);
  93
  94         /* Negative dentry - give up */
  95         if (!simple_positive(top))
  96                 return 0;
  97
  98         /* Timeout of a tree mount is determined by its top dentry */
  99         if (!autofs4_can_expire(top, timeout, do_now))
 100                 return 0;
 101
 102         spin_lock(&dcache_lock);
 103 repeat:
 104         next = this_parent->d_subdirs.next;
 105 resume:
 106         while (next != &this_parent->d_subdirs) {
 107                 struct dentry *dentry = list_entry(next, struct dentry, d_child);
 108
 109                 /* Negative dentry - give up */
 110                 if (!simple_positive(dentry)) {
 111                         next = next->next;
 112                         continue;
 113                 }
 114
 115                 DPRINTK("dentry %p %.*s",
 116                         dentry, (int)dentry->d_name.len, dentry->d_name.name);
 117
 118                 if (!simple_empty_nolock(dentry)) {
 119                         this_parent = dentry;
 120                         goto repeat;
 121                 }
 122
 123                 dentry = dget(dentry);
 124                 spin_unlock(&dcache_lock);
 125
 126                 if (d_mountpoint(dentry)) {
 127                         /* First busy => tree busy */
 128                         if (!autofs4_check_mount(mnt, dentry)) {
 129                                 dput(dentry);
 130                                 return 0;
 131                         }
 132                 }
 133
 134                 dput(dentry);
 135                 spin_lock(&dcache_lock);
 136                 next = next->next;
 137         }
 138
 139         if (this_parent != top) {
 140                 next = this_parent->d_child.next;
 141                 this_parent = this_parent->d_parent;
 142                 goto resume;
 143         }
 144         spin_unlock(&dcache_lock);
 145
 146         return 1;
 147 }
 148
 149 static struct dentry *autofs4_check_leaves(struct vfsmount *mnt,
 150                                            struct dentry *parent,
 151                                            unsigned long timeout,
 152                                            int do_now)
 153 {
 154         struct dentry *this_parent = parent;
 155         struct list_head *next;
 156
 157         DPRINTK("parent %p %.*s",
 158                 parent, (int)parent->d_name.len, parent->d_name.name);
 159
 160         spin_lock(&dcache_lock);
 161 repeat:
 162         next = this_parent->d_subdirs.next;
 163 resume:
 164         while (next != &this_parent->d_subdirs) {
 165                 struct dentry *dentry = list_entry(next, struct dentry, d_child);
 166
 167                 /* Negative dentry - give up */
 168                 if (!simple_positive(dentry)) {
 169                         next = next->next;
 170                         continue;
 171                 }
 172
 173                 DPRINTK("dentry %p %.*s",
 174                         dentry, (int)dentry->d_name.len, dentry->d_name.name);
 175
 176                 if (!list_empty(&dentry->d_subdirs)) {
 177                         this_parent = dentry;
 178                         goto repeat;
 179                 }
 180
 181                 dentry = dget(dentry);
 182                 spin_unlock(&dcache_lock);
 183
 184                 if (d_mountpoint(dentry)) {
 185                         /* Can we expire this guy */
 186                         if (!autofs4_can_expire(dentry, timeout, do_now))
 187                                 goto cont;
 188
 189                         /* Can we umount this guy */
 190                         if (autofs4_check_mount(mnt, dentry))
 191                                 return dentry;
 192
 193                 }
 194 cont:
 195                 dput(dentry);
 196                 spin_lock(&dcache_lock);
 197                 next = next->next;
 198         }
 199
 200         if (this_parent != parent) {
 201                 next = this_parent->d_child.next;
 202                 this_parent = this_parent->d_parent;
 203                 goto resume;
 204         }
 205         spin_unlock(&dcache_lock);
 206
 207         return NULL;
 208 }
 209
 210 /*
 211  * Find an eligible tree to time-out
 212  * A tree is eligible if :-
 213  *  - it is unused by any user process
 214  *  - it has been unused for exp_timeout time
 215  */
 216 static struct dentry *autofs4_expire(struct super_block *sb,
 217                                      struct vfsmount *mnt,
 218                                      struct autofs_sb_info *sbi,
 219                                      int how)
 220 {
 221         unsigned long timeout;
 222         struct dentry *root = sb->s_root;
 223         struct dentry *expired = NULL;
 224         struct list_head *next;
 225         int do_now = how & AUTOFS_EXP_IMMEDIATE;
 226         int exp_leaves = how & AUTOFS_EXP_LEAVES;
 227
 228         if ( !sbi->exp_timeout || !root )
 229                 return NULL;
 230
 231         now = jiffies;
 232         timeout = sbi->exp_timeout;
 233
 234         spin_lock(&dcache_lock);
 235         next = root->d_subdirs.next;
 236
 237         /* On exit from the loop expire is set to a dgot dentry
 238          * to expire or it's NULL */
 239         while ( next != &root->d_subdirs ) {
 240                 struct dentry *dentry = list_entry(next, struct dentry, d_child);
 241
 242                 /* Negative dentry - give up */
 243                 if ( !simple_positive(dentry) ) {
 244                         next = next->next;
 245                         continue;
 246                 }
 247
 248                 dentry = dget(dentry);
 249                 spin_unlock(&dcache_lock);
 250
 251                 /* Case 1: indirect mount or top level direct mount */
 252                 if (d_mountpoint(dentry)) {
 253                         DPRINTK("checking mountpoint %p %.*s",
 254                                 dentry, (int)dentry->d_name.len, dentry->d_name.name);
 255
 256                         /* Can we expire this guy */
 257                         if (!autofs4_can_expire(dentry, timeout, do_now))
 258                                 goto next;
 259
 260                         /* Can we umount this guy */
 261                         if (autofs4_check_mount(mnt, dentry)) {
 262                                 expired = dentry;
 263                                 break;
 264                         }
 265                         goto next;
 266                 }
 267
 268                 if ( simple_empty(dentry) )
 269                         goto next;
 270
 271                 /* Case 2: tree mount, expire iff entire tree is not busy */
 272                 if (!exp_leaves) {
 273                         if (autofs4_check_tree(mnt, dentry, timeout, do_now)) {
 274                         expired = dentry;
 275                         break;
 276                         }
 277                 /* Case 3: direct mount, expire individual leaves */
 278                 } else {
 279                         expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
 280                         if (expired) {
 281                                 dput(dentry);
 282                                 break;
 283                         }
 284                 }
 285 next:
 286                 dput(dentry);
 287                 spin_lock(&dcache_lock);
 288                 next = next->next;
 289         }
 290
 291         if ( expired ) {
 292                 DPRINTK("returning %p %.*s",
 293                         expired, (int)expired->d_name.len, expired->d_name.name);
 294                 spin_lock(&dcache_lock);
 295                 list_del(&expired->d_parent->d_subdirs);
 296                 list_add(&expired->d_parent->d_subdirs, &expired->d_child);
 297                 spin_unlock(&dcache_lock);
 298                 return expired;
 299         }
 300         spin_unlock(&dcache_lock);
 301
 302         return NULL;
 303 }
 304
 305 /* Perform an expiry operation */
 306 int autofs4_expire_run(struct super_block *sb,
 307                       struct vfsmount *mnt,
 308                       struct autofs_sb_info *sbi,
 309                       struct autofs_packet_expire __user *pkt_p)
 310 {
 311         struct autofs_packet_expire pkt;
 312         struct dentry *dentry;
 313
 314         memset(&pkt,0,sizeof pkt);
 315
 316         pkt.hdr.proto_version = sbi->version;
 317         pkt.hdr.type = autofs_ptype_expire;
 318
 319         if ((dentry = autofs4_expire(sb, mnt, sbi, 0)) == NULL)
 320                 return -EAGAIN;
 321
 322         pkt.len = dentry->d_name.len;
 323         memcpy(pkt.name, dentry->d_name.name, pkt.len);
 324         pkt.name[pkt.len] = '\0';
 325         dput(dentry);
 326
 327         if ( copy_to_user(pkt_p, &pkt, sizeof(struct autofs_packet_expire)) )
 328                 return -EFAULT;
 329
 330         return 0;
 331 }
 332
 333 /* Call repeatedly until it returns -EAGAIN, meaning there's nothing
 334    more to be done */
 335 int autofs4_expire_multi(struct super_block *sb, struct vfsmount *mnt,
 336                         struct autofs_sb_info *sbi, int __user *arg)
 337 {
 338         struct dentry *dentry;
 339         int ret = -EAGAIN;
 340         int do_now = 0;
 341
 342         if (arg && get_user(do_now, arg))
 343                 return -EFAULT;
 344
 345         if ((dentry = autofs4_expire(sb, mnt, sbi, do_now)) != NULL) {
 346                 struct autofs_info *de_info = autofs4_dentry_ino(dentry);
 347
 348                 /* This is synchronous because it makes the daemon a
 349                    little easier */
 350                 de_info->flags |= AUTOFS_INF_EXPIRING;
 351                 ret = autofs4_wait(sbi, dentry, NFY_EXPIRE);
 352                 de_info->flags &= ~AUTOFS_INF_EXPIRING;
 353                 dput(dentry);
 354         }
 355
 356         return ret;
 357 }
 358