diff options
Diffstat (limited to 'fs/autofs/expire.c')
| -rw-r--r-- | fs/autofs/expire.c | 662 |
1 files changed, 662 insertions, 0 deletions
diff --git a/fs/autofs/expire.c b/fs/autofs/expire.c new file mode 100644 index 000000000..70e9afe58 --- /dev/null +++ b/fs/autofs/expire.c @@ -0,0 +1,662 @@ +/* + * Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved + * Copyright 1999-2000 Jeremy Fitzhardinge <jeremy@goop.org> + * Copyright 2001-2006 Ian Kent <raven@themaw.net> + * + * This file is part of the Linux kernel and is made available under + * the terms of the GNU General Public License, version 2, or at your + * option, any later version, incorporated herein by reference. + */ + +#include "autofs_i.h" + +/* Check if a dentry can be expired */ +static inline int autofs_can_expire(struct dentry *dentry, + unsigned long timeout, unsigned int how) +{ + struct autofs_info *ino = autofs_dentry_ino(dentry); + + /* dentry in the process of being deleted */ + if (ino == NULL) + return 0; + + if (!(how & AUTOFS_EXP_IMMEDIATE)) { + /* Too young to die */ + if (!timeout || time_after(ino->last_used + timeout, jiffies)) + return 0; + } + return 1; +} + +/* Check a mount point for busyness */ +static int autofs_mount_busy(struct vfsmount *mnt, + struct dentry *dentry, unsigned int how) +{ + struct dentry *top = dentry; + struct path path = {.mnt = mnt, .dentry = dentry}; + int status = 1; + + pr_debug("dentry %p %pd\n", dentry, dentry); + + path_get(&path); + + if (!follow_down_one(&path)) + goto done; + + if (is_autofs_dentry(path.dentry)) { + struct autofs_sb_info *sbi = autofs_sbi(path.dentry->d_sb); + + /* This is an autofs submount, we can't expire it */ + if (autofs_type_indirect(sbi->type)) + goto done; + } + + /* Not a submount, has a forced expire been requested */ + if (how & AUTOFS_EXP_FORCED) { + status = 0; + goto done; + } + + /* Update the expiry counter if fs is busy */ + if (!may_umount_tree(path.mnt)) { + struct autofs_info *ino; + + ino = autofs_dentry_ino(top); + ino->last_used = jiffies; + goto done; + } + + status = 0; +done: + pr_debug("returning = %d\n", status); + path_put(&path); + return status; +} + +/* + * Calculate and dget next entry in the subdirs list under root. + */ +static struct dentry *get_next_positive_subdir(struct dentry *prev, + struct dentry *root) +{ + struct autofs_sb_info *sbi = autofs_sbi(root->d_sb); + struct list_head *next; + struct dentry *q; + + spin_lock(&sbi->lookup_lock); + spin_lock(&root->d_lock); + + if (prev) + next = prev->d_child.next; + else { + prev = dget_dlock(root); + next = prev->d_subdirs.next; + } + +cont: + if (next == &root->d_subdirs) { + spin_unlock(&root->d_lock); + spin_unlock(&sbi->lookup_lock); + dput(prev); + return NULL; + } + + q = list_entry(next, struct dentry, d_child); + + spin_lock_nested(&q->d_lock, DENTRY_D_LOCK_NESTED); + /* Already gone or negative dentry (under construction) - try next */ + if (!d_count(q) || !simple_positive(q)) { + spin_unlock(&q->d_lock); + next = q->d_child.next; + goto cont; + } + dget_dlock(q); + spin_unlock(&q->d_lock); + spin_unlock(&root->d_lock); + spin_unlock(&sbi->lookup_lock); + + dput(prev); + + return q; +} + +/* + * Calculate and dget next entry in top down tree traversal. + */ +static struct dentry *get_next_positive_dentry(struct dentry *prev, + struct dentry *root) +{ + struct autofs_sb_info *sbi = autofs_sbi(root->d_sb); + struct list_head *next; + struct dentry *p, *ret; + + if (prev == NULL) + return dget(root); + + spin_lock(&sbi->lookup_lock); +relock: + p = prev; + spin_lock(&p->d_lock); +again: + next = p->d_subdirs.next; + if (next == &p->d_subdirs) { + while (1) { + struct dentry *parent; + + if (p == root) { + spin_unlock(&p->d_lock); + spin_unlock(&sbi->lookup_lock); + dput(prev); + return NULL; + } + + parent = p->d_parent; + if (!spin_trylock(&parent->d_lock)) { + spin_unlock(&p->d_lock); + cpu_relax(); + goto relock; + } + spin_unlock(&p->d_lock); + next = p->d_child.next; + p = parent; + if (next != &parent->d_subdirs) + break; + } + } + ret = list_entry(next, struct dentry, d_child); + + spin_lock_nested(&ret->d_lock, DENTRY_D_LOCK_NESTED); + /* Negative dentry - try next */ + if (!simple_positive(ret)) { + spin_unlock(&p->d_lock); + lock_set_subclass(&ret->d_lock.dep_map, 0, _RET_IP_); + p = ret; + goto again; + } + dget_dlock(ret); + spin_unlock(&ret->d_lock); + spin_unlock(&p->d_lock); + spin_unlock(&sbi->lookup_lock); + + dput(prev); + + return ret; +} + +/* + * Check a direct mount point for busyness. + * Direct mounts have similar expiry semantics to tree mounts. + * The tree is not busy iff no mountpoints are busy and there are no + * autofs submounts. + */ +static int autofs_direct_busy(struct vfsmount *mnt, + struct dentry *top, + unsigned long timeout, + unsigned int how) +{ + pr_debug("top %p %pd\n", top, top); + + /* Forced expire, user space handles busy mounts */ + if (how & AUTOFS_EXP_FORCED) + return 0; + + /* If it's busy update the expiry counters */ + if (!may_umount_tree(mnt)) { + struct autofs_info *ino; + + ino = autofs_dentry_ino(top); + if (ino) + ino->last_used = jiffies; + return 1; + } + + /* Timeout of a direct mount is determined by its top dentry */ + if (!autofs_can_expire(top, timeout, how)) + return 1; + + return 0; +} + +/* + * Check a directory tree of mount points for busyness + * The tree is not busy iff no mountpoints are busy + */ +static int autofs_tree_busy(struct vfsmount *mnt, + struct dentry *top, + unsigned long timeout, + unsigned int how) +{ + struct autofs_info *top_ino = autofs_dentry_ino(top); + struct dentry *p; + + pr_debug("top %p %pd\n", top, top); + + /* Negative dentry - give up */ + if (!simple_positive(top)) + return 1; + + p = NULL; + while ((p = get_next_positive_dentry(p, top))) { + pr_debug("dentry %p %pd\n", p, p); + + /* + * Is someone visiting anywhere in the subtree ? + * If there's no mount we need to check the usage + * count for the autofs dentry. + * If the fs is busy update the expiry counter. + */ + if (d_mountpoint(p)) { + if (autofs_mount_busy(mnt, p, how)) { + top_ino->last_used = jiffies; + dput(p); + return 1; + } + } else { + struct autofs_info *ino = autofs_dentry_ino(p); + unsigned int ino_count = atomic_read(&ino->count); + + /* allow for dget above and top is already dgot */ + if (p == top) + ino_count += 2; + else + ino_count++; + + if (d_count(p) > ino_count) { + top_ino->last_used = jiffies; + dput(p); + return 1; + } + } + } + + /* Forced expire, user space handles busy mounts */ + if (how & AUTOFS_EXP_FORCED) + return 0; + + /* Timeout of a tree mount is ultimately determined by its top dentry */ + if (!autofs_can_expire(top, timeout, how)) + return 1; + + return 0; +} + +static struct dentry *autofs_check_leaves(struct vfsmount *mnt, + struct dentry *parent, + unsigned long timeout, + unsigned int how) +{ + struct dentry *p; + + pr_debug("parent %p %pd\n", parent, parent); + + p = NULL; + while ((p = get_next_positive_dentry(p, parent))) { + pr_debug("dentry %p %pd\n", p, p); + + if (d_mountpoint(p)) { + /* Can we umount this guy */ + if (autofs_mount_busy(mnt, p, how)) + continue; + + /* This isn't a submount so if a forced expire + * has been requested, user space handles busy + * mounts */ + if (how & AUTOFS_EXP_FORCED) + return p; + + /* Can we expire this guy */ + if (autofs_can_expire(p, timeout, how)) + return p; + } + } + return NULL; +} + +/* Check if we can expire a direct mount (possibly a tree) */ +static struct dentry *autofs_expire_direct(struct super_block *sb, + struct vfsmount *mnt, + struct autofs_sb_info *sbi, + unsigned int how) +{ + struct dentry *root = dget(sb->s_root); + struct autofs_info *ino; + unsigned long timeout; + + if (!root) + return NULL; + + timeout = sbi->exp_timeout; + + if (!autofs_direct_busy(mnt, root, timeout, how)) { + spin_lock(&sbi->fs_lock); + ino = autofs_dentry_ino(root); + /* No point expiring a pending mount */ + if (ino->flags & AUTOFS_INF_PENDING) { + spin_unlock(&sbi->fs_lock); + goto out; + } + ino->flags |= AUTOFS_INF_WANT_EXPIRE; + spin_unlock(&sbi->fs_lock); + synchronize_rcu(); + if (!autofs_direct_busy(mnt, root, timeout, how)) { + spin_lock(&sbi->fs_lock); + ino->flags |= AUTOFS_INF_EXPIRING; + init_completion(&ino->expire_complete); + spin_unlock(&sbi->fs_lock); + return root; + } + spin_lock(&sbi->fs_lock); + ino->flags &= ~AUTOFS_INF_WANT_EXPIRE; + spin_unlock(&sbi->fs_lock); + } +out: + dput(root); + + return NULL; +} + +/* Check if 'dentry' should expire, or return a nearby + * dentry that is suitable. + * If returned dentry is different from arg dentry, + * then a dget() reference was taken, else not. + */ +static struct dentry *should_expire(struct dentry *dentry, + struct vfsmount *mnt, + unsigned long timeout, + unsigned int how) +{ + struct autofs_info *ino = autofs_dentry_ino(dentry); + unsigned int ino_count; + + /* No point expiring a pending mount */ + if (ino->flags & AUTOFS_INF_PENDING) + return NULL; + + /* + * Case 1: (i) indirect mount or top level pseudo direct mount + * (autofs-4.1). + * (ii) indirect mount with offset mount, check the "/" + * offset (autofs-5.0+). + */ + if (d_mountpoint(dentry)) { + pr_debug("checking mountpoint %p %pd\n", dentry, dentry); + + /* Can we umount this guy */ + if (autofs_mount_busy(mnt, dentry, how)) + return NULL; + + /* This isn't a submount so if a forced expire + * has been requested, user space handles busy + * mounts */ + if (how & AUTOFS_EXP_FORCED) + return dentry; + + /* Can we expire this guy */ + if (autofs_can_expire(dentry, timeout, how)) + return dentry; + return NULL; + } + + if (d_really_is_positive(dentry) && d_is_symlink(dentry)) { + pr_debug("checking symlink %p %pd\n", dentry, dentry); + + /* Forced expire, user space handles busy mounts */ + if (how & AUTOFS_EXP_FORCED) + return dentry; + + /* + * A symlink can't be "busy" in the usual sense so + * just check last used for expire timeout. + */ + if (autofs_can_expire(dentry, timeout, how)) + return dentry; + return NULL; + } + + if (simple_empty(dentry)) + return NULL; + + /* Case 2: tree mount, expire iff entire tree is not busy */ + if (!(how & AUTOFS_EXP_LEAVES)) { + /* Not a forced expire? */ + if (!(how & AUTOFS_EXP_FORCED)) { + /* ref-walk currently on this dentry? */ + ino_count = atomic_read(&ino->count) + 1; + if (d_count(dentry) > ino_count) + return NULL; + } + + if (!autofs_tree_busy(mnt, dentry, timeout, how)) + return dentry; + /* + * Case 3: pseudo direct mount, expire individual leaves + * (autofs-4.1). + */ + } else { + struct dentry *expired; + + /* Not a forced expire? */ + if (!(how & AUTOFS_EXP_FORCED)) { + /* ref-walk currently on this dentry? */ + ino_count = atomic_read(&ino->count) + 1; + if (d_count(dentry) > ino_count) + return NULL; + } + + expired = autofs_check_leaves(mnt, dentry, timeout, how); + if (expired) { + if (expired == dentry) + dput(dentry); + return expired; + } + } + return NULL; +} + +/* + * Find an eligible tree to time-out + * A tree is eligible if :- + * - it is unused by any user process + * - it has been unused for exp_timeout time + */ +static struct dentry *autofs_expire_indirect(struct super_block *sb, + struct vfsmount *mnt, + struct autofs_sb_info *sbi, + unsigned int how) +{ + unsigned long timeout; + struct dentry *root = sb->s_root; + struct dentry *dentry; + struct dentry *expired; + struct dentry *found; + struct autofs_info *ino; + + if (!root) + return NULL; + + timeout = sbi->exp_timeout; + + dentry = NULL; + while ((dentry = get_next_positive_subdir(dentry, root))) { + spin_lock(&sbi->fs_lock); + ino = autofs_dentry_ino(dentry); + if (ino->flags & AUTOFS_INF_WANT_EXPIRE) { + spin_unlock(&sbi->fs_lock); + continue; + } + spin_unlock(&sbi->fs_lock); + + expired = should_expire(dentry, mnt, timeout, how); + if (!expired) + continue; + + spin_lock(&sbi->fs_lock); + ino = autofs_dentry_ino(expired); + ino->flags |= AUTOFS_INF_WANT_EXPIRE; + spin_unlock(&sbi->fs_lock); + synchronize_rcu(); + + /* Make sure a reference is not taken on found if + * things have changed. + */ + how &= ~AUTOFS_EXP_LEAVES; + found = should_expire(expired, mnt, timeout, how); + if (found != expired) { // something has changed, continue + dput(found); + goto next; + } + + if (expired != dentry) + dput(dentry); + + spin_lock(&sbi->fs_lock); + goto found; +next: + spin_lock(&sbi->fs_lock); + ino->flags &= ~AUTOFS_INF_WANT_EXPIRE; + spin_unlock(&sbi->fs_lock); + if (expired != dentry) + dput(expired); + } + return NULL; + +found: + pr_debug("returning %p %pd\n", expired, expired); + ino->flags |= AUTOFS_INF_EXPIRING; + init_completion(&ino->expire_complete); + spin_unlock(&sbi->fs_lock); + return expired; +} + +int autofs_expire_wait(const struct path *path, int rcu_walk) +{ + struct dentry *dentry = path->dentry; + struct autofs_sb_info *sbi = autofs_sbi(dentry->d_sb); + struct autofs_info *ino = autofs_dentry_ino(dentry); + int status; + int state; + + /* Block on any pending expire */ + if (!(ino->flags & AUTOFS_INF_WANT_EXPIRE)) + return 0; + if (rcu_walk) + return -ECHILD; + +retry: + spin_lock(&sbi->fs_lock); + state = ino->flags & (AUTOFS_INF_WANT_EXPIRE | AUTOFS_INF_EXPIRING); + if (state == AUTOFS_INF_WANT_EXPIRE) { + spin_unlock(&sbi->fs_lock); + /* + * Possibly being selected for expire, wait until + * it's selected or not. + */ + schedule_timeout_uninterruptible(HZ/10); + goto retry; + } + if (state & AUTOFS_INF_EXPIRING) { + spin_unlock(&sbi->fs_lock); + + pr_debug("waiting for expire %p name=%pd\n", dentry, dentry); + + status = autofs_wait(sbi, path, NFY_NONE); + wait_for_completion(&ino->expire_complete); + + pr_debug("expire done status=%d\n", status); + + if (d_unhashed(dentry)) + return -EAGAIN; + + return status; + } + spin_unlock(&sbi->fs_lock); + + return 0; +} + +/* Perform an expiry operation */ +int autofs_expire_run(struct super_block *sb, + struct vfsmount *mnt, + struct autofs_sb_info *sbi, + struct autofs_packet_expire __user *pkt_p) +{ + struct autofs_packet_expire pkt; + struct autofs_info *ino; + struct dentry *dentry; + int ret = 0; + + memset(&pkt, 0, sizeof(pkt)); + + pkt.hdr.proto_version = sbi->version; + pkt.hdr.type = autofs_ptype_expire; + + dentry = autofs_expire_indirect(sb, mnt, sbi, 0); + if (!dentry) + return -EAGAIN; + + pkt.len = dentry->d_name.len; + memcpy(pkt.name, dentry->d_name.name, pkt.len); + pkt.name[pkt.len] = '\0'; + + if (copy_to_user(pkt_p, &pkt, sizeof(struct autofs_packet_expire))) + ret = -EFAULT; + + spin_lock(&sbi->fs_lock); + ino = autofs_dentry_ino(dentry); + /* avoid rapid-fire expire attempts if expiry fails */ + ino->last_used = jiffies; + ino->flags &= ~(AUTOFS_INF_EXPIRING|AUTOFS_INF_WANT_EXPIRE); + complete_all(&ino->expire_complete); + spin_unlock(&sbi->fs_lock); + + dput(dentry); + + return ret; +} + +int autofs_do_expire_multi(struct super_block *sb, struct vfsmount *mnt, + struct autofs_sb_info *sbi, unsigned int how) +{ + struct dentry *dentry; + int ret = -EAGAIN; + + if (autofs_type_trigger(sbi->type)) + dentry = autofs_expire_direct(sb, mnt, sbi, how); + else + dentry = autofs_expire_indirect(sb, mnt, sbi, how); + + if (dentry) { + struct autofs_info *ino = autofs_dentry_ino(dentry); + const struct path path = { .mnt = mnt, .dentry = dentry }; + + /* This is synchronous because it makes the daemon a + * little easier + */ + ret = autofs_wait(sbi, &path, NFY_EXPIRE); + + spin_lock(&sbi->fs_lock); + /* avoid rapid-fire expire attempts if expiry fails */ + ino->last_used = jiffies; + ino->flags &= ~(AUTOFS_INF_EXPIRING|AUTOFS_INF_WANT_EXPIRE); + complete_all(&ino->expire_complete); + spin_unlock(&sbi->fs_lock); + dput(dentry); + } + + return ret; +} + +/* + * Call repeatedly until it returns -EAGAIN, meaning there's nothing + * more to be done. + */ +int autofs_expire_multi(struct super_block *sb, struct vfsmount *mnt, + struct autofs_sb_info *sbi, int __user *arg) +{ + unsigned int how = 0; + + if (arg && get_user(how, arg)) + return -EFAULT; + + return autofs_do_expire_multi(sb, mnt, sbi, how); +} |