/* * Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved * Copyright 1999-2000 Jeremy Fitzhardinge * Copyright 2001-2006 Ian Kent * * 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, int do_now) { struct autofs_info *ino = autofs_dentry_ino(dentry); /* dentry in the process of being deleted */ if (ino == NULL) return 0; if (!do_now) { /* 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) { 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; } /* 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, int do_now) { pr_debug("top %p %pd\n", top, top); /* 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, do_now)) 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, int do_now) { 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)) { 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; } } } /* Timeout of a tree mount is ultimately determined by its top dentry */ if (!autofs_can_expire(top, timeout, do_now)) return 1; return 0; } static struct dentry *autofs_check_leaves(struct vfsmount *mnt, struct dentry *parent, unsigned long timeout, int do_now) { 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)) continue; /* Can we expire this guy */ if (autofs_can_expire(p, timeout, do_now)) return p; } } return NULL; } /* Check if we can expire a direct mount (possibly a tree) */ struct dentry *autofs_expire_direct(struct super_block *sb, struct vfsmount *mnt, struct autofs_sb_info *sbi, int how) { unsigned long timeout; struct dentry *root = dget(sb->s_root); int do_now = how & AUTOFS_EXP_IMMEDIATE; struct autofs_info *ino; if (!root) return NULL; timeout = sbi->exp_timeout; if (!autofs_direct_busy(mnt, root, timeout, do_now)) { 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, do_now)) { 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, int how) { int do_now = how & AUTOFS_EXP_IMMEDIATE; int exp_leaves = how & AUTOFS_EXP_LEAVES; 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)) return NULL; /* Can we expire this guy */ if (autofs_can_expire(dentry, timeout, do_now)) return dentry; return NULL; } if (d_really_is_positive(dentry) && d_is_symlink(dentry)) { pr_debug("checking symlink %p %pd\n", dentry, 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, do_now)) return dentry; return NULL; } if (simple_empty(dentry)) return NULL; /* Case 2: tree mount, expire iff entire tree is not busy */ if (!exp_leaves) { /* Path 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, do_now)) return dentry; /* * Case 3: pseudo direct mount, expire individual leaves * (autofs-4.1). */ } else { /* Path walk currently on this dentry? */ struct dentry *expired; ino_count = atomic_read(&ino->count) + 1; if (d_count(dentry) > ino_count) return NULL; expired = autofs_check_leaves(mnt, dentry, timeout, do_now); 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 */ struct dentry *autofs_expire_indirect(struct super_block *sb, struct vfsmount *mnt, struct autofs_sb_info *sbi, 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))) { int flags = how; 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, flags); 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. */ flags &= ~AUTOFS_EXP_LEAVES; found = should_expire(expired, mnt, timeout, flags); if (!found || found != expired) /* Something has changed, continue */ 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'; dput(dentry); 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); return ret; } int autofs_do_expire_multi(struct super_block *sb, struct vfsmount *mnt, struct autofs_sb_info *sbi, int when) { struct dentry *dentry; int ret = -EAGAIN; if (autofs_type_trigger(sbi->type)) dentry = autofs_expire_direct(sb, mnt, sbi, when); else dentry = autofs_expire_indirect(sb, mnt, sbi, when); 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) { int do_now = 0; if (arg && get_user(do_now, arg)) return -EFAULT; return autofs_do_expire_multi(sb, mnt, sbi, do_now); }