/* -*- c -*- --------------------------------------------------------------- * * * linux/fs/autofs/expire.c * * 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" static unsigned long now; /* Check if a dentry can be expired */ static inline int autofs4_can_expire(struct dentry *dentry, unsigned long timeout, int do_now) { struct autofs_info *ino = autofs4_dentry_ino(dentry); /* dentry in the process of being deleted */ if (ino == NULL) return 0; /* No point expiring a pending mount */ if (dentry->d_flags & DCACHE_AUTOFS_PENDING) return 0; if (!do_now) { /* Too young to die */ if (time_after(ino->last_used + timeout, now)) return 0; /* update last_used here :- - obviously makes sense if it is in use now - less obviously, prevents rapid-fire expire attempts if expire fails the first time */ ino->last_used = now; } return 1; } /* Check a mount point for busyness */ static int autofs4_mount_busy(struct vfsmount *mnt, struct dentry *dentry) { struct dentry *top = dentry; int status = 1; DPRINTK("dentry %p %.*s", dentry, (int)dentry->d_name.len, dentry->d_name.name); mntget(mnt); dget(dentry); if (!autofs4_follow_mount(&mnt, &dentry)) goto done; /* This is an autofs submount, we can't expire it */ if (is_autofs4_dentry(dentry)) goto done; /* Update the expiry counter if fs is busy */ if (!may_umount_tree(mnt)) { struct autofs_info *ino = autofs4_dentry_ino(top); ino->last_used = jiffies; goto done; } status = 0; done: DPRINTK("returning = %d", status); mntput(mnt); dput(dentry); return status; } /* * Calculate next entry in top down tree traversal. * From next_mnt in namespace.c - elegant. */ static struct dentry *next_dentry(struct dentry *p, struct dentry *root) { struct list_head *next = p->d_subdirs.next; if (next == &p->d_subdirs) { while (1) { if (p == root) return NULL; next = p->d_u.d_child.next; if (next != &p->d_parent->d_subdirs) break; p = p->d_parent; } } return list_entry(next, struct dentry, d_u.d_child); } /* * 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 autofs4_direct_busy(struct vfsmount *mnt, struct dentry *top, unsigned long timeout, int do_now) { DPRINTK("top %p %.*s", top, (int) top->d_name.len, top->d_name.name); /* If it's busy update the expiry counters */ if (!may_umount_tree(mnt)) { struct autofs_info *ino = autofs4_dentry_ino(top); if (ino) ino->last_used = jiffies; return 1; } /* Timeout of a direct mount is determined by its top dentry */ if (!autofs4_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 autofs4_tree_busy(struct vfsmount *mnt, struct dentry *top, unsigned long timeout, int do_now) { struct autofs_info *top_ino = autofs4_dentry_ino(top); struct dentry *p; DPRINTK("top %p %.*s", top, (int)top->d_name.len, top->d_name.name); /* Negative dentry - give up */ if (!simple_positive(top)) return 1; spin_lock(&dcache_lock); for (p = top; p; p = next_dentry(p, top)) { /* Negative dentry - give up */ if (!simple_positive(p)) continue; DPRINTK("dentry %p %.*s", p, (int) p->d_name.len, p->d_name.name); p = dget(p); spin_unlock(&dcache_lock); /* * 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 (autofs4_mount_busy(mnt, p)) { top_ino->last_used = jiffies; dput(p); return 1; } } else { struct autofs_info *ino = autofs4_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 (atomic_read(&p->d_count) > ino_count) { top_ino->last_used = jiffies; dput(p); return 1; } } dput(p); spin_lock(&dcache_lock); } spin_unlock(&dcache_lock); /* Timeout of a tree mount is ultimately determined by its top dentry */ if (!autofs4_can_expire(top, timeout, do_now)) return 1; return 0; } static struct dentry *autofs4_check_leaves(struct vfsmount *mnt, struct dentry *parent, unsigned long timeout, int do_now) { struct dentry *p; DPRINTK("parent %p %.*s", parent, (int)parent->d_name.len, parent->d_name.name); spin_lock(&dcache_lock); for (p = parent; p; p = next_dentry(p, parent)) { /* Negative dentry - give up */ if (!simple_positive(p)) continue; DPRINTK("dentry %p %.*s", p, (int) p->d_name.len, p->d_name.name); p = dget(p); spin_unlock(&dcache_lock); if (d_mountpoint(p)) { /* Can we umount this guy */ if (autofs4_mount_busy(mnt, p)) goto cont; /* Can we expire this guy */ if (autofs4_can_expire(p, timeout, do_now)) return p; } cont: dput(p); spin_lock(&dcache_lock); } spin_unlock(&dcache_lock); return NULL; } /* Check if we can expire a direct mount (possibly a tree) */ static struct dentry *autofs4_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; if (!sbi->exp_timeout || !root) return NULL; now = jiffies; timeout = sbi->exp_timeout; /* Lock the tree as we must expire as a whole */ spin_lock(&sbi->fs_lock); if (!autofs4_direct_busy(mnt, root, timeout, do_now)) { struct autofs_info *ino = autofs4_dentry_ino(root); /* Set this flag early to catch sys_chdir and the like */ ino->flags |= AUTOFS_INF_EXPIRING; spin_unlock(&sbi->fs_lock); return root; } spin_unlock(&sbi->fs_lock); dput(root); 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 *autofs4_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 *expired = NULL; struct list_head *next; int do_now = how & AUTOFS_EXP_IMMEDIATE; int exp_leaves = how & AUTOFS_EXP_LEAVES; if ( !sbi->exp_timeout || !root ) return NULL; now = jiffies; timeout = sbi->exp_timeout; spin_lock(&dcache_lock); next = root->d_subdirs.next; /* On exit from the loop expire is set to a dgot dentry * to expire or it's NULL */ while ( next != &root->d_subdirs ) { struct dentry *dentry = list_entry(next, struct dentry, d_u.d_child); /* Negative dentry - give up */ if (!simple_positive(dentry)) { next = next->next; continue; } dentry = dget(dentry); spin_unlock(&dcache_lock); /* * 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)) { DPRINTK("checking mountpoint %p %.*s", dentry, (int)dentry->d_name.len, dentry->d_name.name); /* Can we umount this guy */ if (autofs4_mount_busy(mnt, dentry)) goto next; /* Can we expire this guy */ if (autofs4_can_expire(dentry, timeout, do_now)) { expired = dentry; break; } goto next; } if (simple_empty(dentry)) goto next; /* Case 2: tree mount, expire iff entire tree is not busy */ if (!exp_leaves) { /* Lock the tree as we must expire as a whole */ spin_lock(&sbi->fs_lock); if (!autofs4_tree_busy(mnt, dentry, timeout, do_now)) { struct autofs_info *inf = autofs4_dentry_ino(dentry); /* Set this flag early to catch sys_chdir and the like */ inf->flags |= AUTOFS_INF_EXPIRING; spin_unlock(&sbi->fs_lock); expired = dentry; break; } spin_unlock(&sbi->fs_lock); /* * Case 3: pseudo direct mount, expire individual leaves * (autofs-4.1). */ } else { expired = autofs4_check_leaves(mnt, dentry, timeout, do_now); if (expired) { dput(dentry); break; } } next: dput(dentry); spin_lock(&dcache_lock); next = next->next; } if (expired) { DPRINTK("returning %p %.*s", expired, (int)expired->d_name.len, expired->d_name.name); spin_lock(&dcache_lock); list_del(&expired->d_parent->d_subdirs); list_add(&expired->d_parent->d_subdirs, &expired->d_u.d_child); spin_unlock(&dcache_lock); return expired; } spin_unlock(&dcache_lock); return NULL; } /* Perform an expiry operation */ int autofs4_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 dentry *dentry; memset(&pkt,0,sizeof pkt); pkt.hdr.proto_version = sbi->version; pkt.hdr.type = autofs_ptype_expire; if ((dentry = autofs4_expire_indirect(sb, mnt, sbi, 0)) == NULL) 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)) ) return -EFAULT; return 0; } /* Call repeatedly until it returns -EAGAIN, meaning there's nothing more to be done */ int autofs4_expire_multi(struct super_block *sb, struct vfsmount *mnt, struct autofs_sb_info *sbi, int __user *arg) { struct dentry *dentry; int ret = -EAGAIN; int do_now = 0; if (arg && get_user(do_now, arg)) return -EFAULT; if (sbi->type & AUTOFS_TYPE_DIRECT) dentry = autofs4_expire_direct(sb, mnt, sbi, do_now); else dentry = autofs4_expire_indirect(sb, mnt, sbi, do_now); if (dentry) { struct autofs_info *ino = autofs4_dentry_ino(dentry); /* This is synchronous because it makes the daemon a little easier */ ino->flags |= AUTOFS_INF_EXPIRING; ret = autofs4_wait(sbi, dentry, NFY_EXPIRE); ino->flags &= ~AUTOFS_INF_EXPIRING; dput(dentry); } return ret; }