/* * linux/fs/namei.c * * Copyright (C) 1991, 1992 Linus Torvalds */ /* * Some corrections by tytso. */ /* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname * lookup logic. */ /* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture. */ #include #include #include #include #include #include #include #include #include #include #define ACC_MODE(x) ("\000\004\002\006"[(x)&O_ACCMODE]) /* [Feb-1997 T. Schoebel-Theuer] * Fundamental changes in the pathname lookup mechanisms (namei) * were necessary because of omirr. The reason is that omirr needs * to know the _real_ pathname, not the user-supplied one, in case * of symlinks (and also when transname replacements occur). * * The new code replaces the old recursive symlink resolution with * an iterative one (in case of non-nested symlink chains). It does * this with calls to _follow_link(). * As a side effect, dir_namei(), _namei() and follow_link() are now * replaced with a single function lookup_dentry() that can handle all * the special cases of the former code. * * With the new dcache, the pathname is stored at each inode, at least as * long as the refcount of the inode is positive. As a side effect, the * size of the dcache depends on the inode cache and thus is dynamic. * * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink * resolution to correspond with current state of the code. * * Note that the symlink resolution is not *completely* iterative. * There is still a significant amount of tail- and mid- recursion in * the algorithm. Also, note that _readlink() is not used in * lookup_dentry(): lookup_dentry() on the result of _readlink() * may return different results than _follow_link(). Many virtual * filesystems (including /proc) exhibit this behavior. */ /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation: * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL * and the name already exists in form of a symlink, try to create the new * name indicated by the symlink. The old code always complained that the * name already exists, due to not following the symlink even if its target * is nonexistent. The new semantics affects also mknod() and link() when * the name is a symlink pointing to a non-existant name. * * I don't know which semantics is the right one, since I have no access * to standards. But I found by trial that HP-UX 9.0 has the full "new" * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the * "old" one. Personally, I think the new semantics is much more logical. * Note that "ln old new" where "new" is a symlink pointing to a non-existing * file does succeed in both HP-UX and SunOs, but not in Solaris * and in the old Linux semantics. */ /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink * semantics. See the comments in "open_namei" and "do_link" below. * * [10-Sep-98 Alan Modra] Another symlink change. */ /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks: * inside the path - always follow. * in the last component in creation/removal/renaming - never follow. * if LOOKUP_FOLLOW passed - follow. * if the pathname has trailing slashes - follow. * otherwise - don't follow. * (applied in that order). * * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT * restored for 2.4. This is the last surviving part of old 4.2BSD bug. * During the 2.4 we need to fix the userland stuff depending on it - * hopefully we will be able to get rid of that wart in 2.5. So far only * XEmacs seems to be relying on it... */ /* In order to reduce some races, while at the same time doing additional * checking and hopefully speeding things up, we copy filenames to the * kernel data space before using them.. * * POSIX.1 2.4: an empty pathname is invalid (ENOENT). * PATH_MAX includes the nul terminator --RR. */ static inline int do_getname(const char *filename, char *page) { int retval; unsigned long len = PATH_MAX; if ((unsigned long) filename >= TASK_SIZE) { if (!segment_eq(get_fs(), KERNEL_DS)) return -EFAULT; } else if (TASK_SIZE - (unsigned long) filename < PATH_MAX) len = TASK_SIZE - (unsigned long) filename; retval = strncpy_from_user((char *)page, filename, len); if (retval > 0) { if (retval < len) return 0; return -ENAMETOOLONG; } else if (!retval) retval = -ENOENT; return retval; } char * getname(const char * filename) { char *tmp, *result; result = ERR_PTR(-ENOMEM); tmp = __getname(); if (tmp) { int retval = do_getname(filename, tmp); result = tmp; if (retval < 0) { putname(tmp); result = ERR_PTR(retval); } } return result; } /* * vfs_permission() * * is used to check for read/write/execute permissions on a file. * We use "fsuid" for this, letting us set arbitrary permissions * for filesystem access without changing the "normal" uids which * are used for other things.. */ int vfs_permission(struct inode * inode, int mask) { umode_t mode = inode->i_mode; if (mask & MAY_WRITE) { /* * Nobody gets write access to a read-only fs. */ if (IS_RDONLY(inode) && (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) return -EROFS; /* * Nobody gets write access to an immutable file. */ if (IS_IMMUTABLE(inode)) return -EACCES; } if (current->fsuid == inode->i_uid) mode >>= 6; else if (in_group_p(inode->i_gid)) mode >>= 3; /* * If the DACs are ok we don't need any capability check. */ if (((mode & mask & (MAY_READ|MAY_WRITE|MAY_EXEC)) == mask)) return 0; /* * Read/write DACs are always overridable. * Executable DACs are overridable if at least one exec bit is set. */ if ((mask & (MAY_READ|MAY_WRITE)) || (inode->i_mode & S_IXUGO)) if (capable(CAP_DAC_OVERRIDE)) return 0; /* * Searching includes executable on directories, else just read. */ if (mask == MAY_READ || (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE))) if (capable(CAP_DAC_READ_SEARCH)) return 0; return -EACCES; } int permission(struct inode * inode,int mask) { if (inode->i_op && inode->i_op->permission) { int retval; lock_kernel(); retval = inode->i_op->permission(inode, mask); unlock_kernel(); return retval; } return vfs_permission(inode, mask); } /* * get_write_access() gets write permission for a file. * put_write_access() releases this write permission. * This is used for regular files. * We cannot support write (and maybe mmap read-write shared) accesses and * MAP_DENYWRITE mmappings simultaneously. The i_writecount field of an inode * can have the following values: * 0: no writers, no VM_DENYWRITE mappings * < 0: (-i_writecount) vm_area_structs with VM_DENYWRITE set exist * > 0: (i_writecount) users are writing to the file. * * Normally we operate on that counter with atomic_{inc,dec} and it's safe * except for the cases where we don't hold i_writecount yet. Then we need to * use {get,deny}_write_access() - these functions check the sign and refuse * to do the change if sign is wrong. Exclusion between them is provided by * spinlock (arbitration_lock) and I'll rip the second arsehole to the first * who will try to move it in struct inode - just leave it here. */ static spinlock_t arbitration_lock = SPIN_LOCK_UNLOCKED; int get_write_access(struct inode * inode) { spin_lock(&arbitration_lock); if (atomic_read(&inode->i_writecount) < 0) { spin_unlock(&arbitration_lock); return -ETXTBSY; } atomic_inc(&inode->i_writecount); spin_unlock(&arbitration_lock); return 0; } int deny_write_access(struct file * file) { spin_lock(&arbitration_lock); if (atomic_read(&file->f_dentry->d_inode->i_writecount) > 0) { spin_unlock(&arbitration_lock); return -ETXTBSY; } atomic_dec(&file->f_dentry->d_inode->i_writecount); spin_unlock(&arbitration_lock); return 0; } void path_release(struct nameidata *nd) { dput(nd->dentry); mntput(nd->mnt); } /* * Internal lookup() using the new generic dcache. * SMP-safe */ static struct dentry * cached_lookup(struct dentry * parent, struct qstr * name, int flags) { struct dentry * dentry = d_lookup(parent, name); if (dentry && dentry->d_op && dentry->d_op->d_revalidate) { if (!dentry->d_op->d_revalidate(dentry, flags) && !d_invalidate(dentry)) { dput(dentry); dentry = NULL; } } return dentry; } /* * This is called when everything else fails, and we actually have * to go to the low-level filesystem to find out what we should do.. * * We get the directory semaphore, and after getting that we also * make sure that nobody added the entry to the dcache in the meantime.. * SMP-safe */ static struct dentry * real_lookup(struct dentry * parent, struct qstr * name, int flags) { struct dentry * result; struct inode *dir = parent->d_inode; down(&dir->i_sem); /* * First re-do the cached lookup just in case it was created * while we waited for the directory semaphore.. * * FIXME! This could use version numbering or similar to * avoid unnecessary cache lookups. */ result = d_lookup(parent, name); if (!result) { struct dentry * dentry = d_alloc(parent, name); result = ERR_PTR(-ENOMEM); if (dentry) { lock_kernel(); result = dir->i_op->lookup(dir, dentry); unlock_kernel(); if (result) dput(dentry); else result = dentry; } up(&dir->i_sem); return result; } /* * Uhhuh! Nasty case: the cache was re-populated while * we waited on the semaphore. Need to revalidate. */ up(&dir->i_sem); if (result->d_op && result->d_op->d_revalidate) { if (!result->d_op->d_revalidate(result, flags) && !d_invalidate(result)) { dput(result); result = ERR_PTR(-ENOENT); } } return result; } /* * This limits recursive symlink follows to 8, while * limiting consecutive symlinks to 40. * * Without that kind of total limit, nasty chains of consecutive * symlinks can cause almost arbitrarily long lookups. */ static inline int do_follow_link(struct dentry *dentry, struct nameidata *nd) { int err; if (current->link_count >= 5) goto loop; if (current->total_link_count >= 40) goto loop; if (current->need_resched) { current->state = TASK_RUNNING; schedule(); } current->link_count++; current->total_link_count++; UPDATE_ATIME(dentry->d_inode); err = dentry->d_inode->i_op->follow_link(dentry, nd); current->link_count--; return err; loop: path_release(nd); return -ELOOP; } static inline int __follow_up(struct vfsmount **mnt, struct dentry **base) { struct vfsmount *parent; struct dentry *dentry; spin_lock(&dcache_lock); parent=(*mnt)->mnt_parent; if (parent == *mnt) { spin_unlock(&dcache_lock); return 0; } mntget(parent); dentry=dget((*mnt)->mnt_mountpoint); spin_unlock(&dcache_lock); dput(*base); *base = dentry; mntput(*mnt); *mnt = parent; return 1; } int follow_up(struct vfsmount **mnt, struct dentry **dentry) { return __follow_up(mnt, dentry); } static inline int __follow_down(struct vfsmount **mnt, struct dentry **dentry) { struct vfsmount *mounted; spin_lock(&dcache_lock); mounted = lookup_mnt(*mnt, *dentry); if (mounted) { *mnt = mntget(mounted); spin_unlock(&dcache_lock); dput(*dentry); mntput(mounted->mnt_parent); *dentry = dget(mounted->mnt_root); return 1; } spin_unlock(&dcache_lock); return 0; } int follow_down(struct vfsmount **mnt, struct dentry **dentry) { return __follow_down(mnt,dentry); } static inline void follow_dotdot(struct nameidata *nd) { while(1) { struct vfsmount *parent; struct dentry *dentry; read_lock(¤t->fs->lock); if (nd->dentry == current->fs->root && nd->mnt == current->fs->rootmnt) { read_unlock(¤t->fs->lock); break; } read_unlock(¤t->fs->lock); spin_lock(&dcache_lock); if (nd->dentry != nd->mnt->mnt_root) { dentry = dget(nd->dentry->d_parent); spin_unlock(&dcache_lock); dput(nd->dentry); nd->dentry = dentry; break; } parent=nd->mnt->mnt_parent; if (parent == nd->mnt) { spin_unlock(&dcache_lock); break; } mntget(parent); dentry=dget(nd->mnt->mnt_mountpoint); spin_unlock(&dcache_lock); dput(nd->dentry); nd->dentry = dentry; mntput(nd->mnt); nd->mnt = parent; } while (d_mountpoint(nd->dentry) && __follow_down(&nd->mnt, &nd->dentry)) ; } /* * Name resolution. * * This is the basic name resolution function, turning a pathname * into the final dentry. * * We expect 'base' to be positive and a directory. */ int link_path_walk(const char * name, struct nameidata *nd) { struct dentry *dentry; struct inode *inode; int err; unsigned int lookup_flags = nd->flags; while (*name=='/') name++; if (!*name) goto return_base; inode = nd->dentry->d_inode; if (current->link_count) lookup_flags = LOOKUP_FOLLOW; /* At this point we know we have a real path component. */ for(;;) { unsigned long hash; struct qstr this; unsigned int c; err = permission(inode, MAY_EXEC); dentry = ERR_PTR(err); if (err) break; this.name = name; c = *(const unsigned char *)name; hash = init_name_hash(); do { name++; hash = partial_name_hash(c, hash); c = *(const unsigned char *)name; } while (c && (c != '/')); this.len = name - (const char *) this.name; this.hash = end_name_hash(hash); /* remove trailing slashes? */ if (!c) goto last_component; while (*++name == '/'); if (!*name) goto last_with_slashes; /* * "." and ".." are special - ".." especially so because it has * to be able to know about the current root directory and * parent relationships. */ if (this.name[0] == '.') switch (this.len) { default: break; case 2: if (this.name[1] != '.') break; follow_dotdot(nd); inode = nd->dentry->d_inode; /* fallthrough */ case 1: continue; } /* * See if the low-level filesystem might want * to use its own hash.. */ if (nd->dentry->d_op && nd->dentry->d_op->d_hash) { err = nd->dentry->d_op->d_hash(nd->dentry, &this); if (err < 0) break; } /* This does the actual lookups.. */ dentry = cached_lookup(nd->dentry, &this, LOOKUP_CONTINUE); if (!dentry) { dentry = real_lookup(nd->dentry, &this, LOOKUP_CONTINUE); err = PTR_ERR(dentry); if (IS_ERR(dentry)) break; } /* Check mountpoints.. */ while (d_mountpoint(dentry) && __follow_down(&nd->mnt, &dentry)) ; err = -ENOENT; inode = dentry->d_inode; if (!inode) goto out_dput; err = -ENOTDIR; if (!inode->i_op) goto out_dput; if (inode->i_op->follow_link) { err = do_follow_link(dentry, nd); dput(dentry); if (err) goto return_err; err = -ENOENT; inode = nd->dentry->d_inode; if (!inode) break; err = -ENOTDIR; if (!inode->i_op) break; } else { dput(nd->dentry); nd->dentry = dentry; } err = -ENOTDIR; if (!inode->i_op->lookup) break; continue; /* here ends the main loop */ last_with_slashes: lookup_flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; last_component: if (lookup_flags & LOOKUP_PARENT) goto lookup_parent; if (this.name[0] == '.') switch (this.len) { default: break; case 2: if (this.name[1] != '.') break; follow_dotdot(nd); inode = nd->dentry->d_inode; /* fallthrough */ case 1: goto return_base; } if (nd->dentry->d_op && nd->dentry->d_op->d_hash) { err = nd->dentry->d_op->d_hash(nd->dentry, &this); if (err < 0) break; } dentry = cached_lookup(nd->dentry, &this, 0); if (!dentry) { dentry = real_lookup(nd->dentry, &this, 0); err = PTR_ERR(dentry); if (IS_ERR(dentry)) break; } while (d_mountpoint(dentry) && __follow_down(&nd->mnt, &dentry)) ; inode = dentry->d_inode; if ((lookup_flags & LOOKUP_FOLLOW) && inode && inode->i_op && inode->i_op->follow_link) { err = do_follow_link(dentry, nd); dput(dentry); if (err) goto return_err; inode = nd->dentry->d_inode; } else { dput(nd->dentry); nd->dentry = dentry; } err = -ENOENT; if (!inode) goto no_inode; if (lookup_flags & LOOKUP_DIRECTORY) { err = -ENOTDIR; if (!inode->i_op || !inode->i_op->lookup) break; } goto return_base; no_inode: err = -ENOENT; if (lookup_flags & (LOOKUP_POSITIVE|LOOKUP_DIRECTORY)) break; goto return_base; lookup_parent: nd->last = this; nd->last_type = LAST_NORM; if (this.name[0] != '.') goto return_base; if (this.len == 1) nd->last_type = LAST_DOT; else if (this.len == 2 && this.name[1] == '.') nd->last_type = LAST_DOTDOT; return_base: return 0; out_dput: dput(dentry); break; } path_release(nd); return_err: return err; } int path_walk(const char * name, struct nameidata *nd) { current->total_link_count = 0; return link_path_walk(name, nd); } /* SMP-safe */ /* returns 1 if everything is done */ static int __emul_lookup_dentry(const char *name, struct nameidata *nd) { if (path_walk(name, nd)) return 0; /* something went wrong... */ if (!nd->dentry->d_inode || S_ISDIR(nd->dentry->d_inode->i_mode)) { struct nameidata nd_root; /* * NAME was not found in alternate root or it's a directory. Try to find * it in the normal root: */ nd_root.last_type = LAST_ROOT; nd_root.flags = nd->flags; read_lock(¤t->fs->lock); nd_root.mnt = mntget(current->fs->rootmnt); nd_root.dentry = dget(current->fs->root); read_unlock(¤t->fs->lock); if (path_walk(name, &nd_root)) return 1; if (nd_root.dentry->d_inode) { path_release(nd); nd->dentry = nd_root.dentry; nd->mnt = nd_root.mnt; nd->last = nd_root.last; return 1; } path_release(&nd_root); } return 1; } void set_fs_altroot(void) { char *emul = __emul_prefix(); struct nameidata nd; struct vfsmount *mnt = NULL, *oldmnt; struct dentry *dentry = NULL, *olddentry; if (emul) { read_lock(¤t->fs->lock); nd.mnt = mntget(current->fs->rootmnt); nd.dentry = dget(current->fs->root); read_unlock(¤t->fs->lock); nd.flags = LOOKUP_FOLLOW|LOOKUP_DIRECTORY|LOOKUP_POSITIVE; if (path_walk(emul,&nd) == 0) { mnt = nd.mnt; dentry = nd.dentry; } } write_lock(¤t->fs->lock); oldmnt = current->fs->altrootmnt; olddentry = current->fs->altroot; current->fs->altrootmnt = mnt; current->fs->altroot = dentry; write_unlock(¤t->fs->lock); if (olddentry) { dput(olddentry); mntput(oldmnt); } } /* SMP-safe */ static inline int walk_init_root(const char *name, struct nameidata *nd) { read_lock(¤t->fs->lock); if (current->fs->altroot && !(nd->flags & LOOKUP_NOALT)) { nd->mnt = mntget(current->fs->altrootmnt); nd->dentry = dget(current->fs->altroot); read_unlock(¤t->fs->lock); if (__emul_lookup_dentry(name,nd)) return 0; read_lock(¤t->fs->lock); } nd->mnt = mntget(current->fs->rootmnt); nd->dentry = dget(current->fs->root); read_unlock(¤t->fs->lock); return 1; } /* SMP-safe */ int path_init(const char *name, unsigned int flags, struct nameidata *nd) { nd->last_type = LAST_ROOT; /* if there are only slashes... */ nd->flags = flags; if (*name=='/') return walk_init_root(name,nd); read_lock(¤t->fs->lock); nd->mnt = mntget(current->fs->pwdmnt); nd->dentry = dget(current->fs->pwd); read_unlock(¤t->fs->lock); return 1; } /* * Restricted form of lookup. Doesn't follow links, single-component only, * needs parent already locked. Doesn't follow mounts. * SMP-safe. */ struct dentry * lookup_hash(struct qstr *name, struct dentry * base) { struct dentry * dentry; struct inode *inode; int err; inode = base->d_inode; err = permission(inode, MAY_EXEC); dentry = ERR_PTR(err); if (err) goto out; /* * See if the low-level filesystem might want * to use its own hash.. */ if (base->d_op && base->d_op->d_hash) { err = base->d_op->d_hash(base, name); dentry = ERR_PTR(err); if (err < 0) goto out; } dentry = cached_lookup(base, name, 0); if (!dentry) { struct dentry *new = d_alloc(base, name); dentry = ERR_PTR(-ENOMEM); if (!new) goto out; lock_kernel(); dentry = inode->i_op->lookup(inode, new); unlock_kernel(); if (!dentry) dentry = new; else dput(new); } out: return dentry; } /* SMP-safe */ struct dentry * lookup_one_len(const char * name, struct dentry * base, int len) { unsigned long hash; struct qstr this; unsigned int c; this.name = name; this.len = len; if (!len) goto access; hash = init_name_hash(); while (len--) { c = *(const unsigned char *)name++; if (c == '/' || c == '\0') goto access; hash = partial_name_hash(c, hash); } this.hash = end_name_hash(hash); return lookup_hash(&this, base); access: return ERR_PTR(-EACCES); } /* * namei() * * is used by most simple commands to get the inode of a specified name. * Open, link etc use their own routines, but this is enough for things * like 'chmod' etc. * * namei exists in two versions: namei/lnamei. The only difference is * that namei follows links, while lnamei does not. * SMP-safe */ int __user_walk(const char *name, unsigned flags, struct nameidata *nd) { char *tmp; int err; tmp = getname(name); err = PTR_ERR(tmp); if (!IS_ERR(tmp)) { err = 0; if (path_init(tmp, flags, nd)) err = path_walk(tmp, nd); putname(tmp); } return err; } /* * It's inline, so penalty for filesystems that don't use sticky bit is * minimal. */ static inline int check_sticky(struct inode *dir, struct inode *inode) { if (!(dir->i_mode & S_ISVTX)) return 0; if (inode->i_uid == current->fsuid) return 0; if (dir->i_uid == current->fsuid) return 0; return !capable(CAP_FOWNER); } /* * Check whether we can remove a link victim from directory dir, check * whether the type of victim is right. * 1. We can't do it if dir is read-only (done in permission()) * 2. We should have write and exec permissions on dir * 3. We can't remove anything from append-only dir * 4. We can't do anything with immutable dir (done in permission()) * 5. If the sticky bit on dir is set we should either * a. be owner of dir, or * b. be owner of victim, or * c. have CAP_FOWNER capability * 6. If the victim is append-only or immutable we can't do antyhing with * links pointing to it. * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR. * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR. * 9. We can't remove a root or mountpoint. */ static inline int may_delete(struct inode *dir,struct dentry *victim, int isdir) { int error; if (!victim->d_inode || victim->d_parent->d_inode != dir) return -ENOENT; error = permission(dir,MAY_WRITE | MAY_EXEC); if (error) return error; if (IS_APPEND(dir)) return -EPERM; if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)|| IS_IMMUTABLE(victim->d_inode)) return -EPERM; if (isdir) { if (!S_ISDIR(victim->d_inode->i_mode)) return -ENOTDIR; if (IS_ROOT(victim)) return -EBUSY; } else if (S_ISDIR(victim->d_inode->i_mode)) return -EISDIR; return 0; } /* Check whether we can create an object with dentry child in directory * dir. * 1. We can't do it if child already exists (open has special treatment for * this case, but since we are inlined it's OK) * 2. We can't do it if dir is read-only (done in permission()) * 3. We should have write and exec permissions on dir * 4. We can't do it if dir is immutable (done in permission()) */ static inline int may_create(struct inode *dir, struct dentry *child) { if (child->d_inode) return -EEXIST; if (IS_DEADDIR(dir)) return -ENOENT; return permission(dir,MAY_WRITE | MAY_EXEC); } /* * Special case: O_CREAT|O_EXCL implies O_NOFOLLOW for security * reasons. * * O_DIRECTORY translates into forcing a directory lookup. */ static inline int lookup_flags(unsigned int f) { unsigned long retval = LOOKUP_FOLLOW; if (f & O_NOFOLLOW) retval &= ~LOOKUP_FOLLOW; if ((f & (O_CREAT|O_EXCL)) == (O_CREAT|O_EXCL)) retval &= ~LOOKUP_FOLLOW; if (f & O_DIRECTORY) retval |= LOOKUP_DIRECTORY; return retval; } int vfs_create(struct inode *dir, struct dentry *dentry, int mode) { int error; mode &= S_IALLUGO; mode |= S_IFREG; down(&dir->i_zombie); error = may_create(dir, dentry); if (error) goto exit_lock; error = -EACCES; /* shouldn't it be ENOSYS? */ if (!dir->i_op || !dir->i_op->create) goto exit_lock; DQUOT_INIT(dir); lock_kernel(); error = dir->i_op->create(dir, dentry, mode); unlock_kernel(); exit_lock: up(&dir->i_zombie); if (!error) inode_dir_notify(dir, DN_CREATE); return error; } /* * open_namei() * * namei for open - this is in fact almost the whole open-routine. * * Note that the low bits of "flag" aren't the same as in the open * system call - they are 00 - no permissions needed * 01 - read permission needed * 10 - write permission needed * 11 - read/write permissions needed * which is a lot more logical, and also allows the "no perm" needed * for symlinks (where the permissions are checked later). * SMP-safe */ int open_namei(const char * pathname, int flag, int mode, struct nameidata *nd) { int acc_mode, error = 0; struct inode *inode; struct dentry *dentry; struct dentry *dir; int count = 0; acc_mode = ACC_MODE(flag); /* * The simplest case - just a plain lookup. */ if (!(flag & O_CREAT)) { if (path_init(pathname, lookup_flags(flag), nd)) error = path_walk(pathname, nd); if (error) return error; dentry = nd->dentry; goto ok; } /* * Create - we need to know the parent. */ if (path_init(pathname, LOOKUP_PARENT, nd)) error = path_walk(pathname, nd); if (error) return error; /* * We have the parent and last component. First of all, check * that we are not asked to creat(2) an obvious directory - that * will not do. */ error = -EISDIR; if (nd->last_type != LAST_NORM || nd->last.name[nd->last.len]) goto exit; dir = nd->dentry; down(&dir->d_inode->i_sem); dentry = lookup_hash(&nd->last, nd->dentry); do_last: error = PTR_ERR(dentry); if (IS_ERR(dentry)) { up(&dir->d_inode->i_sem); goto exit; } /* Negative dentry, just create the file */ if (!dentry->d_inode) { error = vfs_create(dir->d_inode, dentry, mode & ~current->fs->umask); up(&dir->d_inode->i_sem); dput(nd->dentry); nd->dentry = dentry; if (error) goto exit; /* Don't check for write permission, don't truncate */ acc_mode = 0; flag &= ~O_TRUNC; goto ok; } /* * It already exists. */ up(&dir->d_inode->i_sem); error = -EEXIST; if (flag & O_EXCL) goto exit_dput; if (d_mountpoint(dentry)) { error = -ELOOP; if (flag & O_NOFOLLOW) goto exit_dput; while (__follow_down(&nd->mnt,&dentry) && d_mountpoint(dentry)); } error = -ENOENT; if (!dentry->d_inode) goto exit_dput; if (dentry->d_inode->i_op && dentry->d_inode->i_op->follow_link) goto do_link; dput(nd->dentry); nd->dentry = dentry; error = -EISDIR; if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) goto exit; ok: error = -ENOENT; inode = dentry->d_inode; if (!inode) goto exit; error = -ELOOP; if (S_ISLNK(inode->i_mode)) goto exit; error = -EISDIR; if (S_ISDIR(inode->i_mode) && (flag & FMODE_WRITE)) goto exit; error = permission(inode,acc_mode); if (error) goto exit; /* * FIFO's, sockets and device files are special: they don't * actually live on the filesystem itself, and as such you * can write to them even if the filesystem is read-only. */ if (S_ISFIFO(inode->i_mode) || S_ISSOCK(inode->i_mode)) { flag &= ~O_TRUNC; } else if (S_ISBLK(inode->i_mode) || S_ISCHR(inode->i_mode)) { error = -EACCES; if (nd->mnt->mnt_flags & MNT_NODEV) goto exit; flag &= ~O_TRUNC; } else { error = -EROFS; if (IS_RDONLY(inode) && (flag & 2)) goto exit; } /* * An append-only file must be opened in append mode for writing. */ error = -EPERM; if (IS_APPEND(inode)) { if ((flag & FMODE_WRITE) && !(flag & O_APPEND)) goto exit; if (flag & O_TRUNC) goto exit; } /* * Ensure there are no outstanding leases on the file. */ error = get_lease(inode, flag); if (error) goto exit; if (flag & O_TRUNC) { error = get_write_access(inode); if (error) goto exit; /* * Refuse to truncate files with mandatory locks held on them. */ error = locks_verify_locked(inode); if (!error) { DQUOT_INIT(inode); error = do_truncate(dentry, 0); } put_write_access(inode); if (error) goto exit; } else if (flag & FMODE_WRITE) DQUOT_INIT(inode); return 0; exit_dput: dput(dentry); exit: path_release(nd); return error; do_link: error = -ELOOP; if (flag & O_NOFOLLOW) goto exit_dput; /* * This is subtle. Instead of calling do_follow_link() we do the * thing by hands. The reason is that this way we have zero link_count * and path_walk() (called from ->follow_link) honoring LOOKUP_PARENT. * After that we have the parent and last component, i.e. * we are in the same situation as after the first path_walk(). * Well, almost - if the last component is normal we get its copy * stored in nd->last.name and we will have to putname() it when we * are done. Procfs-like symlinks just set LAST_BIND. */ UPDATE_ATIME(dentry->d_inode); error = dentry->d_inode->i_op->follow_link(dentry, nd); dput(dentry); if (error) return error; if (nd->last_type == LAST_BIND) { dentry = nd->dentry; goto ok; } error = -EISDIR; if (nd->last_type != LAST_NORM) goto exit; if (nd->last.name[nd->last.len]) { putname(nd->last.name); goto exit; } error = -ELOOP; if (count++==32) { putname(nd->last.name); goto exit; } dir = nd->dentry; down(&dir->d_inode->i_sem); dentry = lookup_hash(&nd->last, nd->dentry); putname(nd->last.name); goto do_last; } /* SMP-safe */ static struct dentry *lookup_create(struct nameidata *nd, int is_dir) { struct dentry *dentry; down(&nd->dentry->d_inode->i_sem); dentry = ERR_PTR(-EEXIST); if (nd->last_type != LAST_NORM) goto fail; dentry = lookup_hash(&nd->last, nd->dentry); if (IS_ERR(dentry)) goto fail; if (!is_dir && nd->last.name[nd->last.len] && !dentry->d_inode) goto enoent; return dentry; enoent: dput(dentry); dentry = ERR_PTR(-ENOENT); fail: return dentry; } int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev) { int error = -EPERM; down(&dir->i_zombie); if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD)) goto exit_lock; error = may_create(dir, dentry); if (error) goto exit_lock; error = -EPERM; if (!dir->i_op || !dir->i_op->mknod) goto exit_lock; DQUOT_INIT(dir); lock_kernel(); error = dir->i_op->mknod(dir, dentry, mode, dev); unlock_kernel(); exit_lock: up(&dir->i_zombie); if (!error) inode_dir_notify(dir, DN_CREATE); return error; } asmlinkage long sys_mknod(const char * filename, int mode, dev_t dev) { int error = 0; char * tmp; struct dentry * dentry; struct nameidata nd; if (S_ISDIR(mode)) return -EPERM; tmp = getname(filename); if (IS_ERR(tmp)) return PTR_ERR(tmp); if (path_init(tmp, LOOKUP_PARENT, &nd)) error = path_walk(tmp, &nd); if (error) goto out; dentry = lookup_create(&nd, 0); error = PTR_ERR(dentry); mode &= ~current->fs->umask; if (!IS_ERR(dentry)) { switch (mode & S_IFMT) { case 0: case S_IFREG: error = vfs_create(nd.dentry->d_inode,dentry,mode); break; case S_IFCHR: case S_IFBLK: case S_IFIFO: case S_IFSOCK: error = vfs_mknod(nd.dentry->d_inode,dentry,mode,dev); break; case S_IFDIR: error = -EPERM; break; default: error = -EINVAL; } dput(dentry); } up(&nd.dentry->d_inode->i_sem); path_release(&nd); out: putname(tmp); return error; } int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode) { int error; down(&dir->i_zombie); error = may_create(dir, dentry); if (error) goto exit_lock; error = -EPERM; if (!dir->i_op || !dir->i_op->mkdir) goto exit_lock; DQUOT_INIT(dir); mode &= (S_IRWXUGO|S_ISVTX); lock_kernel(); error = dir->i_op->mkdir(dir, dentry, mode); unlock_kernel(); exit_lock: up(&dir->i_zombie); if (!error) inode_dir_notify(dir, DN_CREATE); return error; } asmlinkage long sys_mkdir(const char * pathname, int mode) { int error = 0; char * tmp; tmp = getname(pathname); error = PTR_ERR(tmp); if (!IS_ERR(tmp)) { struct dentry *dentry; struct nameidata nd; if (path_init(tmp, LOOKUP_PARENT, &nd)) error = path_walk(tmp, &nd); if (error) goto out; dentry = lookup_create(&nd, 1); error = PTR_ERR(dentry); if (!IS_ERR(dentry)) { error = vfs_mkdir(nd.dentry->d_inode, dentry, mode & ~current->fs->umask); dput(dentry); } up(&nd.dentry->d_inode->i_sem); path_release(&nd); out: putname(tmp); } return error; } /* * We try to drop the dentry early: we should have * a usage count of 2 if we're the only user of this * dentry, and if that is true (possibly after pruning * the dcache), then we drop the dentry now. * * A low-level filesystem can, if it choses, legally * do a * * if (!d_unhashed(dentry)) * return -EBUSY; * * if it cannot handle the case of removing a directory * that is still in use by something else.. */ static void d_unhash(struct dentry *dentry) { dget(dentry); switch (atomic_read(&dentry->d_count)) { default: shrink_dcache_parent(dentry); if (atomic_read(&dentry->d_count) != 2) break; case 2: d_drop(dentry); } } int vfs_rmdir(struct inode *dir, struct dentry *dentry) { int error; error = may_delete(dir, dentry, 1); if (error) return error; if (!dir->i_op || !dir->i_op->rmdir) return -EPERM; DQUOT_INIT(dir); double_down(&dir->i_zombie, &dentry->d_inode->i_zombie); d_unhash(dentry); if (IS_DEADDIR(dir)) error = -ENOENT; else if (d_mountpoint(dentry)) error = -EBUSY; else { lock_kernel(); error = dir->i_op->rmdir(dir, dentry); unlock_kernel(); if (!error) dentry->d_inode->i_flags |= S_DEAD; } double_up(&dir->i_zombie, &dentry->d_inode->i_zombie); if (!error) { inode_dir_notify(dir, DN_DELETE); d_delete(dentry); } dput(dentry); return error; } asmlinkage long sys_rmdir(const char * pathname) { int error = 0; char * name; struct dentry *dentry; struct nameidata nd; name = getname(pathname); if(IS_ERR(name)) return PTR_ERR(name); if (path_init(name, LOOKUP_PARENT, &nd)) error = path_walk(name, &nd); if (error) goto exit; switch(nd.last_type) { case LAST_DOTDOT: error = -ENOTEMPTY; goto exit1; case LAST_DOT: error = -EINVAL; goto exit1; case LAST_ROOT: error = -EBUSY; goto exit1; } down(&nd.dentry->d_inode->i_sem); dentry = lookup_hash(&nd.last, nd.dentry); error = PTR_ERR(dentry); if (!IS_ERR(dentry)) { error = vfs_rmdir(nd.dentry->d_inode, dentry); dput(dentry); } up(&nd.dentry->d_inode->i_sem); exit1: path_release(&nd); exit: putname(name); return error; } int vfs_unlink(struct inode *dir, struct dentry *dentry) { int error; down(&dir->i_zombie); error = may_delete(dir, dentry, 0); if (!error) { error = -EPERM; if (dir->i_op && dir->i_op->unlink) { DQUOT_INIT(dir); if (d_mountpoint(dentry)) error = -EBUSY; else { lock_kernel(); error = dir->i_op->unlink(dir, dentry); unlock_kernel(); if (!error) d_delete(dentry); } } } up(&dir->i_zombie); if (!error) inode_dir_notify(dir, DN_DELETE); return error; } asmlinkage long sys_unlink(const char * pathname) { int error = 0; char * name; struct dentry *dentry; struct nameidata nd; name = getname(pathname); if(IS_ERR(name)) return PTR_ERR(name); if (path_init(name, LOOKUP_PARENT, &nd)) error = path_walk(name, &nd); if (error) goto exit; error = -EISDIR; if (nd.last_type != LAST_NORM) goto exit1; down(&nd.dentry->d_inode->i_sem); dentry = lookup_hash(&nd.last, nd.dentry); error = PTR_ERR(dentry); if (!IS_ERR(dentry)) { /* Why not before? Because we want correct error value */ if (nd.last.name[nd.last.len]) goto slashes; error = vfs_unlink(nd.dentry->d_inode, dentry); exit2: dput(dentry); } up(&nd.dentry->d_inode->i_sem); exit1: path_release(&nd); exit: putname(name); return error; slashes: error = !dentry->d_inode ? -ENOENT : S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR; goto exit2; } int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname) { int error; down(&dir->i_zombie); error = may_create(dir, dentry); if (error) goto exit_lock; error = -EPERM; if (!dir->i_op || !dir->i_op->symlink) goto exit_lock; DQUOT_INIT(dir); lock_kernel(); error = dir->i_op->symlink(dir, dentry, oldname); unlock_kernel(); exit_lock: up(&dir->i_zombie); if (!error) inode_dir_notify(dir, DN_CREATE); return error; } asmlinkage long sys_symlink(const char * oldname, const char * newname) { int error = 0; char * from; char * to; from = getname(oldname); if(IS_ERR(from)) return PTR_ERR(from); to = getname(newname); error = PTR_ERR(to); if (!IS_ERR(to)) { struct dentry *dentry; struct nameidata nd; if (path_init(to, LOOKUP_PARENT, &nd)) error = path_walk(to, &nd); if (error) goto out; dentry = lookup_create(&nd, 0); error = PTR_ERR(dentry); if (!IS_ERR(dentry)) { error = vfs_symlink(nd.dentry->d_inode, dentry, from); dput(dentry); } up(&nd.dentry->d_inode->i_sem); path_release(&nd); out: putname(to); } putname(from); return error; } int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry) { struct inode *inode; int error; down(&dir->i_zombie); error = -ENOENT; inode = old_dentry->d_inode; if (!inode) goto exit_lock; error = may_create(dir, new_dentry); if (error) goto exit_lock; error = -EXDEV; if (dir->i_dev != inode->i_dev) goto exit_lock; /* * A link to an append-only or immutable file cannot be created. */ error = -EPERM; if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) goto exit_lock; if (!dir->i_op || !dir->i_op->link) goto exit_lock; DQUOT_INIT(dir); lock_kernel(); error = dir->i_op->link(old_dentry, dir, new_dentry); unlock_kernel(); exit_lock: up(&dir->i_zombie); if (!error) inode_dir_notify(dir, DN_CREATE); return error; } /* * Hardlinks are often used in delicate situations. We avoid * security-related surprises by not following symlinks on the * newname. --KAB * * We don't follow them on the oldname either to be compatible * with linux 2.0, and to avoid hard-linking to directories * and other special files. --ADM */ asmlinkage long sys_link(const char * oldname, const char * newname) { int error; char * from; char * to; from = getname(oldname); if(IS_ERR(from)) return PTR_ERR(from); to = getname(newname); error = PTR_ERR(to); if (!IS_ERR(to)) { struct dentry *new_dentry; struct nameidata nd, old_nd; error = 0; if (path_init(from, LOOKUP_POSITIVE, &old_nd)) error = path_walk(from, &old_nd); if (error) goto exit; if (path_init(to, LOOKUP_PARENT, &nd)) error = path_walk(to, &nd); if (error) goto out; error = -EXDEV; if (old_nd.mnt != nd.mnt) goto out_release; new_dentry = lookup_create(&nd, 0); error = PTR_ERR(new_dentry); if (!IS_ERR(new_dentry)) { error = vfs_link(old_nd.dentry, nd.dentry->d_inode, new_dentry); dput(new_dentry); } up(&nd.dentry->d_inode->i_sem); out_release: path_release(&nd); out: path_release(&old_nd); exit: putname(to); } putname(from); return error; } /* * The worst of all namespace operations - renaming directory. "Perverted" * doesn't even start to describe it. Somebody in UCB had a heck of a trip... * Problems: * a) we can get into loop creation. Check is done in is_subdir(). * b) race potential - two innocent renames can create a loop together. * That's where 4.4 screws up. Current fix: serialization on * sb->s_vfs_rename_sem. We might be more accurate, but that's another * story. * c) we have to lock _three_ objects - parents and victim (if it exists). * And that - after we got ->i_sem on parents (until then we don't know * whether the target exists at all, let alone whether it is a directory * or not). Solution: ->i_zombie. Taken only after ->i_sem. Always taken * on link creation/removal of any kind. And taken (without ->i_sem) on * directory that will be removed (both in rmdir() and here). * d) some filesystems don't support opened-but-unlinked directories, * either because of layout or because they are not ready to deal with * all cases correctly. The latter will be fixed (taking this sort of * stuff into VFS), but the former is not going away. Solution: the same * trick as in rmdir(). * e) conversion from fhandle to dentry may come in the wrong moment - when * we are removing the target. Solution: we will have to grab ->i_zombie * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on * ->i_sem on parents, which works but leads to some truely excessive * locking]. */ int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry) { int error; struct inode *target; if (old_dentry->d_inode == new_dentry->d_inode) return 0; error = may_delete(old_dir, old_dentry, 1); if (error) return error; if (new_dir->i_dev != old_dir->i_dev) return -EXDEV; if (!new_dentry->d_inode) error = may_create(new_dir, new_dentry); else error = may_delete(new_dir, new_dentry, 1); if (error) return error; if (!old_dir->i_op || !old_dir->i_op->rename) return -EPERM; /* * If we are going to change the parent - check write permissions, * we'll need to flip '..'. */ if (new_dir != old_dir) { error = permission(old_dentry->d_inode, MAY_WRITE); } if (error) return error; DQUOT_INIT(old_dir); DQUOT_INIT(new_dir); down(&old_dir->i_sb->s_vfs_rename_sem); error = -EINVAL; if (is_subdir(new_dentry, old_dentry)) goto out_unlock; /* Don't eat your daddy, dear... */ /* This also avoids locking issues */ if (old_dentry->d_parent == new_dentry) goto out_unlock; target = new_dentry->d_inode; if (target) { /* Hastur! Hastur! Hastur! */ triple_down(&old_dir->i_zombie, &new_dir->i_zombie, &target->i_zombie); d_unhash(new_dentry); } else double_down(&old_dir->i_zombie, &new_dir->i_zombie); if (IS_DEADDIR(old_dir)||IS_DEADDIR(new_dir)) error = -ENOENT; else if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry)) error = -EBUSY; else error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry); if (target) { if (!error) target->i_flags |= S_DEAD; triple_up(&old_dir->i_zombie, &new_dir->i_zombie, &target->i_zombie); if (d_unhashed(new_dentry)) d_rehash(new_dentry); dput(new_dentry); } else double_up(&old_dir->i_zombie, &new_dir->i_zombie); if (!error) d_move(old_dentry,new_dentry); out_unlock: up(&old_dir->i_sb->s_vfs_rename_sem); return error; } int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry) { int error; if (old_dentry->d_inode == new_dentry->d_inode) return 0; error = may_delete(old_dir, old_dentry, 0); if (error) return error; if (new_dir->i_dev != old_dir->i_dev) return -EXDEV; if (!new_dentry->d_inode) error = may_create(new_dir, new_dentry); else error = may_delete(new_dir, new_dentry, 0); if (error) return error; if (!old_dir->i_op || !old_dir->i_op->rename) return -EPERM; DQUOT_INIT(old_dir); DQUOT_INIT(new_dir); double_down(&old_dir->i_zombie, &new_dir->i_zombie); if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry)) error = -EBUSY; else error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry); double_up(&old_dir->i_zombie, &new_dir->i_zombie); if (error) return error; /* The following d_move() should become unconditional */ if (!(old_dir->i_sb->s_type->fs_flags & FS_ODD_RENAME)) { d_move(old_dentry, new_dentry); } return 0; } int vfs_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry) { int error; if (S_ISDIR(old_dentry->d_inode->i_mode)) error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry); else error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry); if (!error) { if (old_dir == new_dir) inode_dir_notify(old_dir, DN_RENAME); else { inode_dir_notify(old_dir, DN_DELETE); inode_dir_notify(new_dir, DN_CREATE); } } return error; } static inline int do_rename(const char * oldname, const char * newname) { int error = 0; struct dentry * old_dir, * new_dir; struct dentry * old_dentry, *new_dentry; struct nameidata oldnd, newnd; if (path_init(oldname, LOOKUP_PARENT, &oldnd)) error = path_walk(oldname, &oldnd); if (error) goto exit; if (path_init(newname, LOOKUP_PARENT, &newnd)) error = path_walk(newname, &newnd); if (error) goto exit1; error = -EXDEV; if (oldnd.mnt != newnd.mnt) goto exit2; old_dir = oldnd.dentry; error = -EBUSY; if (oldnd.last_type != LAST_NORM) goto exit2; new_dir = newnd.dentry; if (newnd.last_type != LAST_NORM) goto exit2; double_lock(new_dir, old_dir); old_dentry = lookup_hash(&oldnd.last, old_dir); error = PTR_ERR(old_dentry); if (IS_ERR(old_dentry)) goto exit3; /* source must exist */ error = -ENOENT; if (!old_dentry->d_inode) goto exit4; /* unless the source is a directory trailing slashes give -ENOTDIR */ if (!S_ISDIR(old_dentry->d_inode->i_mode)) { error = -ENOTDIR; if (oldnd.last.name[oldnd.last.len]) goto exit4; if (newnd.last.name[newnd.last.len]) goto exit4; } new_dentry = lookup_hash(&newnd.last, new_dir); error = PTR_ERR(new_dentry); if (IS_ERR(new_dentry)) goto exit4; lock_kernel(); error = vfs_rename(old_dir->d_inode, old_dentry, new_dir->d_inode, new_dentry); unlock_kernel(); dput(new_dentry); exit4: dput(old_dentry); exit3: double_up(&new_dir->d_inode->i_sem, &old_dir->d_inode->i_sem); exit2: path_release(&newnd); exit1: path_release(&oldnd); exit: return error; } asmlinkage long sys_rename(const char * oldname, const char * newname) { int error; char * from; char * to; from = getname(oldname); if(IS_ERR(from)) return PTR_ERR(from); to = getname(newname); error = PTR_ERR(to); if (!IS_ERR(to)) { error = do_rename(from,to); putname(to); } putname(from); return error; } int vfs_readlink(struct dentry *dentry, char *buffer, int buflen, const char *link) { int len; len = PTR_ERR(link); if (IS_ERR(link)) goto out; len = strlen(link); if (len > (unsigned) buflen) len = buflen; if (copy_to_user(buffer, link, len)) len = -EFAULT; out: return len; } static inline int __vfs_follow_link(struct nameidata *nd, const char *link) { int res = 0; char *name; if (IS_ERR(link)) goto fail; if (*link == '/') { path_release(nd); if (!walk_init_root(link, nd)) /* weird __emul_prefix() stuff did it */ goto out; } res = link_path_walk(link, nd); out: if (current->link_count || res || nd->last_type!=LAST_NORM) return res; /* * If it is an iterative symlinks resolution in open_namei() we * have to copy the last component. And all that crap because of * bloody create() on broken symlinks. Furrfu... */ name = __getname(); if (!name) return -ENOMEM; strcpy(name, nd->last.name); nd->last.name = name; return 0; fail: path_release(nd); return PTR_ERR(link); } int vfs_follow_link(struct nameidata *nd, const char *link) { return __vfs_follow_link(nd, link); } /* get the link contents into pagecache */ static char *page_getlink(struct dentry * dentry, struct page **ppage) { struct page * page; struct address_space *mapping = dentry->d_inode->i_mapping; page = read_cache_page(mapping, 0, (filler_t *)mapping->a_ops->readpage, NULL); if (IS_ERR(page)) goto sync_fail; wait_on_page(page); if (!Page_Uptodate(page)) goto async_fail; *ppage = page; return kmap(page); async_fail: page_cache_release(page); return ERR_PTR(-EIO); sync_fail: return (char*)page; } int page_readlink(struct dentry *dentry, char *buffer, int buflen) { struct page *page = NULL; char *s = page_getlink(dentry, &page); int res = vfs_readlink(dentry,buffer,buflen,s); if (page) { kunmap(page); page_cache_release(page); } return res; } int page_follow_link(struct dentry *dentry, struct nameidata *nd) { struct page *page = NULL; char *s = page_getlink(dentry, &page); int res = __vfs_follow_link(nd, s); if (page) { kunmap(page); page_cache_release(page); } return res; } struct inode_operations page_symlink_inode_operations = { readlink: page_readlink, follow_link: page_follow_link, };