/* * fs/sysfs/dir.c - sysfs core and dir operation implementation * * Copyright (c) 2001-3 Patrick Mochel * Copyright (c) 2007 SUSE Linux Products GmbH * Copyright (c) 2007 Tejun Heo <teheo@suse.de> * * This file is released under the GPLv2. * * Please see Documentation/filesystems/sysfs.txt for more information. */ #undef DEBUG #include <linux/fs.h> #include <linux/mount.h> #include <linux/module.h> #include <linux/kobject.h> #include <linux/namei.h> #include <linux/idr.h> #include <linux/completion.h> #include <linux/mutex.h> #include <linux/slab.h> #include "sysfs.h" DEFINE_MUTEX(sysfs_mutex); DEFINE_MUTEX(sysfs_rename_mutex); DEFINE_SPINLOCK(sysfs_assoc_lock); static DEFINE_SPINLOCK(sysfs_ino_lock); static DEFINE_IDA(sysfs_ino_ida); /** * sysfs_link_sibling - link sysfs_dirent into sibling list * @sd: sysfs_dirent of interest * * Link @sd into its sibling list which starts from * sd->s_parent->s_dir.children. * * Locking: * mutex_lock(sysfs_mutex) */ static void sysfs_link_sibling(struct sysfs_dirent *sd) { struct sysfs_dirent *parent_sd = sd->s_parent; struct sysfs_dirent **pos; BUG_ON(sd->s_sibling); /* Store directory entries in order by ino. This allows * readdir to properly restart without having to add a * cursor into the s_dir.children list. */ for (pos = &parent_sd->s_dir.children; *pos; pos = &(*pos)->s_sibling) { if (sd->s_ino < (*pos)->s_ino) break; } sd->s_sibling = *pos; *pos = sd; } /** * sysfs_unlink_sibling - unlink sysfs_dirent from sibling list * @sd: sysfs_dirent of interest * * Unlink @sd from its sibling list which starts from * sd->s_parent->s_dir.children. * * Locking: * mutex_lock(sysfs_mutex) */ static void sysfs_unlink_sibling(struct sysfs_dirent *sd) { struct sysfs_dirent **pos; for (pos = &sd->s_parent->s_dir.children; *pos; pos = &(*pos)->s_sibling) { if (*pos == sd) { *pos = sd->s_sibling; sd->s_sibling = NULL; break; } } } /** * sysfs_get_dentry - get dentry for the given sysfs_dirent * @sd: sysfs_dirent of interest * * Get dentry for @sd. Dentry is looked up if currently not * present. This function descends from the root looking up * dentry for each step. * * LOCKING: * mutex_lock(sysfs_rename_mutex) * * RETURNS: * Pointer to found dentry on success, ERR_PTR() value on error. */ struct dentry *sysfs_get_dentry(struct sysfs_dirent *sd) { struct dentry *dentry = dget(sysfs_sb->s_root); while (dentry->d_fsdata != sd) { struct sysfs_dirent *cur; struct dentry *parent; /* find the first ancestor which hasn't been looked up */ cur = sd; while (cur->s_parent != dentry->d_fsdata) cur = cur->s_parent; /* look it up */ parent = dentry; mutex_lock(&parent->d_inode->i_mutex); dentry = lookup_one_noperm(cur->s_name, parent); mutex_unlock(&parent->d_inode->i_mutex); dput(parent); if (IS_ERR(dentry)) break; } return dentry; } /** * sysfs_get_active - get an active reference to sysfs_dirent * @sd: sysfs_dirent to get an active reference to * * Get an active reference of @sd. This function is noop if @sd * is NULL. * * RETURNS: * Pointer to @sd on success, NULL on failure. */ static struct sysfs_dirent *sysfs_get_active(struct sysfs_dirent *sd) { if (unlikely(!sd)) return NULL; while (1) { int v, t; v = atomic_read(&sd->s_active); if (unlikely(v < 0)) return NULL; t = atomic_cmpxchg(&sd->s_active, v, v + 1); if (likely(t == v)) return sd; if (t < 0) return NULL; cpu_relax(); } } /** * sysfs_put_active - put an active reference to sysfs_dirent * @sd: sysfs_dirent to put an active reference to * * Put an active reference to @sd. This function is noop if @sd * is NULL. */ static void sysfs_put_active(struct sysfs_dirent *sd) { struct completion *cmpl; int v; if (unlikely(!sd)) return; v = atomic_dec_return(&sd->s_active); if (likely(v != SD_DEACTIVATED_BIAS)) return; /* atomic_dec_return() is a mb(), we'll always see the updated * sd->s_sibling. */ cmpl = (void *)sd->s_sibling; complete(cmpl); } /** * sysfs_get_active_two - get active references to sysfs_dirent and parent * @sd: sysfs_dirent of interest * * Get active reference to @sd and its parent. Parent's active * reference is grabbed first. This function is noop if @sd is * NULL. * * RETURNS: * Pointer to @sd on success, NULL on failure. */ struct sysfs_dirent *sysfs_get_active_two(struct sysfs_dirent *sd) { if (sd) { if (sd->s_parent && unlikely(!sysfs_get_active(sd->s_parent))) return NULL; if (unlikely(!sysfs_get_active(sd))) { sysfs_put_active(sd->s_parent); return NULL; } } return sd; } /** * sysfs_put_active_two - put active references to sysfs_dirent and parent * @sd: sysfs_dirent of interest * * Put active references to @sd and its parent. This function is * noop if @sd is NULL. */ void sysfs_put_active_two(struct sysfs_dirent *sd) { if (sd) { sysfs_put_active(sd); sysfs_put_active(sd->s_parent); } } /** * sysfs_deactivate - deactivate sysfs_dirent * @sd: sysfs_dirent to deactivate * * Deny new active references and drain existing ones. */ static void sysfs_deactivate(struct sysfs_dirent *sd) { DECLARE_COMPLETION_ONSTACK(wait); int v; BUG_ON(sd->s_sibling || !(sd->s_flags & SYSFS_FLAG_REMOVED)); sd->s_sibling = (void *)&wait; /* atomic_add_return() is a mb(), put_active() will always see * the updated sd->s_sibling. */ v = atomic_add_return(SD_DEACTIVATED_BIAS, &sd->s_active); if (v != SD_DEACTIVATED_BIAS) wait_for_completion(&wait); sd->s_sibling = NULL; } static int sysfs_alloc_ino(ino_t *pino) { int ino, rc; retry: spin_lock(&sysfs_ino_lock); rc = ida_get_new_above(&sysfs_ino_ida, 2, &ino); spin_unlock(&sysfs_ino_lock); if (rc == -EAGAIN) { if (ida_pre_get(&sysfs_ino_ida, GFP_KERNEL)) goto retry; rc = -ENOMEM; } *pino = ino; return rc; } static void sysfs_free_ino(ino_t ino) { spin_lock(&sysfs_ino_lock); ida_remove(&sysfs_ino_ida, ino); spin_unlock(&sysfs_ino_lock); } void release_sysfs_dirent(struct sysfs_dirent * sd) { struct sysfs_dirent *parent_sd; repeat: /* Moving/renaming is always done while holding reference. * sd->s_parent won't change beneath us. */ parent_sd = sd->s_parent; if (sysfs_type(sd) == SYSFS_KOBJ_LINK) sysfs_put(sd->s_symlink.target_sd); if (sysfs_type(sd) & SYSFS_COPY_NAME) kfree(sd->s_name); kfree(sd->s_iattr); sysfs_free_ino(sd->s_ino); kmem_cache_free(sysfs_dir_cachep, sd); sd = parent_sd; if (sd && atomic_dec_and_test(&sd->s_count)) goto repeat; } static void sysfs_d_iput(struct dentry * dentry, struct inode * inode) { struct sysfs_dirent * sd = dentry->d_fsdata; sysfs_put(sd); iput(inode); } static struct dentry_operations sysfs_dentry_ops = { .d_iput = sysfs_d_iput, }; struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type) { char *dup_name = NULL; struct sysfs_dirent *sd; if (type & SYSFS_COPY_NAME) { name = dup_name = kstrdup(name, GFP_KERNEL); if (!name) return NULL; } sd = kmem_cache_zalloc(sysfs_dir_cachep, GFP_KERNEL); if (!sd) goto err_out1; if (sysfs_alloc_ino(&sd->s_ino)) goto err_out2; atomic_set(&sd->s_count, 1); atomic_set(&sd->s_active, 0); sd->s_name = name; sd->s_mode = mode; sd->s_flags = type; return sd; err_out2: kmem_cache_free(sysfs_dir_cachep, sd); err_out1: kfree(dup_name); return NULL; } static int sysfs_ilookup_test(struct inode *inode, void *arg) { struct sysfs_dirent *sd = arg; return inode->i_ino == sd->s_ino; } /** * sysfs_addrm_start - prepare for sysfs_dirent add/remove * @acxt: pointer to sysfs_addrm_cxt to be used * @parent_sd: parent sysfs_dirent * * This function is called when the caller is about to add or * remove sysfs_dirent under @parent_sd. This function acquires * sysfs_mutex, grabs inode for @parent_sd if available and lock * i_mutex of it. @acxt is used to keep and pass context to * other addrm functions. * * LOCKING: * Kernel thread context (may sleep). sysfs_mutex is locked on * return. i_mutex of parent inode is locked on return if * available. */ void sysfs_addrm_start(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *parent_sd) { struct inode *inode; memset(acxt, 0, sizeof(*acxt)); acxt->parent_sd = parent_sd; /* Lookup parent inode. inode initialization is protected by * sysfs_mutex, so inode existence can be determined by * looking up inode while holding sysfs_mutex. */ mutex_lock(&sysfs_mutex); inode = ilookup5(sysfs_sb, parent_sd->s_ino, sysfs_ilookup_test, parent_sd); if (inode) { WARN_ON(inode->i_state & I_NEW); /* parent inode available */ acxt->parent_inode = inode; /* sysfs_mutex is below i_mutex in lock hierarchy. * First, trylock i_mutex. If fails, unlock * sysfs_mutex and lock them in order. */ if (!mutex_trylock(&inode->i_mutex)) { mutex_unlock(&sysfs_mutex); mutex_lock(&inode->i_mutex); mutex_lock(&sysfs_mutex); } } } /** * __sysfs_add_one - add sysfs_dirent to parent without warning * @acxt: addrm context to use * @sd: sysfs_dirent to be added * * Get @acxt->parent_sd and set sd->s_parent to it and increment * nlink of parent inode if @sd is a directory and link into the * children list of the parent. * * This function should be called between calls to * sysfs_addrm_start() and sysfs_addrm_finish() and should be * passed the same @acxt as passed to sysfs_addrm_start(). * * LOCKING: * Determined by sysfs_addrm_start(). * * RETURNS: * 0 on success, -EEXIST if entry with the given name already * exists. */ int __sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd) { if (sysfs_find_dirent(acxt->parent_sd, sd->s_name)) return -EEXIST; sd->s_parent = sysfs_get(acxt->parent_sd); if (sysfs_type(sd) == SYSFS_DIR && acxt->parent_inode) inc_nlink(acxt->parent_inode); acxt->cnt++; sysfs_link_sibling(sd); return 0; } /** * sysfs_add_one - add sysfs_dirent to parent * @acxt: addrm context to use * @sd: sysfs_dirent to be added * * Get @acxt->parent_sd and set sd->s_parent to it and increment * nlink of parent inode if @sd is a directory and link into the * children list of the parent. * * This function should be called between calls to * sysfs_addrm_start() and sysfs_addrm_finish() and should be * passed the same @acxt as passed to sysfs_addrm_start(). * * LOCKING: * Determined by sysfs_addrm_start(). * * RETURNS: * 0 on success, -EEXIST if entry with the given name already * exists. */ int sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd) { int ret; ret = __sysfs_add_one(acxt, sd); WARN(ret == -EEXIST, KERN_WARNING "sysfs: duplicate filename '%s' " "can not be created\n", sd->s_name); return ret; } /** * sysfs_remove_one - remove sysfs_dirent from parent * @acxt: addrm context to use * @sd: sysfs_dirent to be removed * * Mark @sd removed and drop nlink of parent inode if @sd is a * directory. @sd is unlinked from the children list. * * This function should be called between calls to * sysfs_addrm_start() and sysfs_addrm_finish() and should be * passed the same @acxt as passed to sysfs_addrm_start(). * * LOCKING: * Determined by sysfs_addrm_start(). */ void sysfs_remove_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd) { BUG_ON(sd->s_flags & SYSFS_FLAG_REMOVED); sysfs_unlink_sibling(sd); sd->s_flags |= SYSFS_FLAG_REMOVED; sd->s_sibling = acxt->removed; acxt->removed = sd; if (sysfs_type(sd) == SYSFS_DIR && acxt->parent_inode) drop_nlink(acxt->parent_inode); acxt->cnt++; } /** * sysfs_drop_dentry - drop dentry for the specified sysfs_dirent * @sd: target sysfs_dirent * * Drop dentry for @sd. @sd must have been unlinked from its * parent on entry to this function such that it can't be looked * up anymore. */ static void sysfs_drop_dentry(struct sysfs_dirent *sd) { struct inode *inode; struct dentry *dentry; inode = ilookup(sysfs_sb, sd->s_ino); if (!inode) return; /* Drop any existing dentries associated with sd. * * For the dentry to be properly freed we need to grab a * reference to the dentry under the dcache lock, unhash it, * and then put it. The playing with the dentry count allows * dput to immediately free the dentry if it is not in use. */ repeat: spin_lock(&dcache_lock); list_for_each_entry(dentry, &inode->i_dentry, d_alias) { if (d_unhashed(dentry)) continue; dget_locked(dentry); spin_lock(&dentry->d_lock); __d_drop(dentry); spin_unlock(&dentry->d_lock); spin_unlock(&dcache_lock); dput(dentry); goto repeat; } spin_unlock(&dcache_lock); /* adjust nlink and update timestamp */ mutex_lock(&inode->i_mutex); inode->i_ctime = CURRENT_TIME; drop_nlink(inode); if (sysfs_type(sd) == SYSFS_DIR) drop_nlink(inode); mutex_unlock(&inode->i_mutex); iput(inode); } /** * sysfs_addrm_finish - finish up sysfs_dirent add/remove * @acxt: addrm context to finish up * * Finish up sysfs_dirent add/remove. Resources acquired by * sysfs_addrm_start() are released and removed sysfs_dirents are * cleaned up. Timestamps on the parent inode are updated. * * LOCKING: * All mutexes acquired by sysfs_addrm_start() are released. */ void sysfs_addrm_finish(struct sysfs_addrm_cxt *acxt) { /* release resources acquired by sysfs_addrm_start() */ mutex_unlock(&sysfs_mutex); if (acxt->parent_inode) { struct inode *inode = acxt->parent_inode; /* if added/removed, update timestamps on the parent */ if (acxt->cnt) inode->i_ctime = inode->i_mtime = CURRENT_TIME; mutex_unlock(&inode->i_mutex); iput(inode); } /* kill removed sysfs_dirents */ while (acxt->removed) { struct sysfs_dirent *sd = acxt->removed; acxt->removed = sd->s_sibling; sd->s_sibling = NULL; sysfs_drop_dentry(sd); sysfs_deactivate(sd); sysfs_put(sd); } } /** * sysfs_find_dirent - find sysfs_dirent with the given name * @parent_sd: sysfs_dirent to search under * @name: name to look for * * Look for sysfs_dirent with name @name under @parent_sd. * * LOCKING: * mutex_lock(sysfs_mutex) * * RETURNS: * Pointer to sysfs_dirent if found, NULL if not. */ struct sysfs_dirent *sysfs_find_dirent(struct sysfs_dirent *parent_sd, const unsigned char *name) { struct sysfs_dirent *sd; for (sd = parent_sd->s_dir.children; sd; sd = sd->s_sibling) if (!strcmp(sd->s_name, name)) return sd; return NULL; } /** * sysfs_get_dirent - find and get sysfs_dirent with the given name * @parent_sd: sysfs_dirent to search under * @name: name to look for * * Look for sysfs_dirent with name @name under @parent_sd and get * it if found. * * LOCKING: * Kernel thread context (may sleep). Grabs sysfs_mutex. * * RETURNS: * Pointer to sysfs_dirent if found, NULL if not. */ struct sysfs_dirent *sysfs_get_dirent(struct sysfs_dirent *parent_sd, const unsigned char *name) { struct sysfs_dirent *sd; mutex_lock(&sysfs_mutex); sd = sysfs_find_dirent(parent_sd, name); sysfs_get(sd); mutex_unlock(&sysfs_mutex); return sd; } EXPORT_SYMBOL_GPL(sysfs_get_dirent); static int create_dir(struct kobject *kobj, struct sysfs_dirent *parent_sd, const char *name, struct sysfs_dirent **p_sd) { umode_t mode = S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO; struct sysfs_addrm_cxt acxt; struct sysfs_dirent *sd; int rc; /* allocate */ sd = sysfs_new_dirent(name, mode, SYSFS_DIR); if (!sd) return -ENOMEM; sd->s_dir.kobj = kobj; /* link in */ sysfs_addrm_start(&acxt, parent_sd); rc = sysfs_add_one(&acxt, sd); sysfs_addrm_finish(&acxt); if (rc == 0) *p_sd = sd; else sysfs_put(sd); return rc; } int sysfs_create_subdir(struct kobject *kobj, const char *name, struct sysfs_dirent **p_sd) { return create_dir(kobj, kobj->sd, name, p_sd); } /** * sysfs_create_dir - create a directory for an object. * @kobj: object we're creating directory for. */ int sysfs_create_dir(struct kobject * kobj) { struct sysfs_dirent *parent_sd, *sd; int error = 0; BUG_ON(!kobj); if (kobj->parent) parent_sd = kobj->parent->sd; else parent_sd = &sysfs_root; error = create_dir(kobj, parent_sd, kobject_name(kobj), &sd); if (!error) kobj->sd = sd; return error; } static struct dentry * sysfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd) { struct dentry *ret = NULL; struct sysfs_dirent *parent_sd = dentry->d_parent->d_fsdata; struct sysfs_dirent *sd; struct inode *inode; mutex_lock(&sysfs_mutex); sd = sysfs_find_dirent(parent_sd, dentry->d_name.name); /* no such entry */ if (!sd) { ret = ERR_PTR(-ENOENT); goto out_unlock; } /* attach dentry and inode */ inode = sysfs_get_inode(sd); if (!inode) { ret = ERR_PTR(-ENOMEM); goto out_unlock; } /* instantiate and hash dentry */ dentry->d_op = &sysfs_dentry_ops; dentry->d_fsdata = sysfs_get(sd); d_instantiate(dentry, inode); d_rehash(dentry); out_unlock: mutex_unlock(&sysfs_mutex); return ret; } const struct inode_operations sysfs_dir_inode_operations = { .lookup = sysfs_lookup, .setattr = sysfs_setattr, }; static void remove_dir(struct sysfs_dirent *sd) { struct sysfs_addrm_cxt acxt; sysfs_addrm_start(&acxt, sd->s_parent); sysfs_remove_one(&acxt, sd); sysfs_addrm_finish(&acxt); } void sysfs_remove_subdir(struct sysfs_dirent *sd) { remove_dir(sd); } static void __sysfs_remove_dir(struct sysfs_dirent *dir_sd) { struct sysfs_addrm_cxt acxt; struct sysfs_dirent **pos; if (!dir_sd) return; pr_debug("sysfs %s: removing dir\n", dir_sd->s_name); sysfs_addrm_start(&acxt, dir_sd); pos = &dir_sd->s_dir.children; while (*pos) { struct sysfs_dirent *sd = *pos; if (sysfs_type(sd) != SYSFS_DIR) sysfs_remove_one(&acxt, sd); else pos = &(*pos)->s_sibling; } sysfs_addrm_finish(&acxt); remove_dir(dir_sd); } /** * sysfs_remove_dir - remove an object's directory. * @kobj: object. * * The only thing special about this is that we remove any files in * the directory before we remove the directory, and we've inlined * what used to be sysfs_rmdir() below, instead of calling separately. */ void sysfs_remove_dir(struct kobject * kobj) { struct sysfs_dirent *sd = kobj->sd; spin_lock(&sysfs_assoc_lock); kobj->sd = NULL; spin_unlock(&sysfs_assoc_lock); __sysfs_remove_dir(sd); } int sysfs_rename_dir(struct kobject * kobj, const char *new_name) { struct sysfs_dirent *sd = kobj->sd; struct dentry *parent = NULL; struct dentry *old_dentry = NULL, *new_dentry = NULL; const char *dup_name = NULL; int error; mutex_lock(&sysfs_rename_mutex); error = 0; if (strcmp(sd->s_name, new_name) == 0) goto out; /* nothing to rename */ /* get the original dentry */ old_dentry = sysfs_get_dentry(sd); if (IS_ERR(old_dentry)) { error = PTR_ERR(old_dentry); old_dentry = NULL; goto out; } parent = old_dentry->d_parent; /* lock parent and get dentry for new name */ mutex_lock(&parent->d_inode->i_mutex); mutex_lock(&sysfs_mutex); error = -EEXIST; if (sysfs_find_dirent(sd->s_parent, new_name)) goto out_unlock; error = -ENOMEM; new_dentry = d_alloc_name(parent, new_name); if (!new_dentry) goto out_unlock; /* rename sysfs_dirent */ error = -ENOMEM; new_name = dup_name = kstrdup(new_name, GFP_KERNEL); if (!new_name) goto out_unlock; dup_name = sd->s_name; sd->s_name = new_name; /* rename */ d_add(new_dentry, NULL); d_move(old_dentry, new_dentry); error = 0; out_unlock: mutex_unlock(&sysfs_mutex); mutex_unlock(&parent->d_inode->i_mutex); kfree(dup_name); dput(old_dentry); dput(new_dentry); out: mutex_unlock(&sysfs_rename_mutex); return error; } int sysfs_move_dir(struct kobject *kobj, struct kobject *new_parent_kobj) { struct sysfs_dirent *sd = kobj->sd; struct sysfs_dirent *new_parent_sd; struct dentry *old_parent, *new_parent = NULL; struct dentry *old_dentry = NULL, *new_dentry = NULL; int error; mutex_lock(&sysfs_rename_mutex); BUG_ON(!sd->s_parent); new_parent_sd = new_parent_kobj->sd ? new_parent_kobj->sd : &sysfs_root; error = 0; if (sd->s_parent == new_parent_sd) goto out; /* nothing to move */ /* get dentries */ old_dentry = sysfs_get_dentry(sd); if (IS_ERR(old_dentry)) { error = PTR_ERR(old_dentry); old_dentry = NULL; goto out; } old_parent = old_dentry->d_parent; new_parent = sysfs_get_dentry(new_parent_sd); if (IS_ERR(new_parent)) { error = PTR_ERR(new_parent); new_parent = NULL; goto out; } again: mutex_lock(&old_parent->d_inode->i_mutex); if (!mutex_trylock(&new_parent->d_inode->i_mutex)) { mutex_unlock(&old_parent->d_inode->i_mutex); goto again; } mutex_lock(&sysfs_mutex); error = -EEXIST; if (sysfs_find_dirent(new_parent_sd, sd->s_name)) goto out_unlock; error = -ENOMEM; new_dentry = d_alloc_name(new_parent, sd->s_name); if (!new_dentry) goto out_unlock; error = 0; d_add(new_dentry, NULL); d_move(old_dentry, new_dentry); /* Remove from old parent's list and insert into new parent's list. */ sysfs_unlink_sibling(sd); sysfs_get(new_parent_sd); sysfs_put(sd->s_parent); sd->s_parent = new_parent_sd; sysfs_link_sibling(sd); out_unlock: mutex_unlock(&sysfs_mutex); mutex_unlock(&new_parent->d_inode->i_mutex); mutex_unlock(&old_parent->d_inode->i_mutex); out: dput(new_parent); dput(old_dentry); dput(new_dentry); mutex_unlock(&sysfs_rename_mutex); return error; } /* Relationship between s_mode and the DT_xxx types */ static inline unsigned char dt_type(struct sysfs_dirent *sd) { return (sd->s_mode >> 12) & 15; } static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir) { struct dentry *dentry = filp->f_path.dentry; struct sysfs_dirent * parent_sd = dentry->d_fsdata; struct sysfs_dirent *pos; ino_t ino; if (filp->f_pos == 0) { ino = parent_sd->s_ino; if (filldir(dirent, ".", 1, filp->f_pos, ino, DT_DIR) == 0) filp->f_pos++; } if (filp->f_pos == 1) { if (parent_sd->s_parent) ino = parent_sd->s_parent->s_ino; else ino = parent_sd->s_ino; if (filldir(dirent, "..", 2, filp->f_pos, ino, DT_DIR) == 0) filp->f_pos++; } if ((filp->f_pos > 1) && (filp->f_pos < INT_MAX)) { mutex_lock(&sysfs_mutex); /* Skip the dentries we have already reported */ pos = parent_sd->s_dir.children; while (pos && (filp->f_pos > pos->s_ino)) pos = pos->s_sibling; for ( ; pos; pos = pos->s_sibling) { const char * name; int len; name = pos->s_name; len = strlen(name); filp->f_pos = ino = pos->s_ino; if (filldir(dirent, name, len, filp->f_pos, ino, dt_type(pos)) < 0) break; } if (!pos) filp->f_pos = INT_MAX; mutex_unlock(&sysfs_mutex); } return 0; } const struct file_operations sysfs_dir_operations = { .read = generic_read_dir, .readdir = sysfs_readdir, };