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/*

 * 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 "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 and I_NEW

         * clearing are protected by sysfs_mutex.  By grabbing it and

         * looking up with _nowait variant, inode state can be

         * determined reliably.

         */

        mutex_lock(&sysfs_mutex);

        inode = ilookup5_nowait(sysfs_sb, parent_sd->s_ino, sysfs_ilookup_test,

                                parent_sd);

        if (inode && !(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);

                }

        } else

                iput(inode);

}

/**

 *      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)

{

        if (sysfs_find_dirent(acxt->parent_sd, sd->s_name)) {

                printk(KERN_WARNING "sysfs: duplicate filename '%s' "

                       "can not be created\n", sd->s_name);

                WARN_ON(1);

                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_remove_one - remove sysfs_dirent from parent

 *      @acxt: addrm context to use

 *      @sd: sysfs_dirent to be added

 *

 *      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;

}

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;