sysfs: Propagate renames to the vfs on demand

By teaching sysfs_revalidate to hide a dentry for
a sysfs_dirent if the sysfs_dirent has been renamed,
and by teaching sysfs_lookup to return the original
dentry if the sysfs dirent has been renamed.  I can
show the results of renames correctly without having to
update the dcache during the directory rename.

This massively simplifies the rename logic allowing a lot
of weird sysfs special cases to be removed along with
a lot of now unnecesary helper code.

Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/namei.c b/fs/namei.c
index d11f404..d3c190c 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1279,28 +1279,6 @@ struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
        return __lookup_hash(&this, base, NULL);
 }
 
-/**
- * lookup_one_noperm - bad hack for sysfs
- * @name:      pathname component to lookup
- * @base:      base directory to lookup from
- *
- * This is a variant of lookup_one_len that doesn't perform any permission
- * checks.   It's a horrible hack to work around the braindead sysfs
- * architecture and should not be used anywhere else.
- *
- * DON'T USE THIS FUNCTION EVER, thanks.
- */
-struct dentry *lookup_one_noperm(const char *name, struct dentry *base)
-{
-       int err;
-       struct qstr this;
-
-       err = __lookup_one_len(name, &this, base, strlen(name));
-       if (err)
-               return ERR_PTR(err);
-       return __lookup_hash(&this, base, NULL);
-}
-
 int user_path_at(int dfd, const char __user *name, unsigned flags,
                 struct path *path)
 {

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index f3af45e..97954c6 100644 (file)
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -25,7 +25,6 @@
 #include "sysfs.h"
 
 DEFINE_MUTEX(sysfs_mutex);
-DEFINE_MUTEX(sysfs_rename_mutex);
 DEFINE_SPINLOCK(sysfs_assoc_lock);
 
 static DEFINE_SPINLOCK(sysfs_ino_lock);
@@ -85,46 +84,6 @@ static void sysfs_unlink_sibling(struct sysfs_dirent *sd)
 }
 
 /**
- *     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
  *
@@ -315,6 +274,14 @@ static int sysfs_dentry_revalidate(struct dentry *dentry, struct nameidata *nd)
        if (sd->s_flags & SYSFS_FLAG_REMOVED)
                goto out_bad;
 
+       /* The sysfs dirent has been moved? */
+       if (dentry->d_parent->d_fsdata != sd->s_parent)
+               goto out_bad;
+
+       /* The sysfs dirent has been renamed */
+       if (strcmp(dentry->d_name.name, sd->s_name) != 0)
+               goto out_bad;
+
        mutex_unlock(&sysfs_mutex);
 out_valid:
        return 1;
@@ -322,6 +289,12 @@ out_bad:
        /* Remove the dentry from the dcache hashes.
         * If this is a deleted dentry we use d_drop instead of d_delete
         * so sysfs doesn't need to cope with negative dentries.
+        *
+        * If this is a dentry that has simply been renamed we
+        * use d_drop to remove it from the dcache lookup on its
+        * old parent.  If this dentry persists later when a lookup
+        * is performed at its new name the dentry will be readded
+        * to the dcache hashes.
         */
        is_dir = (sysfs_type(sd) == SYSFS_DIR);
        mutex_unlock(&sysfs_mutex);
@@ -705,10 +678,15 @@ static struct dentry * sysfs_lookup(struct inode *dir, struct dentry *dentry,
        }
 
        /* instantiate and hash dentry */
-       dentry->d_op = &sysfs_dentry_ops;
-       dentry->d_fsdata = sysfs_get(sd);
-       d_instantiate(dentry, inode);
-       d_rehash(dentry);
+       ret = d_find_alias(inode);
+       if (!ret) {
+               dentry->d_op = &sysfs_dentry_ops;
+               dentry->d_fsdata = sysfs_get(sd);
+               d_add(dentry, inode);
+       } else {
+               d_move(ret, dentry);
+               iput(inode);
+       }
 
  out_unlock:
        mutex_unlock(&sysfs_mutex);
@@ -785,62 +763,32 @@ void sysfs_remove_dir(struct kobject * kobj)
 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);
+       mutex_lock(&sysfs_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;
+               goto out;
 
        /* rename sysfs_dirent */
        error = -ENOMEM;
        new_name = dup_name = kstrdup(new_name, GFP_KERNEL);
        if (!new_name)
-               goto out_unlock;
+               goto out;
 
        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:
+ out:
        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;
 }
 
@@ -848,12 +796,11 @@ 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);
+
+       mutex_lock(&sysfs_mutex);
        new_parent_sd = (new_parent_kobj && new_parent_kobj->sd) ?
                new_parent_kobj->sd : &sysfs_root;
 
@@ -861,61 +808,20 @@ int sysfs_move_dir(struct kobject *kobj, struct kobject *new_parent_kobj)
        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);
+               goto out;
 
        /* Remove from old parent's list and insert into new parent's list. */
        sysfs_unlink_sibling(sd);
        sysfs_get(new_parent_sd);
-       drop_nlink(old_parent->d_inode);
        sysfs_put(sd->s_parent);
        sd->s_parent = new_parent_sd;
-       inc_nlink(new_parent->d_inode);
        sysfs_link_sibling(sd);
 
- out_unlock:
+       error = 0;
+out:
        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;
 }
 

diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index 1ffd555..9f783d4 100644 (file)
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -205,17 +205,6 @@ static inline void set_inode_attr(struct inode * inode, struct iattr * iattr)
        inode->i_ctime = iattr->ia_ctime;
 }
 
-
-/*
- * sysfs has a different i_mutex lock order behavior for i_mutex than other
- * filesystems; sysfs i_mutex is called in many places with subsystem locks
- * held. At the same time, many of the VFS locking rules do not apply to
- * sysfs at all (cross directory rename for example). To untangle this mess
- * (which gives false positives in lockdep), we're giving sysfs inodes their
- * own class for i_mutex.
- */
-static struct lock_class_key sysfs_inode_imutex_key;
-
 static int sysfs_count_nlink(struct sysfs_dirent *sd)
 {
        struct sysfs_dirent *child;
@@ -268,7 +257,6 @@ static void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
        inode->i_mapping->a_ops = &sysfs_aops;
        inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
        inode->i_op = &sysfs_inode_operations;
-       lockdep_set_class(&inode->i_mutex, &sysfs_inode_imutex_key);
 
        set_default_inode_attr(inode, sd->s_mode);
        sysfs_refresh_inode(sd, inode);

diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index 90b3501..98a15bf 100644 (file)
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -103,7 +103,6 @@ extern struct kmem_cache *sysfs_dir_cachep;
  * dir.c
  */
 extern struct mutex sysfs_mutex;
-extern struct mutex sysfs_rename_mutex;
 extern spinlock_t sysfs_assoc_lock;
 
 extern const struct file_operations sysfs_dir_operations;

diff --git a/include/linux/namei.h b/include/linux/namei.h
index ec0f607..0289467 100644 (file)
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -76,7 +76,6 @@ extern struct file *nameidata_to_filp(struct nameidata *nd, int flags);
 extern void release_open_intent(struct nameidata *);
 
 extern struct dentry *lookup_one_len(const char *, struct dentry *, int);
-extern struct dentry *lookup_one_noperm(const char *, struct dentry *);
 
 extern int follow_down(struct path *);
 extern int follow_up(struct path *);