From htejun@gmail.com Wed Jun 13 12:27:41 2007 From: Tejun Heo Cc: Tejun Heo Subject: [PATCH 10/11] sysfs: implement sysfs_get_dentry() Date: Thu, 14 Jun 2007 04:27:25 +0900 Message-Id: <11817628443686-git-send-email-htejun@gmail.com> To: greg@kroah.com, dmitry.torokhov@gmail.com, cornelia.huck@de.ibm.com, oneukum@suse.de, rpurdie@rpsys.net, stern@rowland.harvard.edu, maneesh@in.ibm.com, linux-kernel@vger.kernel.org, htejun@gmail.com From: Tejun Heo Some sysfs operations require dentry and inode. sysfs_get_dentry() looks up and gets dentry for the specified sysfs_dirent. It finds the first ancestor with dentry attached and starts looking up dentries from there. Looking up from the nearest ancestor is necessary to support shadowed directories because we can't reliably lookup dentry for one of the shadows. Dentries for each shadow will be pinned in memory such that they can serve as the starting point for dentry lookup. Signed-off-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman --- fs/sysfs/dir.c | 98 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ fs/sysfs/sysfs.h | 1 2 files changed, 99 insertions(+) --- a/fs/sysfs/dir.c +++ b/fs/sysfs/dir.c @@ -63,6 +63,104 @@ void sysfs_unlink_sibling(struct sysfs_d } /** + * 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 climbs sysfs_dirent tree till it + * reaches a sysfs_dirent with valid dentry attached and descends + * down from there looking up dentry for each step. + * + * LOCKING: + * Kernel thread context (may sleep) + * + * RETURNS: + * Pointer to found dentry on success, ERR_PTR() value on error. + */ +struct dentry *sysfs_get_dentry(struct sysfs_dirent *sd) +{ + struct sysfs_dirent *cur; + struct dentry *parent_dentry, *dentry; + int i, depth; + + /* Find the first parent which has valid s_dentry and get the + * dentry. + */ + mutex_lock(&sysfs_mutex); + restart0: + spin_lock(&sysfs_assoc_lock); + restart1: + spin_lock(&dcache_lock); + + dentry = NULL; + depth = 0; + cur = sd; + while (!cur->s_dentry || !cur->s_dentry->d_inode) { + if (cur->s_flags & SYSFS_FLAG_REMOVED) { + dentry = ERR_PTR(-ENOENT); + depth = 0; + break; + } + cur = cur->s_parent; + depth++; + } + if (!IS_ERR(dentry)) + dentry = dget_locked(cur->s_dentry); + + spin_unlock(&dcache_lock); + spin_unlock(&sysfs_assoc_lock); + + /* from the found dentry, look up depth times */ + while (depth--) { + /* find and get depth'th ancestor */ + for (cur = sd, i = 0; cur && i < depth; i++) + cur = cur->s_parent; + + /* This can happen if tree structure was modified due + * to move/rename. Restart. + */ + if (i != depth) { + dput(dentry); + goto restart0; + } + + sysfs_get(cur); + + mutex_unlock(&sysfs_mutex); + + /* look it up */ + parent_dentry = dentry; + dentry = lookup_one_len_kern(cur->s_name, parent_dentry, + strlen(cur->s_name)); + dput(parent_dentry); + + if (IS_ERR(dentry)) { + sysfs_put(cur); + return dentry; + } + + mutex_lock(&sysfs_mutex); + spin_lock(&sysfs_assoc_lock); + + /* This, again, can happen if tree structure has + * changed and we looked up the wrong thing. Restart. + */ + if (cur->s_dentry != dentry) { + dput(dentry); + sysfs_put(cur); + goto restart1; + } + + spin_unlock(&sysfs_assoc_lock); + + sysfs_put(cur); + } + + mutex_unlock(&sysfs_mutex); + return dentry; +} + +/** * sysfs_get_active - get an active reference to sysfs_dirent * @sd: sysfs_dirent to get an active reference to * --- a/fs/sysfs/sysfs.h +++ b/fs/sysfs/sysfs.h @@ -54,6 +54,7 @@ struct sysfs_addrm_cxt { extern struct vfsmount * sysfs_mount; extern struct kmem_cache *sysfs_dir_cachep; +extern struct dentry *sysfs_get_dentry(struct sysfs_dirent *sd); extern void sysfs_link_sibling(struct sysfs_dirent *sd); extern void sysfs_unlink_sibling(struct sysfs_dirent *sd); extern struct sysfs_dirent *sysfs_get_active(struct sysfs_dirent *sd);