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authorTejun Heo <htejun@gmail.com>2007-06-13 15:27:25 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2007-07-11 19:09:09 -0400
commit53e0ae92690c52eceb997905d85fbb42de5fff63 (patch)
treeb3bccd211bb09d43c29a751793ac50d8860b8303 /fs/sysfs/dir.c
parenta0edd7c848945a75e2f41673f43bc37d0a5fed15 (diff)
sysfs: implement sysfs_get_dentry()
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 <htejun@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'fs/sysfs/dir.c')
-rw-r--r--fs/sysfs/dir.c98
1 files changed, 98 insertions, 0 deletions
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index c6f3b697064c..987211296106 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -63,6 +63,104 @@ void sysfs_unlink_sibling(struct sysfs_dirent *sd)
63} 63}
64 64
65/** 65/**
66 * sysfs_get_dentry - get dentry for the given sysfs_dirent
67 * @sd: sysfs_dirent of interest
68 *
69 * Get dentry for @sd. Dentry is looked up if currently not
70 * present. This function climbs sysfs_dirent tree till it
71 * reaches a sysfs_dirent with valid dentry attached and descends
72 * down from there looking up dentry for each step.
73 *
74 * LOCKING:
75 * Kernel thread context (may sleep)
76 *
77 * RETURNS:
78 * Pointer to found dentry on success, ERR_PTR() value on error.
79 */
80struct dentry *sysfs_get_dentry(struct sysfs_dirent *sd)
81{
82 struct sysfs_dirent *cur;
83 struct dentry *parent_dentry, *dentry;
84 int i, depth;
85
86 /* Find the first parent which has valid s_dentry and get the
87 * dentry.
88 */
89 mutex_lock(&sysfs_mutex);
90 restart0:
91 spin_lock(&sysfs_assoc_lock);
92 restart1:
93 spin_lock(&dcache_lock);
94
95 dentry = NULL;
96 depth = 0;
97 cur = sd;
98 while (!cur->s_dentry || !cur->s_dentry->d_inode) {
99 if (cur->s_flags & SYSFS_FLAG_REMOVED) {
100 dentry = ERR_PTR(-ENOENT);
101 depth = 0;
102 break;
103 }
104 cur = cur->s_parent;
105 depth++;
106 }
107 if (!IS_ERR(dentry))
108 dentry = dget_locked(cur->s_dentry);
109
110 spin_unlock(&dcache_lock);
111 spin_unlock(&sysfs_assoc_lock);
112
113 /* from the found dentry, look up depth times */
114 while (depth--) {
115 /* find and get depth'th ancestor */
116 for (cur = sd, i = 0; cur && i < depth; i++)
117 cur = cur->s_parent;
118
119 /* This can happen if tree structure was modified due
120 * to move/rename. Restart.
121 */
122 if (i != depth) {
123 dput(dentry);
124 goto restart0;
125 }
126
127 sysfs_get(cur);
128
129 mutex_unlock(&sysfs_mutex);
130
131 /* look it up */
132 parent_dentry = dentry;
133 dentry = lookup_one_len_kern(cur->s_name, parent_dentry,
134 strlen(cur->s_name));
135 dput(parent_dentry);
136
137 if (IS_ERR(dentry)) {
138 sysfs_put(cur);
139 return dentry;
140 }
141
142 mutex_lock(&sysfs_mutex);
143 spin_lock(&sysfs_assoc_lock);
144
145 /* This, again, can happen if tree structure has
146 * changed and we looked up the wrong thing. Restart.
147 */
148 if (cur->s_dentry != dentry) {
149 dput(dentry);
150 sysfs_put(cur);
151 goto restart1;
152 }
153
154 spin_unlock(&sysfs_assoc_lock);
155
156 sysfs_put(cur);
157 }
158
159 mutex_unlock(&sysfs_mutex);
160 return dentry;
161}
162
163/**
66 * sysfs_get_active - get an active reference to sysfs_dirent 164 * sysfs_get_active - get an active reference to sysfs_dirent
67 * @sd: sysfs_dirent to get an active reference to 165 * @sd: sysfs_dirent to get an active reference to
68 * 166 *