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/sysfs/dir.c b/fs/sysfs/dir.c
index f3af45e..97954c6 100644
--- 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 @@
}
/**
- * 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 @@
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 @@
/* 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 @@
}
/* 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 @@
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:
- 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);
+ mutex_unlock(&sysfs_mutex);
+ kfree(dup_name);
return error;
}
@@ -848,12 +796,11 @@
{
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 @@
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;
}