[PATCH 6/8] sysfs: implement plugged creation of sysfs nodes
From: Tejun Heo
Date: Thu Sep 20 2007 - 04:33:34 EST
This patch implements plugged creation of sysfs nodes. If
SYSFS_PLUGGED is specified to any of sysfs_add_*() functions, the
node, its children which get added under it and symlinks pointing to
it or its children won't be visible from userland - lookup and
directory listing won't show them, until the plugged node is
unplugged using sysfs_unplug().
This will be used to prevent userland from seeing sysfs hierarchy for
certain entity (device or whatever) appear piece-by-piece. Also,
initialization failure won't be visible on userland. Everything
including inode nlinks are handled properly.
This will be later combined with uevent_suppress.
Signed-off-by: Tejun Heo <htejun@xxxxxxxxx>
---
fs/sysfs/dir.c | 165 +++++++++++++++++++++++++++++++++++++++++--------
fs/sysfs/inode.c | 3 +-
fs/sysfs/sysfs.h | 2 +
include/linux/sysfs.h | 8 ++-
4 files changed, 149 insertions(+), 29 deletions(-)
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index eac8fef..88ec749 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -118,8 +118,15 @@ struct dentry *sysfs_get_dentry(struct sysfs_dirent *sd)
/* look it up */
parent = dentry;
mutex_lock(&parent->d_inode->i_mutex);
+
dentry = lookup_one_len_kern(cur->s_name, parent,
strlen(cur->s_name));
+ /* negative dentry means @sd is plugged, return -ENOENT */
+ if (!dentry->d_inode) {
+ dput(dentry);
+ dentry = ERR_PTR(-ENOENT);
+ }
+
mutex_unlock(&parent->d_inode->i_mutex);
dput(parent);
@@ -322,12 +329,13 @@ static struct dentry_operations sysfs_dentry_ops = {
/**
* sysfs_new_dirent - allocate and initialize sysfs_dirent
* @name: name for the new sysfs_dirent
- * @mode: mask of bits from S_IRWXUGO | SYSFS_COPY_NAME
+ * @mode: mask of bits from S_IRWXUGO | SYSFS_COPY_NAME | SYSFS_PLUGGED
* @type: one of SYSFS_{DIR|FILE|BIN|LINK}
*
* Allocate and initialize a sysfs_dirent with the specified
* parameters. If SYSFS_COPY_NAME is specified in @mode, @name
- * is duplicated.
+ * is duplicated. If SYSFS_PLUGGED is set, the node is
+ * initialized into plugged state.
*
* LOCKING:
* Kernel thread context (may sleep).
@@ -351,6 +359,10 @@ struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type)
flags |= SYSFS_FLAG_NAME_COPIED;
}
+ /* start plugged? */
+ if (mode & SYSFS_PLUGGED)
+ flags |= SYSFS_FLAG_PLUGGED;
+
/* normalize mode */
mode &= S_IALLUGO;
@@ -512,12 +524,14 @@ static struct inode *sysfs_addrm_get_parent_inode(struct sysfs_addrm_cxt *acxt,
int sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *parent,
struct sysfs_dirent *sd)
{
- struct inode *parent_inode;
+ struct inode *parent_inode = NULL;
if (sysfs_find_dirent(parent, sd->s_name))
return -EEXIST;
- parent_inode = sysfs_addrm_get_parent_inode(acxt, parent);
+ /* if plugged, don't update parent inode, will be updated on unplug */
+ if (!(sd->s_flags & SYSFS_FLAG_PLUGGED))
+ parent_inode = sysfs_addrm_get_parent_inode(acxt, parent);
sd->s_parent = sysfs_get(parent);
@@ -555,11 +569,13 @@ int sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *parent,
*/
void sysfs_remove_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
{
- struct inode *parent_inode;
+ struct inode *parent_inode = NULL;
BUG_ON(sd->s_flags & SYSFS_FLAG_REMOVED);
- parent_inode = sysfs_addrm_get_parent_inode(acxt, sd->s_parent);
+ /* if plugged, don't update parent inode, will be updated on unplug */
+ if (!(sd->s_flags & SYSFS_FLAG_PLUGGED))
+ parent_inode = sysfs_addrm_get_parent_inode(acxt, sd->s_parent);
if (sd->s_flags & SYSFS_FLAG_LINK_CHAINED) {
struct sysfs_dirent *target = sd->s_link.target;
@@ -805,7 +821,9 @@ EXPORT_SYMBOL_GPL(sysfs_find_child);
*
* Add a new directory under @parent with the specified
* parameters. If SYSFS_COPY_NAME is set in @mode, @name is
- * copied before being used.
+ * copied before being used. If SYSFS_PLUGGED is set in @mode,
+ * the new directory will start plugged (won't be visible till
+ * unplugged).
*
* LOCKING:
* Kernel thread context (may sleep).
@@ -830,6 +848,84 @@ struct sysfs_dirent *sysfs_add_dir(struct sysfs_dirent *parent,
}
EXPORT_SYMBOL_GPL(sysfs_add_dir);
+/**
+ * sysfs_unplug - unplug a plugged sysfs_dirent
+ * @sd: sysfs_dirent to unplug
+ *
+ * A plugged sysfs_dirent isn't visible to userland. As are all
+ * its children and symlinks point to the sysfs_dirent or its
+ * children. This function unplugs @sd and makes it visible to
+ * userland.
+ *
+ * LOCKING:
+ * Kernel thread context (may sleep). Uses sysfs_mutex.
+ */
+void sysfs_unplug(struct sysfs_dirent *sd)
+{
+ struct sysfs_addrm_cxt acxt;
+
+ /* Unplugging performs parent inode update delayed from
+ * add/removal. Also, sysfs_op_mutex grabbed by addrm_start
+ * guarantees renaming to see consistent plugged status.
+ */
+ sysfs_addrm_start(&acxt);
+
+ if (sd->s_flags & SYSFS_FLAG_PLUGGED) {
+ struct inode *parent_inode =
+ sysfs_addrm_get_parent_inode(&acxt, sd->s_parent);
+
+ sd->s_flags &= ~SYSFS_FLAG_PLUGGED;
+
+ if (parent_inode) {
+ parent_inode->i_ctime =
+ parent_inode->i_mtime = CURRENT_TIME;
+
+ if (sysfs_type(sd) == SYSFS_DIR)
+ inc_nlink(parent_inode);
+ }
+ }
+
+ sysfs_addrm_finish(&acxt);
+}
+EXPORT_SYMBOL_GPL(sysfs_unplug);
+
+static int sysfs_plugged(struct sysfs_dirent *sd,
+ struct sysfs_dirent *new_parent)
+{
+ struct sysfs_dirent *cur;
+
+ /* @sd itself is plugged? */
+ if (sd->s_flags & SYSFS_FLAG_PLUGGED)
+ return 1;
+
+ /* Parent override for renaming. This is used to determine
+ * whether @sd will be plugged when moved under @new_parent.
+ */
+ if (!new_parent)
+ new_parent = sd->s_parent;
+
+ /* is one of @sd's acnestors plugged? */
+ for (cur = new_parent; cur; cur = cur->s_parent)
+ if (cur->s_flags & SYSFS_FLAG_PLUGGED)
+ return 1;
+
+ /* A symlink is plugged if its target is plugged. Check
+ * whether the target is plugged unless the symlink is known
+ * to be unplugged.
+ */
+ if (sysfs_type(sd) != SYSFS_LINK ||
+ (sd->s_flags & SYSFS_FLAG_LINK_UNPLUGGED))
+ return 0;
+
+ for (cur = sd->s_link.target; cur; cur = cur->s_parent)
+ if (cur->s_flags & SYSFS_FLAG_PLUGGED)
+ return 1;
+
+ /* if unplugged, mark it to accelerate future plugged test */
+ sd->s_flags |= SYSFS_FLAG_LINK_UNPLUGGED;
+ return 0;
+}
+
static struct dentry * sysfs_lookup(struct inode *dir, struct dentry *dentry,
struct nameidata *nd)
{
@@ -842,8 +938,8 @@ static struct dentry * sysfs_lookup(struct inode *dir, struct dentry *dentry,
sd = sysfs_find_dirent(parent_sd, dentry->d_name.name);
- /* no such entry */
- if (!sd)
+ /* no such entry or plugged */
+ if (unlikely(!sd || sysfs_plugged(sd, NULL)))
goto out_unlock;
/* attach dentry and inode */
@@ -1021,6 +1117,10 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
const char * name;
int len;
+ /* skip plugged nodes */
+ if (unlikely(sysfs_plugged(pos, NULL)))
+ continue;
+
name = pos->s_name;
len = strlen(name);
filp->f_pos = ino = pos->s_ino;
@@ -1398,33 +1498,44 @@ EXPORT_SYMBOL_GPL(sysfs_rename);
*/
int sysfs_chmod(struct sysfs_dirent *sd, mode_t mode)
{
- struct dentry *dentry;
- struct inode *inode;
- struct iattr newattrs;
- int rc;
+ mode_t new_mode = (mode & S_IALLUGO) | (sd->s_mode & ~S_IALLUGO);
+ struct dentry *dentry = NULL;
+ struct inode *inode = NULL;
+ int rc = 0;
mutex_lock(&sysfs_op_mutex);
- dentry = sysfs_get_dentry(sd);
- mutex_unlock(&sysfs_op_mutex);
- if (IS_ERR(dentry))
- return PTR_ERR(dentry);
- inode = dentry->d_inode;
+ /* If @sd is plugged, dentry and inode aren't there and can't
+ * be looked up. Just update @sd->s_mode.
+ */
+ if (!sysfs_plugged(sd, NULL)) {
+ struct iattr newattrs;
- mutex_lock(&inode->i_mutex);
+ dentry = sysfs_get_dentry(sd);
+ if (IS_ERR(dentry)) {
+ rc = PTR_ERR(dentry);
+ goto out_unlock_op;
+ }
+ inode = dentry->d_inode;
- newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
- newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
- rc = notify_change(dentry, &newattrs);
+ mutex_lock(&inode->i_mutex);
- if (rc == 0) {
- mutex_lock(&sysfs_mutex);
- sd->s_mode = newattrs.ia_mode;
- mutex_unlock(&sysfs_mutex);
+ newattrs.ia_mode = new_mode;
+ newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
+ rc = notify_change(dentry, &newattrs);
+ if (rc)
+ goto out_unlock_inode;
}
- mutex_unlock(&inode->i_mutex);
+ mutex_lock(&sysfs_mutex);
+ sd->s_mode = new_mode;
+ mutex_unlock(&sysfs_mutex);
+ out_unlock_inode:
+ if (inode)
+ mutex_unlock(&inode->i_mutex);
+ out_unlock_op:
+ mutex_unlock(&sysfs_op_mutex);
dput(dentry);
return rc;
}
diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index 0aeea4b..bd61cca 100644
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -128,7 +128,8 @@ static int sysfs_count_nlink(struct sysfs_dirent *sd)
int nr = 0;
for (child = sd->s_dir.children; child; child = child->s_sibling)
- if (sysfs_type(child) == SYSFS_DIR)
+ if (sysfs_type(child) == SYSFS_DIR &&
+ !(child->s_flags & SYSFS_FLAG_PLUGGED))
nr++;
return nr + 2;
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index f704279..51f346d 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -64,10 +64,12 @@ struct sysfs_dirent {
#define SYSFS_LINK 0x0008
#define SYSFS_FLAG_MASK ~SYSFS_TYPE_MASK
+#define SYSFS_FLAG_PLUGGED 0x0100
#define SYSFS_FLAG_REMOVED 0x0200
#define SYSFS_FLAG_NAME_COPIED 0x0400
#define SYSFS_FLAG_LINK_NAME_FMT_COPIED 0x0800
#define SYSFS_FLAG_LINK_CHAINED 0x1000
+#define SYSFS_FLAG_LINK_UNPLUGGED 0x2000
static inline unsigned int sysfs_type(struct sysfs_dirent *sd)
{
diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index 5afe3bd..5a8c9f1 100644
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -30,9 +30,10 @@ struct vm_area_struct;
*/
#define SYSFS_DIR_MODE (S_IRWXU | S_IRUGO | S_IXUGO)
#define SYSFS_COPY_NAME 010000 /* copy passed @name[_fmt] */
+#define SYSFS_PLUGGED 020000 /* plug the node on creation */
/* collection of all flags for verification */
-#define SYSFS_MODE_FLAGS SYSFS_COPY_NAME
+#define SYSFS_MODE_FLAGS (SYSFS_COPY_NAME | SYSFS_PLUGGED)
struct sysfs_file_ops {
ssize_t (*show)(char *page, void *data, void *parent_data);
@@ -63,6 +64,7 @@ struct sysfs_dirent *sysfs_add_bin(struct sysfs_dirent *parent,
struct sysfs_dirent *sysfs_add_link(struct sysfs_dirent *parent,
const char *name_fmt, mode_t mode,
struct sysfs_dirent *target);
+void sysfs_unplug(struct sysfs_dirent *sd);
struct sysfs_dirent *sysfs_find_child(struct sysfs_dirent *parent,
const char *name);
@@ -106,6 +108,10 @@ static inline struct sysfs_dirent *sysfs_add_link(struct sysfs_dirent *parent,
return NULL;
}
+static inline void sysfs_unplug(struct sysfs_dirent *sd)
+{
+}
+
static inline struct sysfs_dirent *sysfs_find_child(struct sysfs_dirent *parent,
const char *name)
{
--
1.5.0.3
-
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