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Subject[PATCH 3/5] Free sysfs_dirent on file removal


o The following patch implements the code to free up the sysfs_dirents upon
directory or file removal. It uses the sysfs_dirent based tree in order
to remove the directory contents before removing the directory itself.
It could do this without taking dcache_lock in sysfs_remove_dir() as
it doesnot use dentry based tree.


fs/sysfs/dir.c | 48 ++++++++++++++----------------------------------
fs/sysfs/inode.c | 51 ++++++++++++++++++++++++++++++---------------------
2 files changed, 44 insertions(+), 55 deletions(-)
diff -puN fs/sysfs/inode.c~sysfs-backing-store-kill-sysfs_dirent fs/sysfs/inode.c
--- linux-2.6.8-rc2-mm1/fs/sysfs/inode.c~sysfs-backing-store-kill-sysfs_dirent 2004-07-29 15:30:39.000000000 -0500
+++ linux-2.6.8-rc2-mm1-maneesh/fs/sysfs/inode.c 2004-07-29 15:31:07.000000000 -0500
@@ -11,6 +11,8 @@
#include <linux/pagemap.h>
#include <linux/namei.h>
#include <linux/backing-dev.h>
+#include "sysfs.h"
+
extern struct super_block * sysfs_sb;

static struct address_space_operations sysfs_aops = {
@@ -88,33 +90,40 @@ struct dentry * sysfs_get_dentry(struct
return lookup_hash(&qstr,parent);
}

+/* Unhashes the dentry corresponding to given sysfs_dirent
+ * Called with parent inode's i_sem held.
+ */
+void sysfs_drop_dentry(struct sysfs_dirent * sd, struct dentry * parent)
+{
+ struct dentry * dentry = sd->s_dentry;
+
+ if (dentry) {
+ if (!(d_unhashed(dentry) && dentry->d_inode)) {
+ spin_lock(&dcache_lock);
+ dget_locked(dentry);
+ __d_drop(dentry);
+ spin_unlock(&dcache_lock);
+ simple_unlink(parent->d_inode, dentry);
+ } else
+ dput(dentry);
+ }
+}
+
void sysfs_hash_and_remove(struct dentry * dir, const char * name)
{
- struct dentry * victim;
+ struct sysfs_dirent * sd, * parent_sd = dir->d_fsdata;

down(&dir->d_inode->i_sem);
- victim = sysfs_get_dentry(dir,name);
- if (!IS_ERR(victim)) {
- /* make sure dentry is really there */
- if (victim->d_inode &&
- (victim->d_parent->d_inode == dir->d_inode)) {
- pr_debug("sysfs: Removing %s (%d)\n", victim->d_name.name,
- atomic_read(&victim->d_count));
-
- d_drop(victim);
- /* release the target kobject in case of
- * a symlink
- */
- if (S_ISLNK(victim->d_inode->i_mode))
- kobject_put(victim->d_fsdata);
- simple_unlink(dir->d_inode,victim);
+ list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
+ if (!sd->s_element)
+ continue;
+ if (!strcmp(sysfs_get_name(sd), name)) {
+ list_del_init(&sd->s_sibling);
+ sysfs_drop_dentry(sd, dir);
+ sysfs_put(sd);
+ break;
}
- /*
- * Drop reference from sysfs_get_dentry() above.
- */
- dput(victim);
}
up(&dir->d_inode->i_sem);
}

-
diff -puN fs/sysfs/dir.c~sysfs-backing-store-kill-sysfs_dirent fs/sysfs/dir.c
--- linux-2.6.8-rc2-mm1/fs/sysfs/dir.c~sysfs-backing-store-kill-sysfs_dirent 2004-07-29 15:30:39.000000000 -0500
+++ linux-2.6.8-rc2-mm1-maneesh/fs/sysfs/dir.c 2004-07-29 15:31:07.000000000 -0500
@@ -100,8 +100,13 @@ int sysfs_create_dir(struct kobject * ko
static void remove_dir(struct dentry * d)
{
struct dentry * parent = dget(d->d_parent);
+ struct sysfs_dirent * sd;
+
down(&parent->d_inode->i_sem);
d_delete(d);
+ sd = d->d_fsdata;
+ list_del_init(&sd->s_sibling);
+ sysfs_put(d->d_fsdata);
if (d->d_inode)
simple_rmdir(parent->d_inode,d);

@@ -129,47 +134,22 @@ void sysfs_remove_subdir(struct dentry *

void sysfs_remove_dir(struct kobject * kobj)
{
- struct list_head * node;
struct dentry * dentry = dget(kobj->dentry);
+ struct sysfs_dirent * parent_sd = dentry->d_fsdata;
+ struct sysfs_dirent * sd, * tmp;

if (!dentry)
return;

pr_debug("sysfs %s: removing dir\n",dentry->d_name.name);
down(&dentry->d_inode->i_sem);
-
- spin_lock(&dcache_lock);
-restart:
- node = dentry->d_subdirs.next;
- while (node != &dentry->d_subdirs) {
- struct dentry * d = list_entry(node,struct dentry,d_child);
-
- node = node->next;
- pr_debug(" o %s (%d): ",d->d_name.name,atomic_read(&d->d_count));
- if (!d_unhashed(d) && (d->d_inode)) {
- d = dget_locked(d);
- pr_debug("removing");
-
- /**
- * Unlink and unhash.
- */
- __d_drop(d);
- spin_unlock(&dcache_lock);
- /* release the target kobject in case of
- * a symlink
- */
- if (S_ISLNK(d->d_inode->i_mode))
- kobject_put(d->d_fsdata);
-
- simple_unlink(dentry->d_inode,d);
- dput(d);
- pr_debug(" done\n");
- spin_lock(&dcache_lock);
- /* re-acquired dcache_lock, need to restart */
- goto restart;
- }
- }
- spin_unlock(&dcache_lock);
+ list_for_each_entry_safe(sd, tmp, &parent_sd->s_children, s_sibling) {
+ if (!sd->s_element)
+ continue;
+ list_del_init(&sd->s_sibling);
+ sysfs_drop_dentry(sd, dentry);
+ sysfs_put(sd);
+ }
up(&dentry->d_inode->i_sem);

remove_dir(dentry);
_
--
Maneesh Soni
Linux Technology Center,
IBM Austin
email: maneesh@in.ibm.com
Phone: 1-512-838-1896 Fax:
T/L : 6781896
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