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SubjectRe: [PATCH 2/4] Use sysfs_dirent based tree in file removal


o This patch uses the sysfs_dirent based tree while removing sysfs files
and directories. This avoids holding dcache_lock by not using dentry
based vfs tree. Thus simplyfying the removal logic in sysfs.

o It uses two helper routines sysfs_get_name(), to get the name for
sysfs element and sysfs_drop_dentry() to delete the dentry given a
sysfs_dirent.


fs/sysfs/dir.c | 48 ++++++----------------------
fs/sysfs/inode.c | 92 +++++++++++++++++++++++++++++++++++++++----------------
fs/sysfs/sysfs.h | 17 ++++++++++
3 files changed, 94 insertions(+), 63 deletions(-)

diff -puN fs/sysfs/dir.c~sysfs-backing-store-use-sysfs_dirent-tree-in-removal fs/sysfs/dir.c
--- linux-2.6.8-rc4/fs/sysfs/dir.c~sysfs-backing-store-use-sysfs_dirent-tree-in-removal 2004-08-10 15:09:15.000000000 -0500
+++ linux-2.6.8-rc4-maneesh/fs/sysfs/dir.c 2004-08-10 15:12:07.000000000 -0500
@@ -19,7 +19,7 @@ static void sysfs_d_iput(struct dentry *
if (sd) {
BUG_ON(sd->s_dentry != dentry);
sd->s_dentry = NULL;
- release_sysfs_dirent(sd);
+ sysfs_put(sd);
}
iput(inode);
}
@@ -61,7 +61,7 @@ int sysfs_make_dirent(struct sysfs_diren
sd->s_mode = mode;
sd->s_type = type;
sd->s_dentry = dentry;
- dentry->d_fsdata = sd;
+ dentry->d_fsdata = sysfs_get(sd);
dentry->d_op = &sysfs_dentry_ops;

return 0;
@@ -146,6 +146,7 @@ static void remove_dir(struct dentry * d
d_delete(d);
sd = d->d_fsdata;
list_del_init(&sd->s_sibling);
+ sysfs_put(sd);
if (d->d_inode)
simple_rmdir(parent->d_inode,d);

@@ -173,49 +174,22 @@ 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)) {
- struct sysfs_dirent * sd = d->d_fsdata;
- 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(sd->s_element);
-
- list_del_init(&sd->s_sibling);
- 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;
- }
+ 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);
}
- spin_unlock(&dcache_lock);
up(&dentry->d_inode->i_sem);

remove_dir(dentry);
diff -puN fs/sysfs/inode.c~sysfs-backing-store-use-sysfs_dirent-tree-in-removal fs/sysfs/inode.c
--- linux-2.6.8-rc4/fs/sysfs/inode.c~sysfs-backing-store-use-sysfs_dirent-tree-in-removal 2004-08-10 15:09:15.000000000 -0500
+++ linux-2.6.8-rc4-maneesh/fs/sysfs/inode.c 2004-08-10 15:09:15.000000000 -0500
@@ -31,8 +31,8 @@ struct inode * sysfs_new_inode(mode_t mo
struct inode * inode = new_inode(sysfs_sb);
if (inode) {
inode->i_mode = mode;
- inode->i_uid = current->fsuid;
- inode->i_gid = current->fsgid;
+ inode->i_uid = 0;
+ inode->i_gid = 0;
inode->i_blksize = PAGE_CACHE_SIZE;
inode->i_blocks = 0;
inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
@@ -68,7 +68,8 @@ int sysfs_create(struct dentry * dentry,
error = init(inode);
if (!error) {
d_instantiate(dentry, inode);
- dget(dentry); /* Extra count - pin the dentry in core */
+ if (S_ISDIR(mode))
+ dget(dentry); /* pin only directory dentry in core */
} else
iput(inode);
Done:
@@ -90,35 +91,74 @@ struct dentry * sysfs_get_dentry(struct
return lookup_hash(&qstr,parent);
}

+/*
+ * Get the name for corresponding element represented by the given sysfs_dirent
+ */
+const unsigned char * sysfs_get_name(struct sysfs_dirent *sd)
+{
+ struct attribute * attr;
+ struct bin_attribute * bin_attr;
+ struct sysfs_symlink * sl;
+
+ if (!sd || !sd->s_element)
+ BUG();
+
+ switch (sd->s_type) {
+ case SYSFS_DIR:
+ /* Always have a dentry so use that */
+ return sd->s_dentry->d_name.name;
+
+ case SYSFS_KOBJ_ATTR:
+ attr = sd->s_element;
+ return attr->name;
+
+ case SYSFS_KOBJ_BIN_ATTR:
+ bin_attr = sd->s_element;
+ return bin_attr->attr.name;
+
+ case SYSFS_KOBJ_LINK:
+ sl = sd->s_element;
+ return sl->link_name;
+ }
+ return NULL;
+}
+
+
+/*
+ * 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) {
+ spin_lock(&dcache_lock);
+ if (!(d_unhashed(dentry) && dentry->d_inode)) {
+ dget_locked(dentry);
+ __d_drop(dentry);
+ spin_unlock(&dcache_lock);
+ simple_unlink(parent->d_inode, dentry);
+ } else
+ spin_unlock(&dcache_lock);
+ }
+}
+
void sysfs_hash_and_remove(struct dentry * dir, const char * name)
{
- struct dentry * victim;
struct sysfs_dirent * sd;
+ struct sysfs_dirent * 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));
-
- sd = victim->d_fsdata;
- d_drop(victim);
- /* release the target kobject in case of
- * a symlink
- */
- if (S_ISLNK(victim->d_inode->i_mode))
- kobject_put(sd->s_element);
+ 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);
- simple_unlink(dir->d_inode,victim);
- } else
- d_drop(victim);
- /*
- * Drop reference from sysfs_get_dentry() above.
- */
- dput(victim);
+ sysfs_drop_dentry(sd, dir);
+ sysfs_put(sd);
+ break;
+ }
}
up(&dir->d_inode->i_sem);
}
diff -puN fs/sysfs/sysfs.h~sysfs-backing-store-use-sysfs_dirent-tree-in-removal fs/sysfs/sysfs.h
--- linux-2.6.8-rc4/fs/sysfs/sysfs.h~sysfs-backing-store-use-sysfs_dirent-tree-in-removal 2004-08-10 15:09:15.000000000 -0500
+++ linux-2.6.8-rc4-maneesh/fs/sysfs/sysfs.h 2004-08-10 15:12:07.000000000 -0500
@@ -14,6 +14,8 @@ extern void sysfs_hash_and_remove(struct
extern int sysfs_create_subdir(struct kobject *, const char *, struct dentry **);
extern void sysfs_remove_subdir(struct dentry *);

+extern const unsigned char * sysfs_get_name(struct sysfs_dirent *sd);
+extern void sysfs_drop_dentry(struct sysfs_dirent * sd, struct dentry * parent);
extern int sysfs_readlink(struct dentry *, char __user *, int );
extern int sysfs_follow_link(struct dentry *, struct nameidata *);
extern struct rw_semaphore sysfs_rename_sem;
@@ -70,3 +72,18 @@ static inline void release_sysfs_dirent(
kfree(sd);
}

+static inline struct sysfs_dirent * sysfs_get(struct sysfs_dirent * sd)
+{
+ if (sd) {
+ WARN_ON(!atomic_read(&sd->s_count));
+ atomic_inc(&sd->s_count);
+ }
+ return sd;
+}
+
+static inline void sysfs_put(struct sysfs_dirent * sd)
+{
+ if (atomic_dec_and_test(&sd->s_count))
+ release_sysfs_dirent(sd);
+}
+
_
--
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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