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Subject[RFC 1/6] sysfs backing store ver 0.5


=> changes in version 0.5
o Removed ->umount_begin() as mount -o remount does the same function
basically shrink dcache by removing the unsed dentries.

=> changes in version 0.4
o Nil, just re-diffed

=> changes in version 0.3
o Nil, just re-diffed

=> changes in version 0.2
o Nil, just re-diffed

=> changes in version 0.1
o Corrected sysfs_umount_begin(), it doesnot need lock_super() and also the
s_root check is not required. The reason being, that sysfs filesystem is
always mounted internally during init and there is no chance of sysfs super
block going away.

o corrected comments for umount_begin()

============================================================================
o The following patch contains the sysfs_dirent structure definition.
sysfs_dirent can represent kobject, attribute group, text attribute or
binary attribute for kobjects registered with sysfs. sysfs_dirent is
allocated with a ref count (s_count) of 1. Ref count is incremented when
a dentry is associated with the sysfs_dirent and it is decremented when
the corresponding dentry is freed.
o sysfs_dirent's corresponding to the attribute files of a kobject or attribute
group are linked together with s_sibling and are anchored at s_children of
the corresponding kobject's or attribute-group's sysfs_dirent.

o The patch also contains the mount related changes for sysfs backing store.
Because we mount sysfs once while init(), plain umount of sysfs doesnot
free all the un-used dentries (present in LRU list). To use force umount
flag, umount_begin() routine is provided which does a shrink_dcache_parent()
to release all the unused dentries.



fs/sysfs/mount.c | 12 ++++++++++--
include/linux/sysfs.h | 20 ++++++++++++++++++++
2 files changed, 30 insertions(+), 2 deletions(-)
diff -puN include/linux/sysfs.h~sysfs-leaves-mount include/linux/sysfs.h
--- linux-2.6.6-rc3-mm1/include/linux/sysfs.h~sysfs-leaves-mount 2004-05-04 16:03:17.000000000 +0530
+++ linux-2.6.6-rc3-mm1-maneesh/include/linux/sysfs.h 2004-05-04 16:03:17.000000000 +0530
@@ -9,6 +9,8 @@
#ifndef _SYSFS_H_
#define _SYSFS_H_

+#include <asm/atomic.h>
+
struct kobject;
struct module;

@@ -47,6 +49,24 @@ sysfs_remove_dir(struct kobject *);
extern int
sysfs_rename_dir(struct kobject *, const char *new_name);

+struct sysfs_dirent {
+ atomic_t s_count;
+ struct list_head s_sibling;
+ struct list_head s_children;
+ void * s_element;
+ int s_type;
+ umode_t s_mode;
+ struct dentry * s_dentry;
+};
+
+#define SYSFS_ROOT 0x0001
+#define SYSFS_KOBJECT 0x0002
+#define SYSFS_KOBJ_ATTR 0x0004
+#define SYSFS_KOBJ_BIN_ATTR 0x0008
+#define SYSFS_KOBJ_ATTR_GROUP 0x0010
+#define SYSFS_KOBJ_LINK 0x0020
+#define SYSFS_NOT_PINNED (SYSFS_KOBJ_ATTR | SYSFS_KOBJ_BIN_ATTR | SYSFS_KOBJ_LINK)
+
extern int
sysfs_create_file(struct kobject *, const struct attribute *);

diff -puN fs/sysfs/mount.c~sysfs-leaves-mount fs/sysfs/mount.c
--- linux-2.6.6-rc3-mm1/fs/sysfs/mount.c~sysfs-leaves-mount 2004-05-04 16:03:17.000000000 +0530
+++ linux-2.6.6-rc3-mm1-maneesh/fs/sysfs/mount.c 2004-05-04 16:03:17.000000000 +0530
@@ -22,6 +22,13 @@ static struct super_operations sysfs_ops
.drop_inode = generic_delete_inode,
};

+struct sysfs_dirent sysfs_root = {
+ .s_sibling = LIST_HEAD_INIT(sysfs_root.s_sibling),
+ .s_children = LIST_HEAD_INIT(sysfs_root.s_children),
+ .s_element = NULL,
+ .s_type = SYSFS_ROOT,
+};
+
static int sysfs_fill_super(struct super_block *sb, void *data, int silent)
{
struct inode *inode;
@@ -35,8 +42,8 @@ static int sysfs_fill_super(struct super

inode = sysfs_new_inode(S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO);
if (inode) {
- inode->i_op = &simple_dir_inode_operations;
- inode->i_fop = &simple_dir_operations;
+ inode->i_op = &sysfs_dir_inode_operations;
+ inode->i_fop = &sysfs_dir_operations;
/* directory inodes start off with i_nlink == 2 (for "." entry) */
inode->i_nlink++;
} else {
@@ -50,6 +57,7 @@ static int sysfs_fill_super(struct super
iput(inode);
return -ENOMEM;
}
+ root->d_fsdata = &sysfs_root;
sb->s_root = root;
return 0;
}
_
--
Maneesh Soni
Linux Technology Center,
IBM Software Lab, Bangalore, India
email: maneesh@in.ibm.com
Phone: 91-80-25044999 Fax: 91-80-25268553
T/L : 9243696
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