From: Maneesh Soni = 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 | 27 +++++++++++++++++++++++++-- include/linux/sysfs.h | 19 +++++++++++++++++++ 2 files changed, 44 insertions(+), 2 deletions(-) diff -upN reference/fs/sysfs/mount.c current/fs/sysfs/mount.c --- reference/fs/sysfs/mount.c 2003-06-05 14:55:46.000000000 -0700 +++ current/fs/sysfs/mount.c 2004-03-30 21:42:12.000000000 -0800 @@ -20,6 +20,14 @@ struct super_block * sysfs_sb = NULL; static struct super_operations sysfs_ops = { .statfs = simple_statfs, .drop_inode = generic_delete_inode, + .umount_begin = sysfs_umount_begin, +}; + +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) @@ -35,8 +43,8 @@ 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 +58,7 @@ static int sysfs_fill_super(struct super iput(inode); return -ENOMEM; } + root->d_fsdata = &sysfs_root; sb->s_root = root; return 0; } @@ -60,6 +69,20 @@ static struct super_block *sysfs_get_sb( return get_sb_single(fs_type, flags, data, sysfs_fill_super); } +/* For freeing zero refenced dentries / inodes while force unmounting + * + * sysfs is mounted once within kernel during init(), and this keeps the super + * block always active. So in case of user just doing normal umount, + * ->kill_sb is never called. So, in order to immediately free the memory used + * by un-used dentries and inodes, sysfs should to be umounted with force + * option. In anycase there will be normal pruing of unused dentries/inodes + * as usual due to memory pressure. + */ +void sysfs_umount_begin(struct super_block * sb) +{ + shrink_dcache_parent(sb->s_root); +} + static struct file_system_type sysfs_fs_type = { .name = "sysfs", .get_sb = sysfs_get_sb, diff -upN reference/include/linux/sysfs.h current/include/linux/sysfs.h --- reference/include/linux/sysfs.h 2003-10-01 11:41:18.000000000 -0700 +++ current/include/linux/sysfs.h 2004-03-30 21:42:12.000000000 -0800 @@ -9,6 +9,8 @@ #ifndef _SYSFS_H_ #define _SYSFS_H_ +#include + struct kobject; struct module; @@ -42,6 +44,23 @@ sysfs_remove_dir(struct kobject *); extern void 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; + 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 *);