sysfs: count subdirectories

sysfs: count subdirectories

This patch introduces a subdirectory counter for each sysfs directory.

Without the patch, sysfs_refresh_inode would walk all entries of the directory
to calculate the number of subdirectories.

This patch improves time of "ls -la /sys/block" when there are 10000 block
devices from 9 seconds to 0.19 seconds.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

3 files changed, 9 insertions, 13 deletions

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index ea9120a830d8..7d240e6b7176 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -47,6 +47,9 @@ static void sysfs_link_sibling(struct sysfs_dirent *sd)
 
         BUG_ON(sd->s_sibling);
 
+        if (sysfs_type(sd) == SYSFS_DIR)
+                parent_sd->s_dir.subdirs++;
+
         /* Store directory entries in order by ino.  This allows
          * readdir to properly restart without having to add a
          * cursor into the s_dir.children list.
@@ -73,6 +76,9 @@ static void sysfs_unlink_sibling(struct sysfs_dirent *sd)
 {
         struct sysfs_dirent **pos;
 
+        if (sysfs_type(sd) == SYSFS_DIR)
+                sd->s_parent->s_dir.subdirs--;
+
         for (pos = &sd->s_parent->s_dir.children; *pos;
              pos = &(*pos)->s_sibling) {
                 if (*pos == sd) {
diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index e3f091a81c72..1ee18c81df78 100644
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -202,18 +202,6 @@ static inline void set_inode_attr(struct inode * inode, struct iattr * iattr)
         inode->i_ctime = iattr->ia_ctime;
 }
 
-static int sysfs_count_nlink(struct sysfs_dirent *sd)
-{
-        struct sysfs_dirent *child;
-        int nr = 0;
-
-        for (child = sd->s_dir.children; child; child = child->s_sibling)
-                if (sysfs_type(child) == SYSFS_DIR)
-                        nr++;
-
-        return nr + 2;
-}
-
 static void sysfs_refresh_inode(struct sysfs_dirent *sd, struct inode *inode)
 {
         struct sysfs_inode_attrs *iattrs = sd->s_iattr;
@@ -230,7 +218,7 @@ static void sysfs_refresh_inode(struct sysfs_dirent *sd, struct inode *inode)
         }
 
         if (sysfs_type(sd) == SYSFS_DIR)
-                inode->i_nlink = sysfs_count_nlink(sd);
+                inode->i_nlink = sd->s_dir.subdirs + 2;
 }
 
 int sysfs_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index 845ab3ad229d..6348e2c753f6 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -19,6 +19,8 @@ struct sysfs_elem_dir {
         struct kobject          *kobj;
         /* children list starts here and goes through sd->s_sibling */
         struct sysfs_dirent     *children;
+
+        unsigned long           subdirs;
 };
 
 struct sysfs_elem_symlink {