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>

1 files changed, 2 insertions, 0 deletions

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 {