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authorTejun Heo <htejun@gmail.com>2007-06-14 03:45:18 +0900
committerGreg Kroah-Hartman <gregkh@suse.de>2007-07-11 16:09:07 -0700
commit8619f979898397582e366877fd5feeba7560d70c (patch)
tree7d0e92d4c17d92a00dfeba2b840bf89657b30607 /fs/sysfs/sysfs.h
parentb6b4a4399c2a83d1af77c99dee0d0b5cc15ec268 (diff)
sysfs: slim down sysfs_dirent->s_active
Make sysfs_dirent->s_active an atomic_t instead of rwsem. This reduces the size of sysfs_dirent from 136 to 104 on 64bit and from 76 to 60 on 32bit with lock debugging turned off. With lock debugging turned on the reduction is much larger. s_active starts at zero and each active reference increments s_active. Putting a reference decrements s_active. Deactivation subtracts SD_DEACTIVATED_BIAS which is currently INT_MIN and assumed to be small enough to make s_active negative. If s_active is negative, sysfs_get() no longer grants new references. Deactivation succeeds immediately if there is no active user; otherwise, it waits using a completion for the last put. Due to the removal of lockdep tricks, this change makes things less trickier in release_sysfs_dirent(). As all the complexity is contained in three s_active functions, I think it's more readable this way. Signed-off-by: Tejun Heo <htejun@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'fs/sysfs/sysfs.h')
-rw-r--r--fs/sysfs/sysfs.h13
1 files changed, 2 insertions, 11 deletions
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index f8779eaa53ff..ae006b070bf0 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -21,7 +21,7 @@ struct sysfs_elem_bin_attr {
*/
struct sysfs_dirent {
atomic_t s_count;
- struct rw_semaphore s_active;
+ atomic_t s_active;
struct sysfs_dirent * s_parent;
struct list_head s_sibling;
struct list_head s_children;
@@ -42,16 +42,7 @@ struct sysfs_dirent {
atomic_t s_event;
};
-/*
- * A sysfs file which deletes another file when written to need to
- * write lock the s_active of the victim while its s_active is read
- * locked for the write operation. Tell lockdep that this is okay.
- */
-enum sysfs_s_active_class
-{
- SYSFS_S_ACTIVE_NORMAL, /* file r/w access, etc - default */
- SYSFS_S_ACTIVE_DEACTIVATE, /* file deactivation */
-};
+#define SD_DEACTIVATED_BIAS INT_MIN
extern struct vfsmount * sysfs_mount;
extern struct kmem_cache *sysfs_dir_cachep;