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author | Tejun Heo <htejun@gmail.com> | 2007-06-14 03:45:18 +0900 |
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committer | Greg Kroah-Hartman <gregkh@suse.de> | 2007-07-11 16:09:07 -0700 |
commit | 8619f979898397582e366877fd5feeba7560d70c (patch) | |
tree | 7d0e92d4c17d92a00dfeba2b840bf89657b30607 /fs/sysfs/sysfs.h | |
parent | b6b4a4399c2a83d1af77c99dee0d0b5cc15ec268 (diff) | |
download | op-kernel-dev-8619f979898397582e366877fd5feeba7560d70c.zip op-kernel-dev-8619f979898397582e366877fd5feeba7560d70c.tar.gz |
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.h | 13 |
1 files changed, 2 insertions, 11 deletions
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h index f8779ea..ae006b0 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; |