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authorNick Piggin <npiggin@kernel.dk>2010-08-18 04:37:33 +1000
committerAl Viro <viro@zeniv.linux.org.uk>2010-08-18 08:35:46 -0400
commit2a4419b5b2a77f3f4537c14f7ad7df95770655dd (patch)
treead66519a92b995920ecada788e4a08e265747545 /include/linux
parent44672e4fbd40e2dda8bbce7d0f71d24dbfc7e00e (diff)
downloadvexpress-lsk-2a4419b5b2a77f3f4537c14f7ad7df95770655dd.tar.gz
fs: fs_struct rwlock to spinlock
fs: fs_struct rwlock to spinlock struct fs_struct.lock is an rwlock with the read-side used to protect root and pwd members while taking references to them. Taking a reference to a path typically requires just 2 atomic ops, so the critical section is very small. Parallel read-side operations would have cacheline contention on the lock, the dentry, and the vfsmount cachelines, so the rwlock is unlikely to ever give a real parallelism increase. Replace it with a spinlock to avoid one or two atomic operations in typical path lookup fastpath. Signed-off-by: Nick Piggin <npiggin@kernel.dk> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/fs_struct.h14
1 files changed, 7 insertions, 7 deletions
diff --git a/include/linux/fs_struct.h b/include/linux/fs_struct.h
index eca3d520213..a42b5bf02f8 100644
--- a/include/linux/fs_struct.h
+++ b/include/linux/fs_struct.h
@@ -5,7 +5,7 @@
struct fs_struct {
int users;
- rwlock_t lock;
+ spinlock_t lock;
int umask;
int in_exec;
struct path root, pwd;
@@ -23,29 +23,29 @@ extern int unshare_fs_struct(void);
static inline void get_fs_root(struct fs_struct *fs, struct path *root)
{
- read_lock(&fs->lock);
+ spin_lock(&fs->lock);
*root = fs->root;
path_get(root);
- read_unlock(&fs->lock);
+ spin_unlock(&fs->lock);
}
static inline void get_fs_pwd(struct fs_struct *fs, struct path *pwd)
{
- read_lock(&fs->lock);
+ spin_lock(&fs->lock);
*pwd = fs->pwd;
path_get(pwd);
- read_unlock(&fs->lock);
+ spin_unlock(&fs->lock);
}
static inline void get_fs_root_and_pwd(struct fs_struct *fs, struct path *root,
struct path *pwd)
{
- read_lock(&fs->lock);
+ spin_lock(&fs->lock);
*root = fs->root;
path_get(root);
*pwd = fs->pwd;
path_get(pwd);
- read_unlock(&fs->lock);
+ spin_unlock(&fs->lock);
}
#endif /* _LINUX_FS_STRUCT_H */