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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 /drivers
parent44672e4fbd40e2dda8bbce7d0f71d24dbfc7e00e (diff)
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 'drivers')
-rw-r--r--drivers/staging/pohmelfs/path_entry.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/drivers/staging/pohmelfs/path_entry.c b/drivers/staging/pohmelfs/path_entry.c
index cdc4dd50d63..8ec83d2dffb 100644
--- a/drivers/staging/pohmelfs/path_entry.c
+++ b/drivers/staging/pohmelfs/path_entry.c
@@ -44,9 +44,9 @@ int pohmelfs_construct_path_string(struct pohmelfs_inode *pi, void *data, int le
return -ENOENT;
}
- read_lock(&current->fs->lock);
+ spin_lock(&current->fs->lock);
path.mnt = mntget(current->fs->root.mnt);
- read_unlock(&current->fs->lock);
+ spin_unlock(&current->fs->lock);
path.dentry = d;
@@ -91,9 +91,9 @@ int pohmelfs_path_length(struct pohmelfs_inode *pi)
return -ENOENT;
}
- read_lock(&current->fs->lock);
+ spin_lock(&current->fs->lock);
root = dget(current->fs->root.dentry);
- read_unlock(&current->fs->lock);
+ spin_unlock(&current->fs->lock);
spin_lock(&dcache_lock);