On Thu, Jun 07, 2012 at 04:57:13PM -0700, Linus Torvalds wrote:
> Any per-filesystem mutex should do, so if sysfs always holds the
> sysfs_mutex - and never allows user-initiated renames - it should be
> safe.
Frankly, I would very much prefer to have the same locking rules wherever
possible. The locking system is already overcomplicated and making its
analysis fs-dependent as well... <shudder> Sure, we can do that, and that
might even work, until we find out that some piece of code that started
as a helper to some function never called on sysfs dentries had been
reused on the path that *is* reachable on sysfs. At which point we are
suddenly in trouble.
I wouldn't be bothered so much if the overall picture had been simpler;
unfortunately, it isn't.
Eric, how about this - if nothing else, that makes code in there simpler
and less dependent on details of VFS guts:
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index e6bb9b2..5579826 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -363,7 +363,7 @@ static void sysfs_dentry_iput(struct dentry *dentry, struct inode *inode)
iput(inode);
}
-static const struct dentry_operations sysfs_dentry_ops = {
+const struct dentry_operations sysfs_dentry_ops = {
.d_revalidate = sysfs_dentry_revalidate,
.d_delete = sysfs_dentry_delete,
.d_iput = sysfs_dentry_iput,
@@ -795,16 +795,8 @@ static struct dentry * sysfs_lookup(struct inode *dir, struct dentry *dentry,
}
/* instantiate and hash dentry */
- ret = d_find_alias(inode);
- if (!ret) {
- d_set_d_op(dentry, &sysfs_dentry_ops);
- dentry->d_fsdata = sysfs_get(sd);
- d_add(dentry, inode);
- } else {
- d_move(ret, dentry);
- iput(inode);
- }
-
+ dentry->d_fsdata = sysfs_get(sd);
+ ret = d_materialise_unique(dentry, inode);
out_unlock:
mutex_unlock(&sysfs_mutex);
return ret;
diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 52c3bdb..c15a7a3 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -68,6 +68,7 @@ static int sysfs_fill_super(struct super_block *sb, void *data, int silent)
}
root->d_fsdata = &sysfs_root;
sb->s_root = root;
+ sb->s_d_op = &sysfs_dentry_ops;
return 0;
}
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index 661a963..d73c093 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -157,6 +157,7 @@ extern struct kmem_cache *sysfs_dir_cachep;
*/
extern struct mutex sysfs_mutex;
extern spinlock_t sysfs_assoc_lock;
+extern const struct dentry_operations sysfs_dentry_ops;
extern const struct file_operations sysfs_dir_operations;
extern const struct inode_operations sysfs_dir_inode_operations;
--
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