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Subject[PATCH 01/34] vfs: split do_lookup()
Date
From: Miklos Szeredi <mszeredi@suse.cz>

Split do_lookup() into two functions:

lookup_fast() - does cached lookup without i_mutex
lookup_slow() - does lookup with i_mutex

Both follow managed dentries.

The new functions are needed by atomic_open.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---
fs/namei.c | 59 +++++++++++++++++++++++++++++++++++++++++++++--------------
1 files changed, 45 insertions(+), 14 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index 1898198..338410a 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1138,8 +1138,8 @@ static struct dentry *__lookup_hash(struct qstr *name,
* small and for now I'd prefer to have fast path as straight as possible.
* It _is_ time-critical.
*/
-static int do_lookup(struct nameidata *nd, struct qstr *name,
- struct path *path, struct inode **inode)
+static int lookup_fast(struct nameidata *nd, struct qstr *name,
+ struct path *path, struct inode **inode)
{
struct vfsmount *mnt = nd->path.mnt;
struct dentry *dentry, *parent = nd->path.dentry;
@@ -1208,7 +1208,7 @@ unlazy:
goto need_lookup;
}
}
-done:
+
path->mnt = mnt;
path->dentry = dentry;
err = follow_managed(path, nd->flags);
@@ -1222,6 +1222,17 @@ done:
return 0;

need_lookup:
+ return 1;
+}
+
+/* Fast lookup failed, do it the slow way */
+static int lookup_slow(struct nameidata *nd, struct qstr *name,
+ struct path *path)
+{
+ struct dentry *dentry, *parent;
+ int err;
+
+ parent = nd->path.dentry;
BUG_ON(nd->inode != parent->d_inode);

mutex_lock(&parent->d_inode->i_mutex);
@@ -1229,7 +1240,16 @@ need_lookup:
mutex_unlock(&parent->d_inode->i_mutex);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
- goto done;
+ path->mnt = nd->path.mnt;
+ path->dentry = dentry;
+ err = follow_managed(path, nd->flags);
+ if (unlikely(err < 0)) {
+ path_put_conditional(path, nd);
+ return err;
+ }
+ if (err)
+ nd->flags |= LOOKUP_JUMPED;
+ return 0;
}

static inline int may_lookup(struct nameidata *nd)
@@ -1301,21 +1321,26 @@ static inline int walk_component(struct nameidata *nd, struct path *path,
*/
if (unlikely(type != LAST_NORM))
return handle_dots(nd, type);
- err = do_lookup(nd, name, path, &inode);
+ err = lookup_fast(nd, name, path, &inode);
if (unlikely(err)) {
- terminate_walk(nd);
- return err;
- }
- if (!inode) {
- path_to_nameidata(path, nd);
- terminate_walk(nd);
- return -ENOENT;
+ if (err < 0)
+ goto out_err;
+
+ err = lookup_slow(nd, name, path);
+ if (err < 0)
+ goto out_err;
+
+ inode = path->dentry->d_inode;
}
+ err = -ENOENT;
+ if (!inode)
+ goto out_path_put;
+
if (should_follow_link(inode, follow)) {
if (nd->flags & LOOKUP_RCU) {
if (unlikely(unlazy_walk(nd, path->dentry))) {
- terminate_walk(nd);
- return -ECHILD;
+ err = -ECHILD;
+ goto out_err;
}
}
BUG_ON(inode != path->dentry->d_inode);
@@ -1324,6 +1349,12 @@ static inline int walk_component(struct nameidata *nd, struct path *path,
path_to_nameidata(path, nd);
nd->inode = inode;
return 0;
+
+out_path_put:
+ path_to_nameidata(path, nd);
+out_err:
+ terminate_walk(nd);
+ return err;
}

/*
--
1.7.7


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