From: "J. Bruce Fields" <bfields@xxxxxxxxxx>
We shouldn't really have to re-lookup the parents on each pass through.
This should make behavior linear instead of quadratic as a function of
directory depth.
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
---
fs/exportfs/expfs.c | 105 +++++++++++++++++++--------------------------------
1 file changed, 39 insertions(+), 66 deletions(-)
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index afa7c9c..08544ae 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -69,11 +69,7 @@ find_acceptable_alias(struct dentry *result,
return NULL;
}
-/*
- * Find root of a disconnected subtree and return a reference to it.
- */
-static struct dentry *
-find_disconnected_root(struct dentry *dentry)
+static bool dentry_connected(struct dentry *dentry)
{
dget(dentry);
while (!IS_ROOT(dentry)) {
@@ -81,13 +77,14 @@ find_disconnected_root(struct dentry *dentry)
if (!(parent->d_flags & DCACHE_DISCONNECTED)) {
dput(parent);
- break;
+ dput(dentry);
+ return true;
}
dput(dentry);
dentry = parent;
}
- return dentry;
+ return false;
}
static void clear_disconnected(struct dentry *dentry)
@@ -109,11 +106,13 @@ static void clear_disconnected(struct dentry *dentry)
/*
* Return the parent directory on success.
*
- * Return NULL to keep trying.
+ * If it races with a rename or unlink, assume the other operation
+ * connected it, but return NULL to indicate the caller should check
+ * this just to make sure the filesystem isn't nuts.
*
* Otherwise return an error.
*/
-static int reconnect_one(struct vfsmount *mnt, struct dentry *dentry, char *nbuf, int *noprogress)
+static struct dentry *reconnect_one(struct vfsmount *mnt, struct dentry *dentry, char *nbuf)
{
struct dentry *parent;
struct dentry *tmp;
@@ -137,20 +136,17 @@ static int reconnect_one(struct vfsmount *mnt, struct dentry *dentry, char *nbuf
err = PTR_ERR(parent);
dprintk("%s: get_parent of %ld failed, err %d\n",
__func__, dentry->d_inode->i_ino, err);
- return err;
+ return parent;
}
dprintk("%s: find name of %lu in %lu\n", __func__,
dentry->d_inode->i_ino, parent->d_inode->i_ino);
err = exportfs_get_name(mnt, parent, nbuf, dentry);
if (err) {
- dput(parent);
if (err == -ENOENT)
- /* some race between get_parent and
- * get_name? just try again
- */
- return 0;
- return err;
+ return NULL;
+ dput(parent);
+ return ERR_PTR(err);
}
dprintk("%s: found name: %s\n", __func__, nbuf);
mutex_lock(&parent->d_inode->i_mutex);
@@ -160,26 +156,13 @@ static int reconnect_one(struct vfsmount *mnt, struct dentry *dentry, char *nbuf
err = PTR_ERR(tmp);
dprintk("%s: lookup failed: %d\n",
__func__, err);
- dput(parent);
- return err;
+ return NULL;
}
- /* we didn't really want tmp, we really wanted
- * a side-effect of the lookup.
- * hopefully, tmp == dentry, though it isn't really
- * a problem if it isn't
- */
- if (tmp == dentry)
- *noprogress = 0;
- else
- printk("%s: tmp != dentry\n", __func__);
+ /* Note tmp != dentry is possible at this point, but that's OK */
dput(tmp);
- dput(parent);
- if (IS_ROOT(dentry)) {
- /* something went wrong, we have to give up */
- dput(dentry);
- return -ESTALE;
- }
- return 0;
+ if (IS_ROOT(dentry))
+ return ERR_PTR(-ESTALE);
+ return parent;
}
/*
@@ -190,51 +173,41 @@ static int reconnect_one(struct vfsmount *mnt, struct dentry *dentry, char *nbuf
static int
reconnect_path(struct vfsmount *mnt, struct dentry *target_dir, char *nbuf)
{
- int noprogress = 0;
- int err = -ESTALE;
+ struct dentry *dentry, *parent;
- /*
- * It is possible that a confused file system might not let us complete
- * the path to the root. For example, if get_parent returns a directory
- * in which we cannot find a name for the child. While this implies a
- * very sick filesystem we don't want it to cause knfsd to spin. Hence
- * the noprogress counter. If we go through the loop 10 times (2 is
- * probably enough) without getting anywhere, we just give up
- */
- while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) {
- struct dentry *dentry = find_disconnected_root(target_dir);
+ dentry = dget(target_dir);
- if (!IS_ROOT(dentry)) {
- /* must have found a connected parent - great */
- clear_disconnected(target_dir);
- noprogress = 0;
- dput(dentry);
- continue;
- }
+ while (dentry->d_flags & DCACHE_DISCONNECTED) {
if (dentry == mnt->mnt_sb->s_root) {
- printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n");
- clear_disconnected(target_dir);
- noprogress = 0;
+ WARN_ON_ONCE(1);
+ break;
+ }
+ if (!IS_ROOT(dentry)) {
+ parent = dget_parent(dentry);
dput(dentry);
+ dentry = parent;
continue;
}
/*
* We have hit the top of a disconnected path, try to
* find parent and connect.
*/
- err = reconnect_one(mnt, dentry, nbuf, &noprogress);
- if (err)
- return err;
+ parent = reconnect_one(mnt, dentry, nbuf);
dput(dentry);
+ if (!parent)
+ break;
+ if (IS_ERR(parent))
+ return PTR_ERR(parent);
+ dentry = parent;
}
-
- if (target_dir->d_flags & DCACHE_DISCONNECTED) {
- /* something went wrong - oh-well */
- if (!err)
- err = -ESTALE;
- return err;
+ /*
+ * Should be unnecessary, but let's be careful:
+ */
+ if (!dentry_connected(target_dir)) {
+ WARN_ON_ONCE(1);
+ return -ESTALE;
}
-
+ clear_disconnected(target_dir);
return 0;
}
--
1.7.9.5
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