[PATCH 4/6] CIFS: Use d_automount() rather than abusing follow_link()

David Howells
2010-07-22T17:59:17Z

Make CIFS use the new d_automount() dentry operation rather than abusing
follow_link() on directories.

[NOTE: THIS IS UNTESTED!]

[Question: Why does cifs_dfs_do_refmount() when the caller has already done
that and could pass the result through?]

Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Steve French <sfrench@samba.org>
---

fs/cifs/cifs_dfs_ref.c | 145 +++++++++++++++++++++++-------------------------
fs/cifs/cifsfs.h | 6 ++
fs/cifs/dir.c | 2 +
fs/cifs/inode.c | 8 ++-
4 files changed, 83 insertions(+), 78 deletions(-)

diff --git a/fs/cifs/cifs_dfs_ref.c b/fs/cifs/cifs_dfs_ref.c
index 37543e8..bc094f4 100644
--- a/fs/cifs/cifs_dfs_ref.c
+++ b/fs/cifs/cifs_dfs_ref.c
@@ -230,8 +230,8 @@ compose_mount_options_err:
}

-static struct vfsmount *cifs_dfs_do_refmount(const struct vfsmount *mnt_parent,
- struct dentry *dentry, const struct dfs_info3_param *ref)
+static struct vfsmount *cifs_dfs_do_refmount(struct dentry *mntpt,
+ const struct dfs_info3_param *ref)
{
struct cifs_sb_info *cifs_sb;
struct vfsmount *mnt;
@@ -239,12 +239,12 @@ static struct vfsmount *cifs_dfs_do_refmount(const struct vfsmount *mnt_parent,
char *devname = NULL;
char *fullpath;

- cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
+ cifs_sb = CIFS_SB(mntpt->d_inode->i_sb);
/*
* this function gives us a path with a double backslash prefix. We
* require a single backslash for DFS.
*/
- fullpath = build_path_from_dentry(dentry);
+ fullpath = build_path_from_dentry(mntpt);
if (!fullpath)
return ERR_PTR(-ENOMEM);

@@ -262,35 +262,6 @@ static struct vfsmount *cifs_dfs_do_refmount(const struct vfsmount *mnt_parent,

}

-static int add_mount_helper(struct vfsmount *newmnt, struct nameidata *nd,
- struct list_head *mntlist)
-{
- /* stolen from afs code */
- int err;
-
- mntget(newmnt);
- err = do_add_mount(newmnt, &nd->path, nd->path.mnt->mnt_flags | MNT_SHRINKABLE, mntlist);
- switch (err) {
- case 0:
- path_put(&nd->path);
- nd->path.mnt = newmnt;
- nd->path.dentry = dget(newmnt->mnt_root);
- schedule_delayed_work(&cifs_dfs_automount_task,
- cifs_dfs_mountpoint_expiry_timeout);
- break;
- case -EBUSY:
- /* someone else made a mount here whilst we were busy */
- while (d_mountpoint(nd->path.dentry) &&
- follow_down(&nd->path))
- ;
- err = 0;
- default:
- mntput(newmnt);
- break;
- }
- return err;
-}
-
static void dump_referral(const struct dfs_info3_param *ref)
{
cFYI(1, "DFS: ref path: %s", ref->path_name);
@@ -300,34 +271,30 @@ static void dump_referral(const struct dfs_info3_param *ref)
ref->path_consumed);
}

-
-static void*
-cifs_dfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
+/*
+ * Create a vfsmount that we can automount
+ */
+static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt)
{
struct dfs_info3_param *referrals = NULL;
unsigned int num_referrals = 0;
struct cifs_sb_info *cifs_sb;
struct cifsSesInfo *ses;
- char *full_path = NULL;
+ char *full_path;
int xid, i;
- int rc = 0;
- struct vfsmount *mnt = ERR_PTR(-ENOENT);
+ int rc;
+ struct vfsmount *mnt;

cFYI(1, "in %s", __func__);
- BUG_ON(IS_ROOT(dentry));
+ BUG_ON(IS_ROOT(mntpt));

xid = GetXid();

- dput(nd->path.dentry);
- nd->path.dentry = dget(dentry);
-
- cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
+ cifs_sb = CIFS_SB(mntpt->d_inode->i_sb);
+ mnt = ERR_PTR(-EINVAL);
ses = cifs_sb->tcon->ses;
-
- if (!ses) {
- rc = -EINVAL;
- goto out_err;
- }
+ if (!ses)
+ goto free_xid;

/*
* The MSDFS spec states that paths in DFS referral requests and
@@ -335,56 +302,84 @@ cifs_dfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
* the double backslashes usually used in the UNC. This function
* gives us the latter, so we must adjust the result.
*/
- full_path = build_path_from_dentry(dentry);
- if (full_path == NULL) {
- rc = -ENOMEM;
- goto out_err;
- }
+ mnt = ERR_PTR(-ENOMEM);
+ full_path = build_path_from_dentry(mntpt);
+ if (full_path == NULL)
+ goto free_xid;

rc = get_dfs_path(xid, ses , full_path + 1, cifs_sb->local_nls,
&num_referrals, &referrals,
cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);

+ mnt = ERR_PTR(-ENOENT);
for (i = 0; i < num_referrals; i++) {
int len;
- dump_referral(referrals+i);
+ dump_referral(referrals + i);
/* connect to a node */
len = strlen(referrals[i].node_name);
if (len < 2) {
cERROR(1, "%s: Net Address path too short: %s",
__func__, referrals[i].node_name);
- rc = -EINVAL;
- goto out_err;
+ mnt = ERR_PTR(-EINVAL);
+ break;
}
- mnt = cifs_dfs_do_refmount(nd->path.mnt,
- nd->path.dentry, referrals + i);
+ mnt = cifs_dfs_do_refmount(mntpt, referrals + i);
cFYI(1, "%s: cifs_dfs_do_refmount:%s , mnt:%p", __func__,
referrals[i].node_name, mnt);
-
- /* complete mount procedure if we accured submount */
if (!IS_ERR(mnt))
- break;
+ goto success;
}

- /* we need it cause for() above could exit without valid submount */
- rc = PTR_ERR(mnt);
- if (IS_ERR(mnt))
- goto out_err;
-
- rc = add_mount_helper(mnt, nd, &cifs_dfs_automount_list);
+ /* no valid submounts were found; return error from get_dfs_path() by
+ * preference */
+ if (rc != 0)
+ mnt = ERR_PTR(rc);

-out:
- FreeXid(xid);
+success:
free_dfs_info_array(referrals, num_referrals);
kfree(full_path);
+free_xid:
+ FreeXid(xid);
cFYI(1, "leaving %s" , __func__);
return ERR_PTR(rc);
-out_err:
- path_put(&nd->path);
- goto out;
+}
+
+/*
+ * Attempt to automount the referral
+ */
+struct vfsmount *cifs_dfs_d_automount(struct path *path)
+{
+ struct vfsmount *newmnt;
+ int err;
+
+ cFYI(1, "in %s", __func__);
+
+ newmnt = cifs_dfs_do_automount(path->dentry);
+ if (IS_ERR(newmnt)) {
+ cFYI(1, "leaving %s [automount failed]" , __func__);
+ return newmnt;
+ }
+
+ mntget(newmnt);
+ err = do_add_mount(newmnt, path, MNT_SHRINKABLE,
+ &cifs_dfs_automount_list);
+ switch (err) {
+ case 0:
+ schedule_delayed_work(&cifs_dfs_automount_task,
+ cifs_dfs_mountpoint_expiry_timeout);
+ cFYI(1, "leaving %s [ok]" , __func__);
+ return newmnt;
+ case -EBUSY:
+ /* someone else made a mount here whilst we were busy */
+ mntput(newmnt);
+ cFYI(1, "leaving %s [EBUSY]" , __func__);
+ return NULL;
+ default:
+ mntput(newmnt);
+ cFYI(1, "leaving %s [error %d]" , __func__, err);
+ return ERR_PTR(err);
+ }
}

const struct inode_operations cifs_dfs_referral_inode_operations = {
- .follow_link = cifs_dfs_follow_mountpoint,
};
-
diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h
index a7eb65c..d74bda0 100644
--- a/fs/cifs/cifsfs.h
+++ b/fs/cifs/cifsfs.h
@@ -95,6 +95,12 @@ extern int cifs_readdir(struct file *file, void *direntry, filldir_t filldir);
extern const struct dentry_operations cifs_dentry_ops;
extern const struct dentry_operations cifs_ci_dentry_ops;

+#ifdef CONFIG_CIFS_DFS_UPCALL
+extern struct vfsmount *cifs_dfs_d_automount(struct path *path);
+#else
+#define cifs_dfs_d_automount NULL
+#endif
+
/* Functions related to symlinks */
extern void *cifs_follow_link(struct dentry *direntry, struct nameidata *nd);
extern void cifs_put_link(struct dentry *direntry,
diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index e7ae78b..b147905 100644
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -804,6 +804,7 @@ cifs_d_revalidate(struct dentry *direntry, struct nameidata *nd)

const struct dentry_operations cifs_dentry_ops = {
.d_revalidate = cifs_d_revalidate,
+ .d_automount = cifs_dfs_d_automount,
/* d_delete: cifs_d_delete, */ /* not needed except for debugging */
};

@@ -844,4 +845,5 @@ const struct dentry_operations cifs_ci_dentry_ops = {
.d_revalidate = cifs_d_revalidate,
.d_hash = cifs_ci_hash,
.d_compare = cifs_ci_compare,
+ .d_automount = cifs_dfs_d_automount,
};
diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index 6f0683c..011100f 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -31,7 +31,7 @@
#include "cifs_fs_sb.h"

-static void cifs_set_ops(struct inode *inode, const bool is_dfs_referral)
+static void cifs_set_ops(struct inode *inode)
{
struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);

@@ -59,7 +59,7 @@ static void cifs_set_ops(struct inode *inode, const bool is_dfs_referral)
break;
case S_IFDIR:
#ifdef CONFIG_CIFS_DFS_UPCALL
- if (is_dfs_referral) {
+ if (IS_AUTOMOUNT(inode)) {
inode->i_op = &cifs_dfs_referral_inode_operations;
} else {
#else /* NO DFS support, treat as a directory */
@@ -166,7 +166,9 @@ cifs_fattr_to_inode(struct inode *inode, struct cifs_fattr *fattr)
}
spin_unlock(&inode->i_lock);

- cifs_set_ops(inode, fattr->cf_flags & CIFS_FATTR_DFS_REFERRAL);
+ if (fattr->cf_flags & CIFS_FATTR_DFS_REFERRAL)
+ inode->i_flags |= S_AUTOMOUNT;
+ cifs_set_ops(inode);
}

void