cifs: don't use vfsmount to pin superblock for oplock breaks

Filesystems aren't really supposed to do anything with a vfsmount. It's
considered a layering violation since vfsmounts are entirely managed at
the VFS layer.

CIFS currently keeps an active reference to a vfsmount in order to
prevent the superblock vanishing before an oplock break has completed.
What we really want to do instead is to keep sb->s_active high until the
oplock break has completed. This patch borrows the scheme that NFS uses
for handling sillyrenames.

An atomic_t is added to the cifs_sb_info. When it transitions from 0 to
1, an extra reference to the superblock is taken (by bumping the
s_active value). When it transitions from 1 to 0, that reference is
dropped and a the superblock teardown may proceed if there are no more
references to it.

Also, the vfsmount pointer is removed from cifsFileInfo and from
cifs_new_fileinfo, and some bogus forward declarations are removed from
cifsfs.h.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Acked-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

7 files changed, 29 insertions, 18 deletions

diff --git a/fs/cifs/cifs_fs_sb.h b/fs/cifs/cifs_fs_sb.h
index 586ee3d527d2..525ba59a4105 100644
--- a/fs/cifs/cifs_fs_sb.h
+++ b/fs/cifs/cifs_fs_sb.h
@@ -48,6 +48,7 @@ struct cifs_sb_info {
         struct nls_table *local_nls;
         unsigned int rsize;
         unsigned int wsize;
+        atomic_t active;
         uid_t   mnt_uid;
         gid_t   mnt_gid;
         mode_t  mnt_file_mode;
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 3258c822328b..cbd468c880c4 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -83,6 +83,24 @@ extern mempool_t *cifs_sm_req_poolp;
 extern mempool_t *cifs_req_poolp;
 extern mempool_t *cifs_mid_poolp;
 
+void
+cifs_sb_active(struct super_block *sb)
+{
+        struct cifs_sb_info *server = CIFS_SB(sb);
+
+        if (atomic_inc_return(&server->active) == 1)
+                atomic_inc(&sb->s_active);
+}
+
+void
+cifs_sb_deactive(struct super_block *sb)
+{
+        struct cifs_sb_info *server = CIFS_SB(sb);
+
+        if (atomic_dec_and_test(&server->active))
+                deactivate_super(sb);
+}
+
 static int
 cifs_read_super(struct super_block *sb, void *data,
                 const char *devname, int silent)
diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h
index 786bdf36aebf..85544bcab517 100644
--- a/fs/cifs/cifsfs.h
+++ b/fs/cifs/cifsfs.h
@@ -42,10 +42,8 @@ extern const struct address_space_operations cifs_addr_ops;
 extern const struct address_space_operations cifs_addr_ops_smallbuf;
 
 /* Functions related to super block operations */
-/* extern const struct super_operations cifs_super_ops;*/
-extern void cifs_read_inode(struct inode *);
-/*extern void cifs_delete_inode(struct inode *);*/  /* BB not needed yet */
-/* extern void cifs_write_inode(struct inode *); */ /* BB not needed yet */
+extern void cifs_sb_active(struct super_block *sb);
+extern void cifs_sb_deactive(struct super_block *sb);
 
 /* Functions related to inodes */
 extern const struct inode_operations cifs_dir_inode_ops;
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 8289e61937a2..e2b760ef22ff 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -388,7 +388,6 @@ struct cifsFileInfo {
         /* lock scope id (0 if none) */
         struct file *pfile; /* needed for writepage */
         struct dentry *dentry;
-        struct vfsmount *mnt;
         struct tcon_link *tlink;
         struct mutex lock_mutex;
         struct list_head llist; /* list of byte range locks we have. */
diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 29a2ee8ae51f..7f416abd34cf 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -107,7 +107,7 @@ extern struct timespec cnvrtDosUnixTm(__le16 le_date, __le16 le_time,
 
 extern struct cifsFileInfo *cifs_new_fileinfo(struct inode *newinode,
                                 __u16 fileHandle, struct file *file,
-                                struct vfsmount *mnt, struct tcon_link *tlink,
+                                struct tcon_link *tlink,
                                 unsigned int oflags, __u32 oplock);
 extern int cifs_posix_open(char *full_path, struct inode **pinode,
                                 struct super_block *sb,
diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index 6887c412c61a..c205ec9293ea 100644
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -132,8 +132,7 @@ cifs_bp_rename_retry:
 
 struct cifsFileInfo *
 cifs_new_fileinfo(struct inode *newinode, __u16 fileHandle, struct file *file,
-                  struct vfsmount *mnt, struct tcon_link *tlink,
-                  unsigned int oflags, __u32 oplock)
+                  struct tcon_link *tlink, unsigned int oflags, __u32 oplock)
 {
         struct dentry *dentry = file->f_path.dentry;
         struct cifsFileInfo *pCifsFile;
@@ -147,7 +146,6 @@ cifs_new_fileinfo(struct inode *newinode, __u16 fileHandle, struct file *file,
         pCifsFile->pid = current->tgid;
         pCifsFile->uid = current_fsuid();
         pCifsFile->dentry = dget(dentry);
-        pCifsFile->mnt = mnt;
         pCifsFile->pfile = file;
         pCifsFile->invalidHandle = false;
         pCifsFile->closePend = false;
@@ -485,8 +483,7 @@ cifs_create_set_dentry:
                 }
 
                 pfile_info = cifs_new_fileinfo(newinode, fileHandle, filp,
-                                                nd->path.mnt, tlink, oflags,
-                                                oplock);
+                                                tlink, oflags, oplock);
                 if (pfile_info == NULL) {
                         fput(filp);
                         CIFSSMBClose(xid, tcon, fileHandle);
@@ -760,8 +757,7 @@ cifs_lookup(struct inode *parent_dir_inode, struct dentry *direntry,
                         }
 
                         cfile = cifs_new_fileinfo(newInode, fileHandle, filp,
-                                                  nd->path.mnt, tlink,
-                                                  nd->intent.open.flags,
+                                                  tlink, nd->intent.open.flags,
                                                   oplock);
                         if (cfile == NULL) {
                                 fput(filp);
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index c302b9c52644..fd78a355f634 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -282,7 +282,6 @@ int cifs_open(struct inode *inode, struct file *file)
                         }
 
                         pCifsFile = cifs_new_fileinfo(inode, netfid, file,
-                                                        file->f_path.mnt,
                                                         tlink, oflags, oplock);
                         if (pCifsFile == NULL) {
                                 CIFSSMBClose(xid, tcon, netfid);
@@ -375,8 +374,8 @@ int cifs_open(struct inode *inode, struct file *file)
         if (rc != 0)
                 goto out;
 
-        pCifsFile = cifs_new_fileinfo(inode, netfid, file, file->f_path.mnt,
-                                        tlink, file->f_flags, oplock);
+        pCifsFile = cifs_new_fileinfo(inode, netfid, file, tlink,
+                                        file->f_flags, oplock);
         if (pCifsFile == NULL) {
                 rc = -ENOMEM;
                 goto out;
@@ -2381,14 +2380,14 @@ void cifs_oplock_break(struct work_struct *work)
 
 void cifs_oplock_break_get(struct cifsFileInfo *cfile)
 {
-        mntget(cfile->mnt);
+        cifs_sb_active(cfile->dentry->d_sb);
         cifsFileInfo_get(cfile);
 }
 
 void cifs_oplock_break_put(struct cifsFileInfo *cfile)
 {
-        mntput(cfile->mnt);
         cifsFileInfo_put(cfile);
+        cifs_sb_deactive(cfile->dentry->d_sb);
 }
 
 const struct address_space_operations cifs_addr_ops = {