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>

1 files changed, 3 insertions, 7 deletions

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);