cifs: keep dentry reference in cifsFileInfo instead of inode reference

cifsFileInfo is a bit problematic. It contains a reference back to the
struct file itself. This makes it difficult for a cifsFileInfo to exist
without a corresponding struct file.

It would be better instead of the cifsFileInfo just held info pertaining
to the open file on the server instead without any back refrences to the
struct file. This would allow it to exist after the filp to which it was
originally attached was closed.

Much of the use of the file pointer in this struct is to get at the
dentry.  Begin divorcing the cifsFileInfo from the struct file by
keeping a reference to the dentry. Since the dentry will have a
reference to the inode, we can eliminate the "pInode" field too and
convert the igrab/iput to dget/dput.

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>

fs/cifs/cifsglob.h

@@ -387,7 +387,7 @@ struct cifsFileInfo {
 	/* BB add lock scope info here if needed */ ;
 	/* lock scope id (0 if none) */
 	struct file *pfile; /* needed for writepage */
-	struct inode *pInode; /* needed for oplock break */
+	struct dentry *dentry;
 	struct vfsmount *mnt;
 	struct tcon_link *tlink;
 	struct mutex lock_mutex;
@@ -412,7 +412,7 @@ static inline void cifsFileInfo_put(struct cifsFileInfo *cifs_file)
 {
 	if (atomic_dec_and_test(&cifs_file->count)) {
 		cifs_put_tlink(cifs_file->tlink);
-		iput(cifs_file->pInode);
+		dput(cifs_file->dentry);
 		kfree(cifs_file);
 	}
 }

fs/cifs/dir.c

@@ -135,6 +135,7 @@ cifs_new_fileinfo(struct inode *newinode, __u16 fileHandle, struct file *file,
 		  struct vfsmount *mnt, struct tcon_link *tlink,
 		  unsigned int oflags, __u32 oplock)
 {
+	struct dentry *dentry = file->f_path.dentry;
 	struct cifsFileInfo *pCifsFile;
 	struct cifsInodeInfo *pCifsInode;
 
@@ -145,7 +146,7 @@ cifs_new_fileinfo(struct inode *newinode, __u16 fileHandle, struct file *file,
 	pCifsFile->netfid = fileHandle;
 	pCifsFile->pid = current->tgid;
 	pCifsFile->uid = current_fsuid();
-	pCifsFile->pInode = igrab(newinode);
+	pCifsFile->dentry = dget(dentry);
 	pCifsFile->mnt = mnt;
 	pCifsFile->pfile = file;
 	pCifsFile->invalidHandle = false;

fs/cifs/file.c

@@ -2335,7 +2335,7 @@ void cifs_oplock_break(struct work_struct *work)
 {
 	struct cifsFileInfo *cfile = container_of(work, struct cifsFileInfo,
 						  oplock_break);
-	struct inode *inode = cfile->pInode;
+	struct inode *inode = cfile->dentry->d_inode;
 	struct cifsInodeInfo *cinode = CIFS_I(inode);
 	int rc, waitrc = 0;
 

fs/cifs/misc.c

@@ -578,7 +578,7 @@ is_valid_oplock_break(struct smb_hdr *buf, struct TCP_Server_Info *srv)
 				}
 
 				cFYI(1, "file id match, oplock break");
-				pCifsInode = CIFS_I(netfile->pInode);
+				pCifsInode = CIFS_I(netfile->dentry->d_inode);
 				pCifsInode->clientCanCacheAll = false;
 				if (pSMB->OplockLevel == 0)
 					pCifsInode->clientCanCacheRead = false;