cifs: use CreationTime like an i_generation field

Reduce false inode collisions by using the CreationTime like an
i_generation field. This way, even if the server ends up reusing
a uniqueid after a delete/create cycle, we can avoid matching
the inode incorrectly.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/cifsfs.c

@@ -329,6 +329,8 @@ cifs_alloc_inode(struct super_block *sb)
 	cifs_inode->invalid_mapping = false;
 	cifs_inode->vfs_inode.i_blkbits = 14;  /* 2**14 = CIFS_MAX_MSGSIZE */
 	cifs_inode->server_eof = 0;
+	cifs_inode->uniqueid = 0;
+	cifs_inode->createtime = 0;
 
 	/* Can not set i_flags here - they get immediately overwritten
 	   to zero by the VFS */

fs/cifs/cifsglob.h

@@ -453,6 +453,7 @@ struct cifsInodeInfo {
 	bool invalid_mapping:1;		/* pagecache is invalid */
 	u64  server_eof;		/* current file size on server */
 	u64  uniqueid;			/* server inode number */
+	u64  createtime;		/* creation time on server */
 #ifdef CONFIG_CIFS_FSCACHE
 	struct fscache_cookie *fscache;
 #endif
@@ -573,6 +574,7 @@ struct cifs_fattr {
 	u64		cf_uniqueid;
 	u64		cf_eof;
 	u64		cf_bytes;
+	u64		cf_createtime;
 	uid_t		cf_uid;
 	gid_t		cf_gid;
 	umode_t		cf_mode;

fs/cifs/inode.c

@@ -518,6 +518,7 @@ cifs_all_info_to_fattr(struct cifs_fattr *fattr, FILE_ALL_INFO *info,
 
 	fattr->cf_eof = le64_to_cpu(info->EndOfFile);
 	fattr->cf_bytes = le64_to_cpu(info->AllocationSize);
+	fattr->cf_createtime = le64_to_cpu(info->CreationTime);
 
 	if (fattr->cf_cifsattrs & ATTR_DIRECTORY) {
 		fattr->cf_mode = S_IFDIR | cifs_sb->mnt_dir_mode;
@@ -779,6 +780,10 @@ cifs_find_inode(struct inode *inode, void *opaque)
 	if (CIFS_I(inode)->uniqueid != fattr->cf_uniqueid)
 		return 0;
 
+	/* use createtime like an i_generation field */
+	if (CIFS_I(inode)->createtime != fattr->cf_createtime)
+		return 0;
+
 	/* don't match inode of different type */
 	if ((inode->i_mode & S_IFMT) != (fattr->cf_mode & S_IFMT))
 		return 0;
@@ -796,6 +801,7 @@ cifs_init_inode(struct inode *inode, void *opaque)
 	struct cifs_fattr *fattr = (struct cifs_fattr *) opaque;
 
 	CIFS_I(inode)->uniqueid = fattr->cf_uniqueid;
+	CIFS_I(inode)->createtime = fattr->cf_createtime;
 	return 0;
 }
 

fs/cifs/readdir.c

@@ -160,6 +160,7 @@ cifs_dir_info_to_fattr(struct cifs_fattr *fattr, FILE_DIRECTORY_INFO *info,
 	fattr->cf_cifsattrs = le32_to_cpu(info->ExtFileAttributes);
 	fattr->cf_eof = le64_to_cpu(info->EndOfFile);
 	fattr->cf_bytes = le64_to_cpu(info->AllocationSize);
+	fattr->cf_createtime = le64_to_cpu(info->CreationTime);
 	fattr->cf_atime = cifs_NTtimeToUnix(info->LastAccessTime);
 	fattr->cf_ctime = cifs_NTtimeToUnix(info->ChangeTime);
 	fattr->cf_mtime = cifs_NTtimeToUnix(info->LastWriteTime);