cifs: add new cifs_iget function and convert unix codepath to use it

cifs: add new cifs_iget function and convert unix codepath to use it

In order to unify some codepaths, introduce a common cifs_fattr struct
for storing inode attributes. The different codepaths (unix, legacy,
normal, etc...) can fill out this struct with inode info. It can then be
passed as an arg to a common set of routines to get and update inodes.

Add a new cifs_iget function that uses iget5_locked to identify inodes.
This will compare inodes based on the uniqueid value in a cifs_fattr
struct.

Rather than filling out an already-created inode, have
cifs_get_inode_info_unix instead fill out cifs_fattr and hand that off
to cifs_iget. cifs_iget can then properly look for hardlinked inodes.

On the readdir side, add a new cifs_readdir_lookup function that spawns
populated dentries. Redefine FILE_UNIX_INFO so that it's basically a
FILE_UNIX_BASIC_INFO that has a few fields wrapped around it. This
allows us to more easily use the same function for filling out the fattr
as the non-readdir codepath.

With this, we should then have proper hardlink detection and can
eventually get rid of some nasty CIFS-specific hacks for handing them.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/cifsproto.h

@@ -98,9 +98,14 @@ extern struct timespec cnvrtDosUnixTm(__le16 le_date, __le16 le_time,
 extern int cifs_posix_open(char *full_path, struct inode **pinode,
 			   struct super_block *sb, int mode, int oflags,
 			   int *poplock, __u16 *pnetfid, int xid);
-extern void posix_fill_in_inode(struct inode *tmp_inode,
-				FILE_UNIX_BASIC_INFO *pData, int isNewInode);
+extern void cifs_unix_basic_to_fattr(struct cifs_fattr *fattr,
+				     FILE_UNIX_BASIC_INFO *info,
+				     struct cifs_sb_info *cifs_sb);
+extern void cifs_fattr_to_inode(struct inode *inode, struct cifs_fattr *fattr);
 extern struct inode *cifs_new_inode(struct super_block *sb, __u64 *inum);
+extern struct inode *cifs_iget(struct super_block *sb,
+			       struct cifs_fattr *fattr);
+
 extern int cifs_get_inode_info(struct inode **pinode,
 			const unsigned char *search_path,
 			FILE_ALL_INFO *pfile_info,