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>
diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index 7dc6b74..a40054f 100644
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -188,6 +188,7 @@
 	FILE_UNIX_BASIC_INFO *presp_data;
 	__u32 posix_flags = 0;
 	struct cifs_sb_info *cifs_sb = CIFS_SB(sb);
+	struct cifs_fattr fattr;
 
 	cFYI(1, ("posix open %s", full_path));
 
@@ -236,22 +237,21 @@
 	if (presp_data->Type == cpu_to_le32(-1))
 		goto posix_open_ret; /* open ok, caller does qpathinfo */
 
-	/* get new inode and set it up */
 	if (!pinode)
 		goto posix_open_ret; /* caller does not need info */
 
+	cifs_unix_basic_to_fattr(&fattr, presp_data, cifs_sb);
+
+	/* get new inode and set it up */
 	if (*pinode == NULL) {
-		__u64 unique_id = le64_to_cpu(presp_data->UniqueId);
-		*pinode = cifs_new_inode(sb, &unique_id);
+		*pinode = cifs_iget(sb, &fattr);
+		if (!*pinode) {
+			rc = -ENOMEM;
+			goto posix_open_ret;
+		}
+	} else {
+		cifs_fattr_to_inode(*pinode, &fattr);
 	}
-	/* else an inode was passed in. Update its info, don't create one */
-
-	/* We do not need to close the file if new_inode fails since
-	   the caller will retry qpathinfo as long as inode is null */
-	if (*pinode == NULL)
-		goto posix_open_ret;
-
-	posix_fill_in_inode(*pinode, presp_data, 1);
 
 	cifs_fill_fileinfo(*pinode, *pnetfid, cifs_sb->tcon, write_only);