cifs: Fix duplicate fscache cookie warnings

fscache emits a lot of duplicate cookie warnings with cifs because the
index key for the fscache cookies does not include everything that the
cifs_find_inode() function does.  The latter is used with iget5_locked() to
distinguish between inodes in the local inode cache.

Fix this by adding the creation time and file type to the fscache cookie
key.

Additionally, add a couple of comments to note that if one is changed the
other must be also.

Signed-off-by: David Howells <dhowells@redhat.com>
Fixes: 70431bf ("cifs: Support fscache indexing rewrite")
cc: Shyam Prasad N <nspmangalore@gmail.com>
cc: Rohith Surabattula <rohiths.msft@gmail.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: linux-cifs@vger.kernel.org
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: dhowells

fs/smb/client/fscache.c

@@ -12,6 +12,16 @@
 #include "cifs_fs_sb.h"
 #include "cifsproto.h"
 
+/*
+ * Key for fscache inode.  [!] Contents must match comparisons in cifs_find_inode().
+ */
+struct cifs_fscache_inode_key {
+
+	__le64  uniqueid;	/* server inode number */
+	__le64  createtime;	/* creation time on server */
+	u8	type;		/* S_IFMT file type */
+} __packed;
+
 static void cifs_fscache_fill_volume_coherency(
 	struct cifs_tcon *tcon,
 	struct cifs_fscache_volume_coherency_data *cd)
@@ -97,15 +107,19 @@ void cifs_fscache_release_super_cookie(struct cifs_tcon *tcon)
 void cifs_fscache_get_inode_cookie(struct inode *inode)
 {
 	struct cifs_fscache_inode_coherency_data cd;
+	struct cifs_fscache_inode_key key;
 	struct cifsInodeInfo *cifsi = CIFS_I(inode);
 	struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
 	struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
 
+	key.uniqueid	= cpu_to_le64(cifsi->uniqueid);
+	key.createtime	= cpu_to_le64(cifsi->createtime);
+	key.type	= (inode->i_mode & S_IFMT) >> 12;
 	cifs_fscache_fill_coherency(&cifsi->netfs.inode, &cd);
 
 	cifsi->netfs.cache =
 		fscache_acquire_cookie(tcon->fscache, 0,
-				       &cifsi->uniqueid, sizeof(cifsi->uniqueid),
+				       &key, sizeof(key),
 				       &cd, sizeof(cd),
 				       i_size_read(&cifsi->netfs.inode));
 	if (cifsi->netfs.cache)

fs/smb/client/inode.c

@@ -1351,6 +1351,8 @@ cifs_find_inode(struct inode *inode, void *opaque)
 {
 	struct cifs_fattr *fattr = opaque;
 
+	/* [!] The compared values must be the same in struct cifs_fscache_inode_key. */
+
 	/* don't match inode with different uniqueid */
 	if (CIFS_I(inode)->uniqueid != fattr->cf_uniqueid)
 		return 0;