vfs: check i_nlink limits in vfs_{mkdir,rename_dir,link}

New field of struct super_block - ->s_max_links.  Maximal allowed
value of ->i_nlink or 0; in the latter case all checks still need
to be done in ->link/->mkdir/->rename instances.  Note that this
limit applies both to directoris and to non-directories.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/udf/namei.c b/fs/udf/namei.c
index 08bf46e..38de8f2 100644
--- a/fs/udf/namei.c
+++ b/fs/udf/namei.c
@@ -32,8 +32,6 @@
 #include <linux/crc-itu-t.h>
 #include <linux/exportfs.h>
 
-enum { UDF_MAX_LINKS = 0xffff };
-
 static inline int udf_match(int len1, const unsigned char *name1, int len2,
 			    const unsigned char *name2)
 {
@@ -649,10 +647,6 @@
 	struct udf_inode_info *dinfo = UDF_I(dir);
 	struct udf_inode_info *iinfo;
 
-	err = -EMLINK;
-	if (dir->i_nlink >= UDF_MAX_LINKS)
-		goto out;
-
 	err = -EIO;
 	inode = udf_new_inode(dir, S_IFDIR | mode, &err);
 	if (!inode)
@@ -1032,9 +1026,6 @@
 	struct fileIdentDesc cfi, *fi;
 	int err;
 
-	if (inode->i_nlink >= UDF_MAX_LINKS)
-		return -EMLINK;
-
 	fi = udf_add_entry(dir, dentry, &fibh, &cfi, &err);
 	if (!fi) {
 		return err;
@@ -1126,10 +1117,6 @@
 		if (udf_get_lb_pblock(old_inode->i_sb, &tloc, 0) !=
 				old_dir->i_ino)
 			goto end_rename;
-
-		retval = -EMLINK;
-		if (!new_inode && new_dir->i_nlink >= UDF_MAX_LINKS)
-			goto end_rename;
 	}
 	if (!nfi) {
 		nfi = udf_add_entry(new_dir, new_dentry, &nfibh, &ncfi,
diff --git a/fs/udf/super.c b/fs/udf/super.c
index c09a84d..8d8b253 100644
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -75,6 +75,8 @@
 
 #define UDF_DEFAULT_BLOCKSIZE 2048
 
+enum { UDF_MAX_LINKS = 0xffff };
+
 /* These are the "meat" - everything else is stuffing */
 static int udf_fill_super(struct super_block *, void *, int);
 static void udf_put_super(struct super_block *);
@@ -2042,6 +2044,7 @@
 		goto error_out;
 	}
 	sb->s_maxbytes = MAX_LFS_FILESIZE;
+	sb->s_max_links = UDF_MAX_LINKS;
 	return 0;
 
 error_out: