VFS: (Scripted) Convert S_ISLNK/DIR/REG(dentry->d_inode) to d_is_*(dentry)

Convert the following where appropriate:

 (1) S_ISLNK(dentry->d_inode) to d_is_symlink(dentry).

 (2) S_ISREG(dentry->d_inode) to d_is_reg(dentry).

 (3) S_ISDIR(dentry->d_inode) to d_is_dir(dentry).  This is actually more
     complicated than it appears as some calls should be converted to
     d_can_lookup() instead.  The difference is whether the directory in
     question is a real dir with a ->lookup op or whether it's a fake dir with
     a ->d_automount op.

In some circumstances, we can subsume checks for dentry->d_inode not being
NULL into this, provided we the code isn't in a filesystem that expects
d_inode to be NULL if the dirent really *is* negative (ie. if we're going to
use d_inode() rather than d_backing_inode() to get the inode pointer).

Note that the dentry type field may be set to something other than
DCACHE_MISS_TYPE when d_inode is NULL in the case of unionmount, where the VFS
manages the fall-through from a negative dentry to a lower layer.  In such a
case, the dentry type of the negative union dentry is set to the same as the
type of the lower dentry.

However, if you know d_inode is not NULL at the call site, then you can use
the d_is_xxx() functions even in a filesystem.

There is one further complication: a 0,0 chardev dentry may be labelled
DCACHE_WHITEOUT_TYPE rather than DCACHE_SPECIAL_TYPE.  Strictly, this was
intended for special directory entry types that don't have attached inodes.

The following perl+coccinelle script was used:

use strict;

my @callers;
open($fd, 'git grep -l \'S_IS[A-Z].*->d_inode\' |') ||
    die "Can't grep for S_ISDIR and co. callers";
@callers = <$fd>;
close($fd);
unless (@callers) {
    print "No matches\n";
    exit(0);
}

my @cocci = (
    '@@',
    'expression E;',
    '@@',
    '',
    '- S_ISLNK(E->d_inode->i_mode)',
    '+ d_is_symlink(E)',
    '',
    '@@',
    'expression E;',
    '@@',
    '',
    '- S_ISDIR(E->d_inode->i_mode)',
    '+ d_is_dir(E)',
    '',
    '@@',
    'expression E;',
    '@@',
    '',
    '- S_ISREG(E->d_inode->i_mode)',
    '+ d_is_reg(E)' );

my $coccifile = "tmp.sp.cocci";
open($fd, ">$coccifile") || die $coccifile;
print($fd "$_\n") || die $coccifile foreach (@cocci);
close($fd);

foreach my $file (@callers) {
    chomp $file;
    print "Processing ", $file, "\n";
    system("spatch", "--sp-file", $coccifile, $file, "--in-place", "--no-show-diff") == 0 ||
	die "spatch failed";
}

[AV: overlayfs parts skipped]

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/cachefiles/namei.c

@@ -277,7 +277,7 @@ static int cachefiles_bury_object(struct cachefiles_cache *cache,
 	_debug("remove %p from %p", rep, dir);
 
 	/* non-directories can just be unlinked */
-	if (!S_ISDIR(rep->d_inode->i_mode)) {
+	if (!d_is_dir(rep)) {
 		_debug("unlink stale object");
 
 		path.mnt = cache->mnt;
@@ -323,7 +323,7 @@ try_again:
 		return 0;
 	}
 
-	if (!S_ISDIR(cache->graveyard->d_inode->i_mode)) {
+	if (!d_is_dir(cache->graveyard)) {
 		unlock_rename(cache->graveyard, dir);
 		cachefiles_io_error(cache, "Graveyard no longer a directory");
 		return -EIO;
@@ -475,7 +475,7 @@ int cachefiles_walk_to_object(struct cachefiles_object *parent,
 	ASSERT(parent->dentry);
 	ASSERT(parent->dentry->d_inode);
 
-	if (!(S_ISDIR(parent->dentry->d_inode->i_mode))) {
+	if (!(d_is_dir(parent->dentry))) {
 		// TODO: convert file to dir
 		_leave("looking up in none directory");
 		return -ENOBUFS;
@@ -539,7 +539,7 @@ lookup_again:
 			_debug("mkdir -> %p{%p{ino=%lu}}",
 			       next, next->d_inode, next->d_inode->i_ino);
 
-		} else if (!S_ISDIR(next->d_inode->i_mode)) {
+		} else if (!d_is_dir(next)) {
 			pr_err("inode %lu is not a directory\n",
 			       next->d_inode->i_ino);
 			ret = -ENOBUFS;
@@ -568,8 +568,8 @@ lookup_again:
 			_debug("create -> %p{%p{ino=%lu}}",
 			       next, next->d_inode, next->d_inode->i_ino);
 
-		} else if (!S_ISDIR(next->d_inode->i_mode) &&
-			   !S_ISREG(next->d_inode->i_mode)
+		} else if (!d_is_dir(next) &&
+			   !d_is_reg(next)
 			   ) {
 			pr_err("inode %lu is not a file or directory\n",
 			       next->d_inode->i_ino);
@@ -642,7 +642,7 @@ lookup_again:
 
 	/* open a file interface onto a data file */
 	if (object->type != FSCACHE_COOKIE_TYPE_INDEX) {
-		if (S_ISREG(object->dentry->d_inode->i_mode)) {
+		if (d_is_reg(object->dentry)) {
 			const struct address_space_operations *aops;
 
 			ret = -EPERM;
@@ -763,7 +763,7 @@ struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache,
 	/* we need to make sure the subdir is a directory */
 	ASSERT(subdir->d_inode);
 
-	if (!S_ISDIR(subdir->d_inode->i_mode)) {
+	if (!d_is_dir(subdir)) {
 		pr_err("%s is not a directory\n", dirname);
 		ret = -EIO;
 		goto check_error;