Filesystems outside the regular namespace do not have to clear

DCACHE_UNHASHED in order to have a working /proc/$pid/fd/XXX.  Nothing in
proc prevents the fd link from being used if its dentry is not in the
hash.

Also, it does not get put into the dcache hash if DCACHE_UNHASHED is
clear; that depends on the filesystem calling d_add or d_rehash.

So delete the misleading comments and needless code.
Acked-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/anon_inodes.c

@@ -35,24 +35,11 @@ static int anon_inodefs_get_sb(struct file_system_type *fs_type, int flags,
 			     mnt);
 }
 
-static int anon_inodefs_delete_dentry(struct dentry *dentry)
-{
-	/*
-	 * We faked vfs to believe the dentry was hashed when we created it.
-	 * Now we restore the flag so that dput() will work correctly.
-	 */
-	dentry->d_flags |= DCACHE_UNHASHED;
-	return 1;
-}
-
 static struct file_system_type anon_inode_fs_type = {
 	.name		= "anon_inodefs",
 	.get_sb		= anon_inodefs_get_sb,
 	.kill_sb	= kill_anon_super,
 };
-static const struct dentry_operations anon_inodefs_dentry_operations = {
-	.d_delete	= anon_inodefs_delete_dentry,
-};
 
 /*
  * nop .set_page_dirty method so that people can use .page_mkwrite on
@@ -117,9 +104,6 @@ struct file *anon_inode_getfile(const char *name,
 	 */
 	atomic_inc(&anon_inode_inode->i_count);
 
-	dentry->d_op = &anon_inodefs_dentry_operations;
-	/* Do not publish this dentry inside the global dentry hash table */
-	dentry->d_flags &= ~DCACHE_UNHASHED;
 	d_instantiate(dentry, anon_inode_inode);
 
 	error = -ENFILE;

fs/pipe.c

@@ -906,17 +906,6 @@ void free_pipe_info(struct inode *inode)
 }
 
 static struct vfsmount *pipe_mnt __read_mostly;
-static int pipefs_delete_dentry(struct dentry *dentry)
-{
-	/*
-	 * At creation time, we pretended this dentry was hashed
-	 * (by clearing DCACHE_UNHASHED bit in d_flags)
-	 * At delete time, we restore the truth : not hashed.
-	 * (so that dput() can proceed correctly)
-	 */
-	dentry->d_flags |= DCACHE_UNHASHED;
-	return 0;
-}
 
 /*
  * pipefs_dname() is called from d_path().
@@ -928,7 +917,6 @@ static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 }
 
 static const struct dentry_operations pipefs_dentry_operations = {
-	.d_delete	= pipefs_delete_dentry,
 	.d_dname	= pipefs_dname,
 };
 
@@ -988,12 +976,6 @@ struct file *create_write_pipe(int flags)
 		goto err_inode;
 
 	dentry->d_op = &pipefs_dentry_operations;
-	/*
-	 * We dont want to publish this dentry into global dentry hash table.
-	 * We pretend dentry is already hashed, by unsetting DCACHE_UNHASHED
-	 * This permits a working /proc/$pid/fd/XXX on pipes
-	 */
-	dentry->d_flags &= ~DCACHE_UNHASHED;
 	d_instantiate(dentry, inode);
 
 	err = -ENFILE;

net/socket.c

@@ -312,18 +312,6 @@ static struct file_system_type sock_fs_type = {
 	.kill_sb =	kill_anon_super,
 };
 
-static int sockfs_delete_dentry(struct dentry *dentry)
-{
-	/*
-	 * At creation time, we pretended this dentry was hashed
-	 * (by clearing DCACHE_UNHASHED bit in d_flags)
-	 * At delete time, we restore the truth : not hashed.
-	 * (so that dput() can proceed correctly)
-	 */
-	dentry->d_flags |= DCACHE_UNHASHED;
-	return 0;
-}
-
 /*
  * sockfs_dname() is called from d_path().
  */
@@ -334,7 +322,6 @@ static char *sockfs_dname(struct dentry *dentry, char *buffer, int buflen)
 }
 
 static const struct dentry_operations sockfs_dentry_operations = {
-	.d_delete = sockfs_delete_dentry,
 	.d_dname  = sockfs_dname,
 };
 
@@ -383,12 +370,6 @@ static int sock_attach_fd(struct socket *sock, struct file *file, int flags)
 		return -ENOMEM;
 
 	dentry->d_op = &sockfs_dentry_operations;
-	/*
-	 * We dont want to push this dentry into global dentry hash table.
-	 * We pretend dentry is already hashed, by unsetting DCACHE_UNHASHED
-	 * This permits a working /proc/$pid/fd/XXX on sockets
-	 */
-	dentry->d_flags &= ~DCACHE_UNHASHED;
 	d_instantiate(dentry, SOCK_INODE(sock));
 
 	sock->file = file;