From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nick Piggin Subject: Why do fs outside regular namespace clear DCACHE_UNHASHED? Date: Thu, 28 May 2009 09:14:41 +0200 Message-ID: <20090528071441.GE6920@wotan.suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii To: linux-fsdevel@vger.kernel.org Return-path: Received: from cantor.suse.de ([195.135.220.2]:48203 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750907AbZE1HOl (ORCPT ); Thu, 28 May 2009 03:14:41 -0400 Received: from relay2.suse.de (relay-ext.suse.de [195.135.221.8]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.suse.de (Postfix) with ESMTP id 18204749C2 for ; Thu, 28 May 2009 09:14:42 +0200 (CEST) Content-Disposition: inline Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Please humour a relative vfs/procfs newbie... Why do filesystems insist that a dentry must be !DCACHE_UNHASHED in order to work in /proc/pid/fd/? I can't find the code that checks this, and pipefs fds for example _seems_ to work in proc/pid with this patch applied... --- fs/anon_inodes.c | 16 ---------------- fs/pipe.c | 18 ------------------ net/socket.c | 19 ------------------- 3 files changed, 53 deletions(-) Index: linux-2.6/fs/pipe.c =================================================================== --- linux-2.6.orig/fs/pipe.c +++ linux-2.6/fs/pipe.c @@ -873,17 +873,6 @@ 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(). @@ -895,7 +884,6 @@ static char *pipefs_dname(struct dentry } static const struct dentry_operations pipefs_dentry_operations = { - .d_delete = pipefs_delete_dentry, .d_dname = pipefs_dname, }; @@ -955,12 +943,6 @@ 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/$pid/fd/XXX on pipes - */ - dentry->d_flags &= ~DCACHE_UNHASHED; d_instantiate(dentry, inode); err = -ENFILE; Index: linux-2.6/net/socket.c =================================================================== --- linux-2.6.orig/net/socket.c +++ linux-2.6/net/socket.c @@ -307,18 +307,6 @@ static struct file_system_type sock_fs_t .kill_sb = kill_anon_super, }; -static int sockfs_delete_dentry(struct dentry *dentry) -{ - /* - * At creation time, we pretended this dentry was hashed - * (by clearing DCACHE_UNHASHED bit in d_flags) - * At delete time, we restore the truth : not hashed. - * (so that dput() can proceed correctly) - */ - dentry->d_flags |= DCACHE_UNHASHED; - return 0; -} - /* * sockfs_dname() is called from d_path(). */ @@ -329,7 +317,6 @@ static char *sockfs_dname(struct dentry } static const struct dentry_operations sockfs_dentry_operations = { - .d_delete = sockfs_delete_dentry, .d_dname = sockfs_dname, }; @@ -378,12 +365,6 @@ static int sock_attach_fd(struct socket return -ENOMEM; dentry->d_op = &sockfs_dentry_operations; - /* - * We dont want to push this dentry into global dentry hash table. - * We pretend dentry is already hashed, by unsetting DCACHE_UNHASHED - * This permits a working /proc/$pid/fd/XXX on sockets - */ - dentry->d_flags &= ~DCACHE_UNHASHED; d_instantiate(dentry, SOCK_INODE(sock)); sock->file = file; Index: linux-2.6/fs/anon_inodes.c =================================================================== --- linux-2.6.orig/fs/anon_inodes.c +++ linux-2.6/fs/anon_inodes.c @@ -33,24 +33,11 @@ static int anon_inodefs_get_sb(struct fi 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, -}; /** * anon_inode_getfd - creates a new file instance by hooking it up to an @@ -106,9 +93,6 @@ int anon_inode_getfd(const char *name, c */ 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;