[PATCH] configfs: User-driven configuration filesystem

Configfs, a file system for userspace-driven kernel object configuration.
The OCFS2 stack makes extensive use of this for propagation of cluster
configuration information into kernel.

Signed-off-by: Joel Becker <joel.becker@oracle.com>

1 files changed, 162 insertions, 0 deletions

diff --git a/fs/configfs/inode.c b/fs/configfs/inode.c
new file mode 100644
index 000000000000..6b274c6d428f
--- /dev/null
+++ b/fs/configfs/inode.c
@@ -0,0 +1,162 @@
+/* -*- mode: c; c-basic-offset: 8; -*-
+ * vim: noexpandtab sw=8 ts=8 sts=0:
+ *
+ * inode.c - basic inode and dentry operations.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ *
+ * Based on sysfs:
+ *      sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
+ *
+ * configfs Copyright (C) 2005 Oracle.  All rights reserved.
+ *
+ * Please see Documentation/filesystems/configfs.txt for more information.
+ */
+
+#undef DEBUG
+
+#include <linux/pagemap.h>
+#include <linux/namei.h>
+#include <linux/backing-dev.h>
+
+#include <linux/configfs.h>
+#include "configfs_internal.h"
+
+extern struct super_block * configfs_sb;
+
+static struct address_space_operations configfs_aops = {
+        .readpage       = simple_readpage,
+        .prepare_write  = simple_prepare_write,
+        .commit_write   = simple_commit_write
+};
+
+static struct backing_dev_info configfs_backing_dev_info = {
+        .ra_pages       = 0,    /* No readahead */
+        .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
+};
+
+struct inode * configfs_new_inode(mode_t mode)
+{
+        struct inode * inode = new_inode(configfs_sb);
+        if (inode) {
+                inode->i_mode = mode;
+                inode->i_uid = 0;
+                inode->i_gid = 0;
+                inode->i_blksize = PAGE_CACHE_SIZE;
+                inode->i_blocks = 0;
+                inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+                inode->i_mapping->a_ops = &configfs_aops;
+                inode->i_mapping->backing_dev_info = &configfs_backing_dev_info;
+        }
+        return inode;
+}
+
+int configfs_create(struct dentry * dentry, int mode, int (*init)(struct inode *))
+{
+        int error = 0;
+        struct inode * inode = NULL;
+        if (dentry) {
+                if (!dentry->d_inode) {
+                        if ((inode = configfs_new_inode(mode))) {
+                                if (dentry->d_parent && dentry->d_parent->d_inode) {
+                                        struct inode *p_inode = dentry->d_parent->d_inode;
+                                        p_inode->i_mtime = p_inode->i_ctime = CURRENT_TIME;
+                                }
+                                goto Proceed;
+                        }
+                        else
+                                error = -ENOMEM;
+                } else
+                        error = -EEXIST;
+        } else
+                error = -ENOENT;
+        goto Done;
+
+ Proceed:
+        if (init)
+                error = init(inode);
+        if (!error) {
+                d_instantiate(dentry, inode);
+                if (S_ISDIR(mode) || S_ISLNK(mode))
+                        dget(dentry);  /* pin link and directory dentries in core */
+        } else
+                iput(inode);
+ Done:
+        return error;
+}
+
+/*
+ * Get the name for corresponding element represented by the given configfs_dirent
+ */
+const unsigned char * configfs_get_name(struct configfs_dirent *sd)
+{
+        struct attribute * attr;
+
+        if (!sd || !sd->s_element)
+                BUG();
+
+        /* These always have a dentry, so use that */
+        if (sd->s_type & (CONFIGFS_DIR | CONFIGFS_ITEM_LINK))
+                return sd->s_dentry->d_name.name;
+
+        if (sd->s_type & CONFIGFS_ITEM_ATTR) {
+                attr = sd->s_element;
+                return attr->name;
+        }
+        return NULL;
+}
+
+
+/*
+ * Unhashes the dentry corresponding to given configfs_dirent
+ * Called with parent inode's i_sem held.
+ */
+void configfs_drop_dentry(struct configfs_dirent * sd, struct dentry * parent)
+{
+        struct dentry * dentry = sd->s_dentry;
+
+        if (dentry) {
+                spin_lock(&dcache_lock);
+                if (!(d_unhashed(dentry) && dentry->d_inode)) {
+                        dget_locked(dentry);
+                        __d_drop(dentry);
+                        spin_unlock(&dcache_lock);
+                        simple_unlink(parent->d_inode, dentry);
+                } else
+                        spin_unlock(&dcache_lock);
+        }
+}
+
+void configfs_hash_and_remove(struct dentry * dir, const char * name)
+{
+        struct configfs_dirent * sd;
+        struct configfs_dirent * parent_sd = dir->d_fsdata;
+
+        down(&dir->d_inode->i_sem);
+        list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
+                if (!sd->s_element)
+                        continue;
+                if (!strcmp(configfs_get_name(sd), name)) {
+                        list_del_init(&sd->s_sibling);
+                        configfs_drop_dentry(sd, dir);
+                        configfs_put(sd);
+                        break;
+                }
+        }
+        up(&dir->d_inode->i_sem);
+}
+
+