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authorJoel Becker <joel.becker@oracle.com>2005-12-15 14:29:43 -0800
committerJoel Becker <joel.becker@oracle.com>2006-01-03 11:45:28 -0800
commit7063fbf2261194f72ee75afca67b3b38b554b5fa (patch)
tree7bfe4eeab8ce784b767cf30886623d456c384718 /fs/configfs/file.c
parent88026842b0a760145aa71d69e74fbc9ec118ca44 (diff)
[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>
Diffstat (limited to 'fs/configfs/file.c')
-rw-r--r--fs/configfs/file.c360
1 files changed, 360 insertions, 0 deletions
diff --git a/fs/configfs/file.c b/fs/configfs/file.c
new file mode 100644
index 00000000000..af1ffc9a15c
--- /dev/null
+++ b/fs/configfs/file.c
@@ -0,0 +1,360 @@
+/* -*- mode: c; c-basic-offset: 8; -*-
+ * vim: noexpandtab sw=8 ts=8 sts=0:
+ *
+ * file.c - operations for regular (text) files.
+ *
+ * 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.
+ */
+
+#include <linux/fs.h>
+#include <linux/module.h>
+#include <linux/dnotify.h>
+#include <linux/slab.h>
+#include <asm/uaccess.h>
+#include <asm/semaphore.h>
+
+#include <linux/configfs.h>
+#include "configfs_internal.h"
+
+
+struct configfs_buffer {
+ size_t count;
+ loff_t pos;
+ char * page;
+ struct configfs_item_operations * ops;
+ struct semaphore sem;
+ int needs_read_fill;
+};
+
+
+/**
+ * fill_read_buffer - allocate and fill buffer from item.
+ * @dentry: dentry pointer.
+ * @buffer: data buffer for file.
+ *
+ * Allocate @buffer->page, if it hasn't been already, then call the
+ * config_item's show() method to fill the buffer with this attribute's
+ * data.
+ * This is called only once, on the file's first read.
+ */
+static int fill_read_buffer(struct dentry * dentry, struct configfs_buffer * buffer)
+{
+ struct configfs_attribute * attr = to_attr(dentry);
+ struct config_item * item = to_item(dentry->d_parent);
+ struct configfs_item_operations * ops = buffer->ops;
+ int ret = 0;
+ ssize_t count;
+
+ if (!buffer->page)
+ buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
+ if (!buffer->page)
+ return -ENOMEM;
+
+ count = ops->show_attribute(item,attr,buffer->page);
+ buffer->needs_read_fill = 0;
+ BUG_ON(count > (ssize_t)PAGE_SIZE);
+ if (count >= 0)
+ buffer->count = count;
+ else
+ ret = count;
+ return ret;
+}
+
+
+/**
+ * flush_read_buffer - push buffer to userspace.
+ * @buffer: data buffer for file.
+ * @userbuf: user-passed buffer.
+ * @count: number of bytes requested.
+ * @ppos: file position.
+ *
+ * Copy the buffer we filled in fill_read_buffer() to userspace.
+ * This is done at the reader's leisure, copying and advancing
+ * the amount they specify each time.
+ * This may be called continuously until the buffer is empty.
+ */
+static int flush_read_buffer(struct configfs_buffer * buffer, char __user * buf,
+ size_t count, loff_t * ppos)
+{
+ int error;
+
+ if (*ppos > buffer->count)
+ return 0;
+
+ if (count > (buffer->count - *ppos))
+ count = buffer->count - *ppos;
+
+ error = copy_to_user(buf,buffer->page + *ppos,count);
+ if (!error)
+ *ppos += count;
+ return error ? -EFAULT : count;
+}
+
+/**
+ * configfs_read_file - read an attribute.
+ * @file: file pointer.
+ * @buf: buffer to fill.
+ * @count: number of bytes to read.
+ * @ppos: starting offset in file.
+ *
+ * Userspace wants to read an attribute file. The attribute descriptor
+ * is in the file's ->d_fsdata. The target item is in the directory's
+ * ->d_fsdata.
+ *
+ * We call fill_read_buffer() to allocate and fill the buffer from the
+ * item's show() method exactly once (if the read is happening from
+ * the beginning of the file). That should fill the entire buffer with
+ * all the data the item has to offer for that attribute.
+ * We then call flush_read_buffer() to copy the buffer to userspace
+ * in the increments specified.
+ */
+
+static ssize_t
+configfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
+{
+ struct configfs_buffer * buffer = file->private_data;
+ ssize_t retval = 0;
+
+ down(&buffer->sem);
+ if (buffer->needs_read_fill) {
+ if ((retval = fill_read_buffer(file->f_dentry,buffer)))
+ goto out;
+ }
+ pr_debug("%s: count = %d, ppos = %lld, buf = %s\n",
+ __FUNCTION__,count,*ppos,buffer->page);
+ retval = flush_read_buffer(buffer,buf,count,ppos);
+out:
+ up(&buffer->sem);
+ return retval;
+}
+
+
+/**
+ * fill_write_buffer - copy buffer from userspace.
+ * @buffer: data buffer for file.
+ * @userbuf: data from user.
+ * @count: number of bytes in @userbuf.
+ *
+ * Allocate @buffer->page if it hasn't been already, then
+ * copy the user-supplied buffer into it.
+ */
+
+static int
+fill_write_buffer(struct configfs_buffer * buffer, const char __user * buf, size_t count)
+{
+ int error;
+
+ if (!buffer->page)
+ buffer->page = (char *)get_zeroed_page(GFP_KERNEL);
+ if (!buffer->page)
+ return -ENOMEM;
+
+ if (count > PAGE_SIZE)
+ count = PAGE_SIZE;
+ error = copy_from_user(buffer->page,buf,count);
+ buffer->needs_read_fill = 1;
+ return error ? -EFAULT : count;
+}
+
+
+/**
+ * flush_write_buffer - push buffer to config_item.
+ * @file: file pointer.
+ * @buffer: data buffer for file.
+ *
+ * Get the correct pointers for the config_item and the attribute we're
+ * dealing with, then call the store() method for the attribute,
+ * passing the buffer that we acquired in fill_write_buffer().
+ */
+
+static int
+flush_write_buffer(struct dentry * dentry, struct configfs_buffer * buffer, size_t count)
+{
+ struct configfs_attribute * attr = to_attr(dentry);
+ struct config_item * item = to_item(dentry->d_parent);
+ struct configfs_item_operations * ops = buffer->ops;
+
+ return ops->store_attribute(item,attr,buffer->page,count);
+}
+
+
+/**
+ * configfs_write_file - write an attribute.
+ * @file: file pointer
+ * @buf: data to write
+ * @count: number of bytes
+ * @ppos: starting offset
+ *
+ * Similar to configfs_read_file(), though working in the opposite direction.
+ * We allocate and fill the data from the user in fill_write_buffer(),
+ * then push it to the config_item in flush_write_buffer().
+ * There is no easy way for us to know if userspace is only doing a partial
+ * write, so we don't support them. We expect the entire buffer to come
+ * on the first write.
+ * Hint: if you're writing a value, first read the file, modify only the
+ * the value you're changing, then write entire buffer back.
+ */
+
+static ssize_t
+configfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
+{
+ struct configfs_buffer * buffer = file->private_data;
+
+ down(&buffer->sem);
+ count = fill_write_buffer(buffer,buf,count);
+ if (count > 0)
+ count = flush_write_buffer(file->f_dentry,buffer,count);
+ if (count > 0)
+ *ppos += count;
+ up(&buffer->sem);
+ return count;
+}
+
+static int check_perm(struct inode * inode, struct file * file)
+{
+ struct config_item *item = configfs_get_config_item(file->f_dentry->d_parent);
+ struct configfs_attribute * attr = to_attr(file->f_dentry);
+ struct configfs_buffer * buffer;
+ struct configfs_item_operations * ops = NULL;
+ int error = 0;
+
+ if (!item || !attr)
+ goto Einval;
+
+ /* Grab the module reference for this attribute if we have one */
+ if (!try_module_get(attr->ca_owner)) {
+ error = -ENODEV;
+ goto Done;
+ }
+
+ if (item->ci_type)
+ ops = item->ci_type->ct_item_ops;
+ else
+ goto Eaccess;
+
+ /* File needs write support.
+ * The inode's perms must say it's ok,
+ * and we must have a store method.
+ */
+ if (file->f_mode & FMODE_WRITE) {
+
+ if (!(inode->i_mode & S_IWUGO) || !ops->store_attribute)
+ goto Eaccess;
+
+ }
+
+ /* File needs read support.
+ * The inode's perms must say it's ok, and we there
+ * must be a show method for it.
+ */
+ if (file->f_mode & FMODE_READ) {
+ if (!(inode->i_mode & S_IRUGO) || !ops->show_attribute)
+ goto Eaccess;
+ }
+
+ /* No error? Great, allocate a buffer for the file, and store it
+ * it in file->private_data for easy access.
+ */
+ buffer = kmalloc(sizeof(struct configfs_buffer),GFP_KERNEL);
+ if (buffer) {
+ memset(buffer,0,sizeof(struct configfs_buffer));
+ init_MUTEX(&buffer->sem);
+ buffer->needs_read_fill = 1;
+ buffer->ops = ops;
+ file->private_data = buffer;
+ } else
+ error = -ENOMEM;
+ goto Done;
+
+ Einval:
+ error = -EINVAL;
+ goto Done;
+ Eaccess:
+ error = -EACCES;
+ module_put(attr->ca_owner);
+ Done:
+ if (error && item)
+ config_item_put(item);
+ return error;
+}
+
+static int configfs_open_file(struct inode * inode, struct file * filp)
+{
+ return check_perm(inode,filp);
+}
+
+static int configfs_release(struct inode * inode, struct file * filp)
+{
+ struct config_item * item = to_item(filp->f_dentry->d_parent);
+ struct configfs_attribute * attr = to_attr(filp->f_dentry);
+ struct module * owner = attr->ca_owner;
+ struct configfs_buffer * buffer = filp->private_data;
+
+ if (item)
+ config_item_put(item);
+ /* After this point, attr should not be accessed. */
+ module_put(owner);
+
+ if (buffer) {
+ if (buffer->page)
+ free_page((unsigned long)buffer->page);
+ kfree(buffer);
+ }
+ return 0;
+}
+
+struct file_operations configfs_file_operations = {
+ .read = configfs_read_file,
+ .write = configfs_write_file,
+ .llseek = generic_file_llseek,
+ .open = configfs_open_file,
+ .release = configfs_release,
+};
+
+
+int configfs_add_file(struct dentry * dir, const struct configfs_attribute * attr, int type)
+{
+ struct configfs_dirent * parent_sd = dir->d_fsdata;
+ umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG;
+ int error = 0;
+
+ down(&dir->d_inode->i_sem);
+ error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode, type);
+ up(&dir->d_inode->i_sem);
+
+ return error;
+}
+
+
+/**
+ * configfs_create_file - create an attribute file for an item.
+ * @item: item we're creating for.
+ * @attr: atrribute descriptor.
+ */
+
+int configfs_create_file(struct config_item * item, const struct configfs_attribute * attr)
+{
+ BUG_ON(!item || !item->ci_dentry || !attr);
+
+ return configfs_add_file(item->ci_dentry, attr,
+ CONFIGFS_ITEM_ATTR);
+}
+