From 7063fbf2261194f72ee75afca67b3b38b554b5fa Mon Sep 17 00:00:00 2001 From: Joel Becker Date: Thu, 15 Dec 2005 14:29:43 -0800 Subject: [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 --- fs/configfs/file.c | 360 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 360 insertions(+) create mode 100644 fs/configfs/file.c (limited to 'fs/configfs/file.c') diff --git a/fs/configfs/file.c b/fs/configfs/file.c new file mode 100644 index 000000000000..af1ffc9a15c0 --- /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 +#include +#include +#include +#include +#include + +#include +#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); +} + -- cgit v1.2.3