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-rw-r--r--fs/configfs/file.c336
1 files changed, 336 insertions, 0 deletions
diff --git a/fs/configfs/file.c b/fs/configfs/file.c
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+++ b/fs/configfs/file.c
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+/* -*- 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/slab.h>
+#include <linux/mutex.h>
+#include <asm/uaccess.h>
+
+#include <linux/configfs.h>
+#include "configfs_internal.h"
+
+/*
+ * A simple attribute can only be 4096 characters. Why 4k? Because the
+ * original code limited it to PAGE_SIZE. That's a bad idea, though,
+ * because an attribute of 16k on ia64 won't work on x86. So we limit to
+ * 4k, our minimum common page size.
+ */
+#define SIMPLE_ATTR_SIZE 4096
+
+struct configfs_buffer {
+ size_t count;
+ loff_t pos;
+ char * page;
+ struct configfs_item_operations * ops;
+ struct mutex mutex;
+ 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)SIMPLE_ATTR_SIZE);
+ if (count >= 0)
+ buffer->count = count;
+ else
+ ret = count;
+ return ret;
+}
+
+/**
+ * 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;
+
+ mutex_lock(&buffer->mutex);
+ if (buffer->needs_read_fill) {
+ if ((retval = fill_read_buffer(file->f_path.dentry,buffer)))
+ goto out;
+ }
+ pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
+ __func__, count, *ppos, buffer->page);
+ retval = simple_read_from_buffer(buf, count, ppos, buffer->page,
+ buffer->count);
+out:
+ mutex_unlock(&buffer->mutex);
+ return retval;
+}
+
+
+/**
+ * fill_write_buffer - copy buffer from userspace.
+ * @buffer: data buffer for file.
+ * @buf: 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_free_pages(GFP_KERNEL, 0);
+ if (!buffer->page)
+ return -ENOMEM;
+
+ if (count >= SIMPLE_ATTR_SIZE)
+ count = SIMPLE_ATTR_SIZE - 1;
+ error = copy_from_user(buffer->page,buf,count);
+ buffer->needs_read_fill = 1;
+ /* if buf is assumed to contain a string, terminate it by \0,
+ * so e.g. sscanf() can scan the string easily */
+ buffer->page[count] = 0;
+ return error ? -EFAULT : count;
+}
+
+
+/**
+ * flush_write_buffer - push buffer to config_item.
+ * @dentry: dentry to the attribute
+ * @buffer: data buffer for file.
+ * @count: number of bytes
+ *
+ * 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;
+ ssize_t len;
+
+ mutex_lock(&buffer->mutex);
+ len = fill_write_buffer(buffer, buf, count);
+ if (len > 0)
+ len = flush_write_buffer(file->f_path.dentry, buffer, len);
+ if (len > 0)
+ *ppos += len;
+ mutex_unlock(&buffer->mutex);
+ return len;
+}
+
+static int check_perm(struct inode * inode, struct file * file)
+{
+ struct config_item *item = configfs_get_config_item(file->f_path.dentry->d_parent);
+ struct configfs_attribute * attr = to_attr(file->f_path.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 = kzalloc(sizeof(struct configfs_buffer),GFP_KERNEL);
+ if (!buffer) {
+ error = -ENOMEM;
+ goto Enomem;
+ }
+ mutex_init(&buffer->mutex);
+ buffer->needs_read_fill = 1;
+ buffer->ops = ops;
+ file->private_data = buffer;
+ goto Done;
+
+ Einval:
+ error = -EINVAL;
+ goto Done;
+ Eaccess:
+ error = -EACCES;
+ Enomem:
+ 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_path.dentry->d_parent);
+ struct configfs_attribute * attr = to_attr(filp->f_path.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);
+ mutex_destroy(&buffer->mutex);
+ kfree(buffer);
+ }
+ return 0;
+}
+
+const 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,
+};
+
+/**
+ * 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)
+{
+ struct dentry *dir = item->ci_dentry;
+ struct configfs_dirent *parent_sd = dir->d_fsdata;
+ umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG;
+ int error = 0;
+
+ mutex_lock_nested(&d_inode(dir)->i_mutex, I_MUTEX_NORMAL);
+ error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode,
+ CONFIGFS_ITEM_ATTR);
+ mutex_unlock(&d_inode(dir)->i_mutex);
+
+ return error;
+}
+