diff options
Diffstat (limited to 'fs/configfs/file.c')
| -rw-r--r-- | fs/configfs/file.c | 568 |
1 files changed, 568 insertions, 0 deletions
diff --git a/fs/configfs/file.c b/fs/configfs/file.c new file mode 100644 index 000000000..38eb80e29 --- /dev/null +++ b/fs/configfs/file.c @@ -0,0 +1,568 @@ +/* -*- 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 <linux/vmalloc.h> +#include <linux/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; + bool read_in_progress; + bool write_in_progress; + char *bin_buffer; + int bin_buffer_size; + int cb_max_size; + struct config_item *item; + struct module *owner; + union { + struct configfs_attribute *attr; + struct configfs_bin_attribute *bin_attr; + }; +}; + +static inline struct configfs_fragment *to_frag(struct file *file) +{ + struct configfs_dirent *sd = file->f_path.dentry->d_fsdata; + + return sd->s_frag; +} + +static int fill_read_buffer(struct file *file, struct configfs_buffer *buffer) +{ + struct configfs_fragment *frag = to_frag(file); + ssize_t count = -ENOENT; + + if (!buffer->page) + buffer->page = (char *) get_zeroed_page(GFP_KERNEL); + if (!buffer->page) + return -ENOMEM; + + down_read(&frag->frag_sem); + if (!frag->frag_dead) + count = buffer->attr->show(buffer->item, buffer->page); + up_read(&frag->frag_sem); + + if (count < 0) + return count; + if (WARN_ON_ONCE(count > (ssize_t)SIMPLE_ATTR_SIZE)) + return -EIO; + buffer->needs_read_fill = 0; + buffer->count = count; + return 0; +} + +/** + * 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) { + retval = fill_read_buffer(file, buffer); + if (retval) + 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; +} + +/** + * configfs_read_bin_file - read a binary attribute. + * @file: file pointer. + * @buf: buffer to fill. + * @count: number of bytes to read. + * @ppos: starting offset in file. + * + * Userspace wants to read a binary attribute file. The attribute + * descriptor is in the file's ->d_fsdata. The target item is in the + * directory's ->d_fsdata. + * + * We check whether we need to refill the buffer. If so we will + * call the attributes' attr->read() twice. The first time we + * will pass a NULL as a buffer pointer, which the attributes' method + * will use to return the size of the buffer required. If no error + * occurs we will allocate the buffer using vmalloc and call + * attr->read() again passing that buffer as an argument. + * Then we just copy to user-space using simple_read_from_buffer. + */ + +static ssize_t +configfs_read_bin_file(struct file *file, char __user *buf, + size_t count, loff_t *ppos) +{ + struct configfs_fragment *frag = to_frag(file); + struct configfs_buffer *buffer = file->private_data; + ssize_t retval = 0; + ssize_t len = min_t(size_t, count, PAGE_SIZE); + + mutex_lock(&buffer->mutex); + + /* we don't support switching read/write modes */ + if (buffer->write_in_progress) { + retval = -ETXTBSY; + goto out; + } + buffer->read_in_progress = true; + + if (buffer->needs_read_fill) { + /* perform first read with buf == NULL to get extent */ + down_read(&frag->frag_sem); + if (!frag->frag_dead) + len = buffer->bin_attr->read(buffer->item, NULL, 0); + else + len = -ENOENT; + up_read(&frag->frag_sem); + if (len <= 0) { + retval = len; + goto out; + } + + /* do not exceed the maximum value */ + if (buffer->cb_max_size && len > buffer->cb_max_size) { + retval = -EFBIG; + goto out; + } + + buffer->bin_buffer = vmalloc(len); + if (buffer->bin_buffer == NULL) { + retval = -ENOMEM; + goto out; + } + buffer->bin_buffer_size = len; + + /* perform second read to fill buffer */ + down_read(&frag->frag_sem); + if (!frag->frag_dead) + len = buffer->bin_attr->read(buffer->item, + buffer->bin_buffer, len); + else + len = -ENOENT; + up_read(&frag->frag_sem); + if (len < 0) { + retval = len; + vfree(buffer->bin_buffer); + buffer->bin_buffer_size = 0; + buffer->bin_buffer = NULL; + goto out; + } + + buffer->needs_read_fill = 0; + } + + retval = simple_read_from_buffer(buf, count, ppos, buffer->bin_buffer, + buffer->bin_buffer_size); +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; +} + +static int +flush_write_buffer(struct file *file, struct configfs_buffer *buffer, size_t count) +{ + struct configfs_fragment *frag = to_frag(file); + int res = -ENOENT; + + down_read(&frag->frag_sem); + if (!frag->frag_dead) + res = buffer->attr->store(buffer->item, buffer->page, count); + up_read(&frag->frag_sem); + return res; +} + + +/** + * 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, buffer, len); + if (len > 0) + *ppos += len; + mutex_unlock(&buffer->mutex); + return len; +} + +/** + * configfs_write_bin_file - write a binary attribute. + * @file: file pointer + * @buf: data to write + * @count: number of bytes + * @ppos: starting offset + * + * Writing to a binary attribute file is similar to a normal read. + * We buffer the consecutive writes (binary attribute files do not + * support lseek) in a continuously growing buffer, but we don't + * commit until the close of the file. + */ + +static ssize_t +configfs_write_bin_file(struct file *file, const char __user *buf, + size_t count, loff_t *ppos) +{ + struct configfs_buffer *buffer = file->private_data; + void *tbuf = NULL; + ssize_t len; + + mutex_lock(&buffer->mutex); + + /* we don't support switching read/write modes */ + if (buffer->read_in_progress) { + len = -ETXTBSY; + goto out; + } + buffer->write_in_progress = true; + + /* buffer grows? */ + if (*ppos + count > buffer->bin_buffer_size) { + + if (buffer->cb_max_size && + *ppos + count > buffer->cb_max_size) { + len = -EFBIG; + goto out; + } + + tbuf = vmalloc(*ppos + count); + if (tbuf == NULL) { + len = -ENOMEM; + goto out; + } + + /* copy old contents */ + if (buffer->bin_buffer) { + memcpy(tbuf, buffer->bin_buffer, + buffer->bin_buffer_size); + vfree(buffer->bin_buffer); + } + + /* clear the new area */ + memset(tbuf + buffer->bin_buffer_size, 0, + *ppos + count - buffer->bin_buffer_size); + buffer->bin_buffer = tbuf; + buffer->bin_buffer_size = *ppos + count; + } + + len = simple_write_to_buffer(buffer->bin_buffer, + buffer->bin_buffer_size, ppos, buf, count); +out: + mutex_unlock(&buffer->mutex); + return len; +} + +static int __configfs_open_file(struct inode *inode, struct file *file, int type) +{ + struct dentry *dentry = file->f_path.dentry; + struct configfs_fragment *frag = to_frag(file); + struct configfs_attribute *attr; + struct configfs_buffer *buffer; + int error; + + error = -ENOMEM; + buffer = kzalloc(sizeof(struct configfs_buffer), GFP_KERNEL); + if (!buffer) + goto out; + + error = -ENOENT; + down_read(&frag->frag_sem); + if (unlikely(frag->frag_dead)) + goto out_free_buffer; + + error = -EINVAL; + buffer->item = to_item(dentry->d_parent); + if (!buffer->item) + goto out_free_buffer; + + attr = to_attr(dentry); + if (!attr) + goto out_free_buffer; + + if (type & CONFIGFS_ITEM_BIN_ATTR) { + buffer->bin_attr = to_bin_attr(dentry); + buffer->cb_max_size = buffer->bin_attr->cb_max_size; + } else { + buffer->attr = attr; + } + + buffer->owner = attr->ca_owner; + /* Grab the module reference for this attribute if we have one */ + error = -ENODEV; + if (!try_module_get(buffer->owner)) + goto out_free_buffer; + + error = -EACCES; + if (!buffer->item->ci_type) + goto out_put_module; + + buffer->ops = buffer->item->ci_type->ct_item_ops; + + /* 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)) + goto out_put_module; + if ((type & CONFIGFS_ITEM_ATTR) && !attr->store) + goto out_put_module; + if ((type & CONFIGFS_ITEM_BIN_ATTR) && !buffer->bin_attr->write) + goto out_put_module; + } + + /* 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)) + goto out_put_module; + if ((type & CONFIGFS_ITEM_ATTR) && !attr->show) + goto out_put_module; + if ((type & CONFIGFS_ITEM_BIN_ATTR) && !buffer->bin_attr->read) + goto out_put_module; + } + + mutex_init(&buffer->mutex); + buffer->needs_read_fill = 1; + buffer->read_in_progress = false; + buffer->write_in_progress = false; + file->private_data = buffer; + up_read(&frag->frag_sem); + return 0; + +out_put_module: + module_put(buffer->owner); +out_free_buffer: + up_read(&frag->frag_sem); + kfree(buffer); +out: + return error; +} + +static int configfs_release(struct inode *inode, struct file *filp) +{ + struct configfs_buffer *buffer = filp->private_data; + + module_put(buffer->owner); + if (buffer->page) + free_page((unsigned long)buffer->page); + mutex_destroy(&buffer->mutex); + kfree(buffer); + return 0; +} + +static int configfs_open_file(struct inode *inode, struct file *filp) +{ + return __configfs_open_file(inode, filp, CONFIGFS_ITEM_ATTR); +} + +static int configfs_open_bin_file(struct inode *inode, struct file *filp) +{ + return __configfs_open_file(inode, filp, CONFIGFS_ITEM_BIN_ATTR); +} + +static int configfs_release_bin_file(struct inode *inode, struct file *file) +{ + struct configfs_buffer *buffer = file->private_data; + + buffer->read_in_progress = false; + + if (buffer->write_in_progress) { + struct configfs_fragment *frag = to_frag(file); + buffer->write_in_progress = false; + + down_read(&frag->frag_sem); + if (!frag->frag_dead) { + /* result of ->release() is ignored */ + buffer->bin_attr->write(buffer->item, + buffer->bin_buffer, + buffer->bin_buffer_size); + } + up_read(&frag->frag_sem); + } + + vfree(buffer->bin_buffer); + buffer->bin_buffer = NULL; + buffer->bin_buffer_size = 0; + buffer->needs_read_fill = 1; + + configfs_release(inode, file); + 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, +}; + +const struct file_operations configfs_bin_file_operations = { + .read = configfs_read_bin_file, + .write = configfs_write_bin_file, + .llseek = NULL, /* bin file is not seekable */ + .open = configfs_open_bin_file, + .release = configfs_release_bin_file, +}; + +/** + * 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; + + inode_lock_nested(d_inode(dir), I_MUTEX_NORMAL); + error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode, + CONFIGFS_ITEM_ATTR, parent_sd->s_frag); + inode_unlock(d_inode(dir)); + + return error; +} + +/** + * configfs_create_bin_file - create a binary attribute file for an item. + * @item: item we're creating for. + * @attr: atrribute descriptor. + */ + +int configfs_create_bin_file(struct config_item *item, + const struct configfs_bin_attribute *bin_attr) +{ + struct dentry *dir = item->ci_dentry; + struct configfs_dirent *parent_sd = dir->d_fsdata; + umode_t mode = (bin_attr->cb_attr.ca_mode & S_IALLUGO) | S_IFREG; + int error = 0; + + inode_lock_nested(dir->d_inode, I_MUTEX_NORMAL); + error = configfs_make_dirent(parent_sd, NULL, (void *) bin_attr, mode, + CONFIGFS_ITEM_BIN_ATTR, parent_sd->s_frag); + inode_unlock(dir->d_inode); + + return error; +} |