configfs: implement binary attributes
ConfigFS lacked binary attributes up until now. This patch
introduces support for binary attributes in a somewhat similar
manner of sysfs binary attributes albeit with changes that
fit the configfs usage model.
Problems that configfs binary attributes fix are everything that
requires a binary blob as part of the configuration of a resource,
such as bitstream loading for FPGAs, DTBs for dynamically created
devices etc.
Look at Documentation/filesystems/configfs/configfs.txt for internals
and howto use them.
This patch is against linux-next as of today that contains
Christoph's configfs rework.
Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
[hch: folded a fix from Geert Uytterhoeven <geert+renesas@glider.be>]
[hch: a few tiny updates based on review feedback]
Signed-off-by: Christoph Hellwig <hch@lst.de>
diff --git a/fs/configfs/file.c b/fs/configfs/file.c
index d39099e..3687187 100644
--- a/fs/configfs/file.c
+++ b/fs/configfs/file.c
@@ -28,6 +28,7 @@
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/mutex.h>
+#include <linux/vmalloc.h>
#include <asm/uaccess.h>
#include <linux/configfs.h>
@@ -48,6 +49,10 @@
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;
};
@@ -123,6 +128,87 @@
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_buffer *buffer = file->private_data;
+ struct dentry *dentry = file->f_path.dentry;
+ struct config_item *item = to_item(dentry->d_parent);
+ struct configfs_bin_attribute *bin_attr = to_bin_attr(dentry);
+ 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 = 1;
+
+ if (buffer->needs_read_fill) {
+ /* perform first read with buf == NULL to get extent */
+ len = bin_attr->read(item, NULL, 0);
+ if (len <= 0) {
+ retval = len;
+ goto out;
+ }
+
+ /* do not exceed the maximum value */
+ if (bin_attr->cb_max_size && len > bin_attr->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 */
+ len = bin_attr->read(item, buffer->bin_buffer, len);
+ 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.
@@ -209,10 +295,80 @@
return len;
}
-static int check_perm(struct inode * inode, struct file * file)
+/**
+ * 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;
+ struct dentry *dentry = file->f_path.dentry;
+ struct configfs_bin_attribute *bin_attr = to_bin_attr(dentry);
+ 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 = 1;
+
+ /* buffer grows? */
+ if (*ppos + count > buffer->bin_buffer_size) {
+
+ if (bin_attr->cb_max_size &&
+ *ppos + count > bin_attr->cb_max_size) {
+ len = -EFBIG;
+ }
+
+ 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);
+ if (len > 0)
+ *ppos += len;
+out:
+ mutex_unlock(&buffer->mutex);
+ return len;
+}
+
+static int check_perm(struct inode * inode, struct file * file, int type)
{
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_bin_attribute *bin_attr = NULL;
struct configfs_buffer * buffer;
struct configfs_item_operations * ops = NULL;
int error = 0;
@@ -220,6 +376,9 @@
if (!item || !attr)
goto Einval;
+ if (type & CONFIGFS_ITEM_BIN_ATTR)
+ bin_attr = to_bin_attr(file->f_path.dentry);
+
/* Grab the module reference for this attribute if we have one */
if (!try_module_get(attr->ca_owner)) {
error = -ENODEV;
@@ -236,9 +395,14 @@
* and we must have a store method.
*/
if (file->f_mode & FMODE_WRITE) {
- if (!(inode->i_mode & S_IWUGO) || !attr->store)
+ if (!(inode->i_mode & S_IWUGO))
goto Eaccess;
+ if ((type & CONFIGFS_ITEM_ATTR) && !attr->store)
+ goto Eaccess;
+
+ if ((type & CONFIGFS_ITEM_BIN_ATTR) && !bin_attr->write)
+ goto Eaccess;
}
/* File needs read support.
@@ -246,7 +410,13 @@
* must be a show method for it.
*/
if (file->f_mode & FMODE_READ) {
- if (!(inode->i_mode & S_IRUGO) || !attr->show)
+ if (!(inode->i_mode & S_IRUGO))
+ goto Eaccess;
+
+ if ((type & CONFIGFS_ITEM_ATTR) && !attr->show)
+ goto Eaccess;
+
+ if ((type & CONFIGFS_ITEM_BIN_ATTR) && !bin_attr->read)
goto Eaccess;
}
@@ -260,6 +430,8 @@
}
mutex_init(&buffer->mutex);
buffer->needs_read_fill = 1;
+ buffer->read_in_progress = 0;
+ buffer->write_in_progress = 0;
buffer->ops = ops;
file->private_data = buffer;
goto Done;
@@ -277,12 +449,7 @@
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)
+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);
@@ -303,6 +470,47 @@
return 0;
}
+static int configfs_open_file(struct inode *inode, struct file *filp)
+{
+ return check_perm(inode, filp, CONFIGFS_ITEM_ATTR);
+}
+
+static int configfs_open_bin_file(struct inode *inode, struct file *filp)
+{
+ return check_perm(inode, filp, CONFIGFS_ITEM_BIN_ATTR);
+}
+
+static int configfs_release_bin_file(struct inode *inode, struct file *filp)
+{
+ struct configfs_buffer *buffer = filp->private_data;
+ struct dentry *dentry = filp->f_path.dentry;
+ struct config_item *item = to_item(dentry->d_parent);
+ struct configfs_bin_attribute *bin_attr = to_bin_attr(dentry);
+ ssize_t len = 0;
+ int ret;
+
+ buffer->read_in_progress = 0;
+
+ if (buffer->write_in_progress) {
+ buffer->write_in_progress = 0;
+
+ len = bin_attr->write(item, buffer->bin_buffer,
+ buffer->bin_buffer_size);
+
+ /* vfree on NULL is safe */
+ vfree(buffer->bin_buffer);
+ buffer->bin_buffer = NULL;
+ buffer->bin_buffer_size = 0;
+ buffer->needs_read_fill = 1;
+ }
+
+ ret = configfs_release(inode, filp);
+ if (len < 0)
+ return len;
+ return ret;
+}
+
+
const struct file_operations configfs_file_operations = {
.read = configfs_read_file,
.write = configfs_write_file,
@@ -311,6 +519,14 @@
.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.
@@ -332,3 +548,24 @@
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;
+
+ mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_NORMAL);
+ error = configfs_make_dirent(parent_sd, NULL, (void *) bin_attr, mode,
+ CONFIGFS_ITEM_BIN_ATTR);
+ mutex_unlock(&dir->d_inode->i_mutex);
+
+ return error;
+}