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configfs: stash the data we need into configfs_buffer at open time 

simplifies the ->read()/->write()/->release() instances nicely

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Al Viro 2019-08-30 11:30:03 -04:00 committed by Christoph Hellwig
parent 089cf7f6ec
commit ff4dd08197
1 changed files with 94 additions and 133 deletions
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227
fs/configfs/file.c
View File

@ -39,24 +39,18 @@ struct configfs_buffer {
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;
};
};
/**
* 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)
static int fill_read_buffer(struct configfs_buffer * buffer)
{
struct configfs_attribute * attr = to_attr(dentry);
struct config_item * item = to_item(dentry->d_parent);
int ret = 0;
ssize_t count;
if (!buffer->page)
@ -64,15 +58,15 @@ static int fill_read_buffer(struct dentry * dentry, struct configfs_buffer * buf
if (!buffer->page)
return -ENOMEM;
count = attr->show(item, buffer->page);
count = buffer->attr->show(buffer->item, buffer->page);
if (count < 0)
return count;
if (WARN_ON_ONCE(count > (ssize_t)SIMPLE_ATTR_SIZE))
return -EIO;
BUG_ON(count > (ssize_t)SIMPLE_ATTR_SIZE);
if (count >= 0) {
buffer->needs_read_fill = 0;
buffer->count = count;
} else
ret = count;
return ret;
buffer->needs_read_fill = 0;
buffer->count = count;
return 0;
}
/**
@ -97,12 +91,13 @@ static int fill_read_buffer(struct dentry * dentry, struct configfs_buffer * buf
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;
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)))
retval = fill_read_buffer(buffer);
if (retval)
goto out;
}
pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
@ -139,9 +134,6 @@ 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);
@ -156,14 +148,14 @@ configfs_read_bin_file(struct file *file, char __user *buf,
if (buffer->needs_read_fill) {
/* perform first read with buf == NULL to get extent */
len = bin_attr->read(item, NULL, 0);
len = buffer->bin_attr->read(buffer->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) {
if (buffer->cb_max_size && len > buffer->cb_max_size) {
retval = -EFBIG;
goto out;
}
@ -176,7 +168,8 @@ configfs_read_bin_file(struct file *file, char __user *buf,
buffer->bin_buffer_size = len;
/* perform second read to fill buffer */
len = bin_attr->read(item, buffer->bin_buffer, len);
len = buffer->bin_attr->read(buffer->item,
buffer->bin_buffer, len);
if (len < 0) {
retval = len;
vfree(buffer->bin_buffer);
@ -226,25 +219,10 @@ fill_write_buffer(struct configfs_buffer * buffer, const char __user * buf, size
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)
flush_write_buffer(struct configfs_buffer *buffer, size_t count)
{
struct configfs_attribute * attr = to_attr(dentry);
struct config_item * item = to_item(dentry->d_parent);
return attr->store(item, buffer->page, count);
return buffer->attr->store(buffer->item, buffer->page, count);
}
@ -268,13 +246,13 @@ flush_write_buffer(struct dentry * dentry, struct configfs_buffer * buffer, size
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;
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);
len = flush_write_buffer(buffer, len);
if (len > 0)
*ppos += len;
mutex_unlock(&buffer->mutex);
@ -299,8 +277,6 @@ 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;
@ -316,8 +292,8 @@ configfs_write_bin_file(struct file *file, const char __user *buf,
/* buffer grows? */
if (*ppos + count > buffer->bin_buffer_size) {
if (bin_attr->cb_max_size &&
*ppos + count > bin_attr->cb_max_size) {
if (buffer->cb_max_size &&
*ppos + count > buffer->cb_max_size) {
len = -EFBIG;
goto out;
}
@ -349,31 +325,45 @@ out:
return len;
}
static int check_perm(struct inode * inode, struct file * file, int type)
static int __configfs_open_file(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;
struct dentry *dentry = file->f_path.dentry;
struct configfs_attribute *attr;
struct configfs_buffer *buffer;
int error;
if (!item || !attr)
goto Einval;
error = -ENOMEM;
buffer = kzalloc(sizeof(struct configfs_buffer), GFP_KERNEL);
if (!buffer)
goto out;
if (type & CONFIGFS_ITEM_BIN_ATTR)
bin_attr = to_bin_attr(file->f_path.dentry);
error = -EINVAL;
buffer->item = configfs_get_config_item(dentry->d_parent);
if (!buffer->item)
goto out_free_buffer;
/* Grab the module reference for this attribute if we have one */
if (!try_module_get(attr->ca_owner)) {
error = -ENODEV;
goto Done;
attr = to_attr(dentry);
if (!attr)
goto out_put_item;
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;
}
if (item->ci_type)
ops = item->ci_type->ct_item_ops;
else
goto Eaccess;
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_put_item;
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,
@ -381,13 +371,11 @@ static int check_perm(struct inode * inode, struct file * file, int type)
*/
if (file->f_mode & FMODE_WRITE) {
if (!(inode->i_mode & S_IWUGO))
goto Eaccess;
goto out_put_module;
if ((type & CONFIGFS_ITEM_ATTR) && !attr->store)
goto Eaccess;
if ((type & CONFIGFS_ITEM_BIN_ATTR) && !bin_attr->write)
goto Eaccess;
goto out_put_module;
if ((type & CONFIGFS_ITEM_BIN_ATTR) && !buffer->bin_attr->write)
goto out_put_module;
}
/* File needs read support.
@ -396,90 +384,65 @@ static int check_perm(struct inode * inode, struct file * file, int type)
*/
if (file->f_mode & FMODE_READ) {
if (!(inode->i_mode & S_IRUGO))
goto Eaccess;
goto out_put_module;
if ((type & CONFIGFS_ITEM_ATTR) && !attr->show)
goto Eaccess;
if ((type & CONFIGFS_ITEM_BIN_ATTR) && !bin_attr->read)
goto Eaccess;
goto out_put_module;
if ((type & CONFIGFS_ITEM_BIN_ATTR) && !buffer->bin_attr->read)
goto out_put_module;
}
/* 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->read_in_progress = false;
buffer->write_in_progress = false;
buffer->ops = ops;
file->private_data = buffer;
goto Done;
return 0;
Einval:
error = -EINVAL;
goto Done;
Eaccess:
error = -EACCES;
Enomem:
module_put(attr->ca_owner);
Done:
if (error && item)
config_item_put(item);
out_put_module:
module_put(buffer->owner);
out_put_item:
config_item_put(buffer->item);
out_free_buffer:
kfree(buffer);
out:
return error;
}
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;
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);
}
if (buffer->item)
config_item_put(buffer->item);
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 check_perm(inode, filp, CONFIGFS_ITEM_ATTR);
return __configfs_open_file(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);
return __configfs_open_file(inode, filp, CONFIGFS_ITEM_BIN_ATTR);
}
static int configfs_release_bin_file(struct inode *inode, struct file *filp)
static int configfs_release_bin_file(struct inode *inode, struct file *file)
{
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;
struct configfs_buffer *buffer = file->private_data;
buffer->read_in_progress = false;
if (buffer->write_in_progress) {
buffer->write_in_progress = false;
len = bin_attr->write(item, buffer->bin_buffer,
/* result of ->release() is ignored */
buffer->bin_attr->write(buffer->item, buffer->bin_buffer,
buffer->bin_buffer_size);
/* vfree on NULL is safe */
@ -489,10 +452,8 @@ static int configfs_release_bin_file(struct inode *inode, struct file *filp)
buffer->needs_read_fill = 1;
}
ret = configfs_release(inode, filp);
if (len < 0)
return len;
return ret;
configfs_release(inode, file);
return 0;
}