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Subject[PATCH 11/14] sysfs: implement bin_buffer
Date
From
Implement bin_buffer which contains a mutex and pointer to PAGE_SIZE
buffer to properly synchronize accesses to per-openfile buffer and
prepare for immediate-kobj-disconnect.

Signed-off-by: Tejun Heo <htejun@gmail.com>
---
fs/sysfs/bin.c | 64 ++++++++++++++++++++++++++++++++++++++++++-------------
1 files changed, 49 insertions(+), 15 deletions(-)
diff --git a/fs/sysfs/bin.c b/fs/sysfs/bin.c
index 0f0027b..1dd1bf1 100644
--- a/fs/sysfs/bin.c
+++ b/fs/sysfs/bin.c
@@ -20,6 +20,11 @@

#include "sysfs.h"

+struct bin_buffer {
+ struct mutex mutex;
+ void *buffer;
+};
+
static int
fill_read(struct dentry *dentry, char *buffer, loff_t off, size_t count)
{
@@ -36,7 +41,7 @@ fill_read(struct dentry *dentry, char *buffer, loff_t off, size_t count)
static ssize_t
read(struct file *file, char __user *userbuf, size_t bytes, loff_t *off)
{
- char *buffer = file->private_data;
+ struct bin_buffer *bb = file->private_data;
struct dentry *dentry = file->f_path.dentry;
int size = dentry->d_inode->i_size;
loff_t offs = *off;
@@ -49,17 +54,23 @@ read(struct file *file, char __user *userbuf, size_t bytes, loff_t *off)
count = size - offs;
}

- count = fill_read(dentry, buffer, offs, count);
+ mutex_lock(&bb->mutex);
+
+ count = fill_read(dentry, bb->buffer, offs, count);
if (count < 0)
- return count;
+ goto out_unlock;

- if (copy_to_user(userbuf, buffer, count))
- return -EFAULT;
+ if (copy_to_user(userbuf, bb->buffer, count)) {
+ count = -EFAULT;
+ goto out_unlock;
+ }

pr_debug("offs = %lld, *off = %lld, count = %zd\n", offs, *off, count);

*off = offs + count;

+ out_unlock:
+ mutex_unlock(&bb->mutex);
return count;
}

@@ -79,7 +90,7 @@ flush_write(struct dentry *dentry, char *buffer, loff_t offset, size_t count)
static ssize_t write(struct file *file, const char __user *userbuf,
size_t bytes, loff_t *off)
{
- char *buffer = file->private_data;
+ struct bin_buffer *bb = file->private_data;
struct dentry *dentry = file->f_path.dentry;
int size = dentry->d_inode->i_size;
loff_t offs = *off;
@@ -92,25 +103,38 @@ static ssize_t write(struct file *file, const char __user *userbuf,
count = size - offs;
}

- if (copy_from_user(buffer, userbuf, count))
- return -EFAULT;
+ mutex_lock(&bb->mutex);
+
+ if (copy_from_user(bb->buffer, userbuf, count)) {
+ count = -EFAULT;
+ goto out_unlock;
+ }

- count = flush_write(dentry, buffer, offs, count);
+ count = flush_write(dentry, bb->buffer, offs, count);
if (count > 0)
*off = offs + count;
+
+ out_unlock:
+ mutex_unlock(&bb->mutex);
return count;
}

static int mmap(struct file *file, struct vm_area_struct *vma)
{
+ struct bin_buffer *bb = file->private_data;
struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
struct bin_attribute *attr = attr_sd->s_elem.bin_attr.bin_attr;
struct kobject *kobj = to_kobj(file->f_path.dentry->d_parent);
+ int rc;

if (!attr->mmap)
return -EINVAL;

- return attr->mmap(kobj, attr, vma);
+ mutex_lock(&bb->mutex);
+ rc = attr->mmap(kobj, attr, vma);
+ mutex_unlock(&bb->mutex);
+
+ return rc;
}

static int open(struct inode * inode, struct file * file)
@@ -118,6 +142,7 @@ static int open(struct inode * inode, struct file * file)
struct kobject *kobj = sysfs_get_kobject(file->f_path.dentry->d_parent);
struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
struct bin_attribute *attr = attr_sd->s_elem.bin_attr.bin_attr;
+ struct bin_buffer *bb = NULL;
int error = -EINVAL;

if (!kobj || !attr)
@@ -135,14 +160,22 @@ static int open(struct inode * inode, struct file * file)
goto Error;

error = -ENOMEM;
- file->private_data = kmalloc(PAGE_SIZE, GFP_KERNEL);
- if (!file->private_data)
+ bb = kzalloc(sizeof(*bb), GFP_KERNEL);
+ if (!bb)
goto Error;

+ bb->buffer = kmalloc(PAGE_SIZE, GFP_KERNEL);
+ if (!bb->buffer)
+ goto Error;
+
+ mutex_init(&bb->mutex);
+ file->private_data = bb;
+
error = 0;
- goto Done;
+ goto Done;

Error:
+ kfree(bb);
module_put(attr->attr.owner);
Done:
if (error)
@@ -155,11 +188,12 @@ static int release(struct inode * inode, struct file * file)
struct kobject * kobj = to_kobj(file->f_path.dentry->d_parent);
struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
struct bin_attribute *attr = attr_sd->s_elem.bin_attr.bin_attr;
- u8 * buffer = file->private_data;
+ struct bin_buffer *bb = file->private_data;

kobject_put(kobj);
module_put(attr->attr.owner);
- kfree(buffer);
+ kfree(bb->buffer);
+ kfree(bb);
return 0;
}

--
1.5.0.3

-
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