sysfs: implement bin_buffer

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/sysfs/bin.c b/fs/sysfs/bin.c
index 67a0d50..5dc47fe 100644 (file)
--- 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 = %d\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;
 }