sysfs: skip bin_buffer->buffer while reading

After b31ca3f5dfc ("sysfs: fix deadlock"), bin read() first writes
data to bb->buffer and bounces it to a transient kernel buffer which
is then copied out to userland.  The double bouncing doesn't add
anything.  Let's just use the transient buffer directly.

While at it, rename @temp to @buf for clarity.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/sysfs/bin.c b/fs/sysfs/bin.c
index d49e6ca..d2142c0 100644 (file)
--- a/fs/sysfs/bin.c
+++ b/fs/sysfs/bin.c
@@ -72,7 +72,7 @@ read(struct file *file, char __user *userbuf, size_t bytes, loff_t *off)
        int size = file_inode(file)->i_size;
        loff_t offs = *off;
        int count = min_t(size_t, bytes, PAGE_SIZE);
-       char *temp;
+       char *buf;
 
        if (!bytes)
                return 0;
@@ -84,23 +84,18 @@ read(struct file *file, char __user *userbuf, size_t bytes, loff_t *off)
                        count = size - offs;
        }
 
-       temp = kmalloc(count, GFP_KERNEL);
-       if (!temp)
+       buf = kmalloc(count, GFP_KERNEL);
+       if (!buf)
                return -ENOMEM;
 
        mutex_lock(&bb->mutex);
+       count = fill_read(file, buf, offs, count);
+       mutex_unlock(&bb->mutex);
 
-       count = fill_read(file, bb->buffer, offs, count);
-       if (count < 0) {
-               mutex_unlock(&bb->mutex);
+       if (count < 0)
                goto out_free;
-       }
-
-       memcpy(temp, bb->buffer, count);
 
-       mutex_unlock(&bb->mutex);
-
-       if (copy_to_user(userbuf, temp, count)) {
+       if (copy_to_user(userbuf, buf, count)) {
                count = -EFAULT;
                goto out_free;
        }
@@ -110,7 +105,7 @@ read(struct file *file, char __user *userbuf, size_t bytes, loff_t *off)
        *off = offs + count;
 
  out_free:
-       kfree(temp);
+       kfree(buf);
        return count;
 }