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sysfs: skip bin_buffer->buffer while reading 

After b31ca3f5df ("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>
This commit is contained in:
Tejun Heo 2013-10-01 17:42:03 -04:00 committed by Greg Kroah-Hartman
parent 13c589d5b0
commit 91270162bf
1 changed files with 9 additions and 14 deletions
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23
fs/sysfs/bin.c
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@ -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, bb->buffer, offs, count);
if (count < 0) {
mutex_unlock(&bb->mutex);
goto out_free;
}
memcpy(temp, bb->buffer, count);
count = fill_read(file, buf, offs, count);
mutex_unlock(&bb->mutex);
if (copy_to_user(userbuf, temp, count)) {
if (count < 0)
goto out_free;
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;
}