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ashmem: switch to ->read_iter 

And use the proper VFS helper for using the backing file.

Also make sure we hold ashmem_lock while updating f_pos to make sure that
it's not racy.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Christoph Hellwig 2017-09-01 17:39:09 +02:00 committed by Al Viro
parent cc4a41fe55
commit 8a2af06415
1 changed files with 8 additions and 21 deletions
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29
drivers/staging/android/ashmem.c
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@ -294,19 +294,9 @@ static int ashmem_release(struct inode *ignored, struct file *file)
return 0;
}
/**
* ashmem_read() - Reads a set of bytes from an Ashmem-enabled file
* @file: The associated backing file.
* @buf: The buffer of data being written to
* @len: The number of bytes being read
* @pos: The position of the first byte to read.
*
* Return: 0 if successful, or another return code if not.
*/
static ssize_t ashmem_read(struct file *file, char __user *buf,
size_t len, loff_t *pos)
static ssize_t ashmem_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
struct ashmem_area *asma = file->private_data;
struct ashmem_area *asma = iocb->ki_filp->private_data;
int ret = 0;
mutex_lock(&ashmem_mutex);
@ -320,20 +310,17 @@ static ssize_t ashmem_read(struct file *file, char __user *buf,
goto out_unlock;
}
mutex_unlock(&ashmem_mutex);
/*
* asma and asma->file are used outside the lock here. We assume
* once asma->file is set it will never be changed, and will not
* be destroyed until all references to the file are dropped and
* ashmem_release is called.
*/
ret = __vfs_read(asma->file, buf, len, pos);
if (ret >= 0)
/** Update backing file pos, since f_ops->read() doesn't */
asma->file->f_pos = *pos;
return ret;
mutex_unlock(&ashmem_mutex);
ret = vfs_iter_read(asma->file, iter, &iocb->ki_pos, 0);
mutex_lock(&ashmem_mutex);
if (ret > 0)
asma->file->f_pos = iocb->ki_pos;
out_unlock:
mutex_unlock(&ashmem_mutex);
return ret;
@ -834,7 +821,7 @@ static const struct file_operations ashmem_fops = {
.owner = THIS_MODULE,
.open = ashmem_open,
.release = ashmem_release,
.read = ashmem_read,
.read_iter = ashmem_read_iter,
.llseek = ashmem_llseek,
.mmap = ashmem_mmap,
.unlocked_ioctl = ashmem_ioctl,