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Subject[PATCH 01/17] ashmem: switch to ->read_iter
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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>
---
drivers/staging/android/ashmem.c | 29 ++++++++---------------------
1 file changed, 8 insertions(+), 21 deletions(-)

diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c
index 6ba270e0494d..0f695df14c9d 100644
--- a/drivers/staging/android/ashmem.c
+++ b/drivers/staging/android/ashmem.c
@@ -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,
--
2.11.0
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