linux-kernel - Re: [PATCH] Return short read or 0 at end of a raw device, not EIO

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Date:	Mon, 29 Sep 2014 12:46:57 -0400
From:	Jeff Moyer <jmoyer@...hat.com>
To:	David Jeffery <djeffery@...hat.com>
Cc:	linux-kernel@...r.kernel.org, axboe@...nel.dk
Subject: Re: [PATCH] Return short read or 0 at end of a raw device, not EIO

David Jeffery <djeffery@...hat.com> writes:

> Changes to the basic direct I/O code have broken the raw driver when reading
> to the end of a raw device.  Instead of returning a short read for a read that
> extends partially beyond the device's end or 0 when at the end of the device,
> these reads now return EIO.
>
> The raw driver needs the same end of device handling as was added for normal
> block devices.  Using blkdev_read_iter, which has the needed size checks,
> prevents the EIO conditions at the end of the device.
>
> Signed-off-by: David Jeffery <djeffery@...hat.com>

Looks good to me.

Reviewed-by: Jeff Moyer <jmoyer@...hat.com>

> ---
>
>  drivers/char/raw.c |    2 +-
>  fs/block_dev.c     |    3 ++-
>  include/linux/fs.h |    1 +
>  3 files changed, 4 insertions(+), 2 deletions(-)
>
>
> diff --git a/drivers/char/raw.c b/drivers/char/raw.c
> index 0102dc7..a24891b 100644
> --- a/drivers/char/raw.c
> +++ b/drivers/char/raw.c
> @@ -285,7 +285,7 @@ static long raw_ctl_compat_ioctl(struct file *file, unsigned int cmd,
>  
>  static const struct file_operations raw_fops = {
>  	.read		= new_sync_read,
> -	.read_iter	= generic_file_read_iter,
> +	.read_iter	= blkdev_read_iter,
>  	.write		= new_sync_write,
>  	.write_iter	= blkdev_write_iter,
>  	.fsync		= blkdev_fsync,
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index 6d72746..12aa041 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -1591,7 +1591,7 @@ ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
>  }
>  EXPORT_SYMBOL_GPL(blkdev_write_iter);
>  
> -static ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
> +ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
>  {
>  	struct file *file = iocb->ki_filp;
>  	struct inode *bd_inode = file->f_mapping->host;
> @@ -1605,6 +1605,7 @@ static ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
>  	iov_iter_truncate(to, size);
>  	return generic_file_read_iter(iocb, to);
>  }
> +EXPORT_SYMBOL_GPL(blkdev_read_iter);
>  
>  /*
>   * Try to release a page associated with block device when the system
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 9418772..0c20168 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2455,6 +2455,7 @@ extern ssize_t new_sync_read(struct file *filp, char __user *buf, size_t len, lo
>  extern ssize_t new_sync_write(struct file *filp, const char __user *buf, size_t len, loff_t *ppos);
>  
>  /* fs/block_dev.c */
> +extern ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to);
>  extern ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from);
>  extern int blkdev_fsync(struct file *filp, loff_t start, loff_t end,
>  			int datasync);
> --
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