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

Jeff Moyer
2014-09-29T16:47:05Z

David Jeffery <djeffery@redhat.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@redhat.com>

Looks good to me.

Reviewed-by: Jeff Moyer <jmoyer@redhat.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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