On Wed, Jan 31, 2024 at 12:52:34PM -0800, Bart Van Assche wrote:
> Split fcntl_rw_hint() such that there is one helper function per fcntl. No
> functionality is changed by this patch.
>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> Suggested-by: Christoph Hellwig <hch@xxxxxx>
> Reviewed-by: Kanchan Joshi <joshi.k@xxxxxxxxxxx>
> Cc: Jeff Layton <jlayton@xxxxxxxxxx>
> Cc: Chuck Lever <chuck.lever@xxxxxxxxxx>
> Cc: Jens Axboe <axboe@xxxxxxxxx>
> Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
> ---
> fs/fcntl.c | 47 ++++++++++++++++++++++++++---------------------
> 1 file changed, 26 insertions(+), 21 deletions(-)
>
> diff --git a/fs/fcntl.c b/fs/fcntl.c
> index f3bc4662455f..5fa2d95114bf 100644
> --- a/fs/fcntl.c
> +++ b/fs/fcntl.c
> @@ -290,32 +290,35 @@ static bool rw_hint_valid(u64 hint)
> }
> }
>
> -static long fcntl_rw_hint(struct file *file, unsigned int cmd,
> - unsigned long arg)
> +static long fcntl_get_rw_hint(struct file *file, unsigned int cmd,
> + unsigned long arg)
> {
> struct inode *inode = file_inode(file);
> u64 __user *argp = (u64 __user *)arg;
> - u64 hint;
> + u64 hint = inode->i_write_hint;
>
> - switch (cmd) {
> - case F_GET_RW_HINT:
> - hint = inode->i_write_hint;
> - if (copy_to_user(argp, &hint, sizeof(*argp)))
> - return -EFAULT;
> - return 0;
> - case F_SET_RW_HINT:
> - if (copy_from_user(&hint, argp, sizeof(hint)))
> - return -EFAULT;
> - if (!rw_hint_valid(hint))
> - return -EINVAL;
> + if (copy_to_user(argp, &hint, sizeof(*argp)))
> + return -EFAULT;
> + return 0;
> +}
>
> - inode_lock(inode);
> - inode->i_write_hint = hint;
> - inode_unlock(inode);
> - return 0;
> - default:
> +static long fcntl_set_rw_hint(struct file *file, unsigned int cmd,
> + unsigned long arg)
> +{
> + struct inode *inode = file_inode(file);
> + u64 __user *argp = (u64 __user *)arg;
> + u64 hint;
> +
> + if (copy_from_user(&hint, argp, sizeof(hint)))
> + return -EFAULT;
> + if (!rw_hint_valid(hint))
> return -EINVAL;
> - }
> +
> + inode_lock(inode);
> + inode->i_write_hint = hint;
> + inode_unlock(inode);
What is this locking serialising against? The inode may or may not
be locked when we access this in IO path, so why isn't this just
WRITE_ONCE() here and READ_ONCE() in the IO paths?
-Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
