On Tue, May 09, 2017 at 07:22:13AM -0500, Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
>
> This flag informs kernel to bail out if an AIO request will block
> for reasons such as file allocations, or a writeback triggered,
> or would block while allocating requests while performing
> direct I/O.
>
> Unfortunately, aio_flags is not checked for validity, which would
> break existing applications which have it set to anything besides zero
> or IOCB_FLAG_RESFD. So, we are using aio_reserved1 and renaming it
> to aio_rw_flags.
>
> RWF_NOWAIT is translated to IOCB_NOWAIT for iocb->ki_flags.
>
> The check for -EOPNOTSUPP is placed in generic_file_write_iter(). This
> is called by most filesystems, either through fsops.write_iter() or through
> the function defined by write_iter(). If not, we perform the check defined
> by .write_iter() which is called for direct IO specifically.
>
> Filesystems xfs, btrfs and ext4 would be supported in the following patches.
>
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
> ---
> fs/9p/vfs_file.c | 3 +++
> fs/aio.c | 6 ++++++
> fs/ceph/file.c | 3 +++
> fs/cifs/file.c | 3 +++
> fs/fuse/file.c | 3 +++
> fs/nfs/direct.c | 3 +++
> fs/ocfs2/file.c | 3 +++
> include/linux/fs.h | 5 ++++-
> include/uapi/linux/fs.h | 1 +
> mm/filemap.c | 3 +++
> 10 files changed, 32 insertions(+), 1 deletion(-)
>
> diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
> index 3de3b4a89d89..403681db7723 100644
> --- a/fs/9p/vfs_file.c
> +++ b/fs/9p/vfs_file.c
> @@ -411,6 +411,9 @@ v9fs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
> loff_t origin;
> int err = 0;
>
> + if (iocb->ki_flags & IOCB_NOWAIT)
> + return -EOPNOTSUPP;
> +
> retval = generic_write_checks(iocb, from);
> if (retval <= 0)
> return retval;
> diff --git a/fs/aio.c b/fs/aio.c
> index 020fa0045e3c..ea9f8581d902 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -1592,6 +1592,12 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
> goto out_put_req;
> }
>
> + if ((req->common.ki_flags & IOCB_NOWAIT) &&
> + !(req->common.ki_flags & IOCB_DIRECT)) {
Weird indentation. Either align after the opening if brace:
if ((req->common.ki_flags & IOCB_NOWAIT) &&
!(req->common.ki_flags & IOCB_DIRECT)) {
or using two tabs:
if ((req->common.ki_flags & IOCB_NOWAIT) &&
!(req->common.ki_flags & IOCB_DIRECT)) {
if the first version looks confusing, but never using the same
indentation level as the following code.
Except for that the patch looks fine to me:
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
