Re: [PATCH 04/10] fs: Introduce RWF_NOWAIT

[Jan Kara <jack@suse.cz>]

On Wed 24-05-17 11:41:44, Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@suse.com>
> 
> RWF_NOWAIT 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.
> 
> 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@suse.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Looks good now. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza


> ---
>  fs/9p/vfs_file.c        |  3 +++
>  fs/aio.c                | 13 +++++++++++++
>  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, 39 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..9616dc733103 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -1592,6 +1592,19 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
>  		goto out_put_req;
>  	}
>  
> +	if (req->common.ki_flags & IOCB_NOWAIT) {
> +		if (!(req->common.ki_flags & IOCB_DIRECT)) {
> +			ret = -EOPNOTSUPP;
> +			goto out_put_req;
> +		}
> +
> +		if ((iocb->aio_lio_opcode != IOCB_CMD_PWRITE) &&
> +		    (iocb->aio_lio_opcode != IOCB_CMD_PWRITEV)) {
> +			ret = -EINVAL;
> +			goto out_put_req;
> +		}
> +	}
> +
>  	ret = put_user(KIOCB_KEY, &user_iocb->aio_key);
>  	if (unlikely(ret)) {
>  		pr_debug("EFAULT: aio_key\n");
> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
> index 3fdde0b283c9..a53fd2675b1b 100644
> --- a/fs/ceph/file.c
> +++ b/fs/ceph/file.c
> @@ -1300,6 +1300,9 @@ static ssize_t ceph_write_iter(struct kiocb *iocb, struct iov_iter *from)
>  	int err, want, got;
>  	loff_t pos;
>  
> +	if (iocb->ki_flags & IOCB_NOWAIT)
> +		return -EOPNOTSUPP;
> +
>  	if (ceph_snap(inode) != CEPH_NOSNAP)
>  		return -EROFS;
>  
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index 0fd081bd2a2f..ff84fa9ddb6c 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -2725,6 +2725,9 @@ ssize_t cifs_user_writev(struct kiocb *iocb, struct iov_iter *from)
>  	 * write request.
>  	 */
>  
> +	if (iocb->ki_flags & IOCB_NOWAIT)
> +		return -EOPNOTSUPP;
> +
>  	rc = generic_write_checks(iocb, from);
>  	if (rc <= 0)
>  		return rc;
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 3ee4fdc3da9e..812c7bd0c290 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -1425,6 +1425,9 @@ static ssize_t fuse_direct_write_iter(struct kiocb *iocb, struct iov_iter *from)
>  	struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(file);
>  	ssize_t res;
>  
> +	if (iocb->ki_flags & IOCB_NOWAIT)
> +		return -EOPNOTSUPP;
> +
>  	if (is_bad_inode(inode))
>  		return -EIO;
>  
> diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
> index 6fb9fad2d1e6..c8e7dd76126c 100644
> --- a/fs/nfs/direct.c
> +++ b/fs/nfs/direct.c
> @@ -979,6 +979,9 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter)
>  	dfprintk(FILE, "NFS: direct write(%pD2, %zd@%Ld)\n",
>  		file, iov_iter_count(iter), (long long) iocb->ki_pos);
>  
> +	if (iocb->ki_flags & IOCB_NOWAIT)
> +		return -EOPNOTSUPP;
> +
>  	result = generic_write_checks(iocb, iter);
>  	if (result <= 0)
>  		return result;
> diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
> index bfeb647459d9..e7f8ba890305 100644
> --- a/fs/ocfs2/file.c
> +++ b/fs/ocfs2/file.c
> @@ -2235,6 +2235,9 @@ static ssize_t ocfs2_file_write_iter(struct kiocb *iocb,
>  	if (count == 0)
>  		return 0;
>  
> +	if (iocb->ki_flags & IOCB_NOWAIT)
> +		return -EOPNOTSUPP;
> +
>  	direct_io = iocb->ki_flags & IOCB_DIRECT ? 1 : 0;
>  
>  	inode_lock(inode);
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index dc0ab585cd56..2a7d14af6d12 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -268,6 +268,7 @@ struct writeback_control;
>  #define IOCB_DSYNC		(1 << 4)
>  #define IOCB_SYNC		(1 << 5)
>  #define IOCB_WRITE		(1 << 6)
> +#define IOCB_NOWAIT		(1 << 7)
>  
>  struct kiocb {
>  	struct file		*ki_filp;
> @@ -3060,7 +3061,7 @@ static inline int iocb_flags(struct file *file)
>  
>  static inline int kiocb_set_rw_flags(struct kiocb *ki, int flags)
>  {
> -	if (unlikely(flags & ~(RWF_HIPRI | RWF_DSYNC | RWF_SYNC)))
> +	if (unlikely(flags & ~(RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT)))
>  		return -EOPNOTSUPP;
>  
>  	if (flags & RWF_HIPRI)
> @@ -3069,6 +3070,8 @@ static inline int kiocb_set_rw_flags(struct kiocb *ki, int flags)
>  		ki->ki_flags |= IOCB_DSYNC;
>  	if (flags & RWF_SYNC)
>  		ki->ki_flags |= (IOCB_DSYNC | IOCB_SYNC);
> +	if (flags & RWF_NOWAIT)
> +		ki->ki_flags |= IOCB_NOWAIT;
>  	return 0;
>  }
>  
> diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
> index 24e61a54feaa..29969fb7f9a7 100644
> --- a/include/uapi/linux/fs.h
> +++ b/include/uapi/linux/fs.h
> @@ -360,5 +360,6 @@ struct fscrypt_key {
>  #define RWF_HIPRI			0x00000001 /* high priority request, poll if possible */
>  #define RWF_DSYNC			0x00000002 /* per-IO O_DSYNC */
>  #define RWF_SYNC			0x00000004 /* per-IO O_SYNC */
> +#define RWF_NOWAIT			0x00000008 /* per-IO, return -EAGAIN if operation would block */
>  
>  #endif /* _UAPI_LINUX_FS_H */
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 87aba7698584..097213275461 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -3006,6 +3006,9 @@ ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
>  	struct inode *inode = file->f_mapping->host;
>  	ssize_t ret;
>  
> +	if (iocb->ki_flags & IOCB_NOWAIT)
> +		return -EOPNOTSUPP;
> +
>  	inode_lock(inode);
>  	ret = generic_write_checks(iocb, from);
>  	if (ret > 0)
> -- 
> 2.12.0
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR