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From: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>
To: Goldwyn Rodrigues <rgoldwyn-l3A5Bk7waGM@public.gmane.org>
Cc: linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	jack-IBi9RG/b67k@public.gmane.org,
	hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org,
	linux-block-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-btrfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-xfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	sagi-NQWnxTmZq1alnMjI0IkVqw@public.gmane.org,
	avi-VrcmuVmyx1hWk0Htik3J/w@public.gmane.org,
	axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org,
	linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Goldwyn Rodrigues <rgoldwyn-IBi9RG/b67k@public.gmane.org>
Subject: Re: [PATCH 04/10] fs: Introduce RWF_NOWAIT
Date: Mon, 15 May 2017 11:47:09 +0200
Message-ID: <20170515094709.GA16182@quack2.suse.cz> (raw)
In-Reply-To: <20170511191710.31959-5-rgoldwyn-l3A5Bk7waGM@public.gmane.org>

On Thu 11-05-17 14:17:04, Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn-IBi9RG/b67k@public.gmane.org>
> 
> 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.
...
> diff --git a/fs/aio.c b/fs/aio.c
> index 020fa0045e3c..34027b67e2f4 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)) {
> +		ret = -EOPNOTSUPP;
> +		goto out_put_req;
> +	}
> +
>  	ret = put_user(KIOCB_KEY, &user_iocb->aio_key);
>  	if (unlikely(ret)) {
>  		pr_debug("EFAULT: aio_key\n");

I think you need to also check here that the IO is write. So that NOWAIT
reads don't silently pass.

								Honza
-- 
Jan Kara <jack-IBi9RG/b67k@public.gmane.org>
SUSE Labs, CR

  parent reply index

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-11 19:17 [PATCH 0/10 v8] No wait AIO Goldwyn Rodrigues
2017-05-11 19:17 ` [PATCH 01/10] fs: Separate out kiocb flags setup based on RWF_* flags Goldwyn Rodrigues
2017-05-11 19:17 ` [PATCH 02/10] fs: Introduce filemap_range_has_page() Goldwyn Rodrigues
     [not found] ` <20170511191710.31959-1-rgoldwyn-l3A5Bk7waGM@public.gmane.org>
2017-05-11 19:17   ` [PATCH 03/10] fs: Use RWF_* flags for AIO operations Goldwyn Rodrigues
2017-05-11 19:17 ` [PATCH 04/10] fs: Introduce RWF_NOWAIT Goldwyn Rodrigues
     [not found]   ` <20170511191710.31959-5-rgoldwyn-l3A5Bk7waGM@public.gmane.org>
2017-05-15  9:47     ` Jan Kara [this message]
2017-05-11 19:17 ` [PATCH 05/10] fs: return if direct write will trigger writeback Goldwyn Rodrigues
2017-05-11 19:17 ` [PATCH 06/10] fs: Introduce IOMAP_NOWAIT Goldwyn Rodrigues
2017-05-11 19:17 ` [PATCH 07/10] fs: return on congested block device Goldwyn Rodrigues
2017-05-11 19:17 ` [PATCH 08/10] ext4: nowait aio support Goldwyn Rodrigues
2017-05-11 19:17 ` [PATCH 09/10] xfs: " Goldwyn Rodrigues
2017-05-11 19:17 ` [PATCH 10/10] btrfs: " Goldwyn Rodrigues
2017-05-24 16:41 [PATCH 0/10 v9] No wait AIO Goldwyn Rodrigues
2017-05-24 16:41 ` [PATCH 04/10] fs: Introduce RWF_NOWAIT Goldwyn Rodrigues
2017-05-25  8:30   ` Jan Kara
2017-06-05  5:35 [PATCH 0/10 v10] No wait AIO Goldwyn Rodrigues
2017-06-05  5:35 ` [PATCH 04/10] fs: Introduce RWF_NOWAIT Goldwyn Rodrigues
2017-06-06 11:19 [PATCH 0/10 v11] No wait AIO Goldwyn Rodrigues
2017-06-06 11:19 ` [PATCH 04/10] fs: Introduce RWF_NOWAIT Goldwyn Rodrigues
     [not found]   ` <20170606111939.27272-5-rgoldwyn-l3A5Bk7waGM@public.gmane.org>
2017-06-10  5:27     ` Al Viro

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