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Subject: Re: [PATCH] ext4: Do not block RWF_NOWAIT dio write on unallocated
 space
To:     Jan Kara <jack@suse.cz>, Ted Tso <tytso@mit.edu>
Cc:     linux-ext4@vger.kernel.org
References: <20200708153516.9507-1-jack@suse.cz>
From:   Ritesh Harjani <riteshh@linux.ibm.com>
Date:   Wed, 8 Jul 2020 23:25:44 +0530
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On 7/8/20 9:05 PM, Jan Kara wrote:
> Since commit 378f32bab371 ("ext4: introduce direct I/O write using iomap
> infrastructure") we don't properly bail out of RWF_NOWAIT direct IO
> write if underlying blocks are not allocated. Also
> ext4_dio_write_checks() does not honor RWF_NOWAIT when re-acquiring
> i_rwsem. Fix both issues.
> 
> Fixes: 378f32bab371 ("ext4: introduce direct I/O write using iomap infrastructure")
> Reported-by: Filipe Manana <fdmanana@gmail.com>
> Signed-off-by: Jan Kara <jack@suse.cz>

LGTM, feel free to add
Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com>

> ---
>   fs/ext4/file.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> index 2a01e31a032c..8f742b53f1d4 100644
> --- a/fs/ext4/file.c
> +++ b/fs/ext4/file.c
> @@ -428,6 +428,10 @@ static ssize_t ext4_dio_write_checks(struct kiocb *iocb, struct iov_iter *from,
>   	 */
>   	if (*ilock_shared && (!IS_NOSEC(inode) || *extend ||
>   	     !ext4_overwrite_io(inode, offset, count))) {
> +		if (iocb->ki_flags & IOCB_NOWAIT) {
> +			ret = -EAGAIN;
> +			goto out;
> +		}
>   		inode_unlock_shared(inode);
>   		*ilock_shared = false;
>   		inode_lock(inode);
>