linux-ext4 - Re: [PATCH 8/8] nowait aio: btrfs

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Date:   Tue, 18 Apr 2017 13:39:02 +0200
From:   David Sterba <dsterba@...e.cz>
To:     Goldwyn Rodrigues <rgoldwyn@...e.de>
Cc:     linux-fsdevel@...r.kernel.org, jack@...e.com, hch@...radead.org,
        linux-block@...r.kernel.org, linux-btrfs@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org,
        sagi@...mberg.me, avi@...lladb.com, axboe@...nel.dk,
        linux-api@...r.kernel.org, willy@...radead.org,
        tom.leiming@...il.com, Goldwyn Rodrigues <rgoldwyn@...e.com>
Subject: Re: [PATCH 8/8] nowait aio: btrfs

On Fri, Apr 14, 2017 at 07:02:57AM -0500, Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@...e.com>
> 
> Return EAGAIN if any of the following checks fail
>  + i_rwsem is not lockable
>  + NODATACOW or PREALLOC is not set
>  + Cannot nocow at the desired location
>  + Writing beyond end of file which is not allocated
> 
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@...e.com>

Acked-by: David Sterba <dsterba@...e.com>

> +	if ((iocb->ki_flags & IOCB_NOWAIT) &&
> +			(iocb->ki_flags & IOCB_DIRECT)) {
> +		/* Don't sleep on inode rwsem */
> +		if (!inode_trylock(inode))
> +			return -EAGAIN;
> +		/*
> +		 * We will allocate space in case nodatacow is not set,
> +		 * so bail
> +		 */
> +		if (!(BTRFS_I(inode)->flags & (BTRFS_INODE_NODATACOW |
> +					      BTRFS_INODE_PREALLOC)) ||
> +		    check_can_nocow(BTRFS_I(inode), pos, &count) <= 0) {
> +			inode_unlock(inode);
> +			return -EAGAIN;
> +		}
> +	} else

	} else {

> +		inode_lock(inode);

	}