linux-ext4 - Re: [PATCH v2 3/4] ext4: Add iomap support for inline data

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Message-ID: <20170928175748.23b7wkjiqavpunvj@thunk.org>
Date:   Thu, 28 Sep 2017 13:57:48 -0400
From:   Theodore Ts'o <tytso@....edu>
To:     Andreas Gruenbacher <agruenba@...hat.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-xfs@...r.kernel.org, Jan Kara <jack@...e.cz>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v2 3/4] ext4: Add iomap support for inline data

On Thu, Sep 14, 2017 at 11:50:46AM +0200, Andreas Gruenbacher wrote:
> +int ext4_inline_data_iomap(struct inode *inode, struct iomap *iomap)
> +{
> +	__u64 addr;
> +	int error = -EAGAIN;
> +	struct ext4_iloc iloc;
> +
> +	down_read(&EXT4_I(inode)->xattr_sem);
> +	if (!ext4_has_inline_data(inode))
> +		goto out;
	....
> +out:
> +	up_read(&EXT4_I(inode)->xattr_sem);
> +	return error;
> +}


If we race with the inline data flag getting cleared,
ext4_iomap_begin() will return with -EAGAIN.  As near as I can tell,
this will get reflected all the way up to userspace, instead of having
the retry happen in the kernel.  Is this intentional?

It looks like a user visible change, no?

						- Ted