linux-ext4 - Re: [PATCH 1/3] vfs: Add page_cache_seek_hole

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Message-ID: <CAHc6FU4FdeceDTZHDN4NtH2oA2Yq-XcmAceVaSJY3y2g40-w0g@mail.gmail.com>
Date:   Mon, 26 Jun 2017 12:51:29 +0200
From:   Andreas Gruenbacher <agruenba@...hat.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-ext4 <linux-ext4@...r.kernel.org>,
        linux-xfs@...r.kernel.org, Jan Kara <jack@...e.cz>
Subject: Re: [PATCH 1/3] vfs: Add page_cache_seek_hole_data helper

On Mon, Jun 26, 2017 at 12:41 PM, Christoph Hellwig <hch@...radead.org> wrote:
> On Fri, Jun 23, 2017 at 02:19:31AM +0200, Andreas Gruenbacher wrote:
>> Both ext4 and xfs implement seeking for the next hole or piece of data
>> in unwritten extents by scanning the page cache, and both versions share
>> the same bug when iterating the buffers of a page: the start offset into
>> the page isn't taken into account, so when a page fits more than two
>> filesystem blocks, things will go wrong.  For example, on a filesystem
>> with a block size of 1k, the following command will fail:
>>
>>   xfs_io -f -c "falloc 0 4k" \
>>             -c "pwrite 1k 1k" \
>>             -c "pwrite 3k 1k" \
>>             -c "seek -a -r 0" foo
>
> Can you wire this up for xfstests, please?

I did:

  https://marc.info/?l=fstests&m=149817668119033

Andreas