From: Christoph Hellwig <hch@infradead.org>
To: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@infradead.org>,
Jeff Liu <jeff.liu@oracle.com>,
xfs@oss.sgi.com
Subject: Re: SEEK_DATA/SEEK_HOLE support
Date: Tue, 4 Oct 2011 09:02:08 -0400 [thread overview]
Message-ID: <20111004130208.GA19263@infradead.org> (raw)
In-Reply-To: <20111003234305.GM3159@dastard>
On Tue, Oct 04, 2011 at 10:43:05AM +1100, Dave Chinner wrote:
> The lookup is pretty simple - if there's cached data over the
> unwritten range, then I'm considering it a data range. If there's no
> cached data over the unwritten extent, it's a hole. That makes the
> lookup simply a case of finding the first cached page in the
> unwritten extent.
>
> It'll end up reading something like this:
>
> iomap = offset_to_extent(offset);
> first_index = extent_to_page_index(iomap);
>
> nr_found = pagevec_lookup(&pvec, inode->i_mapping, first_index, 1);
> if (!nr_found)
> break;
>
> offset = page->index << PAGECACHE_SHIFT;
> pagevec_release(&pvec);
>
> /* If we fell off the end of the extent lookup next extent */
> if (offset >= end_of_extent(iomap)) {
> offset = end_of_extent(iomap);
> goto next_extent;
> }
>
> All the extent manipulations are pretty filesystem specific, so
> there's not much that can be extracted into generic helper, I
> think...
Actually pretty similar code will work just fine if you passt the
start + len of the extents in (which we got from looking it up
fs-specificly):
Note that we have to look for both dirty and writeback pages to
make it safe.
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next prev parent reply other threads:[~2011-10-04 13:02 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-02 15:04 SEEK_DATA/SEEK_HOLE support Jeff Liu
2011-10-02 15:42 ` Christoph Hellwig
2011-10-02 16:06 ` Jeff Liu
2011-10-02 17:59 ` Christoph Hellwig
2011-10-02 19:11 ` Andi Kleen
2011-10-03 4:04 ` Jeff Liu
2011-10-03 23:43 ` Dave Chinner
2011-10-04 13:02 ` Christoph Hellwig [this message]
2011-10-05 4:36 ` Dave Chinner
2011-10-05 5:32 ` Jeff Liu
2011-10-05 9:23 ` Dave Chinner
2011-10-05 13:56 ` Jeff Liu
2011-10-05 7:34 ` Michael Monnerie
2011-10-05 9:36 ` Dave Chinner
2011-10-05 18:22 ` Michael Monnerie
2011-10-06 0:32 ` Dave Chinner
2011-11-14 10:24 ` Christoph Hellwig
2011-11-14 12:47 ` Jeff Liu
2011-11-14 12:50 ` Christoph Hellwig
2011-11-19 8:29 ` XFS SEEK_DATA/SEEK_HOLE support V1 Jeff Liu
2011-11-19 8:34 ` Jeff Liu
2011-11-19 8:37 ` [PATCH] Introduce SEEK_DATA/SEEK_HOLE support to XFS V1 Jeff Liu
2011-11-19 19:11 ` Christoph Hellwig
2011-11-20 13:15 ` Jeff Liu
2011-11-20 0:30 ` Dave Chinner
2011-11-20 13:59 ` Jeff Liu
2011-11-20 15:30 ` Christoph Hellwig
2011-11-20 22:34 ` Dave Chinner
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