On 25.03.2011 21:15, Chris Mason wrote:
Excerpts from Arne Jansen's message of 2011-03-25 16:14:35 -0400:
On 23.03.2011 20:32, Chris Mason wrote:
Excerpts from Arne Jansen's message of 2011-03-23 09:06:02 -0400:
For the implementation I'd need an interface which I haven't been able
to find yet. Currently I can trigger the read of several pages / tree
blocks and wait for the completion of each of them. What I'd need would
be an interface that gives me a callback on each completion or a waiting
function that wakes up on each completion with the information which
pages just completed.
One way to achieve this would be to add a hook, but I gladly take any
implementation hints.
We have the bio endio call backs for this, I think that's the only thing
you can use.
ok, so I'll add a new extent state bit EXTENT_READAHEAD and test for it
in btree_readpage_end_io_hook.
It's also common to use a chain of endio handlers. If you're allocating
any state for the RA, you just save the original endio handler in your
new struct, and then use your own endio handler that does the readahead
smarts.
Do you mean replacing the bio end_io handler or the
readpage_end_io_hook? As I want the pages to end up in the page cache,
I'd like to use as much of the existing infrastructure as possible.
To intercept the bio deep down in the chain would mean to duplicate
some code on the way down and on the way up again.
-Arne
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