* libfs.c:simple_lookup
@ 2007-02-19 20:09 Jan Engelhardt
2007-02-19 21:35 ` libfs.c:simple_lookup Dave Kleikamp
0 siblings, 1 reply; 3+ messages in thread
From: Jan Engelhardt @ 2007-02-19 20:09 UTC (permalink / raw)
To: linux-fsdevel
Hello,
simple_lookup() in fs/libfs.c does some extra steps, namely
dentry->d_op = &simple_dentry_operations;
d_add(dentry, NULL);
as far as I understand, this creates a negative dentry which will be
deleted sometime later again. Is not it easier to not create it at all
(since it is not going to be existent anyway)?
Jan
--
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: libfs.c:simple_lookup
2007-02-19 20:09 libfs.c:simple_lookup Jan Engelhardt
@ 2007-02-19 21:35 ` Dave Kleikamp
2007-02-19 22:49 ` libfs.c:simple_lookup Jan Engelhardt
0 siblings, 1 reply; 3+ messages in thread
From: Dave Kleikamp @ 2007-02-19 21:35 UTC (permalink / raw)
To: Jan Engelhardt; +Cc: linux-fsdevel
On Mon, 2007-02-19 at 21:09 +0100, Jan Engelhardt wrote:
> Hello,
>
>
> simple_lookup() in fs/libfs.c does some extra steps, namely
>
> dentry->d_op = &simple_dentry_operations;
> d_add(dentry, NULL);
>
> as far as I understand, this creates a negative dentry which will be
> deleted sometime later again. Is not it easier to not create it at all
> (since it is not going to be existent anyway)?
I'm not sure I understand the question, so allow me to restate a similar
question, and you can tell me if we're asking the same thing.
In general, the negative dentry avoids the overhead of looking up a
non-existent entry more than once by "remembering" that the entry does
not exist. Since there is almost no overhead to calling
simple_lookup(), would be be better off simply returning without
creating the negative dentry (and letting simple_lookup be called more
often)?
Shaggy
--
David Kleikamp
IBM Linux Technology Center
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: libfs.c:simple_lookup
2007-02-19 21:35 ` libfs.c:simple_lookup Dave Kleikamp
@ 2007-02-19 22:49 ` Jan Engelhardt
0 siblings, 0 replies; 3+ messages in thread
From: Jan Engelhardt @ 2007-02-19 22:49 UTC (permalink / raw)
To: Dave Kleikamp; +Cc: linux-fsdevel
On Feb 19 2007 15:35, Dave Kleikamp wrote:
>On Mon, 2007-02-19 at 21:09 +0100, Jan Engelhardt wrote:
>> Hello,
>>
>>
>> simple_lookup() in fs/libfs.c does some extra steps, namely
>>
>> dentry->d_op = &simple_dentry_operations;
>> d_add(dentry, NULL);
>>
>> as far as I understand, this creates a negative dentry which will be
>> deleted sometime later again. Is not it easier to not create it at all
>> (since it is not going to be existent anyway)?
>
>I'm not sure I understand the question, so allow me to restate a similar
>question, and you can tell me if we're asking the same thing.
>
>In general, the negative dentry avoids the overhead of looking up a
>non-existent entry more than once by "remembering" that the entry does
>not exist.
Ah, thanks. That might indeed make sense for disk-based filesystems.
> Since there is almost no overhead to calling
>simple_lookup(), would be be better off simply returning without
>creating the negative dentry (and letting simple_lookup be called more
>often)?
Yes, that is what I was out at. - The comment above simple_lookup already says
it - if it's not already positive, it does not exist.
Jan
--
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2007-02-19 22:49 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2007-02-19 20:09 libfs.c:simple_lookup Jan Engelhardt
2007-02-19 21:35 ` libfs.c:simple_lookup Dave Kleikamp
2007-02-19 22:49 ` libfs.c:simple_lookup Jan Engelhardt
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