unix_convert() and amount of stat() calls

Stefan (metze) Metzmacher metze at samba.org
Thu Sep 9 09:10:32 MDT 2010

Am 09.09.2010 11:43, schrieb Stefan (metze) Metzmacher:
> Am 09.09.2010 01:09, schrieb Jeremy Allison:
>> On Wed, Sep 08, 2010 at 02:58:10PM -0700, Jeremy Allison wrote:
>>> On Tue, Sep 07, 2010 at 09:40:17PM +0200, Stefan (metze) Metzmacher wrote:
>>>> Hi Jeremy,
>>>> what's the reason that we loop over the components
>>>> from the root to the leaf, when checking them?
>>>> Can't we start with the last component?
>>>> At least if it's related to a wildcard search.
>>>> Maybe we only need to check the last 2 components,
>>>> unless the name is mangled?
>>>> The problem I want to solve in this branch:
>>>> http://gitweb.samba.org/?p=metze/samba/wip.git;a=shortlog;h=refs/heads/samba-3.4.7-ctdb-10
>>>> is this:
>>>> FindFirst with 'path\to\some\dir\with\files\*'
>>>> triggers the following stat calls
>>>> path\to\some\dir\with\files\* => ENOENT (this should be already solved
>>>> with my patches)
>>>> path\
>>>> path\to\
>>>> path\to\some\
>>>> path\to\some\dir\
>>>> path\to\some\dir\with\
>>>> path\to\some\dir\with\files\
>>>> path\to\some\dir\with\files\* => ENOENT
>>> Ok, I have a patch for this. Give me a min and I'll post it.
>> Ok - here's the patch that should fix it. It passes both
>> RAW-CHKPATH and RAW-SEARCH. It adds an optimization into
>> the wildcard lookup code such that it checks if the wildcard
>> is in the last component of the lookup, and if so tries to
>> directly do a stat on the parent directory. If this succeeds
>> it short-circuits the pathname walk and starts the lookup at
>> the last component.
>> This means an incoming pathname of :
>> FindFirst with 'path\to\some\dir\with\files\*'
>> should now do the following stat calls (presuming
>> the directory exists of course):
>> path\to\some\dir\with\files\* => ENOENT
>> path\to\some\dir\with\files = OK
> You mean we only do this, correct?
> path\to\some\dir\with\files = OK
> At least that's what I want and what the code looks like.
>> It doesn't currently add "path\to\some\dir\with\files"
>> into the stat cache (although that could be added) as
>> I'd have to alloc and truncate the incoming path at
>> the same position as the parent directory length, which
>> might be a little tricky. Anyway that's not neccessary
>> for correctness.
>> I'm going to do some more stream testing, and then commit
>> if it looks good. Metze (or Volker) please comment.

Does this backports look ok for you?


Everything below "DEBUG it"

In the findfirst case in 3.4.7 we also trigger a stat() calls for the
pathes ending with \*
in the check_name() function after the unix_convert... I'll try to
optimize that too.


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