[Gluster-devel] Dht readdir filtering out names

[Pranith Kumar Karampuri]

On Fri, Sep 30, 2016 at 9:50 AM, Raghavendra Gowdappa <rgowdapp at redhat.com>
wrote:

>
>
> ----- Original Message -----
> > From: "Pranith Kumar Karampuri" <pkarampu at redhat.com>
> > To: "Raghavendra Gowdappa" <rgowdapp at redhat.com>
> > Cc: "Shyam Ranganathan" <srangana at redhat.com>, "Nithya Balachandran" <
> nbalacha at redhat.com>, "Gluster Devel"
> > <gluster-devel at gluster.org>
> > Sent: Friday, September 30, 2016 9:15:04 AM
> > Subject: Re: Dht readdir filtering out names
> >
> > On Fri, Sep 30, 2016 at 9:13 AM, Raghavendra Gowdappa <
> rgowdapp at redhat.com>
> > wrote:
> >
> > > dht_readdirp_cbk has different behaviour for directories and files.
> > >
> > > 1. If file, pick the dentry (passed from subvols as part of readdirp
> > > response) if the it corresponds to data file.
> > > 2. If directory pick the dentry if readdirp response is from
> hashed-subvol.
> > >
> > > In all other cases, the dentry is skipped and not passed to higher
> > > layers/application. To elaborate, the dentries which are ignored are:
> > > 1. dentries corresponding to linkto files.
> > > 2. dentries from non-hashed subvols corresponding to directories.
> > >
> > > Since the behaviour is different for different filesystem objects, dht
> > > needs ia_type to choose its behaviour.
> > >
> > > ----- Original Message -----
> > > > From: "Pranith Kumar Karampuri" <pkarampu at redhat.com>
> > > > To: "Shyam Ranganathan" <srangana at redhat.com>, "Raghavendra
> Gowdappa" <
> > > rgowdapp at redhat.com>, "Nithya Balachandran"
> > > > <nbalacha at redhat.com>
> > > > Cc: "Gluster Devel" <gluster-devel at gluster.org>
> > > > Sent: Friday, September 30, 2016 8:39:28 AM
> > > > Subject: Dht readdir filtering out names
> > > >
> > > > hi,
> > > >        In dht_readdirp_cbk() there is a check about skipping files
> > > without
> > > > ia_type. Could you help me understand why this check is added? There
> are
> > > > times when users have to delete gfid of the entries and trigger
> something
> > > > like 'find . | xargs stat' to heal the gfids. This case would fail
> if we
> > > > skip entries without gfid, if the lower xlators don't send stat
> > > information
> > > > for them.
> > >
> > > Probably we can make readdirp_cbk not rely on ia_type and pass _all_
> > > dentries received by subvols to application without filtering. However
> we
> > > should make this behaviour optional and use this only for recovery
> setups.
> > > If we don't rely on ia_type (during non error scenarios), applications
> end
> > > up seeing duplicate dentries in readdir listing.
> > >
> >
> > That means dht_readdir() gives duplicate entries? As per the code it
> seems
> > like it...
>
> No. It follows the filtering logic of "pick dentry only from hashed
> subvol". This logic doesn't need ia_type. Now, that you brought the topic
> of dht_readdir, I've another solution for your use case (Basically don't
> use readdirp :) ):
>
> 1. mount glusterfs with "--use-readdirp=no" option.
> 2. disable md-cache/stat-prefetch as it converts all readdir calls into
> readdirp calls
>

Probably the ones in dht as well? i.e. use-readdirp option.


>
> Use this only for recovery setups :).
>
> >
> >
> > >
> > > >
> > > > --
> > > > Pranith
> > > >
> > >
> > > regards,
> > > Raghavendra
> > >
> >
> >
> >
> > --
> > Pranith
> >
>



-- 
Pranith
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