[Gluster-devel] Dht readdir filtering out names

[Pranith Kumar Karampuri]

Does samba/gfapi/nfs-ganesha have options to disable readdirp?

On Fri, Sep 30, 2016 at 10:04 AM, Pranith Kumar Karampuri <
pkarampu at redhat.com> wrote:

> What if the lower xlators want to set the entry->inode to NULL and clear
> the entry->d_stat to force a lookup on the name? i.e.
> gfid-split-brain/ia_type mismatches.
>
> On Fri, Sep 30, 2016 at 10:00 AM, Raghavendra Gowdappa <
> rgowdapp at redhat.com> wrote:
>
>>
>>
>> ----- Original Message -----
>> > From: "Raghavendra Gowdappa" <rgowdapp at redhat.com>
>> > To: "Pranith Kumar Karampuri" <pkarampu 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 9:58:34 AM
>> > Subject: Re: Dht readdir filtering out names
>> >
>> >
>> >
>> > ----- 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 9:53:44 AM
>> > > Subject: Re: Dht readdir filtering out names
>> > >
>> > > 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.
>> >
>> > No. dht doesn't convert a readdir into readdirp. The option you are
>> referring
>> > to might be "readdir-optimize" which is something different.
>>
>> Sorry. I was wrong. There is an option in dht too, to force using
>> readdirp. As you said, we should disable that too.
>>
>> >
>> > >
>> > >
>> > > >
>> > > > Use this only for recovery setups :).
>> > > >
>> > > > >
>> > > > >
>> > > > > >
>> > > > > > >
>> > > > > > > --
>> > > > > > > Pranith
>> > > > > > >
>> > > > > >
>> > > > > > regards,
>> > > > > > Raghavendra
>> > > > > >
>> > > > >
>> > > > >
>> > > > >
>> > > > > --
>> > > > > Pranith
>> > > > >
>> > > >
>> > >
>> > >
>> > >
>> > > --
>> > > Pranith
>> > >
>> >
>>
>
>
>
> --
> Pranith
>



-- 
Pranith
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