[Gluster-devel] Get GFID for a file through libgfapi

[Ankireddypalle Reddy]

Neils,
            Thanks for pointing to the sample code. The use case is to use  GFID as a unique key for maintaining indexing information about a file when it is being backed up from GlusterFS storage.  Extending GFAPI to extract GFID for a file would be great.
             As  per the example If I need to find GFID for a path p1/p2/p3/p4 on a glusterfs volume then should I do a look up for every level?
             LOOKUP (/)->LOOKUP(p1)-> LOOKUP(p2)-> LOOKUP(p3)-> LOOKUP(p4)

Thanks and Regards,
Ram


-----Original Message-----
From: Niels de Vos [mailto:ndevos at redhat.com] 
Sent: Monday, January 09, 2017 3:39 PM
To: Ankireddypalle Reddy
Cc: Gluster Devel (gluster-devel at gluster.org); integration at gluster.org
Subject: Re: [Gluster-devel] Get GFID for a file through libgfapi

On Mon, Jan 09, 2017 at 05:53:03PM +0000, Ankireddypalle Reddy wrote:
> Hi,
>         I am trying to extract the GFID for a file through libgfapi interface. When I try to extract the value of extended attribute glusterfs.gfid through libgfapi I get the errorno: 95.  This works for FUSE though. Is there a way to extract the GFID for a file through libgfapi.

It seems that this is a case where FUSE handles the xatts special. The glusterfs.gfid and glusterfs.gfid.string (VIRTUAL_GFID_XATTR_KEY and
VIRTUAL_GFID_XATTR_KEY_STR) are specifically handled in xlators/mount/fuse/src/fuse-bridge.c.

There is a way to get the GFID, but it probably is rather a cumbersome workaround for you. The handle-API is used heavily by NFS-Ganesha (because NFS uses filehandles more than filenames), and extracts the GFID from the 'struct glfs_object' with glfs_h_extract_handle(). A basic example of how to obtain and extract the handle is in https://github.com/gluster/glusterfs/blob/master/tests/basic/gfapi/bug1291259.c

Could you explain the need for knowing the GFID in the application? We can extend gfapi with fetching the GFID if that would help you.

Niels


PS: we have a new integration at gluster.org where external projects can ask gfapi related questions. The gluster-devel list tends to be a little heavy on traffic for non-Gluster developers.
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