On 01/10/2017 02:55 PM, Niels de Vos wrote:
On Mon, Jan 09, 2017 at 08:58:07PM +0000, Ankireddypalle Reddy wrote:
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)
No, that is not required. You can use glfs_h_lookupat() with the full
path. Note that glfs_h_extract_handle() just does a memcpy() of the GFID
into the given (unsigned char*), the format is of 'uuid_t'.
The handle is an abstraction and hence we do not identify it as a GFID
per-se, isn't asking to assume the handle is the GFID breaking this
abstraction?
IOW, if we publish this, then the handle is always the GFID and
vice-versa, are we fine with this?
Attached is the modified test that shows the UUID without the need for a
lookup of each component of the directory (a LOOKUP will be done by
gfapi if needed).
$ make CFLAGS="-lgfapi -luuid" resolve
cc -lgfapi -luuid resolve.c -o resolve
$ ./resolve storage.example.com media resolve.log
Starting libgfapi_fini
glfs_set_volfile_server : returned 0
glfs_set_logging : returned 0
glfs_init : returned 0
glfs_set_volfile_server : returned 0
glfs_set_logging : returned 0
glfs_init : returned 0
glfs_h_extract_handle : returned 0
UUID of /installation/CentOS-7-x86_64-Everything-1503-01.iso:
b1b20352-c71c-4579-b678-a7a38b0e9a84
glfs_fini : returned 0
End of libgfapi_fini
$ getfattr -n glusterfs.gfid -ehex
/lan/storage.example.com/media/installation/CentOS-7-x86_64-Everything-1503-01.iso
getfattr: Removing leading '/' from absolute path names
# file:
lan/storage.example.com/media/installation/CentOS-7-x86_64-Everything-1503-01.iso
glusterfs.gfid=0xb1b20352c71c4579b678a7a38b0e9a84
HTH,
Niels
Thanks and Regards,
Ram
-----Original Message-----
From: Niels de Vos [mailto:[email protected]]
Sent: Monday, January 09, 2017 3:39 PM
To: Ankireddypalle Reddy
Cc: Gluster Devel ([email protected]); [email protected]
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 [email protected] 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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