libgfapi: adding 'follow' flag to glfs_h_lookupat()

This patch is backport of http://review.gluster.org/#/c/11883/

Previously glfs_h_lookupat won't follow the symlink, this patch
introduces new flag `follow` which will resolve the same. Applications
linking against the new library will need to use the new glfs_h_lookupat
API call.

In order to stay compatible with existing binaries that use the previous
glfs_h_lookupat() function, the old symbol needs to stay available.

Verification that there are two versions of glfs_h_lookupat:

  $ objdump -T /usr/lib64/libgfapi.so.0 | grep -w glfs_h_lookupat
  0000000000015070 g    DF .text  000000000000021e  GFAPI_3.7.4 glfs_h_lookupat
  0000000000015290 g    DF .text  0000000000000008 (GFAPI_3.4.2) glfs_h_lookupat

Testing with a binary (based on anonymous_fd_read_write.c from ./tests/)
that was linked against the old library:

  $ objdump -T ./lookupat | grep -w glfs_h_lookupat
  0000000000000000      DF *UND*  0000000000000000  GFAPI_3.4.2 glfs_h_lookupat

Enable debugging for 'ld.so' so that we can check that the GFAPI_3.4.2
version of the symbol gets loaded:

  $ export LD_DEBUG_OUTPUT=lookupat.ld.log LD_DEBUG=all
  $ ./lookupat
  $ grep -w glfs_h_lookupat lookupat.ld.log.2543
  2543:     symbol=glfs_h_lookupat;  lookup in file=./lookupat [0]
  2543:     symbol=glfs_h_lookupat;  lookup in file=/lib64/libgfapi.so.0 [0]
  2543:     binding file ./lookupat [0] to /lib64/libgfapi.so.0 [0]: normal symbol `glfs_h_lookupat' [GFAPI_3.4.2]

This change has been successfully cherry-picked as 1ead86a8bcbfe4045729466e4b98f765f3c13c8d
in master

Upstream reference
>Change-Id: I8bf9b1c19a0585f681bc1a7f84aad1ccd0f75f6a
>BUG: 1252410
>Signed-off-by: Jiffin Tony Thottan <jthottan@redhat.com>
>Signed-off-by: Niels de Vos <ndevos@redhat.com>
>Reviewed-on: http://review.gluster.org/11883
>Reviewed-by: soumya k <skoduri@redhat.com>
>Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>
>Tested-by: NetBSD Build System <jenkins@build.gluster.org>
Signed-off-by: Jiffin Tony Thottan <jthottan@redhat.com>

Change-Id: Idbbf0cd6802f86c53b16377d90d08ff6d99e7b08
BUG: 1256616
Reviewed-on: http://review.gluster.org/12009
Tested-by: NetBSD Build System <jenkins@build.gluster.org>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>

0 files changed, 0 insertions, 0 deletions