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>

4 files changed, 24 insertions, 9 deletions

diff --git a/api/src/gfapi.aliases b/api/src/gfapi.aliases
index 9776c87fdcb..40b6ed21192 100644
--- a/api/src/gfapi.aliases
+++ b/api/src/gfapi.aliases
@@ -89,7 +89,7 @@ _pub_glfs_dup _glfs_dup$GFAPI_3.4.0
 _pub_glfs_setfsuid _glfs_setfsuid$GFAPI_3.4.2
 _pub_glfs_setfsgid _glfs_setfsgid$GFAPI_3.4.2
 _pub_glfs_setfsgroups _glfs_setfsgroups$GFAPI_3.4.2
-_pub_glfs_h_lookupat _glfs_h_lookupat$GFAPI_3.4.2
+_pub_glfs_h_lookupat34 _glfs_h_lookupat$GFAPI_3.4.2
 _pub_glfs_h_creat _glfs_h_creat$GFAPI_3.4.2
 _pub_glfs_h_mkdir _glfs_h_mkdir$GFAPI_3.4.2
 _pub_glfs_h_mknod _glfs_h_mknod$GFAPI_3.4.2
@@ -138,3 +138,5 @@ _priv_glfs_free_from_ctx _glfs_free_from_ctx$GFAPI_PRIVATE_3.7.0
 _priv_glfs_new_from_ctx _glfs_new_from_ctx$GFAPI_PRIVATE_3.7.0
 _priv_glfs_resolve _glfs_resolve$GFAPI_PRIVATE_3.7.0
 _priv_glfs_process_upcall_event _glfs_process_upcall_event$GFAPI_PRIVATE_3.7.0
+
+_pub_glfs_h_lookupat _glfs_h_lookupat$GFAPI_3.7.4
diff --git a/api/src/gfapi.map b/api/src/gfapi.map
index 48863985135..d42ae2b97af 100644
--- a/api/src/gfapi.map
+++ b/api/src/gfapi.map
@@ -98,7 +98,6 @@ GFAPI_3.4.2 {
 		glfs_setfsuid;
 		glfs_setfsgid;
 		glfs_setfsgroups;
-		glfs_h_lookupat;
 		glfs_h_creat;
 		glfs_h_mkdir;
 		glfs_h_mknod;
@@ -163,3 +162,8 @@ GFAPI_PRIVATE_3.7.0 {
 		glfs_resolve;
 		glfs_process_upcall_event;
 } GFAPI_3.7.0;
+
+GFAPI_3.7.4 {
+	global:
+		glfs_h_lookupat;
+} GFAPI_PRIVATE_3.7.0;
diff --git a/api/src/glfs-handleops.c b/api/src/glfs-handleops.c
index 2e552b763dc..79085ff33a1 100644
--- a/api/src/glfs-handleops.c
+++ b/api/src/glfs-handleops.c
@@ -63,7 +63,7 @@ glfs_iatt_from_stat (struct stat *stat, int valid, struct iatt *iatt,
 
 struct glfs_object *
 pub_glfs_h_lookupat (struct glfs *fs, struct glfs_object *parent,
-                     const char *path, struct stat *stat)
+                     const char *path, struct stat *stat, int follow)
 {
         int                      ret = 0;
         xlator_t                *subvol = NULL;
@@ -100,7 +100,7 @@ pub_glfs_h_lookupat (struct glfs *fs, struct glfs_object *parent,
 
         /* fop/op */
         ret = glfs_resolve_at (fs, subvol, inode, path, &loc, &iatt,
-                                    0 /*TODO: links? */, 0);
+                                    follow, 0);
 
         /* populate out args */
         if (!ret) {
@@ -124,7 +124,16 @@ invalid_fs:
         return object;
 }
 
-GFAPI_SYMVER_PUBLIC_DEFAULT(glfs_h_lookupat, 3.4.2);
+GFAPI_SYMVER_PUBLIC_DEFAULT(glfs_h_lookupat, 3.7.4);
+
+struct glfs_object *
+pub_glfs_h_lookupat34 (struct glfs *fs, struct glfs_object *parent,
+                       const char *path, struct stat *stat)
+{
+        return pub_glfs_h_lookupat (fs, parent, path, stat, 0);
+}
+
+GFAPI_SYMVER_PUBLIC(glfs_h_lookupat34, glfs_h_lookupat, 3.4.2);
 
 int
 pub_glfs_h_statfs (struct glfs *fs, struct glfs_object *object,
diff --git a/api/src/glfs-handles.h b/api/src/glfs-handles.h
index 19c4e8f7a62..71bd21ff98c 100644
--- a/api/src/glfs-handles.h
+++ b/api/src/glfs-handles.h
@@ -153,10 +153,10 @@ enum gfapi_callback_type {
 /* Handle based operations */
 /* Operations that generate handles */
 struct glfs_object *glfs_h_lookupat (struct glfs *fs,
-				     struct glfs_object *parent,
-				     const char *path,
-                                     struct stat *stat) __THROW
-        GFAPI_PUBLIC(glfs_h_lookupat, 3.4.0);
+                                     struct glfs_object *parent,
+                                     const char *path,
+                                     struct stat *stat, int follow) __THROW
+        GFAPI_PUBLIC(glfs_h_lookupat, 3.7.4);
 
 struct glfs_object *glfs_h_creat (struct glfs *fs, struct glfs_object *parent,
 				  const char *path, int flags, mode_t mode,