geo-rep: Handle ERANGE error during listxattr

llistxattr in Geo-rep is two syscall instead of one

SIZE = llistxattr(PATH, &BUF, 0);
BUF = create_buf(SIZE);
_ = llistxattr(PATH, &BUF, SIZE);

So if any new xattrs added just after first call by any other worker,
second syscall will fail with ERANGE error.

Now Geo-rep sends BUF with large size(256*100) and gets value
with only one syscall. Raises OSError if fails with ERANGE error
even after sending large BUF.

Change-Id: I8ade4bbe9a0a8ea908ed9dedcd3f2ff4c6fe6f51
Signed-off-by: Aravinda VK <avishwan@redhat.com>
BUG: 1313311
Reviewed-on: http://review.gluster.org/13106
Smoke: Gluster Build System <jenkins@build.gluster.com>
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
CentOS-regression: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Kotresh HR <khiremat@redhat.com>
(cherry picked from commit 656a0e64e5f465561ed29297421ec150de32f2a1)
Reviewed-on: http://review.gluster.org/13560

1 files changed, 21 insertions, 7 deletions

diff --git a/geo-replication/syncdaemon/libcxattr.py b/geo-replication/syncdaemon/libcxattr.py
index 74d120fa196..61a4a57a682 100644
--- a/geo-replication/syncdaemon/libcxattr.py
+++ b/geo-replication/syncdaemon/libcxattr.py
@@ -68,7 +68,8 @@ class Xattr(object):
     def llistxattr(cls, path, siz=0):
         ret = cls._query_xattr(path, siz, 'llistxattr')
         if isinstance(ret, str):
-            ret = ret.split('\0')
+            ret = ret.strip('\0')
+            ret = ret.split('\0') if ret else []
         return ret
 
     @classmethod
@@ -86,9 +87,22 @@ class Xattr(object):
     @classmethod
     def llistxattr_buf(cls, path):
         """listxattr variant with size discovery"""
-        size = cls.llistxattr(path)
-        if size == -1:
-            cls.raise_oserr()
-        if size == 0:
-            return []
-        return cls.llistxattr(path, size)
+        try:
+            # Assuming no more than 100 xattrs in a file/directory and
+            # each xattr key length will be less than 256 bytes
+            # llistxattr will be called with bigger size so that
+            # listxattr will not fail with ERANGE. OSError will be
+            # raised if fails even with the large size specified.
+            size = 256 * 100
+            return cls.llistxattr(path, size)
+        except OSError:
+            # If fixed length failed for getting list of xattrs then
+            # use the llistxattr call to get the size and use that
+            # size to get the list of xattrs.
+            size = cls.llistxattr(path)
+            if size == -1:
+                cls.raise_oserr()
+            if size == 0:
+                return []
+
+            return cls.llistxattr(path, size)