From 6bb4a026e56438d2a3ddf298c4f13c38b604ffbd Mon Sep 17 00:00:00 2001
From: Karen Arutyunov <karen@codesynthesis.com>
Date: Thu, 9 Apr 2020 18:40:02 +0300
Subject: Use butl::readsymlink() instead of POSIX readlink() in agent

---
 bbot/agent/agent.cxx | 32 +++++++++++++-------------------
 1 file changed, 13 insertions(+), 19 deletions(-)

diff --git a/bbot/agent/agent.cxx b/bbot/agent/agent.cxx
index 2c4e03e..6c2e0d9 100644
--- a/bbot/agent/agent.cxx
+++ b/bbot/agent/agent.cxx
@@ -7,7 +7,7 @@
 #include <limits.h>    // PATH_MAX
 #include <signal.h>    // signal()
 #include <stdlib.h>    // rand_r()
-#include <unistd.h>    // sleep(), realink(), getuid(), fsync(), [f]stat()
+#include <unistd.h>    // sleep(), getuid(), fsync(), [f]stat()
 #include <sys/types.h> // stat
 #include <sys/stat.h>  // [f]stat()
 #include <sys/file.h>  // flock()
@@ -21,11 +21,12 @@
 #include <chrono>
 #include <random>
 #include <iostream>
+#include <system_error> // generic_category()
 
 #include <libbutl/pager.mxx>
 #include <libbutl/sha256.mxx>
 #include <libbutl/openssl.mxx>
-#include <libbutl/filesystem.mxx> // dir_iterator, try_rmfile()
+#include <libbutl/filesystem.mxx> // dir_iterator, try_rmfile(), readsymlink()
 
 #include <libbbot/manifest.hxx>
 
@@ -572,29 +573,22 @@ try
           // Resolve the link to subvolume path.
           //
           dir_path sp; // <name>-<P>.<R>
+
           try
           {
-            char b [PATH_MAX + 1];
-            ssize_t r (readlink (lp.string ().c_str (), b, sizeof (b)));
+            sp = path_cast<dir_path> (readsymlink (lp));
 
-            if (r == -1)
-            {
-              if (errno != ENOENT)
-                throw_generic_error (errno);
-            }
-            else if (static_cast<size_t> (r) >= sizeof (b))
-              throw_generic_error (EINVAL);
-            else
-            {
-              b[r] = '\0';
-              sp = dir_path (b);
-              if (sp.relative ())
-                sp = md / sp;
-            }
+            if (sp.relative ())
+              sp = md / sp;
           }
           catch (const system_error& e)
           {
-            fail << "unable to read subvolume link " << lp << ": " << e;
+            // Leave the subvolume path empty if the subvolume link doesn't
+            // exist and fail on any other error.
+            //
+            if (e.code ().category () != std::generic_category () ||
+                e.code ().value () != ENOENT)
+              fail << "unable to read subvolume link " << lp << ": " << e;
           }
 
           none = none && sp.empty ();
-- 
cgit v1.1