commit d755bba40f880c01ced8740a26fecc85534454b9
Author: Siddhesh Poyarekar <siddhesh@redhat.com>
Date:   Wed Apr 3 10:56:45 2013 +0530

    Preserve errno across _PC_CHOWN_RESTRICTED call on XFS
    
    Fix BZ #15305.
    
    On kernel versions earlier than 2.6.29, the Linux kernel exported a
    sysctl called restrict_chown for xfs, which could be used to allow
    chown to users other than the owner.  2.6.29 removed this support,
    causing the open_not_cancel_2 to fail and thus modify errno.  The fix
    is to save and restore errno so that the caller sees it as unmodified.
    
    Additionally, since the code to check the sysctl is not useful on
    newer kernels, we add an ifdef so that in future the code block gets
    rmeoved completely.

diff --git a/sysdeps/unix/sysv/linux/kernel-features.h b/sysdeps/unix/sysv/linux/kernel-features.h
index 8fdff7e..ccd4c59 100644
--- a/sysdeps/unix/sysv/linux/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/kernel-features.h
@@ -221,3 +221,9 @@
 #if defined __x86_64__ && __LINUX_KERNEL_VERSION >= 0x030100
 # define __ASSUME_GETCPU_SYSCALL	1
 #endif
+
+/* 2.6.29 removed the XFS restricted_chown sysctl, so it is pointless looking
+   for it in newer kernels.  */
+#if __LINUX_KERNEL_VERSION >= 0x02061d
+# define __ASSUME_XFS_RESTRICTED_CHOWN 1
+#endif
diff --git a/sysdeps/unix/sysv/linux/pathconf.c b/sysdeps/unix/sysv/linux/pathconf.c
index de91a45..723d234 100644
--- a/sysdeps/unix/sysv/linux/pathconf.c
+++ b/sysdeps/unix/sysv/linux/pathconf.c
@@ -289,11 +289,16 @@ __statfs_chown_restricted (int result, const struct statfs *fsbuf)
       return -1;
     }
 
+#if __ASSUME_XFS_RESTRICTED_CHOWN
+  return 1;
+#else
   int fd;
+  int save_errno;
   long int retval = 1;
   switch (fsbuf->f_type)
     {
     case XFS_SUPER_MAGIC:
+      save_errno = errno;
       /* Read the value from /proc/sys/fs/xfs/restrict_chown.  If we cannot
 	 read it default to assume the restriction is in place.  */
       fd = open_not_cancel_2 ("/proc/sys/fs/xfs/restrict_chown", O_RDONLY);
@@ -306,6 +311,7 @@ __statfs_chown_restricted (int result, const struct statfs *fsbuf)
 
 	  close_not_cancel_no_status (fd);
 	}
+      __set_errno (save_errno);
       break;
 
     default:
@@ -313,4 +319,5 @@ __statfs_chown_restricted (int result, const struct statfs *fsbuf)
     }
 
   return retval;
+#endif
 }