Linux 4.2: total_link_count is no longer accessible

The value is now stored in the nameidata structure which
is private to fs/namei.c, so we can't modify it here.

The effect is that using a path that contains 40+ directories
may fail with ELOOP, depending on which directories in the
path were previously used.  After a directory is accessed once
its D_AUTOMOUNT flag is reset and it will no longer count
against the symlink limit in later path lookups.

Change-Id: I90e4cb0e9004b075bff2330d165c67b7a923193f
Reviewed-on: http://gerrit.openafs.org/11926
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>

diff --git a/acinclude.m4 b/acinclude.m4
index 3937f15..74fc776 100644 (file)
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -958,6 +958,7 @@ case $AFS_SYSNAME in *_linux* | *_umlinux*)
                 AC_CHECK_LINUX_STRUCT([task_struct], [sigmask_lock], [sched.h])
                 AC_CHECK_LINUX_STRUCT([task_struct], [tgid], [sched.h])
                 AC_CHECK_LINUX_STRUCT([task_struct], [thread_info], [sched.h])
+                AC_CHECK_LINUX_STRUCT([task_struct], [total_link_count], [sched.h])
                 LINUX_SCHED_STRUCT_TASK_STRUCT_HAS_SIGNAL_RLIM
 
                 dnl Check for typed structure elements

diff --git a/src/afs/LINUX/osi_vnodeops.c b/src/afs/LINUX/osi_vnodeops.c
index 62abc47..481ce87 100644 (file)
--- a/src/afs/LINUX/osi_vnodeops.c
+++ b/src/afs/LINUX/osi_vnodeops.c
@@ -1390,9 +1390,17 @@ afs_dentry_automount(afs_linux_path_t *path)
 {
     struct dentry *target;
 
-    /* avoid symlink resolution limits when resolving; we cannot contribute to
-     * an infinite symlink loop */
+    /* 
+     * Avoid symlink resolution limits when resolving; we cannot contribute to
+     * an infinite symlink loop.
+     *
+     * On newer kernels the field has moved to the private nameidata structure
+     * so we can't adjust it here.  This may cause ELOOP when using a path with
+     * 40 or more directories that are not already in the dentry cache.
+     */
+#if defined(STRUCT_TASK_STRUCT_HAS_TOTAL_LINK_COUNT)
     current->total_link_count--;
+#endif
 
     target = canonical_dentry(path->dentry->d_inode);