From bf8abea4dade111bdf3aeae30bd4bd75d49aca70 Mon Sep 17 00:00:00 2001 From: Olaf Faaland Date: Mon, 13 Mar 2017 10:37:10 -0700 Subject: [PATCH] Linux 4.11 compat: remove stub for __put_task_struct Before kernel 2.6.29 credentials were embedded in task_structs, and zfs had cases where one thread would need to refer to the credential of another thread, forcing it to take a hold on the foreign thread's task_struct to ensure it was not freed. Since 2.6.29, the credential has been moved out of the task_struct into a cred_t. In addition, the mainline kernel originally did not export __put_task_struct() but the RHEL5 kernel did, according to zfsonlinux/spl@e811949a570. As of 2.6.39 the mainline kernel exports it. There is no longer zfs code that takes or releases holds on a task_struct, and so there is no longer any reference to __put_task_struct(). This affects the linux 4.11 kernel because the prototype for __put_task_struct() is in a new include file (linux/sched/task.h) and so the config check failed to detect the exported symbol. Removing the unnecessary stub and corresponding config check. This works on kernels since the oldest one currently supported, 2.6.32 as shipped with Centos/RHEL. Reviewed-by: Chunwei Chen Reviewed-by: Brian Behlendorf Signed-off-by: Olaf Faaland Closes #608 --- config/spl-build.m4 | 20 -------------------- module/spl/spl-generic.c | 16 ---------------- 2 files changed, 36 deletions(-) diff --git a/config/spl-build.m4 b/config/spl-build.m4 index 1dbc87e615..b5aa7adac5 100644 --- a/config/spl-build.m4 +++ b/config/spl-build.m4 @@ -33,7 +33,6 @@ AC_DEFUN([SPL_AC_CONFIG_KERNEL], [ SPL_AC_INODE_TRUNCATE_RANGE SPL_AC_FS_STRUCT_SPINLOCK SPL_AC_KUIDGID_T - SPL_AC_PUT_TASK_STRUCT SPL_AC_KERNEL_FALLOCATE SPL_AC_CONFIG_ZLIB_INFLATE SPL_AC_CONFIG_ZLIB_DEFLATE @@ -1085,25 +1084,6 @@ AC_DEFUN([SPL_AC_KUIDGID_T], [ ]) ]) -dnl # -dnl # 2.6.39 API change, -dnl # __put_task_struct() was exported by the mainline kernel. -dnl # -AC_DEFUN([SPL_AC_PUT_TASK_STRUCT], - [AC_MSG_CHECKING([whether __put_task_struct() is available]) - SPL_LINUX_TRY_COMPILE_SYMBOL([ - #include - ], [ - __put_task_struct(NULL); - ], [__put_task_struct], [], [ - AC_MSG_RESULT(yes) - AC_DEFINE(HAVE_PUT_TASK_STRUCT, 1, - [__put_task_struct() is available]) - ], [ - AC_MSG_RESULT(no) - ]) -]) - dnl # dnl # 2.6.35 API change, dnl # Unused 'struct dentry *' removed from vfs_fsync() prototype. diff --git a/module/spl/spl-generic.c b/module/spl/spl-generic.c index ce60963bd5..a9445eb37a 100644 --- a/module/spl/spl-generic.c +++ b/module/spl/spl-generic.c @@ -459,22 +459,6 @@ ddi_copyout(const void *from, void *to, size_t len, int flags) } EXPORT_SYMBOL(ddi_copyout); -#ifndef HAVE_PUT_TASK_STRUCT -/* - * This is only a stub function which should never be used. The SPL should - * never be putting away the last reference on a task structure so this will - * not be called. However, we still need to define it so the module does not - * have undefined symbol at load time. That all said if this impossible - * thing does somehow happen PANIC immediately so we know about it. - */ -void -__put_task_struct(struct task_struct *t) -{ - PANIC("Unexpectly put last reference on task %d\n", (int)t->pid); -} -EXPORT_SYMBOL(__put_task_struct); -#endif /* HAVE_PUT_TASK_STRUCT */ - /* * Read the unique system identifier from the /etc/hostid file. *