[RESEND PATCH v2] powerpc/fadump: register for fadump as early as possible

[Hari Bathini <hbathini@linux.ibm.com>]

Crash recovery (fadump) is setup in the userspace by some service.
This service rebuilds initrd with dump capture capability, if it is
not already dump capture capable before proceeding to register for
firmware assisted dump (echo 1 > /sys/kernel/fadump/registered). But
arming the kernel with crash recovery support does not have to wait
for userspace configuration. So, register for fadump while setting
it up itself. This can at worst lead to a scenario, where /proc/vmcore
is ready afer crash but the initrd does not know how/where to offload
it, which is always better than not having a /proc/vmcore at all due
to incomplete configuration in the userspace at the time of crash.

Commit 0823c68b054b ("powerpc/fadump: re-register firmware-assisted
dump if already registered") ensures this change does not break
userspace.

Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
---

* Resending the patch after rebasing on latest code.

Changes in V2:
* Updated the changelog with bit more explanation about userspace issue
  with/without this change.
* Added a comment in the code for why setup_fadump function is changed
  from subsys_init() to subsys_init_sync() call.


 arch/powerpc/kernel/fadump.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
index d03e488cfe9c..97d80df4563f 100644
--- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c
@@ -1637,9 +1637,11 @@ int __init setup_fadump(void)
 		if (fw_dump.ops->fadump_process(&fw_dump) < 0)
 			fadump_invalidate_release_mem();
 	}
-	/* Initialize the kernel dump memory structure for FAD registration. */
-	else if (fw_dump.reserve_dump_area_size)
+	/* Initialize the kernel dump memory structure and register with f/w */
+	else if (fw_dump.reserve_dump_area_size) {
 		fw_dump.ops->fadump_init_mem_struct(&fw_dump);
+		register_fadump();
+	}
 
 	/*
 	 * In case of panic, fadump is triggered via ppc_panic_event()
@@ -1651,7 +1653,12 @@ int __init setup_fadump(void)
 
 	return 1;
 }
-subsys_initcall(setup_fadump);
+/*
+ * Replace subsys_initcall() with subsys_initcall_sync() as there is dependency
+ * with crash_save_vmcoreinfo_init() to ensure vmcoreinfo initialization is done
+ * before regisering with f/w.
+ */
+subsys_initcall_sync(setup_fadump);
 #else /* !CONFIG_PRESERVE_FA_DUMP */
 
 /* Scan the Firmware Assisted dump configuration details. */
-- 
2.34.1