[PATCH v3 3/3] powerpc: Implement arch_reserved_kernel_pages

[Srikar Dronamraju]

Currently significant amount of memory is reserved only in kernel
booted to capture kernel dump using the fa_dump method.

Kernels compiled with CONFIG_DEFERRED_STRUCT_PAGE_INIT will initialize
only certain size memory per node. The certain size takes into account
the dentry and inode cache sizes. Currently the cache sizes are
calculated based on the total system memory including the reserved
memory. However such a kernel when booting the same kernel as fadump
kernel will not be able to allocate the required amount of memory to
suffice for the dentry and inode caches. This results in crashes like

Hence only implement arch_reserved_kernel_pages() for CONFIG_FA_DUMP
configurations. The amount reserved will be reduced while calculating
the large caches and will avoid crashes like the below on large systems
such as 32 TB systems.

Dentry cache hash table entries: 536870912 (order: 16, 4294967296 bytes)
vmalloc: allocation failure, allocated 4097114112 of 17179934720 bytes
swapper/0: page allocation failure: order:0, mode:0x2080020(GFP_ATOMIC)
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.6-master+ #3
Call Trace:
[c00000000108fb10] [c0000000007fac88] dump_stack+0xb0/0xf0 (unreliable)
[c00000000108fb50] [c000000000235264] warn_alloc_failed+0x114/0x160
[c00000000108fbf0] [c000000000281484] __vmalloc_node_range+0x304/0x340
[c00000000108fca0] [c00000000028152c] __vmalloc+0x6c/0x90
[c00000000108fd40] [c000000000aecfb0]
alloc_large_system_hash+0x1b8/0x2c0
[c00000000108fe00] [c000000000af7240] inode_init+0x94/0xe4
[c00000000108fe80] [c000000000af6fec] vfs_caches_init+0x8c/0x13c
[c00000000108ff00] [c000000000ac4014] start_kernel+0x50c/0x578
[c00000000108ff90] [c000000000008c6c] start_here_common+0x20/0xa8

Cc: linux-mm at kvack.org
Cc: Mel Gorman <mgorman at techsingularity.net>
Cc: Vlastimil Babka <vbabka at suse.cz>
Cc: Michal Hocko <mhocko at kernel.org>
Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: Michael Ellerman <mpe at ellerman.id.au>
Cc: linuxppc-dev at lists.ozlabs.org
Cc: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
Cc: Hari Bathini <hbathini at linux.vnet.ibm.com>
Cc: Dave Hansen <dave.hansen at intel.com>
Cc: Balbir Singh <bsingharora at gmail.com>
Suggested-by: Michael Ellerman <mpe at ellerman.id.au>
Signed-off-by: Srikar Dronamraju <srikar at linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/mmzone.h | 3 +++
 arch/powerpc/kernel/fadump.c      | 5 +++++
 2 files changed, 8 insertions(+)

diff --git a/arch/powerpc/include/asm/mmzone.h b/arch/powerpc/include/asm/mmzone.h
index 7b58917..4d52ccf 100644
--- a/arch/powerpc/include/asm/mmzone.h
+++ b/arch/powerpc/include/asm/mmzone.h
@@ -41,6 +41,9 @@ u64 memory_hotplug_max(void);
 #else
 #define memory_hotplug_max() memblock_end_of_DRAM()
 #endif /* CONFIG_NEED_MULTIPLE_NODES */
+#ifdef CONFIG_FA_DUMP
+#define __HAVE_ARCH_RESERVED_KERNEL_PAGES
+#endif
 
 #endif /* __KERNEL__ */
 #endif /* _ASM_MMZONE_H_ */
diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
index b3a6633..eeb80de 100644
--- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c
@@ -333,6 +333,11 @@ int __init fadump_reserve_mem(void)
 	return 1;
 }
 
+unsigned long __init arch_reserved_kernel_pages(void)
+{
+	return memblock_reserved_size() / PAGE_SIZE;
+}
+
 /* Look for fadump= cmdline option. */
 static int __init early_fadump_param(char *p)
 {
-- 
1.8.5.6