[PATCH V2 2/2] fadump: Register the memory reserved by fadump

[Srikar Dronamraju]

Fadump kernel reserves large chunks of memory even before the pages are
initialized. This could mean memory that corresponds to several nodes might
fall in memblock reserved regions.

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
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

Register the memory reserved by fadump, so that the cache sizes are
calculated based on the free memory (i.e Total memory - reserved
memory).

Suggested-by: Mel Gorman <mgorman at techsingularity.net>
Signed-off-by: Srikar Dronamraju <srikar at linux.vnet.ibm.com>
---
 arch/powerpc/kernel/fadump.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
index 3cb3b02a..ca5ec88 100644
--- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c
@@ -330,6 +330,7 @@ int __init fadump_reserve_mem(void)
 	}
 	fw_dump.reserve_dump_area_start = base;
 	fw_dump.reserve_dump_area_size = size;
+	set_memory_reserve(size/PAGE_SIZE, true);
 	return 1;
 }
 
-- 
1.8.5.6