[PATCH 0/0] Disable deferred struct page initialisation on Fadump

Srikar Dronamraju srikar at linux.vnet.ibm.com
Tue Aug 2 23:19:05 AEST 2016

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

Kernels compiled with CONFIG_DEFERRED_STRUCT_PAGE_INIT will initialise
only certain size memory per node. The certain size takes into account
the dentry and inode cache sizes. However such a kernel when booting a
secondary 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]
[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

This can be solved by two approaches.
1. Disable deferred struct page initialisation on fadump.

2. Detect reserved nodes and allocate accordingly.
 - Detecting nodes whose memblocks are mostly reserved.
 - Allocating extra memory in other nodes in lieu of the nodes whose
   memory is reserved.

This patchset takes the first approach.

Srikar Dronamraju (2):
  mm: Allow disabling deferred struct page initialisation
  fadump: Disable deferred page struct initialisation

 arch/powerpc/kernel/fadump.c |  1 +
 include/linux/mmzone.h       |  2 +-
 mm/page_alloc.c              | 20 ++++++++++++++++++++
 3 files changed, 22 insertions(+), 1 deletion(-)


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