[PATCH] Trivial fix in __alloc_bootmem_core() when there is no free page in first node's memory

[PATCH] Trivial fix in __alloc_bootmem_core() when there is no free page in first node's memory

[Haren Myneni]

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Hi,
    Hitting BUG_ON() in __alloc_bootmem_core() when there is no free 
page available in the first node's memory. For the case of kdump on 
PPC64 (Power 4 machine), the captured kernel is used two memory regions 
- memory for TCE tables (tce-base and tce-size at top of RAM and 
reserved) and captured kernel memory region (crashk_base and 
crashk_size). Since we reserve the memory for the first node, we should 
be returning from __alloc_bootmem_core() to search for the next node 
(pg_dat).

Currently, find_next_zero_bit() is returning the n^th bit (eidx) when 
there is no free page. Then, test_bit() is failed since we set 0xff only 
for the actual size initially (init_bootmem_core()) even though rounded 
up to one page for bdata->node_bootmem_map. We are hitting the BUG_ON 
after failing to enter second "for" loop.

Please apply.

Thanks
Haren

Signed-off-by: Haren Myneni <haren@us.ibm.com>





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--- 2.6.15-rc5-git1/mm/bootmem.c.orig	2005-12-14 21:28:46.000000000 -0800
+++ 2.6.15-rc5-git1/mm/bootmem.c	2005-12-14 21:35:54.000000000 -0800
@@ -204,6 +204,8 @@ restart_scan:
 		unsigned long j;
 		i = find_next_zero_bit(bdata->node_bootmem_map, eidx, i);
 		i = ALIGN(i, incr);
+		if (i >= eidx)
+			break;
 		if (test_bit(i, bdata->node_bootmem_map))
 			continue;
 		for (j = i + 1; j < i + areasize; ++j) {