Hello.
Russell King - ARM Linux wrote:
I get this warning while compiling for ARM/SA1100:
mm/sparse.c: In function '__section_nr':
mm/sparse.c:135: warning: 'root' is used uninitialized in this function
With a small patch in fs/proc/meminfo.c, I find that NR_SECTION_ROOTS
is zero, which certainly explains the warning.
# cat /proc/meminfo
NR_SECTION_ROOTS=0
NR_MEM_SECTIONS=32
SECTIONS_PER_ROOT=512
SECTIONS_SHIFT=5
MAX_PHYSMEM_BITS=32
hm, who owns sparsemem nowadays? Nobody identifiable.
Does it make physical sense to have SECTIONS_PER_ROOT > NR_MEM_SECTIONS?
Well, it'll be about this number on everything using sparsemem extreme:
#define SECTIONS_PER_ROOT (PAGE_SIZE / sizeof (struct mem_section))
and with only 32 sections, this is going to give a NR_SECTION_ROOTS value
of zero. I think the calculation of NR_SECTIONS_ROOTS is wrong.
#define NR_SECTION_ROOTS (NR_MEM_SECTIONS / SECTIONS_PER_ROOT)
Clearly if we have 1 mem section, we want to have one section root, so
I think this division should round up any fractional part, thusly:
#define NR_SECTION_ROOTS ((NR_MEM_SECTIONS + SECTIONS_PER_ROOT - 1) / SECTIONS_PER_ROOT)
There's DIV_ROUND_UP() macro for this kind of calculation.
WBR, Sergei
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