Description of Problem:
In cyclic mode, makedumpfile recalculates cyclic buffer size as the
largest multiple of the largest block size managed by buddy
allocator, i.e. 4MB, smaller than the cyclic buffer size in order to
enable to process each unit of blocks managed by buddy allocator in
each cycle.
However, makedumpfile does two wrong things in the recalculations:
1) While updating size of cyclic buffer, makedumpfile doesn't update
length of range of cycle in page frame numbers, due to which, if
cyclic buffer size is updated, because cyclic buffer size is always
reduced during udpate, some buffer overrun can happen on the cyclic
buffer. This can cause segmentation violation in the worst case.
2) roundup() is used to calculate bitmap size for maximum block size
managed by buddy allocator, here divideup() is correct, due to
which, although memory filtering is not affected, cyclic buffer size
get too much aligned and less efficient.
Fix patches has already been posted and merged in makedumpfile
development devel branch.
git://git.code.sf.net/p/makedumpfile/code
f8c8218856effc43ea01cd9394761cfb8aeaa8df
a785fa7dd7a7bd7dcbb017d0bea8848243b0924f
Signed-off-by: Baoquan He <bhe@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: WANG Chao <chaowang@redhat.com>
