From: Atsushi Kumagai <kumagai-atsushi@xxxxxxxxxxxxxxxxx> Subject: RE: [PATCH v3 1/2] Generic handling of multi-page exclusions Date: Wed, 14 May 2014 07:54:17 +0000 > Hello Petr, > >>When multiple pages are excluded from the dump, store the extents in >>struct cycle and check if anything is still pending on the next invocation >>of __exclude_unnecessary_pages. This assumes that: >> >> 1. after __exclude_unnecessary_pages is called for a struct mem_map_data >> that extends beyond the current cycle, it is not called again during >> that cycle, >> 2. in the next cycle, __exclude_unnecessary_pages is not called before >> this final struct mem_map_data. >> >>Both assumptions are met if struct mem_map_data segments: >> >> 1. do not overlap, >> 2. are sorted by physical address in ascending order. > > In ELF case, write_elf_pages_cyclic() processes PT_LOAD entries from > PT_LOAD(0), this can break both assumptions unluckily. > Actually this patch doesn't work on my machine: > > LOAD (0) > phys_start : 1000000 > phys_end : 182f000 > virt_start : ffffffff81000000 > virt_end : ffffffff8182f000 > LOAD (1) > phys_start : 1000 > phys_end : 9b400 > virt_start : ffff810000001000 > virt_end : ffff81000009b400 > LOAD (2) > phys_start : 100000 > phys_end : 27000000 > virt_start : ffff810000100000 > virt_end : ffff810027000000 > LOAD (3) > phys_start : 37000000 > phys_end : cff70000 > virt_start : ffff810037000000 > virt_end : ffff8100cff70000 > LOAD (4) > phys_start : 100000000 > phys_end : 170000000 > virt_start : ffff810100000000 > virt_end : ffff810170000000 > > > PT_LOAD(2) includes PT_LOAD(0) and there physical addresses aren't sorted. > > If there is the only "sort issue", it may easy to fix it with a new iterator > like "for_each_pt_load()", it iterates PT_LOAD entries in ascending order > by physical address. > However, I don't have a good idea to solve the overlap issue now... > Is it enough to merge them? Prepare a modified version of PTLOAD list and refer to it in actual processing. I think this also leads to cleaning up readpage_elf() that addresses some overapping memory map issue on ia64. -- Thanks. HATAYAMA, Daisuke
