Re: [Crash-utility] [PATCH] Update for the "kmem -n" option on Linux 5.3-rc1 and later kernels

Update for the "kmem -n" option on Linux 5.3-rc1 and later kernels that contain commit 326e1b8f83a4318b09033ef754f40c785aed5e68, titled "mm/sparsemem: introduce a SECTION_IS_EARLY flag". With this patch, the option displays a new state "E" for the flag, instead of printing incorrect mem_map addresses. Also update the confusing comment with the one from kernel commit def9b71ee651a6fee93a10734b94f93a69cdb2d4, titled "include/linux/mmzone.h: fix explanation of lower bits in the SPARSEMEM mem_map pointer". Signed-off-by: Kazuhito Hagio <k-hagio(a)ab.jp.nec.com&gt; --- help.c | 4 ++-- memory.c | 17 ++++++++++++++--- 2 files changed, 16 insertions(+), 5 deletions(-) diff --git a/help.c b/help.c index d5940f789ffd..a5218a701c01 100644 --- a/help.c +++ b/help.c @@ -6597,8 +6597,8 @@ char *help_kmem[] = { " the cumulative, vm_event_states counter values if they exist.", " -n display memory node, memory section, and memory block data", " and state; the state of each memory section state is encoded", -" as \"P\", \"M\" and/or \"O\", meaning SECTION_MARKED_PRESENT,", -" SECTION_HAS_MEM_MAP and SECTION_IS_ONLINE.", +" as \"P\", \"M\", \"O\" and/or \"E\", meaning SECTION_MARKED_PRESENT,", +" SECTION_HAS_MEM_MAP, SECTION_IS_ONLINE and SECTION_IS_EARLY.", " -z displays per-zone memory statistics.", " -o displays each cpu's offset value that is added to per-cpu symbol", " values to translate them into kernel virtual addresses.", diff --git a/memory.c b/memory.c index 327e5355ec9c..ac7e73679405 100644 --- a/memory.c +++ b/memory.c @@ -17154,13 +17154,22 @@ nr_to_section(ulong nr) /* * We use the lower bits of the mem_map pointer to store - * a little bit of information. There should be at least - * 3 bits here due to 32-bit alignment. + * a little bit of information. The pointer is calculated + * as mem_map - section_nr_to_pfn(pnum). The result is + * aligned to the minimum alignment of the two values: + * 1. All mem_map arrays are page-aligned. + * 2. section_nr_to_pfn() always clears PFN_SECTION_SHIFT + * lowest bits. PFN_SECTION_SHIFT is arch-specific + * (equal SECTION_SIZE_BITS - PAGE_SHIFT), and the + * worst combination is powerpc with 256k pages, + * which results in PFN_SECTION_SHIFT equal 6. + * To sum it up, at least 6 bits are available. */ #define SECTION_MARKED_PRESENT (1UL<<0) #define SECTION_HAS_MEM_MAP (1UL<<1) #define SECTION_IS_ONLINE (1UL<<2) -#define SECTION_MAP_LAST_BIT (1UL<<3) +#define SECTION_IS_EARLY (1UL<<3) +#define SECTION_MAP_LAST_BIT (1UL<<4) #define SECTION_MAP_MASK (~(SECTION_MAP_LAST_BIT-1)) @@ -17257,6 +17266,8 @@ fill_mem_section_state(ulong state, char *buf) bufidx += sprintf(buf + bufidx, "%s", "M"); if (state & SECTION_IS_ONLINE) bufidx += sprintf(buf + bufidx, "%s", "O"); + if (state & SECTION_IS_EARLY) + bufidx += sprintf(buf + bufidx, "%s", "E"); } void -- 2.18.1 -- Crash-utility mailing list Crash-utility(a)redhat.com https://www.redhat.com/mailman/listinfo/crash-utility