[Makedumpfile Patch v3 7/7] mem-usage: allow to work only with -f for kernel version < 4.11

[Pratyush Anand]

PT_LOAD of kcore does not have valid p_paddr values for kernel version
less that v4.11. Therefore, older kernel will no long work for mem-usage
with current makedumpfile code. They can only work when they are patched
with fix to "update physical address for kcore ram and text".

This patch fixes the makedumpfile so that it does not allow to work
older kernel for --mem-usage until someone is sure that kernel is
rightly patched and so uses -f in command line. It also updates man page
and usage info accordingly.

Signed-off-by: Pratyush Anand <panand at redhat.com>
---
 makedumpfile.8 | 9 ++++++++-
 makedumpfile.c | 6 ++++++
 print_info.c   | 3 ++-
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/makedumpfile.8 b/makedumpfile.8
index 9069fb18cdb6..993236486e77 100644
--- a/makedumpfile.8
+++ b/makedumpfile.8
@@ -235,13 +235,20 @@ the ELF format does not support compressed data.
 
 .TP
 \fB\-f\fR
-Force existing DUMPFILE to be overwritten.
+Force existing DUMPFILE to be overwritten and mem-usage to work with older
+kernel as well.
 .br
 .B Example:
 .br
 # makedumpfile \-f \-d 31 \-x vmlinux /proc/vmcore dumpfile
 .br
 This command overwrites \fIDUMPFILE\fR even if it already exists.
+.br
+# makedumpfile \-f \-\-mem\-usage /proc/kcore
+.br
+Kernel version lesser than v4.11 will not work with \-\-mem\-usage
+functionality until it has been patched with upstream commit 464920104bf7.
+Therefore if you have patched your older kernel then use \-f.
 
 .TP
 \fB\-x\fR \fIVMLINUX\fR
diff --git a/makedumpfile.c b/makedumpfile.c
index 3b8e9810468d..e3be1ab0a9ec 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -11269,6 +11269,12 @@ main(int argc, char *argv[])
 			MSG("Try `makedumpfile --help' for more information.\n");
 			goto out;
 		}
+		if (info->kernel_version < KERNEL_VERSION(4, 11, 0) &&
+				!info->flag_force) {
+			MSG("mem-usage not supported for this kernel.\n");
+			MSG("You can try with -f if your kernel's kcore has valid p_paddr\n");
+			goto out;
+		}
 
 		if (!show_mem_usage())
 			goto out;
diff --git a/print_info.c b/print_info.c
index 392d863a4227..72ed8fa0c059 100644
--- a/print_info.c
+++ b/print_info.c
@@ -309,7 +309,8 @@ print_usage(void)
 	MSG("      Print debugging message.\n");
 	MSG("\n");
 	MSG("  [-f]:\n");
-	MSG("      Overwrite DUMPFILE even if it already exists.\n");
+	MSG("      Overwrite DUMPFILE even if it already exists\n");
+	MSG("      Force mem-usage to work with older kernel as well.\n");
 	MSG("\n");
 	MSG("  [-h, --help]:\n");
 	MSG("      Show help message and LZO/snappy support status (enabled/disabled).\n");
-- 
2.9.3