[PATCH] makedumpfile: Use file offset in initialize_mmap()
holzheu at linux.vnet.ibm.com
Tue Mar 3 01:15:43 PST 2015
Thanks for the fix!
Hard to believe that makedumpfile mmap mode on s390 has never worked.
On Fri, 27 Feb 2015 13:14:09 +0100
Petr Tesarik <ptesarik at suse.cz> wrote:
> Hi all,
> update_mmap_range() expects a file offset as its first argument, but
> initialize_mmap() passes a physical address. Since the first segment
> usually starts at physical addr 0 on S/390, but there is no segment
> at file offset 0, update_mmap_range() fails, and makedumpfile falls
> back to read().
And for other architectures the wrong parameter was no problem?
> @Michael: I wonder how you actually tested the kernel mmap patches;
> this bug has prevented mmap on all my s390 systems...
We tested /proc/vmcore mmap with our SCSI stand-alone dump (zfcpdump) and
with small test programs that used mmap.
I did a quick test with your patch and it looks like the mmap mode
on my s390 system is slower than the read mode:
# time ./makedumpfile -d 31 /proc/vmcore out
# time ./makedumpfile -d 31 /proc/vmcore out --non-mmap
We will have to look into this.
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