crawfxrd
commented
5 years ago To confirm, you are using dattobd 0.10.9?
Can you get the line for the RIP?
gdb /path/to/dattobd.ko
(gdb) list *(tracing_mrf+0x2cb)Closed pomipomi closed 5 years ago
crawfxrd
commented
5 years ago To confirm, you are using dattobd 0.10.9?
Can you get the line for the RIP?
gdb /path/to/dattobd.ko
(gdb) list *(tracing_mrf+0x2cb)
pomipomi
commented
5 years ago The file "dattobd.ko" seems located in "/usr/src/dattobd-0.10.9" (no such files in /path/to), so i use
gdb /usr/src/dattobd-0.10.9/dattobd.koroot@ubuntu:/# gdb /usr/src/dattobd-0.10.9/dattobd.ko
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static inline struct inode *page_get_inode(struct page *pg){
if(!pg) return NULL;
if(!pg->mapping) return NULL;
if(PageAnon(pg)) return NULL;
//#if LINUX_VERSION_CODE >= KERNEL_VERSION(4,5,0)
#ifdef TAIL_MAPPING
if (pg->mapping == TAIL_MAPPING) return NULL;
#endif
if(!pg->mapping->host) return NULL;
return pg->mapping->host;
}
This appears to be the same thing as #40.
Try running:
grep -r "TAIL_MAPPING" /usr/src/linux-headers-4.15.0-29/It should output:
/usr/src/linux-headers-4.15.0-29/include/linux/poison.h:#define TAIL_MAPPING ((void *) 0x400 + POISON_POINTER_DELTA)If it does, then there is something wrong with the build of dattobd. In that case, I suggest rebuilding/reinstalling dattobd and trying again.
pomipomi
commented
5 years ago After using
grep -r "TAIL_MAPPING" /usr/src/linux-headers-4.15.0-29//usr/src/linux-headers-4.15.0-29/include/linux/poison.h:#define TAIL_MAPPING ((void *) 0x400 + POISON_POINTER_DELTA)Does it means my dattobd need to rebuild/reinstall ? I've tried to rebuild it and test dbdctl again, but kernel panic still happened. Could I also ask that what's the correct output I should get after I grep TAIL_MAPPING ? Some detailed information might help： 1. The environment I used previously was Ubuntu 18.04 with 4.15.0-29, running on vmware. 2. I reinstall an Ubuntu 18.04 with 4.15.0-50 VM, but the same panic problem happened. 3. I Install Ubuntu 18.04 with 4.15.0-50 on my personal computer(not VM) and use dbdctl several times, but kernel panic seems to disappear this time.... 4. All three devices above get the same output after grepping "TAIL_MAPPING"
crawfxrd
commented
5 years ago I was able to reproduce this on 4.15.
May 21 08:07:13 segv-u1804 kernel: TAIL_MAPPING = dead000000000400
May 21 08:07:13 segv-u1804 kernel: pg->mapping = dead0000ffffffffI don't know where this value comes from. It seems bogus (-1 cast to UL?).
I have not seen the issue on 4.18.0-20-generic. This kernel produces the expected value:
May 21 08:16:05 segv-u1804 kernel: TAIL_MAPPING = dead000000000400
May 21 08:16:05 segv-u1804 kernel: pg->mapping = dead000000000400Just for making sure, what's kind of device did you use to reproduce the question? (PC / VM?)
Maybe skip the address over TAIL_MAPPING or some specific value can deal with this case?
crawfxrd
commented
5 years ago I am using a qemu VM.
@tcaputi any idea on this one?
tcaputi
commented
5 years ago I don't really have a ton of time to look at this now, but this seems to be the same issue that effected the crash utility: https://www.redhat.com/archives/crash-utility/2016-February/msg00010.html
We should probably just find the commit that crash made and do whatever they did.
crawfxrd
commented
5 years ago Looks like using the head (a la pg = compound_head(pg)) instead of checking for a tail would work.
Of interest is page_mapping().
crawfxrd
commented
5 years ago @pomipomi could you try #187?
pomipomi
commented
5 years ago I've used a script to test the patch, looks like the kernel panic problem is solved! (Testing process: add and change files -> transition to incremental -> add and change files -> transition to snapshot)
Thanks for your help!
Environment： Using latest dattobd running on Ubuntu 18.04 Linux ubuntu 4.15.0-29-generic #31-Ubuntu SMP Tue Jul 17 15:39:52 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
Process to reproduce：
System consist two disks
/ is with ext2 /mnt is xfs (using mkfs.xfs with default option) The xfs FS is mounted with default mount option Kernel panic output is: