Re: [PATCH RESEND v6 1/9] pagemap: Introduce ->memory_failure()

Sorry, correction in line.

On 8/19/2021 12:18 AM, Jane Chu wrote:

Hi, Shiyang,

 >  > > 1) What does it take and cost to make
 >  > >     xfs_sb_version_hasrmapbt(&mp->m_sb) to return true?
 >
 > Enable rmpabt feature when making xfs filesystem
 >     `mkfs.xfs -m rmapbt=1 /path/to/device`
 > BTW, reflink is enabled by default.

Thanks!  I tried
mkfs.xfs -d agcount=2,extszinherit=512,su=2m,sw=1 -m reflink=0 -m 
rmapbt=1 -f /dev/pmem0

Again, injected a HW poison to the first page in a dax-file, had
the poison consumed and received a SIGBUS. The result is better -

** SIGBUS(7): canjmp=1, whichstep=0, **
** si_addr(0x0x7ff2d8800000), si_lsb(0x15), si_code(0x4, BUS_MCEERR_AR) **

The SIGBUS payload looks correct.

However, "dmesg" has 2048 lines on sending SIGBUS, one per 512bytes -

Actually that's one per 2MB, even though the poison is located
in pfn 0x1850600 only.

[ 7003.482326] Memory failure: 0x1850600: Sending SIGBUS to 
fsdax_poison_v1:4109 due to hardware memory corruption
[ 7003.507956] Memory failure: 0x1850800: Sending SIGBUS to 
fsdax_poison_v1:4109 due to hardware memory corruption
[ 7003.531681] Memory failure: 0x1850a00: Sending SIGBUS to 
fsdax_poison_v1:4109 due to hardware memory corruption
[ 7003.554190] Memory failure: 0x1850c00: Sending SIGBUS to 
fsdax_poison_v1:4109 due to hardware memory corruption
[ 7003.575831] Memory failure: 0x1850e00: Sending SIGBUS to 
fsdax_poison_v1:4109 due to hardware memory corruption
[ 7003.596796] Memory failure: 0x1851000: Sending SIGBUS to 
fsdax_poison_v1:4109 due to hardware memory corruption
....
[ 7045.738270] Memory failure: 0x194fe00: Sending SIGBUS to 
fsdax_poison_v1:4109 due to hardware memory corruption
[ 7045.758885] Memory failure: 0x1950000: Sending SIGBUS to 
fsdax_poison_v1:4109 due to hardware memory corruption
[ 7045.779495] Memory failure: 0x1950200: Sending SIGBUS to 
fsdax_poison_v1:4109 due to hardware memory corruption
[ 7045.800106] Memory failure: 0x1950400: Sending SIGBUS to 
fsdax_poison_v1:4109 due to hardware memory corruption

That's too much for a single process dealing with a single
poison in a PMD page. If nothing else, given an .si_addr_lsb being 0x15,
it doesn't make sense to send a SIGBUS per 512B block.

Could you determine the user process' mapping size from the filesystem,
and take that as a hint to determine how many iterations to call
mf_dax_kill_procs() ?

Sorry, scratch the 512byte stuff... the filesystem has been
notified the length of the poison blast radius, could it take clue
from that?

thanks,
-jane

thanks!
-jane