RE: [PATCH v5 1/1] dax: enable dax fault handler to report VM_FAULT_HWPOISON

[Dan Williams]

Jane Chu wrote:
> When multiple processes mmap() a dax file, then at some point,
> a process issues a 'load' and consumes a hwpoison, the process
> receives a SIGBUS with si_code = BUS_MCEERR_AR and with si_lsb
> set for the poison scope. Soon after, any other process issues
> a 'load' to the poisoned page (that is unmapped from the kernel
> side by memory_failure), it receives a SIGBUS with
> si_code = BUS_ADRERR and without valid si_lsb.
> 
> This is confusing to user, and is different from page fault due
> to poison in RAM memory, also some helpful information is lost.
> 
> Channel dax backend driver's poison detection to the filesystem
> such that instead of reporting VM_FAULT_SIGBUS, it could report
> VM_FAULT_HWPOISON.
> 
> If user level block IO syscalls fail due to poison, the errno will
> be converted to EIO to maintain block API consistency.
> 
> Signed-off-by: Jane Chu <jane.chu@xxxxxxxxxx>

Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>