Re: [PATCH 2/2] dm-raid1: don't fail the mirror for invalid I/O errors

["Dr. David Alan Gilbert" <linux@treblig.org>]

* Keith Busch (kbusch@kernel.org) wrote:
> On Tue, Jun 16, 2026 at 05:54:28PM +0000, Dr. David Alan Gilbert wrote:
> > OK, for this pair I think would be fair for a Tested-by me as well;
> > they certainly resolve the hang and the WARN/BUGs.
> > I still see the errors as EIO on my tests, and on the older mirror type
> 
> Could you share your reproducer? I'm just using the original recipe you
> sent here:
> 
> https://lore.kernel.org/linux-block/ai7rnH20IYeSmY8s@gallifrey/
> 
> And I'm seeing EINVAL instead EIO.

Interesting; I've got your:
  dm-raid1: don't fail the mirror for invalid I/O errors
  For DM_IO_BIO requests, do_region() built each destination bio by walking..
ontop of e21ee273e6fa3879aec9a27251cfce98156e07c4 which is just before 7.1
  I've not your https://lore.kernel.org/linux-block/20260612223205.465913-1-kbusch@meta.com/

root@dalek:/home/dg# lvcreate  --mirrors 1 -L 1G main /dev/sda2 /dev/sdb2
root@dalek:/home/dg# mkfs.ext4 /dev/mapper/main-lvol0
root@dalek:/home/dg# mount /dev/mapper/main-lvol0 /mnt/tmp/
root@dalek:/home/dg# chmod a+rwx /mnt/tmp

dg@dalek:~$ dd if=/dev/zero of=/mnt/tmp/testfile bs=1024k count=1

my two tests are separate tests:
{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}
dg@dalek:~$ cat dbf.c
#include <errno.h>
#include <fcntl.h>             
#include <asm-generic/fcntl.h>
#include <stdio.h> 
#include <unistd.h>


const char* path="/mnt/tmp/testfile";
static char buf[8192];

int main()                                       
{
  int fd=open(path, O_RDWR|O_DIRECT|O_CLOEXEC);
    
  errno=0;
  int res3=pread(fd, buf, 4096, 0);
  printf("pread of 4096 said: %d (%m)\n", res3);

}
{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}
dg@dalek:~$ cat dbf-write.c
#include <errno.h>
#include <fcntl.h>             
#include <asm-generic/fcntl.h>
#include <stdio.h> 
#include <unistd.h>


const char* path="/mnt/tmp/testfile";
static char buf[8192];

int main()                                       
{
  int fd=open(path, O_RDWR|O_DIRECT|O_CLOEXEC);
    
  errno=0;
  int res3=pwrite(fd, buf, 4096, 0);
  printf("pwrite of 4096 said: %d (%m)\n", res3);

}
{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}{--}


> > get the stuck resync on write, and on the newer mirror I see the write
> > apparently succeed (did it really?)
> 
> There was a time when ext4 used to fallback to buffered io for writes
> but not for reads, but looks like that was fixed since 6.18, so should
> be returning error.
> 
> I tried testing it with a modification to your original read test, and
> it is still failing with EINVAL for me:
> 
>   pread of 4096 said: -1 (Invalid argument)
>   pwrite of 4096 said: -1 (Invalid argument)

Your double test gives me:
dg@dalek:~$ ./dbf-joint 
pread of 4096 said: -1 (Input/output error)
pwrite of 4096 said: 4096 (Input/output error)

> ---
> #define _GNU_SOURCE
> #include <errno.h>
> #include <fcntl.h>
> #include <stdio.h>
> #include <unistd.h>
> 
> const char* path="/mnt/tmp/testfile";
> static char buf[8192];
> 
> int main()
> {
>   int fd=open(path, O_RDWR|O_DIRECT|O_CLOEXEC);
> 
>   errno=0;
>   int res3=pread(fd, buf, 4096, 0);
>   printf("pread of 4096 said: %d (%m)\n", res3);

errno=0;

>   res3=pwrite(fd, buf, 4096, 0);
>   printf("pwrite of 4096 said: %d (%m)\n", res3);
> }

Dave

> --
-- 
 -----Open up your eyes, open up your mind, open up your code -------   
/ Dr. David Alan Gilbert    |       Running GNU/Linux       | Happy  \ 
\        dave @ treblig.org |                               | In Hex /
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