Re: Data corruption in kernel 5.1+ with iSER attached ramdisk

Stephen Rust
2020-04-02T20:02:10Z

Hi Sagi,

> Does the attached patch work for you?

This patch _does_ work for our tests. I see all the writes aligned to
512 bytes as, I think, would be expected. Thanks!

Just for your information, using the bpftrace script earlier in this
thread, the output is as follows. The lines with 2 values shows the
first two arguments to 'bio_add_page()', the lines with 4 values shows
the first 4 arguments to `brd_do_bvec()`.

For the successful case on the new patch:

# bpftrace isert.bt
Attaching 4 probes...
512 3072
512 3072 1 131071
4096 0
4096 0 0 0
4096 0
4096 0 0 8
4096 0
4096 0 0 131064
4096 512
3584 512 1 131064
512 0 1 131071
512 0
512 0 0 131071

And for the failed case on the older unpatched code:

# bpftrace ./isert.bt
Attaching 4 probes...
512 76
512 76 1 131071
4096 0
4096 0 0 0
4096 0
4096 0 0 8
4096 0
4096 0 0 131064
4096 76
4020 76 1 131064
76 0 1 131071
512 0
512 0 0 131071

Thanks again!
Steve