Re: [PATCH] bio-integrity: don't restrict the size of integrity metadata

[Ming Lei <ming.lei@redhat.com>]

On Tue, Sep 03, 2024 at 09:47:59PM +0200, Mikulas Patocka wrote:
> Hi Jens
> 
> I added dm-integrity inline mode in the 6.11 merge window. I've found out
> that it doesn't work with large bios - the reason is that the function
> bio_integrity_add_page refuses to add more metadata than
> queue_max_hw_sectors(q). This restriction is no longer needed, because
> big bios are split automatically. I'd like to ask you if you could send
> this commit to Linus before 6.11 comes out, so that the bug is fixed
> before the final release.
> 
> Mikulas
> 
> 
> From: Mikulas Patocka <mpatocka@redhat.com>
> 
> bio_integrity_add_page restricts the size of the integrity metadata to
> queue_max_hw_sectors(q). This restriction is not needed because oversized
> bios are split automatically. This restriction causes problems with
> dm-integrity 'inline' mode - if we send a large bio to dm-integrity and
> the bio's metadata are larger than queue_max_hw_sectors(q),
> bio_integrity_add_page fails and the bio is ended with BLK_STS_RESOURCE
> error.
> 
> An example that triggers it:
> 
> # modprobe brd rd_size=1048576
> # dmsetup create in1 --table '0 1847320 integrity /dev/ram0 0 64 D 1 fix_padding'
> # dmsetup create in2 --table '0 1847312 integrity /dev/mapper/in1 0 64 I 1 internal_hash:sha512'
> # dd if=/dev/zero of=/dev/mapper/in2 bs=1M oflag=direct status=progress
> dd: error writing '/dev/mapper/in2': Cannot allocate memory
> 1+0 records in
> 0+0 records out
> 0 bytes copied, 0.00169291 s, 0.0 kB/s
> 
> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
> Fixes: fb0987682c62 ("dm-integrity: introduce the Inline mode")
> Fixes: 0ece1d649b6d ("bio-integrity: create multi-page bvecs in bio_integrity_add_page()")

Firstly meta size is always < bio size.

Secondly the check isn't needed either bio_integrity_add_page() is called on
to-be-splited bio(DM), or splited bio(blk-mq).

Reviewed-by: Ming Lei <ming.lei@redhat.com>


Thanks,
Ming