linux-ext4 - Re: regression: data corruption with ext4 on LUKS on nvme with torvalds master

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Date:   Thu, 13 May 2021 14:18:14 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Mikulas Patocka <mpatocka@...hat.com>,
        Milan Broz <gmazyland@...il.com>,
        Theodore Ts'o <tytso@....edu>,
        Changheun Lee <nanich.lee@...sung.com>
Cc:     alex_y_xu@...oo.ca, axboe@...nel.dk, bgoncalv@...hat.com,
        dm-crypt@...ut.de, hch@....de, jaegeuk@...nel.org,
        linux-block@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org,
        ming.lei@...hat.com, yi.zhang@...hat.com, dm-devel@...hat.com
Subject: Re: regression: data corruption with ext4 on LUKS on nvme with
 torvalds master

On 5/13/21 12:22 PM, Mikulas Patocka wrote:
> We already had problems with too large bios in dm-crypt and we fixed it by 
> adding this piece of code:
> 
>         /*
>          * Check if bio is too large, split as needed.
>          */
>         if (unlikely(bio->bi_iter.bi_size > (BIO_MAX_VECS << PAGE_SHIFT)) &&
>             (bio_data_dir(bio) == WRITE || cc->on_disk_tag_size))
>                 dm_accept_partial_bio(bio, ((BIO_MAX_VECS << PAGE_SHIFT) >> SECTOR_SHIFT));
> 
> It will ask the device mapper to split the bio if it is too large. So, 
> crypt_alloc_buffer can't receive a bio that is larger than BIO_MAX_VECS << 
> PAGE_SHIFT.

Hi Mikulas,

Are you perhaps referring to commit 4e870e948fba ("dm crypt: fix error
with too large bios")? Did that commit go upstream before multi-page
bvec support? Can larger bios be supported in case of two or more
contiguous pages now that multi-page bvec support is upstream?

Thanks,

Bart.