linux-kernel - Re: [PATCH] iomap: Fix the write_count in iomap_add_to

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Message-ID: <20200820231140.GE7941@dread.disaster.area>
Date:   Fri, 21 Aug 2020 09:11:40 +1000
From:   Dave Chinner <david@...morbit.com>
To:     Anju T Sudhakar <anju@...ux.vnet.ibm.com>
Cc:     hch@...radead.org, darrick.wong@...cle.com,
        linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, willy@...radead.org,
        riteshh@...ux.ibm.com
Subject: Re: [PATCH] iomap: Fix the write_count in iomap_add_to_ioend().

On Wed, Aug 19, 2020 at 03:58:41PM +0530, Anju T Sudhakar wrote:
> From: Ritesh Harjani <riteshh@...ux.ibm.com>
> 
> __bio_try_merge_page() may return same_page = 1 and merged = 0. 
> This could happen when bio->bi_iter.bi_size + len > UINT_MAX. 

Ummm, silly question, but exactly how are we getting a bio that
large in ->writepages getting built? Even with 64kB pages, that's a
bio with 2^16 pages attached to it. We shouldn't be building single
bios in writeback that large - what storage hardware is allowing
such huge bios to be built? (i.e. can you dump all the values in
/sys/block/<dev>/queue/* for that device for us?)

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com