linux-kernel - Re: commit 762380a "block: add notion of a chunk size for request merging" stops io on btrfs

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Date:	Tue, 17 Jun 2014 19:11:27 -0700
From:	Jens Axboe <axboe@...com>
To:	Konstantinos Skarlatos <k.skarlatos@...il.com>,
	<linux-kernel@...r.kernel.org>
CC:	<linux-btrfs@...r.kernel.org>
Subject: Re: commit 762380a "block: add notion of a chunk size for request
 merging" stops io on btrfs

On 2014-06-17 14:35, Konstantinos Skarlatos wrote:
> Hi all,
> with 3.16-rc1  rsync stops writing to my btrfs filesystem and stays at a
> D+ state.
> git bisect showed that the problematic commit is:
>
> 762380ad9322951cea4ce9d24864265f9c66a916 is the first bad commit
> commit 762380ad9322951cea4ce9d24864265f9c66a916
> Author: Jens Axboe <axboe@...com>
> Date:   Thu Jun 5 13:38:39 2014 -0600
>
>      block: add notion of a chunk size for request merging
>
>      Some drivers have different limits on what size a request should
>      optimally be, depending on the offset of the request. Similar to
>      dividing a device into chunks. Add a setting that allows the driver
>      to inform the block layer of such a chunk size. The block layer will
>      then prevent merging across the chunks.
>
>      This is needed to optimally support NVMe with a non-zero stripe size.
>
>      Signed-off-by: Jens Axboe <axboe@...com>

That's odd, should not have any effect since nobody enables stripe sizes 
in the kernel. I'll double check, perhaps it's not always being cleared.

Ah wait, does the attached help?


-- 
Jens Axboe


View attachment "max-sectors.patch" of type "text/x-patch" (469 bytes)