RE: [PATCH v4 4/7] block: introduce write-hint to stream-id conversion

[kanchan]

> Why not just use the bio write hint? We already disallow merging of dissimilar write hints, so req->bio->bi_write_hint is known to be identical with the rest of the bio's in that chain.

Yes, that is better. Thanks for suggesting it.

-----Original Message-----
From: Jens Axboe [mailto:axboe@xxxxxxxxx] 
Sent: Wednesday, April 17, 2019 11:28 PM
To: Kanchan Joshi <joshi.k@xxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; linux-block@xxxxxxxxxxxxxxx; linux-nvme@xxxxxxxxxxxxxxxxxxx; linux-fsdevel@xxxxxxxxxxxxxxx; linux-ext4@xxxxxxxxxxxxxxx
Cc: prakash.v@xxxxxxxxxxx
Subject: Re: [PATCH v4 4/7] block: introduce write-hint to stream-id conversion

On 4/17/19 11:50 AM, Kanchan Joshi wrote:
> This patch moves write-hint-to-stream-id conversion in block-layer.
> Earlier this was done by driver (nvme). Current conversion is of the 
> form "streamid = write-hint - 1", for both user and kernel streams.
> Conversion takes stream limit (maintained in request queue) into 
> account. Write-hints beyond the exposed limit turn to 0.
> A new field 'streamid' has been added in request. While 'write-hint'
> field continues to exist. It keeps original value passed from upper 
> layer, and used during merging checks.

Why not just use the bio write hint? We already disallow merging of dissimilar write hints, so req->bio->bi_write_hint is known to be identical with the rest of the bio's in that chain.

--
Jens Axboe