lkml.org 
[lkml]   [2015]   [Jul]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] block: add a bi_error field to struct bio
On 07/20/2015 07:29 AM, Christoph Hellwig wrote:
> Currently we have two different ways to signal an I/O error on a BIO:
>
> (1) by clearing the BIO_UPTODATE flag
> (2) by returning a Linux errno value to the bi_end_io callback
>
> The first one has the drawback of only communicating a single possible
> error (-EIO), and the second one has the drawback of not beeing persistent
> when bios are queued up, and are not passed along from child to parent
> bio in the ever more popular chaining scenario. Having both mechanisms
> available has the additional drawback of utterly confusing driver authors
> and introducing bugs where various I/O submitters only deal with one of
> them, and the others have to add boilerplate code to deal with both kinds
> of error returns.
>
> So add a new bi_error field to store an errno value directly in struct
> bio and remove the existing mechanisms to clean all this up.

I think this is a good change, the only part I _really_ dislike is that
this now bumps a struct bio from 2 cache lines to 3. Have you done any
perf testing?

--
Jens Axboe



\
 
 \ /
  Last update: 2015-07-22 21:21    [W:0.750 / U:0.008 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site