lkml.org 
[lkml]   [2016]   [Apr]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] block: make sure big bio is splitted into at most 256 bvecs
On Tue, Apr 05, 2016 at 04:45:55PM -0800, Kent Overstreet wrote:
> On Tue, Apr 05, 2016 at 05:41:47PM -0700, Shaohua Li wrote:
> > On Tue, Apr 05, 2016 at 04:36:04PM -0800, Kent Overstreet wrote:
> > > On Tue, Apr 05, 2016 at 05:30:07PM -0700, Shaohua Li wrote:
> > > > this one:
> > > > http://marc.info/?l=linux-kernel&m=145926976808760&w=2
> > >
> > > Ah. that patch won't actually fix the bug, since md isn't using
> > > blk_default_limits, it's using blk_set_stacking_limits().
> >
> > Not really, the limit is set by under layer disk not md, otherwise it
> > should be BLK_SAFE_MAX_SECTORS, but the reported bio has 2560 sectors.
> > blk_set_stacking_limits() will use it.
>
> What? Well, that could should just be deleted, there's no reason anymore for md
> to care about the queue limits of the devices underneath it.
>
> Regardless, using BLK_DEF_MAX_SECTORS to limit # of pages in the biovec is
> _crazy_. Why would you even do that? We have a separate field in queue limits
> for # max segments, use it.

We don't limit the max segments in blk_queue_max_segments(), but we can
add. On the other hand, limit max segments to 256 could be a problem,
because bvec page isn't always 4k, this might make some bio smaller.

\
 
 \ /
  Last update: 2016-04-06 03:21    [W:0.641 / U:0.064 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site