svn commit: r295707 - in head/sys: cddl/contrib/opensolaris/uts/common/fs/zfs dev/mmc dev/virtio/block geom geom/journal geom/mirror geom/raid geom/raid3 kern

Steven Hartland steven at multiplay.co.uk
Mon May 9 17:14:54 UTC 2016



On 09/05/2016 18:04, Alan Somers wrote:
>
>
> On Wed, Feb 17, 2016 at 10:16 AM, Warner Losh <imp at freebsd.org 
> <mailto:imp at freebsd.org>> wrote:
>
>     Author: imp
>     Date: Wed Feb 17 17:16:02 2016
>     New Revision: 295707
>     URL: https://svnweb.freebsd.org/changeset/base/295707
>
>     Log:
>       Create an API to reset a struct bio (g_reset_bio). This is mandatory
>       for all struct bio you get back from g_{new,alloc}_bio. Temporary
>       bios that you create on the stack or elsewhere should use this
>     before
>       first use of the bio, and between uses of the bio. At the moment, it
>       is nothing more than a wrapper around bzero, but that may change in
>       the future. The wrapper also removes one place where we encode the
>       size of struct bio in the KBI.
>
>     Modified:
>     head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_geom.c
>       head/sys/dev/mmc/mmcsd.c
>       head/sys/dev/virtio/block/virtio_blk.c
>       head/sys/geom/geom.h
>       head/sys/geom/geom_io.c
>       head/sys/geom/journal/g_journal.c
>       head/sys/geom/mirror/g_mirror.c
>       head/sys/geom/raid/g_raid.c
>       head/sys/geom/raid3/g_raid3.c
>       head/sys/kern/kern_physio.c
>
>
> smh noticed that while your commit message says that g_reset_bio is 
> mandatory after g_{new,alloc}_bio, your diff only replaced existing 
> calls to bzero.  You didn't insert g_reset_bio calls after all 
> g_alloc_bio calls, for example in vdev_geom_io_start.  Do you intend 
> to follow up this change with a g_reset_bio everywhere that 
> g_alloc_bio is called, or did you mean that g_reset_bio is optional 
> after all bios returned by g_{new,alloc}_bio?
>
Yer I was just penning this too:
This commit was just referenced in https://reviews.freebsd.org/D6153

It seems rather odd to require all callers to g_{new,alloc}_bio to also 
call g_reset_bio.

I assume this is because uma can return an existing object instead of 
fresh one hence its not guaranteed to be bzeroed? If so why have the 
caller responsible, seems petty error prone. A quick look at users of 
g_alloc_bio it seems like this is something that's not done currently 
done in all places, even some usages of memset still hanging around, are 
these cases a bug?

If the concept of this was to ensure correctly initialised objects from 
uma would the callback handers to uma_zcreate not be a better option as 
that would guarantee things are correct instead of leaving it to the caller?

As a side matter, this area really needs some man pages so the its clear 
to all what is needed and when.

     Regards
     Steve



More information about the svn-src-head mailing list