On 09/05/2016 18:04, Alan Somers wrote:
On Wed, Feb 17, 2016 at 10:16 AM, Warner Losh <i...@freebsd.org
<mailto:i...@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
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