Re: Patch "dm: ensure bio submission follows a depth-first tree walk" has been added to the 4.15-stable tree

Re: Patch "dm: ensure bio submission follows a depth-first tree walk" has been added to the 4.15-stable tree

[Mike Snitzer]

On Thu, Mar 22 2018 at  9:06am -0400,
gregkh@linuxfoundation.org <gregkh@linuxfoundation.org> wrote:

> 
> This is a note to let you know that I've just added the patch titled
> 
>     dm: ensure bio submission follows a depth-first tree walk
> 
> to the 4.15-stable tree which can be found at:
>     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> 
> The filename of the patch is:
>      dm-ensure-bio-submission-follows-a-depth-first-tree-walk.patch
> and it can be found in the queue-4.15 subdirectory.
> 
> If you, or anyone else, feels it should not be added to the stable tree,
> please let <stable@vger.kernel.org> know about it.

The following applies to 4.14 stable@ too.

I think it very questionable to pull this into stable trees.  How'd it
even elevate to be considered for stable@?

But if you do, you definitely need this additional upstream commit:
8dd601fa8317 ("dm: correctly handle chained bios in dec_pending()")

Even with that I'm not excited about supporting some partial backport of
these changes because there were a lot more related changes -- only
taking a subset makes these stable@ kernels unicorns.. I deal with
enough unicorn vendor kernels (but on my terms, with my control over
what is "supportable"):

Anyway, other related commits are:
80cd17578310 dm crypt: remove BIOSET_NEED_RESCUER flag
c110a4b6e603 dm io: remove BIOSET_NEED_RESCUER flag from bios bioset
f31c21e4365c dm: remove unused 'num_write_bios' target interface
318716ddea08 dm: safely allocate multiple bioset bios
4a3f54d94d5c dm: remove BIOSET_NEED_RESCUER based dm_offload infrastructure
0776aa0e30aa dm: ensure bio-based DM's bioset and io_pool support targets' maximum IOs
3d7f45625a84 dm: fix __send_changing_extent_only() to send first bio and chain remainder

So NAK from me.  If others have a compelling argument I'm open to
considering.

Mike

Re: Patch "dm: ensure bio submission follows a depth-first tree walk" has been added to the 4.15-stable tree

[Mikulas Patocka]

I agree.

The patch "dm: ensure bio submission follows a depth-first tree walk" 
doesn't really fix any bug (and it may introduce new bugs), so it isn't 
applicable to the stable kernel branches.

The kernel 4.15 and below have a "dm_offload" mechanism that avoids the 
possible deadlocks in dm, there is no reason why this should be converted 
to the "depth-first tree walk".

Mikulas


On Thu, 22 Mar 2018, Mike Snitzer wrote:

> On Thu, Mar 22 2018 at  9:06am -0400,
> gregkh@linuxfoundation.org <gregkh@linuxfoundation.org> wrote:
> 
> > 
> > This is a note to let you know that I've just added the patch titled
> > 
> >     dm: ensure bio submission follows a depth-first tree walk
> > 
> > to the 4.15-stable tree which can be found at:
> >     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> > 
> > The filename of the patch is:
> >      dm-ensure-bio-submission-follows-a-depth-first-tree-walk.patch
> > and it can be found in the queue-4.15 subdirectory.
> > 
> > If you, or anyone else, feels it should not be added to the stable tree,
> > please let <stable@vger.kernel.org> know about it.
> 
> The following applies to 4.14 stable@ too.
> 
> I think it very questionable to pull this into stable trees.  How'd it
> even elevate to be considered for stable@?
> 
> But if you do, you definitely need this additional upstream commit:
> 8dd601fa8317 ("dm: correctly handle chained bios in dec_pending()")
> 
> Even with that I'm not excited about supporting some partial backport of
> these changes because there were a lot more related changes -- only
> taking a subset makes these stable@ kernels unicorns.. I deal with
> enough unicorn vendor kernels (but on my terms, with my control over
> what is "supportable"):
> 
> Anyway, other related commits are:
> 80cd17578310 dm crypt: remove BIOSET_NEED_RESCUER flag
> c110a4b6e603 dm io: remove BIOSET_NEED_RESCUER flag from bios bioset
> f31c21e4365c dm: remove unused 'num_write_bios' target interface
> 318716ddea08 dm: safely allocate multiple bioset bios
> 4a3f54d94d5c dm: remove BIOSET_NEED_RESCUER based dm_offload infrastructure
> 0776aa0e30aa dm: ensure bio-based DM's bioset and io_pool support targets' maximum IOs
> 3d7f45625a84 dm: fix __send_changing_extent_only() to send first bio and chain remainder
> 
> So NAK from me.  If others have a compelling argument I'm open to
> considering.
> 
> Mike
> 

Re: Patch "dm: ensure bio submission follows a depth-first tree walk" has been added to the 4.15-stable tree

[Greg KH]

On Thu, Mar 22, 2018 at 09:47:59AM -0400, Mike Snitzer wrote:
> On Thu, Mar 22 2018 at  9:06am -0400,
> gregkh@linuxfoundation.org <gregkh@linuxfoundation.org> wrote:
> 
> > 
> > This is a note to let you know that I've just added the patch titled
> > 
> >     dm: ensure bio submission follows a depth-first tree walk
> > 
> > to the 4.15-stable tree which can be found at:
> >     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> > 
> > The filename of the patch is:
> >      dm-ensure-bio-submission-follows-a-depth-first-tree-walk.patch
> > and it can be found in the queue-4.15 subdirectory.
> > 
> > If you, or anyone else, feels it should not be added to the stable tree,
> > please let <stable@vger.kernel.org> know about it.
> 
> The following applies to 4.14 stable@ too.
> 
> I think it very questionable to pull this into stable trees.  How'd it
> even elevate to be considered for stable@?
> 
> But if you do, you definitely need this additional upstream commit:
> 8dd601fa8317 ("dm: correctly handle chained bios in dec_pending()")
> 
> Even with that I'm not excited about supporting some partial backport of
> these changes because there were a lot more related changes -- only
> taking a subset makes these stable@ kernels unicorns.. I deal with
> enough unicorn vendor kernels (but on my terms, with my control over
> what is "supportable"):
> 
> Anyway, other related commits are:
> 80cd17578310 dm crypt: remove BIOSET_NEED_RESCUER flag
> c110a4b6e603 dm io: remove BIOSET_NEED_RESCUER flag from bios bioset
> f31c21e4365c dm: remove unused 'num_write_bios' target interface
> 318716ddea08 dm: safely allocate multiple bioset bios
> 4a3f54d94d5c dm: remove BIOSET_NEED_RESCUER based dm_offload infrastructure
> 0776aa0e30aa dm: ensure bio-based DM's bioset and io_pool support targets' maximum IOs
> 3d7f45625a84 dm: fix __send_changing_extent_only() to send first bio and chain remainder
> 
> So NAK from me.  If others have a compelling argument I'm open to
> considering.

Thanks for letting me know, I've now dropped this from the 4.15.y,
4.14.y, and 4.9.y stable patch queues.

greg k-h