Re: [PATCH 41/80] staging: lustre: lmv: separate master object with master stripe

[Dan Carpenter]

On Fri, Feb 09, 2018 at 12:39:18PM +1100, NeilBrown wrote:
> On Tue, Aug 16 2016, James Simmons wrote:
> 
> >  
> > +static inline bool
> > +lsm_md_eq(const struct lmv_stripe_md *lsm1, const struct lmv_stripe_md 
> > *lsm2)
> > +{
> > +   int idx;
> > +
> > +   if (lsm1->lsm_md_magic != lsm2->lsm_md_magic ||
> > +   lsm1->lsm_md_stripe_count != lsm2->lsm_md_stripe_count ||
> > +   lsm1->lsm_md_master_mdt_index != lsm2->lsm_md_master_mdt_index ||
> > +   lsm1->lsm_md_hash_type != lsm2->lsm_md_hash_type ||
> > +   lsm1->lsm_md_layout_version != lsm2->lsm_md_layout_version ||
> > +   !strcmp(lsm1->lsm_md_pool_name, lsm2->lsm_md_pool_name))
> > +   return false;
> 
> Hi James and all,
>  This patch (8f18c8a48b736c2f in linux) is different from the
>  corresponding patch in lustre-release (60e07b972114df).
> 
> In that patch, the last clause in the 'if' condition is
> 
> +   strcmp(lsm1->lsm_md_pool_name,
> + lsm2->lsm_md_pool_name) != 0)
> 
> Whoever converted it to "!strcmp()" inverted the condition.  This is a
> perfect example of why I absolutely *loathe* the "!strcmp()" construct!!

People think that "if (!strcmp()) " is prefered kernel style but it's
not.

if (foo != NULL) {

The != NULL is a double negative.  I don't think it adds anything.
Some kernel developers like this style because it's explicit about the
type.  I have never seen any bugs caused by this format or solved by
this format.  Anyway checkpatch complains.

if (ret != 0) {

In this situation "ret" is not a number, it's an error code.  The != 0
is a double negative and complicated to think about.  Btw, I sort of
prefer "if (ret)" to "if (ret < 0)", not because of style but it's
easier for Smatch.  No subsystems are totally consistent so the (by
definition inconsistent) "if (ret < 0)" checks cause false positives in
Smatch.

if (len != 0)

This is OK.  "len" is a number.

if (strcmp(one, two) != 0) {

With strcmp() I really prefer == 0 and != 0 because it works like this:

strcmp(one, two) == 0  --> means one == two
strcmp(one, two) < 0   --> means one < two
strcmp(one, two) != 0  --> means one != two

Either style is accepted in the kernel but I think == 0 just makes so
much sense.  I mostly see bugs from this when people are "fixing" the
style from == 0 to !strcmp() so my sample is very biased.  Normally, if
the original author writes the code any bugs are caught in testing so
either way is going to be bug free.

But the only thing that checkpatch complains about is == NULL and
!= NULL.

regards,
dan carpenter
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Re: [PATCH 41/80] staging: lustre: lmv: separate master object with master stripe

[James Simmons]

> > +static inline bool
> > +lsm_md_eq(const struct lmv_stripe_md *lsm1, const struct lmv_stripe_md 
> > *lsm2)
> > +{
> > +   int idx;
> > +
> > +   if (lsm1->lsm_md_magic != lsm2->lsm_md_magic ||
> > +   lsm1->lsm_md_stripe_count != lsm2->lsm_md_stripe_count ||
> > +   lsm1->lsm_md_master_mdt_index != lsm2->lsm_md_master_mdt_index ||
> > +   lsm1->lsm_md_hash_type != lsm2->lsm_md_hash_type ||
> > +   lsm1->lsm_md_layout_version != lsm2->lsm_md_layout_version ||
> > +   !strcmp(lsm1->lsm_md_pool_name, lsm2->lsm_md_pool_name))
> > +   return false;
> 
> Hi James and all,
>  This patch (8f18c8a48b736c2f in linux) is different from the
>  corresponding patch in lustre-release (60e07b972114df).
> 
> In that patch, the last clause in the 'if' condition is
> 
> +   strcmp(lsm1->lsm_md_pool_name,
> + lsm2->lsm_md_pool_name) != 0)
> 
> Whoever converted it to "!strcmp()" inverted the condition.  This is a
> perfect example of why I absolutely *loathe* the "!strcmp()" construct!!
> 
> This causes many tests in the 'sanity' test suite to return
> -ENOMEM (that had me puzzled for a while!!).
> This seems to suggest that no-one has been testing the mainline linux
> lustre.
> It also seems to suggest that there is a good chance that there
> are other bugs that have crept in while no-one has really been caring.
> Given that the sanity test suite doesn't complete for me, but just
> hangs (in test_27z I think), that seems particularly likely.
> 
> 
> So my real question - to anyone interested in lustre for mainline linux
> - is: can we actually trust this code at all?
> I'm seriously tempted to suggest that we just
>   rm -r drivers/staging/lustre
> 
> drivers/staging is great for letting the community work on code that has
> been "thrown over the wall" and is not openly developed elsewhere, but
> that is not the case for lustre.  lustre has (or seems to have) an open
> development process.  Having on-going development happen both there and
> in drivers/staging seems a waste of resources.
> 
> Might it make sense to instead start cleaning up the code in
> lustre-release so as to make it meet the upstream kernel standards.
> Then when the time is right, the kernel code can be moved *out* of
> lustre-release and *in* to linux.  Then development can continue in
> Linux (just like it does with other Linux filesystems).
> 
> An added bonus of this is that there is an obvious path to getting
> server support in mainline Linux.  The current situation of client-only
> support seems weird given how interdependent the two are.
> 
> What do others think?  Is there any chance that the current lustre in
> Linux will ever be more than a poor second-cousin to the external
> lustre-release.  If there isn't, should we just discard it now and move
> on?

If you think that the OpenSFS/Intel branch (lustre-release) is the land
of milk and honey you are very wrong. Take for example the UAPI header
cleanup I push to the linux client several months ago. That work took
5 years to complete. I had to complete that work in the Intel branch
since it impacted our tools. This isn't the only example. I worked along
side Intel for increasing striping of a file to more then the 160 stripe
limit Lustre use to have. That work took 3 years to complete. If the
patch is more than one line it will normally take 1 to 2 months to land.
It is common to have patches 6 months or more in age.

This is one of the major reasons I'm involved in the upstream client
work. If lustre remains a tiny under manned community it is doomed to
remain a niche file system. For years I have tried to recruit new
developers to help out and even gave talks at lustre conferences on
internals. That effort was meet with little success. This is not the
case with the linux lustre client. We do have people contributing
including you. So the reality is that if we removed the lustre client
it would be at least 3+ years before the code would be ready to merged
back in. It would be another 3+ years before it left staging. Many
cleanups in the linux client which impact many lines of code have not
been ported to the Intel branch. It would take forever to get those in.
Honestly I gave up some time ago for those types of cleanups. The cleanups
done in the upstream client would have to be redone. What we really
need is to expand the community. Recently a lot of work has gone into
supporting Ubuntu for our utilities. I hope this helps to get Canonical
involved with the upstream lustre client.

The upstream client is not as bad as you think. A year ago no one in
their right mind would touch the upstream client but their are actually
sites using it today. Its not perfect but it is usable and it is improving
all the time. Yes we have quite a few bugs to squash that show up in
our test suite but the barrier to leaving staging is much much smaller
than it used to be. Once the number of bugs reported in test suite
becomes reasonable we can start 

Re: [PATCH 41/80] staging: lustre: lmv: separate master object with master stripe

[NeilBrown]

On Thu, Feb 08 2018, Oleg Drokin wrote:

>> On Feb 8, 2018, at 8:39 PM, NeilBrown  wrote:
>> 
>> On Tue, Aug 16 2016, James Simmons wrote:
>
> my that’s an old patch
>
>> 
...
>> 
>> Whoever converted it to "!strcmp()" inverted the condition.  This is a
>> perfect example of why I absolutely *loathe* the "!strcmp()" construct!!
>> 
>> This causes many tests in the 'sanity' test suite to return
>> -ENOMEM (that had me puzzled for a while!!).
>
> huh? I am not seeing anything of the sort and I was running sanity
> all the time until a recent pause (but going to resume).

That does surprised me - I reproduce it every time.
I have two VMs running a SLE12-SP2 kernel with patches from
lustre-release applied.  These are servers. They have 2 3G virtual disks
each.
I have two over VMs running current mainline.  These are clients.

I guess your 'recent pause' included between v4.15-rc1 (8e55b6fd0660)
and v4.15-rc6 (a93639090a27) - a full month when lustre wouldn't work at
all :-(


>
>> This seems to suggest that no-one has been testing the mainline linux
>> lustre.
>> It also seems to suggest that there is a good chance that there
>> are other bugs that have crept in while no-one has really been caring.
>> Given that the sanity test suite doesn't complete for me, but just
>> hangs (in test_27z I think), that seems particularly likely.
>
> Works for me, here’s a run from earlier today on 4.15.0:

Well that's encouraging .. I haven't looked into this one yet - I'm not
even sure where to start.

>
>> So my real question - to anyone interested in lustre for mainline linux
>> - is: can we actually trust this code at all?
>
> Absolutely. Seems that you just stumbled upon a corner case that was not
> being hit by people that do the testing, so you have something unique about
> your setup, I guess.
>
>> I'm seriously tempted to suggest that we just
>>  rm -r drivers/staging/lustre
>> 
>> drivers/staging is great for letting the community work on code that has
>> been "thrown over the wall" and is not openly developed elsewhere, but
>> that is not the case for lustre.  lustre has (or seems to have) an open
>> development process.  Having on-going development happen both there and
>> in drivers/staging seems a waste of resources.
>
> It is a bit of a waste of resources, but there are some other things here.
> E.g. we cannot have any APIs with no users in the kernel.
> Also some people like to have in-kernel modules coming with their distros
> (there were some users that used staging client on ubuntu as their
> setup).
>
> Instead the plan was to clean up the staging client into acceptable state,
> move it out of staging, bring in all the missing features and then
> drop the client (more or less) from the lustre-release.

That sounds like a great plan.  Any idea why it didn't happen?
It seems there is a lot of upstream work mixed in with the clean up, and
I don't think that really helps anyone.

Is it at all realistic that the client might be removed from
lustre-release?  That might be a good goal to work towards.

>
>> Might it make sense to instead start cleaning up the code in
>> lustre-release so as to make it meet the upstream kernel standards.
>> Then when the time is right, the kernel code can be moved *out* of
>> lustre-release and *in* to linux.  Then development can continue in
>> Linux (just like it does with other Linux filesystems).
>
> While we can be cleaning lustre in lustre-release, there are some things
> we cannot do as easily, e.g. decoupling Lustre client from the server.
> Also it would not attract any reviews from all the janitor or
> (more importantly) Al Viro and other people with a sharp eyes.
>
>> An added bonus of this is that there is an obvious path to getting
>> server support in mainline Linux.  The current situation of client-only
>> support seems weird given how interdependent the two are.
>
> Given the pushback Lustre client was given I have no hope Lustre server
> will get into mainline in my lifetime.

Even if it is horrible it would be nice to have it in staging... I guess
the changes required to ext4 prohibit that... I don't suppose it can be
made to work with mainline ext4 in a reduced-functionality-and-performance
way??

I think it would be a lot easier to motivate forward progress if there
were a credible end goal of everything being in mainline.

>
>> What do others think?  Is there any chance that the current lustre in
>> Linux will ever be more than a poor second-cousin to the external
>> lustre-release.  If there isn't, should we just discard it now and move
>> on?
>
>
> I think many useful cleanups and fixes came from the staging tree at
> the very least.
> The biggest problem with it all is that we are in staging tree so
> we cannot bring it to parity much. And we are in staging tree because
> there’s a whole bunch of “cleanups” requested that take a lot of effort
> (in both implementing them and then in finding other ways of achieving
> things that were done in 

Re: [PATCH 41/80] staging: lustre: lmv: separate master object with master stripe

[Oleg Drokin]

> On Feb 8, 2018, at 8:39 PM, NeilBrown  wrote:
> 
> On Tue, Aug 16 2016, James Simmons wrote:

my that’s an old patch

> 
>> 
>> +static inline bool
>> +lsm_md_eq(const struct lmv_stripe_md *lsm1, const struct lmv_stripe_md 
>> *lsm2)
>> +{
>> +int idx;
>> +
>> +if (lsm1->lsm_md_magic != lsm2->lsm_md_magic ||
>> +lsm1->lsm_md_stripe_count != lsm2->lsm_md_stripe_count ||
>> +lsm1->lsm_md_master_mdt_index != lsm2->lsm_md_master_mdt_index ||
>> +lsm1->lsm_md_hash_type != lsm2->lsm_md_hash_type ||
>> +lsm1->lsm_md_layout_version != lsm2->lsm_md_layout_version ||
>> +!strcmp(lsm1->lsm_md_pool_name, lsm2->lsm_md_pool_name))
>> +return false;
> 
> Hi James and all,
> This patch (8f18c8a48b736c2f in linux) is different from the
> corresponding patch in lustre-release (60e07b972114df).
> 
> In that patch, the last clause in the 'if' condition is
> 
> +   strcmp(lsm1->lsm_md_pool_name,
> + lsm2->lsm_md_pool_name) != 0)
> 
> Whoever converted it to "!strcmp()" inverted the condition.  This is a
> perfect example of why I absolutely *loathe* the "!strcmp()" construct!!
> 
> This causes many tests in the 'sanity' test suite to return
> -ENOMEM (that had me puzzled for a while!!).

huh? I am not seeing anything of the sort and I was running sanity
all the time until a recent pause (but going to resume).

> This seems to suggest that no-one has been testing the mainline linux
> lustre.
> It also seems to suggest that there is a good chance that there
> are other bugs that have crept in while no-one has really been caring.
> Given that the sanity test suite doesn't complete for me, but just
> hangs (in test_27z I think), that seems particularly likely.

Works for me, here’s a run from earlier today on 4.15.0:
== sanity test 27z: check SEQ/OID on the MDT and OST filesystems 
= 16:43:58 (1518126238)
1+0 records in
1+0 records out
1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.0169548 s, 61.8 MB/s
2+0 records in
2+0 records out
2097152 bytes (2.1 MB, 2.0 MiB) copied, 0.02782 s, 75.4 MB/s
check file /mnt/lustre/d27z.sanity/f27z.sanity-1
FID seq 0x20401, oid 0x4640 ver 0x0
LOV seq 0x20401, oid 0x4640, count: 1
want: stripe:0 ost:0 oid:314/0x13a seq:0
Stopping /mnt/lustre-ost1 (opts:) on centos6-17
pdsh@fedora1: centos6-17: ssh exited with exit code 1
pdsh@fedora1: centos6-17: ssh exited with exit code 1
pdsh@fedora1: centos6-17: ssh exited with exit code 1
Starting ost1:   -o loop /tmp/lustre-ost1 /mnt/lustre-ost1
Failed to initialize ZFS library: 256
h2tcp: deprecated, use h2nettype instead
centos6-17.localnet: executing set_default_debug vfstrace rpctrace dlmtrace 
neterror ha config ioctl super all -lnet -lnd -pinger 16
pdsh@fedora1: centos6-17: ssh exited with exit code 1
pdsh@fedora1: centos6-17: ssh exited with exit code 1
Started lustre-OST
/mnt/lustre-ost1/O/0/d26/314: parent=[0x20401:0x4640:0x0] stripe=0 
stripe_size=0 stripe_count=0
check file /mnt/lustre/d27z.sanity/f27z.sanity-2
FID seq 0x20401, oid 0x4642 ver 0x0
LOV seq 0x20401, oid 0x4642, count: 2
want: stripe:0 ost:1 oid:1187/0x4a3 seq:0
Stopping /mnt/lustre-ost2 (opts:) on centos6-17
pdsh@fedora1: centos6-17: ssh exited with exit code 1
pdsh@fedora1: centos6-17: ssh exited with exit code 1
pdsh@fedora1: centos6-17: ssh exited with exit code 1
Starting ost2:   -o loop /tmp/lustre-ost2 /mnt/lustre-ost2
Failed to initialize ZFS library: 256
h2tcp: deprecated, use h2nettype instead
centos6-17.localnet: executing set_default_debug vfstrace rpctrace dlmtrace 
neterror ha config ioctl super all -lnet -lnd -pinger 16
pdsh@fedora1: centos6-17: ssh exited with exit code 1
pdsh@fedora1: centos6-17: ssh exited with exit code 1
Started lustre-OST0001
/mnt/lustre-ost2/O/0/d3/1187: parent=[0x20401:0x4642:0x0] stripe=0 
stripe_size=0 stripe_count=0
want: stripe:1 ost:0 oid:315/0x13b seq:0
got: objid=0 seq=0 parent=[0x20401:0x4642:0x0] stripe=1
Resetting fail_loc on all nodes...done.
16:44:32 (1518126272) waiting for centos6-16 network 5 secs ...
16:44:32 (1518126272) network interface is UP
16:44:33 (1518126273) waiting for centos6-17 network 5 secs ...
16:44:33 (1518126273) network interface is UP


> So my real question - to anyone interested in lustre for mainline linux
> - is: can we actually trust this code at all?

Absolutely. Seems that you just stumbled upon a corner case that was not
being hit by people that do the testing, so you have something unique about
your setup, I guess.

> I'm seriously tempted to suggest that we just
>  rm -r drivers/staging/lustre
> 
> drivers/staging is great for letting the community work on code that has
> been "thrown over the wall" and is not openly developed elsewhere, but
> that is not the case for lustre.  lustre has (or seems to have) an open
> development process.  Having on-going development happen both there and
> in drivers/staging seems a waste of resources.

Re: [PATCH 41/80] staging: lustre: lmv: separate master object with master stripe

[NeilBrown]

On Tue, Aug 16 2016, James Simmons wrote:

>  
> +static inline bool
> +lsm_md_eq(const struct lmv_stripe_md *lsm1, const struct lmv_stripe_md *lsm2)
> +{
> + int idx;
> +
> + if (lsm1->lsm_md_magic != lsm2->lsm_md_magic ||
> + lsm1->lsm_md_stripe_count != lsm2->lsm_md_stripe_count ||
> + lsm1->lsm_md_master_mdt_index != lsm2->lsm_md_master_mdt_index ||
> + lsm1->lsm_md_hash_type != lsm2->lsm_md_hash_type ||
> + lsm1->lsm_md_layout_version != lsm2->lsm_md_layout_version ||
> + !strcmp(lsm1->lsm_md_pool_name, lsm2->lsm_md_pool_name))
> + return false;

Hi James and all,
 This patch (8f18c8a48b736c2f in linux) is different from the
 corresponding patch in lustre-release (60e07b972114df).

In that patch, the last clause in the 'if' condition is

+   strcmp(lsm1->lsm_md_pool_name,
+ lsm2->lsm_md_pool_name) != 0)

Whoever converted it to "!strcmp()" inverted the condition.  This is a
perfect example of why I absolutely *loathe* the "!strcmp()" construct!!

This causes many tests in the 'sanity' test suite to return
-ENOMEM (that had me puzzled for a while!!).
This seems to suggest that no-one has been testing the mainline linux
lustre.
It also seems to suggest that there is a good chance that there
are other bugs that have crept in while no-one has really been caring.
Given that the sanity test suite doesn't complete for me, but just
hangs (in test_27z I think), that seems particularly likely.


So my real question - to anyone interested in lustre for mainline linux
- is: can we actually trust this code at all?
I'm seriously tempted to suggest that we just
  rm -r drivers/staging/lustre

drivers/staging is great for letting the community work on code that has
been "thrown over the wall" and is not openly developed elsewhere, but
that is not the case for lustre.  lustre has (or seems to have) an open
development process.  Having on-going development happen both there and
in drivers/staging seems a waste of resources.

Might it make sense to instead start cleaning up the code in
lustre-release so as to make it meet the upstream kernel standards.
Then when the time is right, the kernel code can be moved *out* of
lustre-release and *in* to linux.  Then development can continue in
Linux (just like it does with other Linux filesystems).

An added bonus of this is that there is an obvious path to getting
server support in mainline Linux.  The current situation of client-only
support seems weird given how interdependent the two are.

What do others think?  Is there any chance that the current lustre in
Linux will ever be more than a poor second-cousin to the external
lustre-release.  If there isn't, should we just discard it now and move
on?

Thanks,
NeilBrown



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