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| Started by | Arnd Bergmann <arnd@arndb.de> |
|---|---|
| First post | 2016-06-13 15:10 +0200 |
| Last post | 2016-06-13 17:00 +0200 |
| Articles | 3 — 2 participants |
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[PATCH] ceph: fix symbol versioning for ceph_monc_do_statfs Arnd Bergmann <arnd@arndb.de> - 2016-06-13 15:10 +0200
Re: [PATCH] ceph: fix symbol versioning for ceph_monc_do_statfs Ilya Dryomov <idryomov@gmail.com> - 2016-06-13 15:20 +0200
Re: [PATCH] ceph: fix symbol versioning for ceph_monc_do_statfs Arnd Bergmann <arnd@arndb.de> - 2016-06-13 17:00 +0200
| From | Arnd Bergmann <arnd@arndb.de> |
|---|---|
| Date | 2016-06-13 15:10 +0200 |
| Subject | [PATCH] ceph: fix symbol versioning for ceph_monc_do_statfs |
| Message-ID | <rJzMS-6In-27@gated-at.bofh.it> |
The genksyms helper in the kernel cannot parse a type definition
like "typeof(((type *)0)->keyfld)" that is used in the DEFINE_RB_FUNCS
helper, causing the following EXPORT_SYMBOL() statement to be ignored
when computing the crcs, and triggering a warning about this:
WARNING: "ceph_monc_do_statfs" [fs/ceph/ceph.ko] has no CRC
To work around the problem, we can rewrite the type to reference
an undefined 'extern' symbol instead of a NULL pointer. This is
evidently ok for genksyms, and it no longer complains about the
line when calling it with 'genksyms -w'.
I've looked briefly into extending genksyms instead, but it seems
really hard to do. Jan Beulich introduced basic support for 'typeof'
a while ago in dc53324060f3 ("genksyms: fix typeof() handling"),
but that is not sufficient for the expression we have here.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: fcd00b68bbe2 ("libceph: DEFINE_RB_FUNCS macro")
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Michal Marek <mmarek@suse.cz>
---
include/linux/ceph/libceph.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/include/linux/ceph/libceph.h b/include/linux/ceph/libceph.h
index 690985daad1c..6b79a6ba39ca 100644
--- a/include/linux/ceph/libceph.h
+++ b/include/linux/ceph/libceph.h
@@ -214,8 +214,9 @@ static void erase_##name(struct rb_root *root, type *t) \
}
#define DEFINE_RB_LOOKUP_FUNC(name, type, keyfld, nodefld) \
+extern type __lookup_##name##_key; \
static type *lookup_##name(struct rb_root *root, \
- typeof(((type *)0)->keyfld) key) \
+ typeof(__lookup_##name##_key.keyfld) key) \
{ \
struct rb_node *n = root->rb_node; \
\
--
2.7.0
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| From | Ilya Dryomov <idryomov@gmail.com> |
|---|---|
| Date | 2016-06-13 15:20 +0200 |
| Message-ID | <rJzWx-6Md-17@gated-at.bofh.it> |
| In reply to | #1420813 |
On Mon, Jun 13, 2016 at 3:04 PM, Arnd Bergmann <arnd@arndb.de> wrote:
> The genksyms helper in the kernel cannot parse a type definition
> like "typeof(((type *)0)->keyfld)" that is used in the DEFINE_RB_FUNCS
> helper, causing the following EXPORT_SYMBOL() statement to be ignored
> when computing the crcs, and triggering a warning about this:
>
> WARNING: "ceph_monc_do_statfs" [fs/ceph/ceph.ko] has no CRC
>
> To work around the problem, we can rewrite the type to reference
> an undefined 'extern' symbol instead of a NULL pointer. This is
> evidently ok for genksyms, and it no longer complains about the
> line when calling it with 'genksyms -w'.
>
> I've looked briefly into extending genksyms instead, but it seems
> really hard to do. Jan Beulich introduced basic support for 'typeof'
> a while ago in dc53324060f3 ("genksyms: fix typeof() handling"),
> but that is not sufficient for the expression we have here.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Fixes: fcd00b68bbe2 ("libceph: DEFINE_RB_FUNCS macro")
> Cc: Jan Beulich <jbeulich@suse.com>
> Cc: Michal Marek <mmarek@suse.cz>
> ---
> include/linux/ceph/libceph.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/ceph/libceph.h b/include/linux/ceph/libceph.h
> index 690985daad1c..6b79a6ba39ca 100644
> --- a/include/linux/ceph/libceph.h
> +++ b/include/linux/ceph/libceph.h
> @@ -214,8 +214,9 @@ static void erase_##name(struct rb_root *root, type *t) \
> }
>
> #define DEFINE_RB_LOOKUP_FUNC(name, type, keyfld, nodefld) \
> +extern type __lookup_##name##_key; \
> static type *lookup_##name(struct rb_root *root, \
> - typeof(((type *)0)->keyfld) key) \
> + typeof(__lookup_##name##_key.keyfld) key) \
> { \
> struct rb_node *n = root->rb_node; \
> \
Out of curiosity, did you figure out why is it that only
ceph_monc_do_statfs() is affected and not the other exports in
net/ceph/osd_client.c?
Thanks,
Ilya
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| From | Arnd Bergmann <arnd@arndb.de> |
|---|---|
| Date | 2016-06-13 17:00 +0200 |
| Message-ID | <rJBvj-7FA-11@gated-at.bofh.it> |
| In reply to | #1420821 |
On Monday, June 13, 2016 3:19:12 PM CEST Ilya Dryomov wrote:
> > diff --git a/include/linux/ceph/libceph.h b/include/linux/ceph/libceph.h
> > index 690985daad1c..6b79a6ba39ca 100644
> > --- a/include/linux/ceph/libceph.h
> > +++ b/include/linux/ceph/libceph.h
> > @@ -214,8 +214,9 @@ static void erase_##name(struct rb_root *root, type *t) \
> > }
> >
> > #define DEFINE_RB_LOOKUP_FUNC(name, type, keyfld, nodefld) \
> > +extern type __lookup_##name##_key; \
> > static type *lookup_##name(struct rb_root *root, \
> > - typeof(((type *)0)->keyfld) key) \
> > + typeof(__lookup_##name##_key.keyfld) key) \
> > { \
> > struct rb_node *n = root->rb_node; \
> > \
>
> Out of curiosity, did you figure out why is it that only
> ceph_monc_do_statfs() is affected and not the other exports in
> net/ceph/osd_client.c?
No, I did not investigate it further at that point. My guess is that
something resets the state of the genksyms parser when it encounters
some tokens (like the semicolon I added earlier, or an EXPORT_SYMBOL
statement), and that this happens in one file but not the other.
Arnd
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