[Qemu-devel] [PATCH] block: Remove -errno return value from bdrv_assign_node_name

[Qemu-devel] [PATCH] block: Remove -errno return value from bdrv_assign_node_name

[Kevin Wolf]

It takes an errp argument. That's enough for error handling.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/block.c b/block.c
index acb70fd..b4f3f77 100644
--- a/block.c
+++ b/block.c
@@ -783,18 +783,18 @@ static int bdrv_open_flags(BlockDriverState *bs, int flags)
     return open_flags;
 }
 
-static int bdrv_assign_node_name(BlockDriverState *bs,
-                                 const char *node_name,
-                                 Error **errp)
+static void bdrv_assign_node_name(BlockDriverState *bs,
+                                  const char *node_name,
+                                  Error **errp)
 {
     if (!node_name) {
-        return 0;
+        return;
     }
 
     /* empty string node name is invalid */
     if (node_name[0] == '\0') {
         error_setg(errp, "Empty node name");
-        return -EINVAL;
+        return;
     }
 
     /* takes care of avoiding namespaces collisions */
@@ -807,14 +807,12 @@ static int bdrv_assign_node_name(BlockDriverState *bs,
     /* takes care of avoiding duplicates node names */
     if (bdrv_find_node(node_name)) {
         error_setg(errp, "Duplicate node name");
-        return -EINVAL;
+        return;
     }
 
     /* copy node name into the bs and insert it into the graph list */
     pstrcpy(bs->node_name, sizeof(bs->node_name), node_name);
     QTAILQ_INSERT_TAIL(&graph_bdrv_states, bs, node_list);
-
-    return 0;
 }
 
 /*
@@ -849,9 +847,10 @@ static int bdrv_open_common(BlockDriverState *bs, BlockDriverState *file,
     trace_bdrv_open_common(bs, filename ?: "", flags, drv->format_name);
 
     node_name = qdict_get_try_str(options, "node-name");
-    ret = bdrv_assign_node_name(bs, node_name, errp);
-    if (ret < 0) {
-        return ret;
+    bdrv_assign_node_name(bs, node_name, &local_err);
+    if (error_is_set(&local_err)) {
+        error_propagate(errp, local_err);
+        return -EINVAL;
     }
     qdict_del(options, "node-name");
 
-- 
1.8.3.1

Re: [Qemu-devel] [PATCH] block: Remove -errno return value from bdrv_assign_node_name

[Markus Armbruster]

Kevin Wolf <kwolf@redhat.com> writes:

> It takes an errp argument. That's enough for error handling.
>
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block.c | 21 ++++++++++-----------
>  1 file changed, 10 insertions(+), 11 deletions(-)
>
> diff --git a/block.c b/block.c
> index acb70fd..b4f3f77 100644
> --- a/block.c
> +++ b/block.c
> @@ -783,18 +783,18 @@ static int bdrv_open_flags(BlockDriverState *bs, int flags)
>      return open_flags;
>  }
>  
> -static int bdrv_assign_node_name(BlockDriverState *bs,
> -                                 const char *node_name,
> -                                 Error **errp)
> +static void bdrv_assign_node_name(BlockDriverState *bs,
> +                                  const char *node_name,
> +                                  Error **errp)
>  {
>      if (!node_name) {
> -        return 0;
> +        return;
>      }
>  
>      /* empty string node name is invalid */
>      if (node_name[0] == '\0') {
>          error_setg(errp, "Empty node name");
> -        return -EINVAL;
> +        return;
>      }
>  
>      /* takes care of avoiding namespaces collisions */
> @@ -807,14 +807,12 @@ static int bdrv_assign_node_name(BlockDriverState *bs,
>      /* takes care of avoiding duplicates node names */
>      if (bdrv_find_node(node_name)) {
>          error_setg(errp, "Duplicate node name");
> -        return -EINVAL;
> +        return;
>      }
>  
>      /* copy node name into the bs and insert it into the graph list */
>      pstrcpy(bs->node_name, sizeof(bs->node_name), node_name);
>      QTAILQ_INSERT_TAIL(&graph_bdrv_states, bs, node_list);
> -
> -    return 0;
>  }
>  
>  /*
> @@ -849,9 +847,10 @@ static int bdrv_open_common(BlockDriverState *bs, BlockDriverState *file,
>      trace_bdrv_open_common(bs, filename ?: "", flags, drv->format_name);
>  
>      node_name = qdict_get_try_str(options, "node-name");
> -    ret = bdrv_assign_node_name(bs, node_name, errp);
> -    if (ret < 0) {
> -        return ret;
> +    bdrv_assign_node_name(bs, node_name, &local_err);
> +    if (error_is_set(&local_err)) {
> +        error_propagate(errp, local_err);
> +        return -EINVAL;
>      }
>      qdict_del(options, "node-name");

Please use 'if (local_err)' instead of 'if (error_is_set(&local_err))'.
See commit 84d18f0.

I don't like functions returning their only value through a pointer
rather than the function value, but I guess it's how Error wants to be
used.

Re: [Qemu-devel] [PATCH] block: Remove -errno return value from bdrv_assign_node_name

[Kevin Wolf]

Am 18.03.2014 um 11:09 hat Markus Armbruster geschrieben:
> Kevin Wolf <kwolf@redhat.com> writes:
> 
> > It takes an errp argument. That's enough for error handling.
> >
> > Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> > ---
> >  block.c | 21 ++++++++++-----------
> >  1 file changed, 10 insertions(+), 11 deletions(-)
> >
> > diff --git a/block.c b/block.c
> > index acb70fd..b4f3f77 100644
> > --- a/block.c
> > +++ b/block.c
> > @@ -783,18 +783,18 @@ static int bdrv_open_flags(BlockDriverState *bs, int flags)
> >      return open_flags;
> >  }
> >  
> > -static int bdrv_assign_node_name(BlockDriverState *bs,
> > -                                 const char *node_name,
> > -                                 Error **errp)
> > +static void bdrv_assign_node_name(BlockDriverState *bs,
> > +                                  const char *node_name,
> > +                                  Error **errp)
> >  {
> >      if (!node_name) {
> > -        return 0;
> > +        return;
> >      }
> >  
> >      /* empty string node name is invalid */
> >      if (node_name[0] == '\0') {
> >          error_setg(errp, "Empty node name");
> > -        return -EINVAL;
> > +        return;
> >      }
> >  
> >      /* takes care of avoiding namespaces collisions */
> > @@ -807,14 +807,12 @@ static int bdrv_assign_node_name(BlockDriverState *bs,
> >      /* takes care of avoiding duplicates node names */
> >      if (bdrv_find_node(node_name)) {
> >          error_setg(errp, "Duplicate node name");
> > -        return -EINVAL;
> > +        return;
> >      }
> >  
> >      /* copy node name into the bs and insert it into the graph list */
> >      pstrcpy(bs->node_name, sizeof(bs->node_name), node_name);
> >      QTAILQ_INSERT_TAIL(&graph_bdrv_states, bs, node_list);
> > -
> > -    return 0;
> >  }
> >  
> >  /*
> > @@ -849,9 +847,10 @@ static int bdrv_open_common(BlockDriverState *bs, BlockDriverState *file,
> >      trace_bdrv_open_common(bs, filename ?: "", flags, drv->format_name);
> >  
> >      node_name = qdict_get_try_str(options, "node-name");
> > -    ret = bdrv_assign_node_name(bs, node_name, errp);
> > -    if (ret < 0) {
> > -        return ret;
> > +    bdrv_assign_node_name(bs, node_name, &local_err);
> > +    if (error_is_set(&local_err)) {
> > +        error_propagate(errp, local_err);
> > +        return -EINVAL;
> >      }
> >      qdict_del(options, "node-name");
> 
> Please use 'if (local_err)' instead of 'if (error_is_set(&local_err))'.
> See commit 84d18f0.

I can do that; this patch predates your change and I just dug it out
from an old branch. Note that there are still many places that use
error_is_set() where it's not necessary, including documentation that
should show how to do things right, e.g. docs/writing-qmp-commands.txt.

(By the way, would the actual problem with Coverity in commit 84d18f0
not be fixed more easily and for all instances by making error_is_set()
a static inline function in the header?)

What was the proper use case for error_is_set() again? Or can we get rid
of it? As long as it's there, you'll keep getting new offenders.

Kevin

Re: [Qemu-devel] [PATCH] block: Remove -errno return value from bdrv_assign_node_name

[Markus Armbruster]

Kevin Wolf <kwolf@redhat.com> writes:

> Am 18.03.2014 um 11:09 hat Markus Armbruster geschrieben:
>> Kevin Wolf <kwolf@redhat.com> writes:
>> 
>> > It takes an errp argument. That's enough for error handling.
>> >
>> > Signed-off-by: Kevin Wolf <kwolf@redhat.com>
>> > ---
>> >  block.c | 21 ++++++++++-----------
>> >  1 file changed, 10 insertions(+), 11 deletions(-)
>> >
>> > diff --git a/block.c b/block.c
>> > index acb70fd..b4f3f77 100644
>> > --- a/block.c
>> > +++ b/block.c
>> > @@ -783,18 +783,18 @@ static int bdrv_open_flags(BlockDriverState *bs, int flags)
>> >      return open_flags;
>> >  }
>> >  
>> > -static int bdrv_assign_node_name(BlockDriverState *bs,
>> > -                                 const char *node_name,
>> > -                                 Error **errp)
>> > +static void bdrv_assign_node_name(BlockDriverState *bs,
>> > +                                  const char *node_name,
>> > +                                  Error **errp)
>> >  {
>> >      if (!node_name) {
>> > -        return 0;
>> > +        return;
>> >      }
>> >  
>> >      /* empty string node name is invalid */
>> >      if (node_name[0] == '\0') {
>> >          error_setg(errp, "Empty node name");
>> > -        return -EINVAL;
>> > +        return;
>> >      }
>> >  
>> >      /* takes care of avoiding namespaces collisions */
>> > @@ -807,14 +807,12 @@ static int bdrv_assign_node_name(BlockDriverState *bs,
>> >      /* takes care of avoiding duplicates node names */
>> >      if (bdrv_find_node(node_name)) {
>> >          error_setg(errp, "Duplicate node name");
>> > -        return -EINVAL;
>> > +        return;
>> >      }
>> >  
>> >      /* copy node name into the bs and insert it into the graph list */
>> >      pstrcpy(bs->node_name, sizeof(bs->node_name), node_name);
>> >      QTAILQ_INSERT_TAIL(&graph_bdrv_states, bs, node_list);
>> > -
>> > -    return 0;
>> >  }
>> >  
>> >  /*
>> > @@ -849,9 +847,10 @@ static int bdrv_open_common(BlockDriverState *bs, BlockDriverState *file,
>> >      trace_bdrv_open_common(bs, filename ?: "", flags, drv->format_name);
>> >  
>> >      node_name = qdict_get_try_str(options, "node-name");
>> > -    ret = bdrv_assign_node_name(bs, node_name, errp);
>> > -    if (ret < 0) {
>> > -        return ret;
>> > +    bdrv_assign_node_name(bs, node_name, &local_err);
>> > +    if (error_is_set(&local_err)) {
>> > +        error_propagate(errp, local_err);
>> > +        return -EINVAL;
>> >      }
>> >      qdict_del(options, "node-name");
>> 
>> Please use 'if (local_err)' instead of 'if (error_is_set(&local_err))'.
>> See commit 84d18f0.
>
> I can do that; this patch predates your change and I just dug it out
> from an old branch.

No harm done :)

>                     Note that there are still many places that use
> error_is_set() where it's not necessary, including documentation that
> should show how to do things right, e.g. docs/writing-qmp-commands.txt.

The documentation I simply missed.  The others probably crept in after I
prepared the patch that became commit 84d18f0.  Such things usually take
an extra iteration or two.

> (By the way, would the actual problem with Coverity in commit 84d18f0
> not be fixed more easily and for all instances by making error_is_set()
> a static inline function in the header?)

I wouldn't bet on it.  Coverity is pretty good at looking through
compilation unit boundaries, but it gets easily spooked by null tests.

> What was the proper use case for error_is_set() again? Or can we get rid
> of it? As long as it's there, you'll keep getting new offenders.

I don't like it myself, and I think we can get rid of it.

Re: [Qemu-devel] [PATCH] block: Remove -errno return value from bdrv_assign_node_name

[Markus Armbruster]

Markus Armbruster <armbru@redhat.com> writes:

> Kevin Wolf <kwolf@redhat.com> writes:
[...]
>> What was the proper use case for error_is_set() again? Or can we get rid
>> of it? As long as it's there, you'll keep getting new offenders.
>
> I don't like it myself, and I think we can get rid of it.

At first glance, quite a few uses of error_set() look like bugs, usually
latent ones.  I guess we better examine them one by one.  Yet another
tree-wide cleanups... getting those committed has been a royal pain.