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SubjectRe: [PATCH] btrfs: relocation: fix unused variable
On Tue, Jan 29, 2019 at 04:21:27PM +0100, David Sterba wrote:
> On Tue, Jan 29, 2019 at 02:01:46PM +0100, Anders Roxell wrote:
> > When CONFIG_BRTFS_ASSERT isn't enabled, variable root_objectid isn't used.
> >
> > fs/btrfs/relocation.c: In function ‘insert_dirty_subv’:
> > fs/btrfs/relocation.c:2138:6: warning: unused variable ‘root_objectid’ [-Wunused-variable]
> > u64 root_objectid = root->root_key.objectid;
> > ^~~~~~~~~~~~~
> >
> > Reworked by adding a runtime check in the assfail function instead of
> > the '#ifdef CONFIG_BTRFS_ASSERT #else ...", so the compiler sees the
> > condition being passed into an inline function after preprocessing.
>
> I've fixed the warning by avoiding the local variable but I like your
> fix in general, thanks.

Committed with this changelog:

"btrfs: let the assertion expression compile in all configs

A compiler warning (in a patch in development) pointed to a variable
that was used only inside and ASSERT:

u64 root_objectid = root->root_key.objectid;
ASSERT(root_objectid == ...);

fs/btrfs/relocation.c: In function ‘insert_dirty_subv’:
fs/btrfs/relocation.c:2138:6: warning: unused variable ‘root_objectid’ [-Wunused-variable]
u64 root_objectid = root->root_key.objectid;
^~~~~~~~~~~~~

When CONFIG_BRTFS_ASSERT isn't enabled, variable root_objectid isn't used.

Rework the assertion helper by adding a runtime check instead of the
'#ifdef CONFIG_BTRFS_ASSERT #else ...", so the compiler sees the
condition being passed into an inline function after preprocessing."

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