[PATCH -mm] nilfs2: Use __field_struct() for a bitwise field

[Ryusuke Konishi]

From: Bart Van Assche <bvanassche@xxxxxxx>

As one can see in include/trace/stages/stage4_event_fields.h, the
implementation of __field() uses the is_signed_type() macro. As one can see
in commit dcf8e5633e2e ("tracing: Define the is_signed_type() macro once"),
there has been an attempt to not make is_signed_type() trigger sparse
warnings for bitwise types. Despite that change, sparse complains when
passing a bitwise type to is_signed_type(). It is not clear to me why.

Follow the example of <trace/events/initcall.h> and suppress the following
sparse warnings by changing __field() into __field_struct():

 fs/nilfs2/segment.c: note: in included file (through
   include/trace/trace_events.h, include/trace/define_trace.h,
   include/trace/events/nilfs2.h):
 ./include/trace/events/nilfs2.h:191:1: warning: cast to restricted
   blk_opf_t
 ./include/trace/events/nilfs2.h:191:1: warning: restricted blk_opf_t
   degrades to integer
 ./include/trace/events/nilfs2.h:191:1: warning: restricted blk_opf_t
   degrades to integer

Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-kbuild-all/202401092241.I4mm9OWl-lkp@xxxxxxxxx/
Reported-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Closes: https://lore.kernel.org/all/20240430080019.4242-2-konishi.ryusuke@xxxxxxxxx/
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
---
Hi Andrew, Bart has completed a patch that fixes the sparse warnings
related to event trace header, as he kindly shared the link with you
earlier.

Here is the patch (I added a few tags), could you add this to your
tree queue?
I'll send this via email just in case since we don't usually exchange
links.

The patch "nilfs2: use integer type instead of enum req_op for event
tracing header" that I sent is no longer needed, so I will withdraw it.

Thanks,
Ryusuke Konishi

 include/trace/events/nilfs2.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/include/trace/events/nilfs2.h b/include/trace/events/nilfs2.h
index 8efc6236f57c..8880c11733dd 100644
--- a/include/trace/events/nilfs2.h
+++ b/include/trace/events/nilfs2.h
@@ -200,7 +200,11 @@ TRACE_EVENT(nilfs2_mdt_submit_block,
 		    __field(struct inode *, inode)
 		    __field(unsigned long, ino)
 		    __field(unsigned long, blkoff)
-		    __field(enum req_op, mode)
+		    /*
+		     * Use field_struct() to avoid is_signed_type() on the
+		     * bitwise type enum req_op.
+		     */
+		    __field_struct(enum req_op, mode)
 	    ),
 
 	    TP_fast_assign(
-- 
2.34.1