From 33580d667bb20e00356fd06500f5197ef1baa1f5 Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Tue, 7 May 2024 23:24:54 +0900 Subject: [PATCH] nilfs2: use __field_struct() for a bitwise field 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(). The reason is that in its definition below, an inequality comparison will be made against bitwise types, which are random collections of bits (the casts to bitwise types themselves are semantically valid and not problematic): #define is_signed_type(type) (((type)(-1)) < (__force type)1) So, as a workaround, follow the example of and suppress the following sparse warnings by changing __field() into __field_struct() that doesn't use is_signed_type(): 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 [konishi.ryusuke: describe the reason for the warnings per Linus's explanation] Link: https://lkml.kernel.org/r/20240507222041.4876-1-konishi.ryusuke@gmail.com Link: https://lkml.kernel.org/r/20240507142454.3344-1-konishi.ryusuke@gmail.com Signed-off-by: Bart Van Assche Signed-off-by: Ryusuke Konishi Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202401092241.I4mm9OWl-lkp@intel.com/ Reported-by: Ryusuke Konishi Closes: https://lore.kernel.org/all/20240430080019.4242-2-konishi.ryusuke@gmail.com/ Cc: Linus Torvalds Cc: Rasmus Villemoes Signed-off-by: Andrew Morton --- 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( -- 2.25.1