kiocb_set_rw_flags() generates a poor code with several memory writes
and a lot of jumps. Help compilers to optimise it.
Tested with gcc 9.2 on x64-86, and as a result, it its output now is a
plain code without jumps accumulating in a register before a memory
write.
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
v2: check for 0 flags in advance (Matthew Wilcox)
include/linux/fs.h | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 98e0349adb52..22b46fc8fdfa 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3402,22 +3402,28 @@ static inline int iocb_flags(struct file *file)
static inline int kiocb_set_rw_flags(struct kiocb *ki, rwf_t flags)
{
+ int kiocb_flags = 0;
+
+ if (!flags)
+ return 0;
if (unlikely(flags & ~RWF_SUPPORTED))
return -EOPNOTSUPP;
if (flags & RWF_NOWAIT) {
if (!(ki->ki_filp->f_mode & FMODE_NOWAIT))
return -EOPNOTSUPP;
- ki->ki_flags |= IOCB_NOWAIT;
+ kiocb_flags |= IOCB_NOWAIT;
}
if (flags & RWF_HIPRI)
- ki->ki_flags |= IOCB_HIPRI;
+ kiocb_flags |= IOCB_HIPRI;
if (flags & RWF_DSYNC)
- ki->ki_flags |= IOCB_DSYNC;
+ kiocb_flags |= IOCB_DSYNC;
if (flags & RWF_SYNC)
- ki->ki_flags |= (IOCB_DSYNC | IOCB_SYNC);
+ kiocb_flags |= (IOCB_DSYNC | IOCB_SYNC);
if (flags & RWF_APPEND)
- ki->ki_flags |= IOCB_APPEND;
+ kiocb_flags |= IOCB_APPEND;
+
+ ki->ki_flags |= kiocb_flags;
return 0;
}
--
2.24.0
