在 2021/10/18 下午3:02, Noah Goldstein 写道:
This commit reorganizes the branches in the tail of io_write so that
the 'ret2 == -EAGAIN' check is not repeated and done first.
The previous version was duplicating the 'ret2 == -EAGAIN'. As well
'ret2 != -EAGAIN' gurantees the 'done:' path so it makes sense to
move that check to the front before the likely more expensive branches
which require memory derefences.
Signed-off-by: Noah Goldstein <goldstein.w.n@xxxxxxxxx>
---
Generally I would want to rewrite this as:
```
if (ret2 != -EAGAIN
|| (req->flags & REQ_F_NOWAIT)
|| (!force_nonblock && !(req->ctx->flags & IORING_SETUP_IOPOLL)))
kiocb_done(kiocb, ret2, issue_flags);
else {
...
```
To me, this one is clear enough and short, but I think better to:
if (ret2 != -EAGAIN || (req->flags & REQ_F_NOWAIT) ||
(!force_nonblock && !(req->ctx->flags & IORING_SETUP_IOPOLL))
if the first line doesn't exceed the line limit.
Reviewed-by: Hao Xu <haoxu@xxxxxxxxxxxxxxxxx>
But the style of the file seems to be to use gotos. If the above is
prefereable, let me know and I'll post a new version.
fs/io_uring.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index d1e672e7a2d1..932fc84d70d3 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3648,12 +3648,15 @@ static int io_write(struct io_kiocb *req, unsigned int issue_flags)
*/
if (ret2 == -EOPNOTSUPP && (kiocb->ki_flags & IOCB_NOWAIT))
ret2 = -EAGAIN;
+
+ if (ret2 != -EAGAIN)
+ goto done;
/* no retry on NONBLOCK nor RWF_NOWAIT */
- if (ret2 == -EAGAIN && (req->flags & REQ_F_NOWAIT))
+ if (req->flags & REQ_F_NOWAIT)
goto done;
- if (!force_nonblock || ret2 != -EAGAIN) {
+ if (!force_nonblock) {
/* IOPOLL retry should happen for io-wq threads */
- if (ret2 == -EAGAIN && (req->ctx->flags & IORING_SETUP_IOPOLL))
+ if (req->ctx->flags & IORING_SETUP_IOPOLL)
goto copy_iov;
done:
kiocb_done(kiocb, ret2, issue_flags);
