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io_uring: move reissue into regular IO path

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It's non-obvious how retry is done for block backed files, when it happens
off the kiocb done path. It also makes it tricky to deal with the iov_iter
handling.

Just mark the req as needing a reissue, and handling it from the
submission path instead. This makes it directly obvious that we're not
re-importing the iovec from userspace past the submit point, and it means
that we can just reuse our usual -EAGAIN retry path from the read/write
handling.

At some point in the future, we'll gain the ability to always reliably
return -EAGAIN through the stack. A previous attempt on the block side
didn't pan out and got reverted, hence the need to check for this
information out-of-band right now.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2021-04-01 20:41:15 -06:00
parent 07204f2157
commit 230d50d448
1 changed files with 13 additions and 4 deletions
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17
fs/io_uring.c
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@ -697,6 +697,7 @@ enum {
REQ_F_NO_FILE_TABLE_BIT,
REQ_F_LTIMEOUT_ACTIVE_BIT,
REQ_F_COMPLETE_INLINE_BIT,
REQ_F_REISSUE_BIT,
/* not a real bit, just to check we're not overflowing the space */
__REQ_F_LAST_BIT,
@ -740,6 +741,8 @@ enum {
REQ_F_LTIMEOUT_ACTIVE = BIT(REQ_F_LTIMEOUT_ACTIVE_BIT),
/* completion is deferred through io_comp_state */
REQ_F_COMPLETE_INLINE = BIT(REQ_F_COMPLETE_INLINE_BIT),
/* caller should reissue async */
REQ_F_REISSUE = BIT(REQ_F_REISSUE_BIT),
};
struct async_poll {
@ -2503,8 +2506,10 @@ static void __io_complete_rw(struct io_kiocb *req, long res, long res2,
if (req->rw.kiocb.ki_flags & IOCB_WRITE)
kiocb_end_write(req);
if ((res == -EAGAIN || res == -EOPNOTSUPP) && io_rw_reissue(req))
if ((res == -EAGAIN || res == -EOPNOTSUPP) && io_rw_should_reissue(req)) {
req->flags |= REQ_F_REISSUE;
return;
}
if (res != req->result)
req_set_fail_links(req);
if (req->flags & REQ_F_BUFFER_SELECTED)
@ -3283,9 +3288,7 @@ static int io_read(struct io_kiocb *req, unsigned int issue_flags)
ret = io_iter_do_read(req, iter);
if (ret == -EIOCBQUEUED) {
goto out_free;
} else if (ret == -EAGAIN) {
if (ret == -EAGAIN || (req->flags & REQ_F_REISSUE)) {
/* IOPOLL retry should happen for io-wq threads */
if (!force_nonblock && !(req->ctx->flags & IORING_SETUP_IOPOLL))
goto done;
@ -3295,6 +3298,8 @@ static int io_read(struct io_kiocb *req, unsigned int issue_flags)
/* some cases will consume bytes even on error returns */
iov_iter_revert(iter, io_size - iov_iter_count(iter));
ret = 0;
} else if (ret == -EIOCBQUEUED) {
goto out_free;
} else if (ret <= 0 || ret == io_size || !force_nonblock ||
(req->flags & REQ_F_NOWAIT) || !(req->flags & REQ_F_ISREG)) {
/* read all, failed, already did sync or don't want to retry */
@ -3407,6 +3412,9 @@ static int io_write(struct io_kiocb *req, unsigned int issue_flags)
else
ret2 = -EINVAL;
if (req->flags & REQ_F_REISSUE)
ret2 = -EAGAIN;
/*
* Raw bdev writes will return -EOPNOTSUPP for IOCB_NOWAIT. Just
* retry them without IOCB_NOWAIT.
@ -6160,6 +6168,7 @@ static void io_wq_submit_work(struct io_wq_work *work)
ret = -ECANCELED;
if (!ret) {
req->flags &= ~REQ_F_REISSUE;
do {
ret = io_issue_sqe(req, 0);
/*