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io_uring: use iov_iter state save/restore helpers 

Get rid of the need to do re-expand and revert on an iterator when we
encounter a short IO, or failure that warrants a retry. Use the new
state save/restore helpers instead.

We keep the iov_iter_state persistent across retries, if we need to
restart the read or write operation. If there's a pending retry, the
operation will always exit with the state correctly saved.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2021-09-10 11:19:14 -06:00
parent 8fb0f47a9d
commit cd65869512
1 changed files with 61 additions and 21 deletions
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82
fs/io_uring.c
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@ -712,6 +712,7 @@ struct io_async_rw {
struct iovec fast_iov[UIO_FASTIOV];
const struct iovec *free_iovec;
struct iov_iter iter;
struct iov_iter_state iter_state;
size_t bytes_done;
struct wait_page_queue wpq;
};
@ -2608,8 +2609,7 @@ static bool io_resubmit_prep(struct io_kiocb *req)
if (!rw)
return !io_req_prep_async(req);
/* may have left rw->iter inconsistent on -EIOCBQUEUED */
iov_iter_revert(&rw->iter, req->result - iov_iter_count(&rw->iter));
iov_iter_restore(&rw->iter, &rw->iter_state);
return true;
}
@ -3310,12 +3310,17 @@ static int io_setup_async_rw(struct io_kiocb *req, const struct iovec *iovec,
if (!force && !io_op_defs[req->opcode].needs_async_setup)
return 0;
if (!req->async_data) {
struct io_async_rw *iorw;
if (io_alloc_async_data(req)) {
kfree(iovec);
return -ENOMEM;
}
io_req_map_rw(req, iovec, fast_iov, iter);
iorw = req->async_data;
/* we've copied and mapped the iter, ensure state is saved */
iov_iter_save_state(&iorw->iter, &iorw->iter_state);
}
return 0;
}
@ -3334,6 +3339,7 @@ static inline int io_rw_prep_async(struct io_kiocb *req, int rw)
iorw->free_iovec = iov;
if (iov)
req->flags |= REQ_F_NEED_CLEANUP;
iov_iter_save_state(&iorw->iter, &iorw->iter_state);
return 0;
}
@ -3437,19 +3443,28 @@ static int io_read(struct io_kiocb *req, unsigned int issue_flags)
struct kiocb *kiocb = &req->rw.kiocb;
struct iov_iter __iter, *iter = &__iter;
struct io_async_rw *rw = req->async_data;
ssize_t io_size, ret, ret2;
bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
struct iov_iter_state __state, *state;
ssize_t ret, ret2;
if (rw) {
iter = &rw->iter;
state = &rw->iter_state;
/*
* We come here from an earlier attempt, restore our state to
* match in case it doesn't. It's cheap enough that we don't
* need to make this conditional.
*/
iov_iter_restore(iter, state);
iovec = NULL;
} else {
ret = io_import_iovec(READ, req, &iovec, iter, !force_nonblock);
if (ret < 0)
return ret;
state = &__state;
iov_iter_save_state(iter, state);
}
io_size = iov_iter_count(iter);
req->result = io_size;
req->result = iov_iter_count(iter);
/* Ensure we clear previously set non-block flag */
if (!force_nonblock)
@ -3463,7 +3478,7 @@ static int io_read(struct io_kiocb *req, unsigned int issue_flags)
return ret ?: -EAGAIN;
}
ret = rw_verify_area(READ, req->file, io_kiocb_ppos(kiocb), io_size);
ret = rw_verify_area(READ, req->file, io_kiocb_ppos(kiocb), req->result);
if (unlikely(ret)) {
kfree(iovec);
return ret;
@ -3479,30 +3494,49 @@ static int io_read(struct io_kiocb *req, unsigned int issue_flags)
/* no retry on NONBLOCK nor RWF_NOWAIT */
if (req->flags & REQ_F_NOWAIT)
goto done;
/* some cases will consume bytes even on error returns */
iov_iter_reexpand(iter, iter->count + iter->truncated);
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 ||
} else if (ret <= 0 || ret == req->result || !force_nonblock ||
(req->flags & REQ_F_NOWAIT) || !need_read_all(req)) {
/* read all, failed, already did sync or don't want to retry */
goto done;
}
/*
* Don't depend on the iter state matching what was consumed, or being
* untouched in case of error. Restore it and we'll advance it
* manually if we need to.
*/
iov_iter_restore(iter, state);
ret2 = io_setup_async_rw(req, iovec, inline_vecs, iter, true);
if (ret2)
return ret2;
iovec = NULL;
rw = req->async_data;
/* now use our persistent iterator, if we aren't already */
iter = &rw->iter;
/*
* Now use our persistent iterator and state, if we aren't already.
* We've restored and mapped the iter to match.
*/
if (iter != &rw->iter) {
iter = &rw->iter;
state = &rw->iter_state;
}
do {
io_size -= ret;
/*
* We end up here because of a partial read, either from
* above or inside this loop. Advance the iter by the bytes
* that were consumed.
*/
iov_iter_advance(iter, ret);
if (!iov_iter_count(iter))
break;
rw->bytes_done += ret;
iov_iter_save_state(iter, state);
/* if we can retry, do so with the callbacks armed */
if (!io_rw_should_retry(req)) {
kiocb->ki_flags &= ~IOCB_WAITQ;
@ -3520,7 +3554,8 @@ static int io_read(struct io_kiocb *req, unsigned int issue_flags)
return 0;
/* we got some bytes, but not all. retry. */
kiocb->ki_flags &= ~IOCB_WAITQ;
} while (ret > 0 && ret < io_size);
iov_iter_restore(iter, state);
} while (ret > 0);
done:
kiocb_done(kiocb, ret, issue_flags);
out_free:
@ -3543,19 +3578,24 @@ static int io_write(struct io_kiocb *req, unsigned int issue_flags)
struct kiocb *kiocb = &req->rw.kiocb;
struct iov_iter __iter, *iter = &__iter;
struct io_async_rw *rw = req->async_data;
ssize_t ret, ret2, io_size;
bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
struct iov_iter_state __state, *state;
ssize_t ret, ret2;
if (rw) {
iter = &rw->iter;
state = &rw->iter_state;
iov_iter_restore(iter, state);
iovec = NULL;
} else {
ret = io_import_iovec(WRITE, req, &iovec, iter, !force_nonblock);
if (ret < 0)
return ret;
state = &__state;
iov_iter_save_state(iter, state);
}
io_size = iov_iter_count(iter);
req->result = io_size;
req->result = iov_iter_count(iter);
ret2 = 0;
/* Ensure we clear previously set non-block flag */
if (!force_nonblock)
@ -3572,7 +3612,7 @@ static int io_write(struct io_kiocb *req, unsigned int issue_flags)
(req->flags & REQ_F_ISREG))
goto copy_iov;
ret = rw_verify_area(WRITE, req->file, io_kiocb_ppos(kiocb), io_size);
ret = rw_verify_area(WRITE, req->file, io_kiocb_ppos(kiocb), req->result);
if (unlikely(ret))
goto out_free;
@ -3619,9 +3659,9 @@ done:
kiocb_done(kiocb, ret2, issue_flags);
} else {
copy_iov:
/* some cases will consume bytes even on error returns */
iov_iter_reexpand(iter, iter->count + iter->truncated);
iov_iter_revert(iter, io_size - iov_iter_count(iter));
iov_iter_restore(iter, state);
if (ret2 > 0)
iov_iter_advance(iter, ret2);
ret = io_setup_async_rw(req, iovec, inline_vecs, iter, false);
return ret ?: -EAGAIN;
}