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io_uring: fix -EAGAIN retry with IOPOLL 

We no longer revert the iovec on -EIOCBQUEUED, see commit ab2125df92,
and this started causing issues for IOPOLL on devies that run out of
request slots. Turns out what outside of needing a revert for those, we
also had a bug where we didn't properly setup retry inside the submission
path. That could cause re-import of the iovec, if any, and that could lead
to spurious results if the application had those allocated on the stack.

Catch -EAGAIN retry and make the iovec stable for IOPOLL, just like we do
for !IOPOLL retries.

Cc: <stable@vger.kernel.org> # 5.9+
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Reported-by: Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
master
Jens Axboe 2021-03-01 13:56:00 -07:00
parent dc7bbc9ef3
commit 3e6a0d3c75
1 changed files with 31 additions and 5 deletions
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36
fs/io_uring.c
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@ -2423,23 +2423,32 @@ static bool io_resubmit_prep(struct io_kiocb *req)
return false;
return !io_setup_async_rw(req, iovec, inline_vecs, &iter, false);
}
#endif
static bool io_rw_reissue(struct io_kiocb *req)
static bool io_rw_should_reissue(struct io_kiocb *req)
{
#ifdef CONFIG_BLOCK
umode_t mode = file_inode(req->file)->i_mode;
struct io_ring_ctx *ctx = req->ctx;
if (!S_ISBLK(mode) && !S_ISREG(mode))
return false;
if ((req->flags & REQ_F_NOWAIT) || io_wq_current_is_worker())
if ((req->flags & REQ_F_NOWAIT) || (io_wq_current_is_worker() &&
!(ctx->flags & IORING_SETUP_IOPOLL)))
return false;
/*
* If ref is dying, we might be running poll reap from the exit work.
* Don't attempt to reissue from that path, just let it fail with
* -EAGAIN.
*/
if (percpu_ref_is_dying(&req->ctx->refs))
if (percpu_ref_is_dying(&ctx->refs))
return false;
return true;
}
#endif
static bool io_rw_reissue(struct io_kiocb *req)
{
#ifdef CONFIG_BLOCK
if (!io_rw_should_reissue(req))
return false;
lockdep_assert_held(&req->ctx->uring_lock);
@ -2482,6 +2491,19 @@ static void io_complete_rw_iopoll(struct kiocb *kiocb, long res, long res2)
{
struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw.kiocb);
#ifdef CONFIG_BLOCK
/* Rewind iter, if we have one. iopoll path resubmits as usual */
if (res == -EAGAIN && io_rw_should_reissue(req)) {
struct io_async_rw *rw = req->async_data;
if (rw)
iov_iter_revert(&rw->iter,
req->result - iov_iter_count(&rw->iter));
else if (!io_resubmit_prep(req))
res = -EIO;
}
#endif
if (kiocb->ki_flags & IOCB_WRITE)
kiocb_end_write(req);
@ -3230,6 +3252,8 @@ static int io_read(struct io_kiocb *req, unsigned int issue_flags)
ret = io_iter_do_read(req, iter);
if (ret == -EIOCBQUEUED) {
if (req->async_data)
iov_iter_revert(iter, io_size - iov_iter_count(iter));
goto out_free;
} else if (ret == -EAGAIN) {
/* IOPOLL retry should happen for io-wq threads */
@ -3361,6 +3385,8 @@ static int io_write(struct io_kiocb *req, unsigned int issue_flags)
/* no retry on NONBLOCK nor RWF_NOWAIT */
if (ret2 == -EAGAIN && (req->flags & REQ_F_NOWAIT))
goto done;
if (ret2 == -EIOCBQUEUED && req->async_data)
iov_iter_revert(iter, io_size - iov_iter_count(iter));
if (!force_nonblock || ret2 != -EAGAIN) {
/* IOPOLL retry should happen for io-wq threads */
if ((req->ctx->flags & IORING_SETUP_IOPOLL) && ret2 == -EAGAIN)