forked from luck/tmp_suning_uos_patched
io_uring: internally retry short reads
We've had a few application cases of not handling short reads properly, and it is understandable as short reads aren't really expected if the application isn't doing non-blocking IO. Now that we retain the iov_iter over retries, we can implement internal retry pretty trivially. This ensures that we don't return a short read, even for buffered reads on page cache conflicts. Cleanup the deep nesting and hard to read nature of io_read() as well, it's much more straight forward now to read and understand. Added a few comments explaining the logic as well. Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe
parent
ff6165b2d7
commit
227c0c9673
109
fs/io_uring.c
109
fs/io_uring.c
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@ -510,6 +510,7 @@ struct io_async_rw {
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struct iovec fast_iov[UIO_FASTIOV];
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const struct iovec *free_iovec;
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struct iov_iter iter;
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size_t bytes_done;
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struct wait_page_queue wpq;
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};
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@ -916,7 +917,7 @@ static ssize_t io_import_iovec(int rw, struct io_kiocb *req,
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bool needs_lock);
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static int io_setup_async_rw(struct io_kiocb *req, const struct iovec *iovec,
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const struct iovec *fast_iov,
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struct iov_iter *iter);
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struct iov_iter *iter, bool force);
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static struct kmem_cache *req_cachep;
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@ -2298,7 +2299,7 @@ static bool io_resubmit_prep(struct io_kiocb *req, int error)
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ret = io_import_iovec(rw, req, &iovec, &iter, false);
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if (ret < 0)
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goto end_req;
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ret = io_setup_async_rw(req, iovec, inline_vecs, &iter);
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ret = io_setup_async_rw(req, iovec, inline_vecs, &iter, false);
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if (!ret)
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return true;
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kfree(iovec);
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@ -2588,6 +2589,14 @@ static void kiocb_done(struct kiocb *kiocb, ssize_t ret,
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{
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struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw.kiocb);
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/* add previously done IO, if any */
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if (req->io && req->io->rw.bytes_done > 0) {
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if (ret < 0)
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ret = req->io->rw.bytes_done;
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else
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ret += req->io->rw.bytes_done;
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}
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if (req->flags & REQ_F_CUR_POS)
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req->file->f_pos = kiocb->ki_pos;
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if (ret >= 0 && kiocb->ki_complete == io_complete_rw)
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@ -2935,6 +2944,7 @@ static void io_req_map_rw(struct io_kiocb *req, const struct iovec *iovec,
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memcpy(&rw->iter, iter, sizeof(*iter));
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rw->free_iovec = NULL;
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rw->bytes_done = 0;
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/* can only be fixed buffers, no need to do anything */
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if (iter->type == ITER_BVEC)
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return;
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@ -2971,9 +2981,9 @@ static int io_alloc_async_ctx(struct io_kiocb *req)
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static int io_setup_async_rw(struct io_kiocb *req, const struct iovec *iovec,
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const struct iovec *fast_iov,
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struct iov_iter *iter)
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struct iov_iter *iter, bool force)
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{
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if (!io_op_defs[req->opcode].async_ctx)
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if (!force && !io_op_defs[req->opcode].async_ctx)
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return 0;
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if (!req->io) {
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if (__io_alloc_async_ctx(req))
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@ -3097,8 +3107,7 @@ static inline int kiocb_wait_page_queue_init(struct kiocb *kiocb,
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* succeed, or in rare cases where it fails, we then fall back to using the
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* async worker threads for a blocking retry.
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*/
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static bool io_rw_should_retry(struct io_kiocb *req, struct iovec *iovec,
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struct iovec *fast_iov, struct iov_iter *iter)
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static bool io_rw_should_retry(struct io_kiocb *req)
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{
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struct kiocb *kiocb = &req->rw.kiocb;
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int ret;
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@ -3107,8 +3116,8 @@ static bool io_rw_should_retry(struct io_kiocb *req, struct iovec *iovec,
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if (req->flags & REQ_F_NOWAIT)
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return false;
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/* already tried, or we're doing O_DIRECT */
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if (kiocb->ki_flags & (IOCB_DIRECT | IOCB_WAITQ))
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/* Only for buffered IO */
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if (kiocb->ki_flags & IOCB_DIRECT)
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return false;
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/*
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* just use poll if we can, and don't attempt if the fs doesn't
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@ -3117,16 +3126,6 @@ static bool io_rw_should_retry(struct io_kiocb *req, struct iovec *iovec,
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if (file_can_poll(req->file) || !(req->file->f_mode & FMODE_BUF_RASYNC))
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return false;
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/*
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* If request type doesn't require req->io to defer in general,
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* we need to allocate it here
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*/
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if (!req->io) {
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if (__io_alloc_async_ctx(req))
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return false;
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io_req_map_rw(req, iovec, fast_iov, iter);
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}
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ret = kiocb_wait_page_queue_init(kiocb, &req->io->rw.wpq,
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io_async_buf_func, req);
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if (!ret) {
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@ -3153,8 +3152,8 @@ static int io_read(struct io_kiocb *req, bool force_nonblock,
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struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
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struct kiocb *kiocb = &req->rw.kiocb;
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struct iov_iter __iter, *iter = &__iter;
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ssize_t io_size, ret, ret2;
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size_t iov_count;
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ssize_t io_size, ret, ret2 = 0;
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if (req->io)
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iter = &req->io->rw.iter;
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@ -3164,6 +3163,7 @@ static int io_read(struct io_kiocb *req, bool force_nonblock,
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return ret;
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io_size = ret;
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req->result = io_size;
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ret = 0;
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/* Ensure we clear previously set non-block flag */
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if (!force_nonblock)
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@ -3178,31 +3178,62 @@ static int io_read(struct io_kiocb *req, bool force_nonblock,
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if (unlikely(ret))
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goto out_free;
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ret2 = io_iter_do_read(req, iter);
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ret = io_iter_do_read(req, iter);
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/* Catch -EAGAIN return for forced non-blocking submission */
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if (!force_nonblock || (ret2 != -EAGAIN && ret2 != -EIO)) {
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kiocb_done(kiocb, ret2, cs);
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} else {
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copy_iov:
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ret = io_setup_async_rw(req, iovec, inline_vecs, iter);
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if (!ret) {
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goto done;
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} else if (ret == -EIOCBQUEUED) {
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ret = 0;
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goto out_free;
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} else if (ret == -EAGAIN) {
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ret = io_setup_async_rw(req, iovec, inline_vecs, iter, false);
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if (ret)
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goto out_free;
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/* it's copied and will be cleaned with ->io */
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iovec = NULL;
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/* if we can retry, do so with the callbacks armed */
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if (io_rw_should_retry(req, iovec, inline_vecs, iter)) {
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ret2 = io_iter_do_read(req, iter);
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if (ret2 == -EIOCBQUEUED) {
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goto out_free;
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} else if (ret2 != -EAGAIN) {
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kiocb_done(kiocb, ret2, cs);
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goto out_free;
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}
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}
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return -EAGAIN;
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} else if (ret < 0) {
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goto out_free;
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}
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/* read it all, or we did blocking attempt. no retry. */
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if (!iov_iter_count(iter) || !force_nonblock)
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goto done;
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io_size -= ret;
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copy_iov:
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ret2 = io_setup_async_rw(req, iovec, inline_vecs, iter, true);
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if (ret2) {
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ret = ret2;
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goto out_free;
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}
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/* it's copied and will be cleaned with ->io */
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iovec = NULL;
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/* now use our persistent iterator, if we aren't already */
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iter = &req->io->rw.iter;
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retry:
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req->io->rw.bytes_done += ret;
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/* if we can retry, do so with the callbacks armed */
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if (!io_rw_should_retry(req)) {
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kiocb->ki_flags &= ~IOCB_WAITQ;
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return -EAGAIN;
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}
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/*
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* Now retry read with the IOCB_WAITQ parts set in the iocb. If we
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* get -EIOCBQUEUED, then we'll get a notification when the desired
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* page gets unlocked. We can also get a partial read here, and if we
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* do, then just retry at the new offset.
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*/
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ret = io_iter_do_read(req, iter);
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if (ret == -EIOCBQUEUED) {
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ret = 0;
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goto out_free;
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} else if (ret > 0 && ret < io_size) {
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/* we got some bytes, but not all. retry. */
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goto retry;
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}
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done:
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kiocb_done(kiocb, ret, cs);
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ret = 0;
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out_free:
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if (iovec)
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kfree(iovec);
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@ -3295,7 +3326,7 @@ static int io_write(struct io_kiocb *req, bool force_nonblock,
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kiocb_done(kiocb, ret2, cs);
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} else {
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copy_iov:
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ret = io_setup_async_rw(req, iovec, inline_vecs, iter);
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ret = io_setup_async_rw(req, iovec, inline_vecs, iter, false);
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if (!ret)
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return -EAGAIN;
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}
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