- 12 Apr, 2021 1 commit
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Jens Axboe authored
Joakim reports that in some conditions he sees a multishot poll request being canceled, and that it coincides with getting -EALREADY on modification. As part of the poll update procedure, there's a small window where the request is marked as canceled, and if this coincides with the event actually triggering, then we can get a spurious -ECANCELED and termination of the multishot request. Don't mark the poll request as being canceled for update. We also don't care if we race on removal unless it's a one-shot request, we can safely updated for either case. Fixes: b69de288 ("io_uring: allow events and user_data update of running poll requests") Reported-by:
Joakim Hassila <joj@mac.com> Signed-off-by:
Jens Axboe <axboe@kernel.dk>
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- 11 Apr, 2021 39 commits
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Pavel Begunkov authored
We are safe with overflows in io_sqe_buffer_register() because it will just yield alloc failure, but it's nicer to check explicitly. Signed-off-by:
Pavel Begunkov <asml.silence@gmail.com> Link: https://lore.kernel.org/r/2b0625551be3d97b80a5fd21c8cd79dc1c91f0b5.1616624589.git.asml.silence@gmail.comSigned-off-by:
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Jens Axboe authored
Now that we have any worker being attached to the original task as threads, accounting of CPU time is directly attributed to the original task as well. This means that we no longer have to restrict SQPOLL to needing elevated privileges, as it's really no different from just having the task spawn a busy looping thread in userspace. Reported-by:
Stefano Garzarella <sgarzare@redhat.com> Signed-off-by:
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Jens Axboe authored
io-wq relies on a manager thread to create/fork new workers, as needed. But there's really no strong need for it anymore. We have the following cases that fork a new worker: 1) Work queue. This is done from the task itself always, and it's trivial to create a worker off that path, if needed. 2) All workers have gone to sleep, and we have more work. This is called off the sched out path. For this case, use a task_work items to queue a fork-worker operation. 3) Hashed work completion. Don't think we need to do anything off this case. If need be, it could just use approach 2 as well. Part of this change is incrementing the running worker count before the fork, to avoid cases where we observe we need a worker and then queue creation of one. Then new work comes in, we fork a new one. That last queue operation should have waited for the previous worker to come up, it's quite possible we don't even need it. Hence move the worker running from before we fork it off to more efficiently handle that case. Signed-off-by: -
Jens Axboe authored
fork() fails if signal_pending() is true, but there are two conditions that can lead to that: 1) An actual signal is pending. We want fork to fail for that one, like we always have. 2) TIF_NOTIFY_SIGNAL is pending, because the task has pending task_work. We don't need to make it fail for that case. Allow fork() to proceed if just task_work is pending, by changing the signal_pending() check to task_sigpending(). Signed-off-by: -
Jens Axboe authored
This adds two new POLL_ADD flags, IORING_POLL_UPDATE_EVENTS and IORING_POLL_UPDATE_USER_DATA. As with the other POLL_ADD flag, these are masked into sqe->len. If set, the POLL_ADD will have the following behavior: - sqe->addr must contain the the user_data of the poll request that needs to be modified. This field is otherwise invalid for a POLL_ADD command. - If IORING_POLL_UPDATE_EVENTS is set, sqe->poll_events must contain the new mask for the existing poll request. There are no checks for whether these are identical or not, if a matching poll request is found, then it is re-armed with the new mask. - If IORING_POLL_UPDATE_USER_DATA is set, sqe->off must contain the new user_data for the existing poll request. A POLL_ADD with any of these flags set may complete with any of the following results: 1) 0, which means that we successfully found the existing poll request specified, and performed the re-arm procedure. Any error from that re-arm will be exposed as a completion event for that original poll request, not for the update request. 2) -ENOENT, if no existing poll request was found with the given user_data. 3) -EALREADY, if the existing poll request was already in the process of being removed/canceled/completing. 4) -EACCES, if an attempt was made to modify an internal poll request (eg not one originally issued ass IORING_OP_POLL_ADD). The usual -EINVAL cases apply as well, if any invalid fields are set in the sqe for this command type. Signed-off-by: -
Jens Axboe authored
We'll need this helper for another purpose, for now just abstract it out and have io_poll_cancel() use it for lookups. Signed-off-by: -
Jens Axboe authored
If we hit overflow and fail to allocate an overflow entry for the completion, terminate the multishot poll mode. Signed-off-by: -
Jens Axboe authored
No functional changes in this patch, just preparation for kill multishot poll on CQ overflow. Signed-off-by: -
Jens Axboe authored
The default io_uring poll mode is one-shot, where once the event triggers, the poll command is completed and won't trigger any further events. If we're doing repeated polling on the same file or socket, then it can be more efficient to do multishot, where we keep triggering whenever the event becomes true. This deviates from the usual norm of having one CQE per SQE submitted. Add a CQE flag, IORING_CQE_F_MORE, which tells the application to expect further completion events from the submitted SQE. Right now the only user of this is POLL_ADD in multishot mode. Since sqe->poll_events is using the space that we normally use for adding flags to commands, use sqe->len for the flag space for POLL_ADD. Multishot mode is selected by setting IORING_POLL_ADD_MULTI in sqe->len. An application should expect more CQEs for the specificed SQE if the CQE is flagged with IORING_CQE_F_MORE. In multishot mode, only cancelation or an error will terminate the poll request, in which case the flag will be cleared. Signed-off-by: -
Jens Axboe authored
We should be including the completion flags for better introspection on exactly what completion event was logged. Signed-off-by: -
Pavel Begunkov authored
Instead of using a request itself for overflowed CQE stashing, allocate a separate entry. The disadvantage is that the allocation may fail and it will be accounted as lost (see rings->cq_overflow), so we lose reliability in case of memory pressure if the application is driving the CQ ring into overflow. However, it opens a way for for multiple CQEs per an SQE and even generating SQE-less CQEs. Signed-off-by:
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Jens Axboe authored
Instead of masking these in as part of regular POLL_ADD prep, do it in io_init_poll_iocb(), and include NVAL as that's generally unmaskable, and RDHUP alongside the HUP that is already set. Signed-off-by: -
Pavel Begunkov authored
Expect read/write to succeed and create a hot path for this case, in particular hide all error handling with resubmission under a single check with the desired result. Signed-off-by:
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Pavel Begunkov authored
Move iov_iter_revert() resetting iterator in case of -EIOCBQUEUED into io_resubmit_prep(), so we don't do heavy revert in hot path, also saves a couple of checks. Signed-off-by:
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Pavel Begunkov authored
When reissue_prep failed in io_complete_rw_iopoll(), we change return code to -EIO to prevent io_iopoll_complete() from doing resubmission. Mark requests with a new flag (i.e. REQ_F_DONT_REISSUE) instead and retain the original return value. It also removes io_rw_reissue() from io_iopoll_complete() that will be used later. Signed-off-by:
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Pavel Begunkov authored
file_end_write() is only for regular files, so the function do a couple of dereferences to get inode and check for it. However, we already have REQ_F_ISREG at hand, just use it and inline file_end_write(). Signed-off-by:
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Pavel Begunkov authored
current->files are always valid now even for io-wq threads, so kill not used anymore REQ_F_NO_FILE_TABLE. Signed-off-by:
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Pavel Begunkov authored
req->work is mostly unused unless it's punted, and io_init_req() is too hot for fully initialising it. Fortunately, we can skip init work.next as it's controlled by io-wq, and can not touch work.flags by moving everything related into io_prep_async_work(). The only field left is req->work.creds, but there is nothing can be done, keep maintaining it. Signed-off-by:
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Pavel Begunkov authored
Extract a helper for io_work_get_acct() and io_wqe_get_acct() to avoid duplication. Signed-off-by:
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Pavel Begunkov authored
struct io_uring_task::sqpoll is not used anymore, kill it Signed-off-by:
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Pavel Begunkov authored
io_match_task() matches all requests with PF_EXITING task, even though those may be valid requests. It was necessary for SQPOLL cancellation, but now it kills all requests before exiting via io_uring_cancel_sqpoll(), so it's not needed. Signed-off-by:
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Pavel Begunkov authored
REQ_F_LINK_TIMEOUT is a hint that to look for linked timeouts to cancel, we're leaving it even when it's already fired. Hence don't care to clear it in io_kill_linked_timeout(), it's safe and is called only once. Signed-off-by:
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Pavel Begunkov authored
Inline io_task_work_add() into io_req_task_work_add(). They both work with a request, so keeping them separate doesn't make things much more clear, but merging allows optimise it. Apart from small wins like not reading req->ctx or not calculating @notify in the hot path, i.e. with tctx->task_state set, it avoids doing wake_up_process() for every single add, but only after actually done task_work_add(). Signed-off-by:
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Pavel Begunkov authored
io_put_file() doesn't do a good job at generating a good code. Inline it, so we can check REQ_F_FIXED_FILE first, prioritising FIXED_FILE case over requests without files, and saving a memory load in that case. Signed-off-by:
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Pavel Begunkov authored
Reshuffle io_dismantle_req() checks to put most of slow path stuff under a single if. Signed-off-by:
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Pavel Begunkov authored
Inline io_clean_op(), leaving __io_clean_op() but renaming it. This will be used in following patches. Signed-off-by:
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Pavel Begunkov authored
Both io_req_complete_failed() and __io_req_task_cancel() do the same thing: set failure flag, put both req refs and emit an CQE. The former one is a bit more advance as it puts req back into a req cache, so make it to take over __io_req_task_cancel() and remove the last one. Signed-off-by:
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Pavel Begunkov authored
Add a new helper io_flush_cached_locked_reqs() that splices locked_free_list to free_list, and does it right doing all sync and invariant reinit. Signed-off-by:
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Pavel Begunkov authored
We don't care about ret value in io_free_req_deferred(), make the code a bit more concise. Signed-off-by:
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Pavel Begunkov authored
One big omission is that io_put_req() haven't been marked inline, and at least gcc 9 doesn't inline it, not to mention that it's really hot and extra function call is intolerable, especially when it doesn't put a final ref. Signed-off-by:
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Pavel Begunkov authored
There are two problems: 1) we always allocate refnodes in advance and free them if those haven't been used. It's expensive, takes two allocations, where one of them is percpu. And it may be pretty common not actually using them. 2) Current API with allocating a refnode and setting some of the fields is error prone, we don't ever want to have a file node runninng fixed buffer callback... Solve both with pre-init/get API. Pre-init just leaves the node for later if not used, and for get (i.e. io_rsrc_refnode_get()), you need to explicitly pass all arguments setting callbacks/etc., so it's more resilient. Signed-off-by:
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Pavel Begunkov authored
Emphasize that return value of io_flush_cached_reqs() depends on number of requests in the cache. It looks nicer and might help tools from false-negative analyses. Signed-off-by:
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Pavel Begunkov authored
Move the case of successfully issued request by doing that check first. It's not much of a difference, just generates slightly better code for me. Signed-off-by:
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Pavel Begunkov authored
Inline __io_queue_linked_timeout(), we don't need it Signed-off-by:
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Pavel Begunkov authored
Don't do a function call (io_dismantle_req()) in the middle and place it to near other function calls, otherwise may lead to excessive register spilling. Signed-off-by:
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Pavel Begunkov authored
First of all, w need to set tctx->sqpoll only when we add a new entry into ->xa, so move it from the hot path. Also extract a hot path for io_uring_add_task_file() as an inline helper. Signed-off-by:
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Pavel Begunkov authored
Add unlikely annotations, because my compiler pretty much mispredicts every first check, and apart jumping around in the fast path, it also generates extra instructions, like in advance setting ret value. Signed-off-by:
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Pavel Begunkov authored
__tctx_task_work() guarantees that ctx won't be killed while running task_works, so we can remove now unnecessary ctx pinning for internally armed polling. Signed-off-by:
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Jens Axboe authored
We can set canceled == true and complete out-of-line, ensure that we catch that and correctly return -ECANCELED if the poll operation got canceled. Signed-off-by:
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