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io_uring/rw: don't allow multishot reads without NOWAIT support 

Supporting multishot reads requires support for NOWAIT, as the
alternative would be always having io-wq execute the work item whenever
the poll readiness triggered. Any fast file type will have NOWAIT
support (eg it understands both O_NONBLOCK and IOCB_NOWAIT). If the
given file type does not, then simply resort to single shot execution.

Cc: stable@vger.kernel.org
Fixes: fc68fcda04 ("io_uring/rw: add support for IORING_OP_READ_MULTISHOT")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2024-04-01 11:27:33 -06:00
parent 39cd87c4eb
commit 2a975d426c
1 changed files with 8 additions and 1 deletions
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9
io_uring/rw.c
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@ -936,6 +936,13 @@ int io_read_mshot(struct io_kiocb *req, unsigned int issue_flags)
ret = __io_read(req, issue_flags);
/*
* If the file doesn't support proper NOWAIT, then disable multishot
* and stay in single shot mode.
*/
if (!io_file_supports_nowait(req))
req->flags &= ~REQ_F_APOLL_MULTISHOT;
/*
* If we get -EAGAIN, recycle our buffer and just let normal poll
* handling arm it.
@ -955,7 +962,7 @@ int io_read_mshot(struct io_kiocb *req, unsigned int issue_flags)
/*
* Any successful return value will keep the multishot read armed.
*/
if (ret > 0) {
if (ret > 0 && req->flags & REQ_F_APOLL_MULTISHOT) {
/*
* Put our buffer and post a CQE. If we fail to post a CQE, then
* jump to the termination path. This request is then done.