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io_uring: allow retry for O_NONBLOCK if async is supported 

A common complaint is that using O_NONBLOCK files with io_uring can be a
bit of a pain. Be a bit nicer and allow normal retry IFF the file does
support async behavior. This makes it possible to use io_uring more
reliably with O_NONBLOCK files, for use cases where it either isn't
possible or feasible to modify the file flags.

Cc: stable@vger.kernel.org
Reported-and-tested-by: Dan Melnic <dmm@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2021-09-14 11:08:37 -06:00
parent 9c7b0ba887
commit 5d329e1286
1 changed files with 11 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
fs/io_uring.c
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@ -2843,7 +2843,8 @@ static bool io_file_supports_nowait(struct io_kiocb *req, int rw)
return __io_file_supports_nowait(req->file, rw);
}
static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe)
static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe,
int rw)
{
struct io_ring_ctx *ctx = req->ctx;
struct kiocb *kiocb = &req->rw.kiocb;
@ -2865,8 +2866,13 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe)
if (unlikely(ret))
return ret;
/* don't allow async punt for O_NONBLOCK or RWF_NOWAIT */
if ((kiocb->ki_flags & IOCB_NOWAIT) || (file->f_flags & O_NONBLOCK))
/*
* If the file is marked O_NONBLOCK, still allow retry for it if it
* supports async. Otherwise it's impossible to use O_NONBLOCK files
* reliably. If not, or it IOCB_NOWAIT is set, don't retry.
*/
if ((kiocb->ki_flags & IOCB_NOWAIT) ||
((file->f_flags & O_NONBLOCK) && !io_file_supports_nowait(req, rw)))
req->flags |= REQ_F_NOWAIT;
ioprio = READ_ONCE(sqe->ioprio);
@ -3349,7 +3355,7 @@ static int io_read_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
if (unlikely(!(req->file->f_mode & FMODE_READ)))
return -EBADF;
return io_prep_rw(req, sqe);
return io_prep_rw(req, sqe, READ);
}
/*
@ -3542,7 +3548,7 @@ static int io_write_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
if (unlikely(!(req->file->f_mode & FMODE_WRITE)))
return -EBADF;
return io_prep_rw(req, sqe);
return io_prep_rw(req, sqe, WRITE);
}
static int io_write(struct io_kiocb *req, unsigned int issue_flags)