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io_uring: update kiocb->ki_pos at execution time

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Update kiocb->ki_pos at execution time rather than in io_prep_rw().
io_prep_rw() happens before the job is enqueued to a worker and so the
offset might be read multiple times before being executed once.

Ensures that the file position in a set of _linked_ SQEs will be only
obtained after earlier SQEs have completed, and so will include their
incremented file position.

Signed-off-by: Dylan Yudaken <dylany@fb.com>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Dylan Yudaken 2022-02-22 02:55:02 -08:00 committed by Jens Axboe
parent af9c45eceb
commit d34e1e5b39
1 changed files with 18 additions and 8 deletions
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26
fs/io_uring.c
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@ -3020,14 +3020,6 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe)
req->flags |= io_file_get_flags(file) << REQ_F_SUPPORT_NOWAIT_BIT;
kiocb->ki_pos = READ_ONCE(sqe->off);
if (kiocb->ki_pos == -1) {
if (!(file->f_mode & FMODE_STREAM)) {
req->flags |= REQ_F_CUR_POS;
kiocb->ki_pos = file->f_pos;
} else {
kiocb->ki_pos = 0;
}
}
kiocb->ki_flags = iocb_flags(file);
ret = kiocb_set_rw_flags(kiocb, READ_ONCE(sqe->rw_flags));
if (unlikely(ret))
@ -3094,6 +3086,20 @@ static inline void io_rw_done(struct kiocb *kiocb, ssize_t ret)
}
}
static inline void io_kiocb_update_pos(struct io_kiocb *req)
{
struct kiocb *kiocb = &req->rw.kiocb;
if (kiocb->ki_pos == -1) {
if (!(req->file->f_mode & FMODE_STREAM)) {
req->flags |= REQ_F_CUR_POS;
kiocb->ki_pos = req->file->f_pos;
} else {
kiocb->ki_pos = 0;
}
}
}
static void kiocb_done(struct io_kiocb *req, ssize_t ret,
unsigned int issue_flags)
{
@ -3682,6 +3688,8 @@ static int io_read(struct io_kiocb *req, unsigned int issue_flags)
kiocb->ki_flags &= ~IOCB_NOWAIT;
}
io_kiocb_update_pos(req);
ret = rw_verify_area(READ, req->file, io_kiocb_ppos(kiocb), req->result);
if (unlikely(ret)) {
kfree(iovec);
@ -3811,6 +3819,8 @@ static int io_write(struct io_kiocb *req, unsigned int issue_flags)
kiocb->ki_flags &= ~IOCB_NOWAIT;
}
io_kiocb_update_pos(req);
ret = rw_verify_area(WRITE, req->file, io_kiocb_ppos(kiocb), req->result);
if (unlikely(ret))
goto out_free;