| Message ID | 20190209211346.26060-20-axboe@kernel.dk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [01/19] fs: add an iopoll method to struct file_operations | expand |
On 2/9/19 10:13 PM, Jens Axboe wrote: > Add hint on whether a read was served out of the page cache, or if it > hit media. This is useful for buffered async IO, O_DIRECT reads would > never have this set (for obvious reasons). > > If the read hit page cache, cqe->flags will have IOCQE_FLAG_CACHEHIT > set. > > Signed-off-by: Jens Axboe <axboe@kernel.dk> > --- > fs/io_uring.c | 7 ++++++- > include/uapi/linux/io_uring.h | 5 +++++ > 2 files changed, 11 insertions(+), 1 deletion(-) > > diff --git a/fs/io_uring.c b/fs/io_uring.c > index 11a549b5dcbf..d7a10484d748 100644 > --- a/fs/io_uring.c > +++ b/fs/io_uring.c > @@ -587,11 +587,16 @@ static void io_fput(struct io_kiocb *req) > static void io_complete_rw(struct kiocb *kiocb, long res, long res2) > { > struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw); > + unsigned ev_flags = 0; > > kiocb_end_write(kiocb); > > io_fput(req); > - io_cqring_add_event(req->ctx, req->user_data, res, 0); > + > + if (res > 0 && (req->flags & REQ_F_FORCE_NONBLOCK)) > + ev_flags = IOCQE_FLAG_CACHEHIT; > + > + io_cqring_add_event(req->ctx, req->user_data, res, ev_flags); > io_free_req(req); > } > > diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h > index e23408692118..24906e99fdc7 100644 > --- a/include/uapi/linux/io_uring.h > +++ b/include/uapi/linux/io_uring.h > @@ -69,6 +69,11 @@ struct io_uring_cqe { > __u32 flags; > }; > > +/* > + * io_uring_event->flags > + */ > +#define IOCQE_FLAG_CACHEHIT (1U << 0) /* IO did not hit media */ > + > /* > * Magic offsets for the application to mmap the data it needs > */ > Hmm. The point of this patch being ... what? Just setting a newly introduced flag seems to be a bit pointless. Unless it has some magic interaction with io_cqring_add_event(). But then that function would have had to have knowledge of that flag already, which would be ... odd. Please clarify. Cheers, Hannes
On 2/10/19 2:36 AM, Hannes Reinecke wrote: > On 2/9/19 10:13 PM, Jens Axboe wrote: >> Add hint on whether a read was served out of the page cache, or if it >> hit media. This is useful for buffered async IO, O_DIRECT reads would >> never have this set (for obvious reasons). >> >> If the read hit page cache, cqe->flags will have IOCQE_FLAG_CACHEHIT >> set. >> >> Signed-off-by: Jens Axboe <axboe@kernel.dk> >> --- >> fs/io_uring.c | 7 ++++++- >> include/uapi/linux/io_uring.h | 5 +++++ >> 2 files changed, 11 insertions(+), 1 deletion(-) >> >> diff --git a/fs/io_uring.c b/fs/io_uring.c >> index 11a549b5dcbf..d7a10484d748 100644 >> --- a/fs/io_uring.c >> +++ b/fs/io_uring.c >> @@ -587,11 +587,16 @@ static void io_fput(struct io_kiocb *req) >> static void io_complete_rw(struct kiocb *kiocb, long res, long res2) >> { >> struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw); >> + unsigned ev_flags = 0; >> >> kiocb_end_write(kiocb); >> >> io_fput(req); >> - io_cqring_add_event(req->ctx, req->user_data, res, 0); >> + >> + if (res > 0 && (req->flags & REQ_F_FORCE_NONBLOCK)) >> + ev_flags = IOCQE_FLAG_CACHEHIT; >> + >> + io_cqring_add_event(req->ctx, req->user_data, res, ev_flags); >> io_free_req(req); >> } >> >> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h >> index e23408692118..24906e99fdc7 100644 >> --- a/include/uapi/linux/io_uring.h >> +++ b/include/uapi/linux/io_uring.h >> @@ -69,6 +69,11 @@ struct io_uring_cqe { >> __u32 flags; >> }; >> >> +/* >> + * io_uring_event->flags >> + */ >> +#define IOCQE_FLAG_CACHEHIT (1U << 0) /* IO did not hit media */ >> + >> /* >> * Magic offsets for the application to mmap the data it needs >> */ >> > > Hmm. The point of this patch being ... what? > Just setting a newly introduced flag seems to be a bit pointless. > Unless it has some magic interaction with io_cqring_add_event(). > But then that function would have had to have knowledge of that flag > already, which would be ... odd. Not sure I follow your concern here. The kernel doesn't use the flag, we just set it. It's used to inform the application of whether or not the given read was a cachehit, or if it had to be served by media.
diff --git a/fs/io_uring.c b/fs/io_uring.c index 11a549b5dcbf..d7a10484d748 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -587,11 +587,16 @@ static void io_fput(struct io_kiocb *req) static void io_complete_rw(struct kiocb *kiocb, long res, long res2) { struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw); + unsigned ev_flags = 0; kiocb_end_write(kiocb); io_fput(req); - io_cqring_add_event(req->ctx, req->user_data, res, 0); + + if (res > 0 && (req->flags & REQ_F_FORCE_NONBLOCK)) + ev_flags = IOCQE_FLAG_CACHEHIT; + + io_cqring_add_event(req->ctx, req->user_data, res, ev_flags); io_free_req(req); } diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h index e23408692118..24906e99fdc7 100644 --- a/include/uapi/linux/io_uring.h +++ b/include/uapi/linux/io_uring.h @@ -69,6 +69,11 @@ struct io_uring_cqe { __u32 flags; }; +/* + * io_uring_event->flags + */ +#define IOCQE_FLAG_CACHEHIT (1U << 0) /* IO did not hit media */ + /* * Magic offsets for the application to mmap the data it needs */
Add hint on whether a read was served out of the page cache, or if it hit media. This is useful for buffered async IO, O_DIRECT reads would never have this set (for obvious reasons). If the read hit page cache, cqe->flags will have IOCQE_FLAG_CACHEHIT set. Signed-off-by: Jens Axboe <axboe@kernel.dk> --- fs/io_uring.c | 7 ++++++- include/uapi/linux/io_uring.h | 5 +++++ 2 files changed, 11 insertions(+), 1 deletion(-)