Re: [PATCH v3 4/4] fsx: add IO_URING test

[Zorro Lang <zlang@redhat.com>]

On Sun, Sep 06, 2020 at 11:55:16PM +0800, Zorro Lang wrote:
> On Thu, Sep 03, 2020 at 08:44:13AM -0400, Brian Foster wrote:
> > On Sun, Aug 23, 2020 at 02:30:32PM +0800, Zorro Lang wrote:
> > > New IO_URING test for fsx, use -U option to enable IO_URING test.
> > > 
> > > Signed-off-by: Zorro Lang <zlang@redhat.com>
> > > ---
> > 
> > Note that this one doesn't compile if one of the ifdefs doesn't evaluate
> > true:
> > 
> > fsx.c:2551:6: error: #elif with no expression
> >  2551 | #elif
> >       |      ^
> >     [CC]    fsx
> > fsx.c: In function 'fsx_rw':
> > fsx.c:2551:6: error: #elif with no expression
> >  2551 | #elif
> >       |      ^
> > gmake[2]: *** [Makefile:52: fsx] Error 1
> > gmake[1]: *** [include/buildrules:30: ltp] Error 2
> > make: *** [Makefile:53: default] Error 2
> > 
> > I suspect you want to replace both of those with #else. Otherwise mostly
> > some aesthetic comments...
> 
> Sorry, that's truely a mistake, I'll fix it :)
> 
> > 
> > >  ltp/fsx.c | 158 +++++++++++++++++++++++++++++++++++++++++++++++++-----
> > >  1 file changed, 144 insertions(+), 14 deletions(-)
> > > 
> > > diff --git a/ltp/fsx.c b/ltp/fsx.c
> > > index 7c76655a..05663528 100644
> > > --- a/ltp/fsx.c
> > > +++ b/ltp/fsx.c
> > ...
> > > @@ -176,21 +179,17 @@ int	integrity = 0;			/* -i flag */
> > >  int	fsxgoodfd = 0;
> > >  int	o_direct;			/* -Z */
> > >  int	aio = 0;
> > > +int	uring = 0;
> > >  int	mark_nr = 0;
> > >  
> > >  int page_size;
> > >  int page_mask;
> > >  int mmap_mask;
> > > -#ifdef AIO
> > > -int aio_rw(int rw, int fd, char *buf, unsigned len, unsigned offset);
> > > +int fsx_rw(int rw, int fd, char *buf, unsigned len, unsigned offset);
> > >  #define READ 0
> > >  #define WRITE 1
> > > -#define fsxread(a,b,c,d)	aio_rw(READ, a,b,c,d)
> > > -#define fsxwrite(a,b,c,d)	aio_rw(WRITE, a,b,c,d)
> > > -#else
> > > -#define fsxread(a,b,c,d)	read(a,b,c)
> > > -#define fsxwrite(a,b,c,d)	write(a,b,c)
> > > -#endif
> > > +#define fsxread(a,b,c,d)	fsx_rw(READ, a,b,c,d)
> > > +#define fsxwrite(a,b,c,d)	fsx_rw(WRITE, a,b,c,d)
> > >  
> > 
> > Could we do the refactoring that introduces fsx_rw and shuffles around
> > some of the existing AIO in an initial refactoring patch?
> 
> May I save this pre-patch, if you don't insist on that :-P
> 
> > 
> > >  const char *replayops = NULL;
> > >  const char *recordops = NULL;
> > ...
> > > @@ -2425,13 +2427,131 @@ out_error:
> > >  	errno = -ret;
> > >  	return -1;
> > >  }
> > > +#endif
> > > +
> > > +#ifdef URING
> > 
> > A whitespace line here...
> > 
> > > +struct io_uring ring;
> > > +#define URING_ENTRIES	1024
> > 
> > ... and here would help readability.
> > 
> > > +int
> > > +uring_setup()
> > > +{
> > > +	int ret;
> > > +
> > > +	ret = io_uring_queue_init(URING_ENTRIES, &ring, 0);
> > > +	if (ret != 0) {
> > > +		fprintf(stderr, "uring_setup: io_uring_queue_init failed: %s\n",
> > > +                        strerror(ret));
> > > +                return -1;
> > > +        }
> > > +        return 0;
> > 
> > Looks like some whitespace damage here.
> > 
> > Also, the fsstress patch has a io_uring_queue_exit() call but I don't
> > see one in this patch. Is that not needed?
> 
> There's not aio_destroy() either. I think due to fsstress is a multi-process
> test, so it'd like to destroy io_uring or aio at each process end. But fsx is
> a pure single process test, the io_uring or aio will destroyed when fsx exit.
> I can add io_uring_queue_exit() and aio_destroy() if you think it would be
> better.
> 
> > 
> > > +}
> > >  
> > > -int aio_rw(int rw, int fd, char *buf, unsigned len, unsigned offset)
> > > +int
> > > +__uring_rw(int rw, int fd, char *buf, unsigned len, unsigned offset)
> > 
> > Do we still need the __ in the function names here and for __aio_rw()?
> 
> I don't think it's needed. I use the "__" just due to the old __aio_rw() has. I
> can remove both "__" of __aio_rw and __uring_rw.
> 
> > 
> > >  {
> > > +	struct io_uring_sqe	*sqe;
> > > +	struct io_uring_cqe	*cqe;
> > > +	struct iovec		iovec;
> > >  	int ret;
> > > +	int res, res2 = 0;
> > > +	char *p = buf;
> > > +	unsigned l = len;
> > > +	unsigned o = offset;
> > > +
> > > +
> > > +	/*
> > > +	 * Due to io_uring tries non-blocking IOs (especially read), that
> > > +	 * always cause 'normal' short reading. To avoid this short read
> > > +	 * fail, try to loop read/write (escpecilly read) data.
> > > +	 */
> > > + uring_loop:
> > > +	sqe = io_uring_get_sqe(&ring);
> > > +	if (!sqe) {
> > > +		fprintf(stderr, "uring_rw: io_uring_get_sqe failed: %s\n",
> > > +		        strerror(errno));
> > > +		return -1;
> > > +        }
> > > +
> > > +	iovec.iov_base = p;
> > > +	iovec.iov_len = l;
> > > +	if (rw == READ) {
> > > +		io_uring_prep_readv(sqe, fd, &iovec, 1, o);
> > > +	} else {
> > > +		io_uring_prep_writev(sqe, fd, &iovec, 1, o);
> > > +	}
> > > +
> > > +	ret = io_uring_submit_and_wait(&ring, 1);
> > > +	if (ret != 1) {
> > > +		fprintf(stderr, "errcode=%d\n", -ret);
> > > +		fprintf(stderr, "uring %s: io_uring_submit failed: %s\n",
> > > +		        rw == READ ? "read":"write", strerror(-ret));
> > > +		goto uring_error;
> > > +	}
> > > +
> > > +	ret = io_uring_wait_cqe(&ring, &cqe);
> > > +	if (ret < 0) {
> > > +		if (ret == 0)
> > 
> > That doesn't look right since we only get here if ret < 0.
> 
> Thanks, it should be (ret <= 0)

Sorry, I just checked io_uring_wait_cqe() code, it returns 0 on success.
So my "if (ret == 0)" checking is totally wrong, I'll remove it :)

/*
 * Return an IO completion, waiting for it if necessary. Returns 0 with
 * cqe_ptr filled in on success, -errno on failure.
 */
static inline int io_uring_wait_cqe(struct io_uring *ring,
                                    struct io_uring_cqe **cqe_ptr)

> 
> > 
> > > +			fprintf(stderr, "uring %s: no events available\n",
> > > +			        rw == READ ? "read":"write");
> > > +		else {
> > > +			fprintf(stderr, "errcode=%d\n", -ret);
> > > +			fprintf(stderr, "uring %s: io_uring_wait_cqe failed: %s\n",
> > > +			        rw == READ ? "read":"write", strerror(-ret));
> > > +		}
> > > +		goto uring_error;
> > > +	}
> > > +	res = cqe->res;
> > > +	io_uring_cqe_seen(&ring, cqe);
> > > +
> > > +	res2 += res;
> > > +	if (len != res2) {
> > > +		if (res > 0) {
> > > +			o += res;
> > > +			l -= res;
> > > +			p += res;
> > > +			if (l > 0)
> > > +				goto uring_loop;
> > > +		} else if (res < 0) {
> > > +			ret = res;
> > > +			fprintf(stderr, "errcode=%d\n", -ret);
> > > +			fprintf(stderr, "uring %s: io_uring failed: %s\n",
> > > +			        rw == READ ? "read":"write", strerror(-ret));
> > > +			goto uring_error;
> > 
> > Can we elevate the error checks into the top level rather than nesting
> > logic like this? It's a little confusing to read and it looks
> > particularly odd since we've already done res2 += res before we get
> > here.
> > 
> > Also I'm wondering if this whole function would read a little better as
> > a do {} while() loop rather than using a label and goto.
> 
> Sure, I'll try to change that.
> 
> > 
> > > +		} else {
> > > +			fprintf(stderr, "uring %s bad io length: %d instead of %u\n",
> > > +			        rw == READ ? "read":"write", res2, len);
> > > +		}
> > > +	}
> > > +	return res2;
> > > +
> > > + uring_error:
> > > +	/*
> > > +	 * The caller expects error return in traditional libc
> > > +	 * convention, i.e. -1 and the errno set to error.
> > > +	 */
> > > +	errno = -ret;
> > > +	return -1;
> > > +}
> > > +#endif
> > > +
> > > +int fsx_rw(int rw, int fd, char *buf, unsigned len, unsigned offset)
> > > +{
> > > +	int ret = -1;
> > >  
> > >  	if (aio) {
> > > +#ifdef AIO
> > >  		ret = __aio_rw(rw, fd, buf, len, offset);
> > > +#elif
> > > +		fprintf(stderr, "io_rw: need AIO support!\n");
> > > +		exit(111);
> > > +#endif
> > > +	} else if (uring) {
> > > +#ifdef URING
> > > +		ret = __uring_rw(rw, fd, buf, len, offset);
> > > +#elif
> > > +		fprintf(stderr, "io_rw: need IO_URING support!\n");
> > > +		exit(111);
> > > +#endif
> > 
> > I think the ifdefs would be cleaner if used to define stubbed out
> > variants of the associated functions. E.g.:
> > 
> > #ifdef URING
> > int
> > __uring_rw(int rw, int fd, char *buf, unsigned len, unsigned offset)
> > {
> > 	<do uring I/O>
> > }
> > #else
> > int
> > __uring_rw(int rw, int fd, char *buf, unsigned len, unsigned offset)
> > {
> > 	fprintf(stderr, "io_rw: need IO_URING support!\n");
> > 	exit(111);
> > }
> > #endif
> 
> Sure, will do that.
> 
> Thanks for your review, Brian!
> Zorro
> 
> > 
> > Brian
> > 
> > >  	} else {
> > >  		if (rw == READ)
> > >  			ret = read(fd, buf, len);
> > > @@ -2441,8 +2561,6 @@ int aio_rw(int rw, int fd, char *buf, unsigned len, unsigned offset)
> > >  	return ret;
> > >  }
> > >  
> > > -#endif
> > > -
> > >  #define test_fallocate(mode) __test_fallocate(mode, #mode)
> > >  
> > >  int
> > > @@ -2496,7 +2614,7 @@ main(int argc, char **argv)
> > >  	setvbuf(stdout, (char *)0, _IOLBF, 0); /* line buffered stdout */
> > >  
> > >  	while ((ch = getopt_long(argc, argv,
> > > -				 "b:c:dfg:i:j:kl:m:no:p:qr:s:t:w:xyABD:EFJKHzCILN:OP:RS:WXZ",
> > > +				 "b:c:dfg:i:j:kl:m:no:p:qr:s:t:w:xyABD:EFJKHzCILN:OP:RS:UWXZ",
> > >  				 longopts, NULL)) != EOF)
> > >  		switch (ch) {
> > >  		case 'b':
> > > @@ -2604,6 +2722,9 @@ main(int argc, char **argv)
> > >  		case 'A':
> > >  		        aio = 1;
> > >  			break;
> > > +		case 'U':
> > > +		        uring = 1;
> > > +			break;
> > >  		case 'D':
> > >  			debugstart = getnum(optarg, &endp);
> > >  			if (debugstart < 1)
> > > @@ -2694,6 +2815,11 @@ main(int argc, char **argv)
> > >  	if (argc != 1)
> > >  		usage();
> > >  
> > > +	if (aio && uring) {
> > > +		fprintf(stderr, "-A and -U shouldn't be used together\n");
> > > +		usage();
> > > +	}
> > > +
> > >  	if (integrity && !dirpath) {
> > >  		fprintf(stderr, "option -i <logdev> requires -P <dirpath>\n");
> > >  		usage();
> > > @@ -2784,6 +2910,10 @@ main(int argc, char **argv)
> > >  	if (aio) 
> > >  		aio_setup();
> > >  #endif
> > > +#ifdef URING
> > > +	if (uring)
> > > +		uring_setup();
> > > +#endif
> > >  
> > >  	if (!(o_flags & O_TRUNC)) {
> > >  		off_t ret;
> > > -- 
> > > 2.20.1
> > >