From: Jeff Cody <jcody@redhat.com>
To: jazeltq@gmail.com
Cc: jdurgin@redhat.com, dillaman@redhat.com, kwolf@redhat.com,
mreitz@redhat.com, qemu-block@nongnu.org, qemu-devel@nongnu.org,
ceph-devel@vger.kernel.org, eblake@redhat.com,
tianqing <tianqing@unitedstack.com>
Subject: Re: [Qemu-devel] [RFC v5] RBD: Add support readv,writev for rbd
Date: Thu, 16 Feb 2017 10:51:59 -0500 [thread overview]
Message-ID: <20170216155159.GE8801@localhost.localdomain> (raw)
In-Reply-To: <20170216090002.12511-1-jazeltq@gmail.com>
On Thu, Feb 16, 2017 at 05:00:02PM +0800, jazeltq@gmail.com wrote:
> From: tianqing <tianqing@unitedstack.com>
>
> Rbd can do readv and writev directly, so wo do not need to transform
> iov to buf or vice versa any more.
>
> Signed-off-by: tianqing <tianqing@unitedstack.com>
> ---
> block/rbd.c | 49 ++++++++++++++++++++++++++++++++++++++++++-------
> 1 file changed, 42 insertions(+), 7 deletions(-)
>
> diff --git a/block/rbd.c b/block/rbd.c
> index a57b3e3..75ae1d6 100644
> --- a/block/rbd.c
> +++ b/block/rbd.c
> @@ -47,7 +47,7 @@
> */
>
> /* rbd_aio_discard added in 0.1.2 */
> -#if LIBRBD_VERSION_CODE >= LIBRBD_VERSION(0, 1, 2)
> +#if LIBRBD_VERSION_CODE >= LIBRBD_VERSION(12, 0, 0)
> #define LIBRBD_SUPPORTS_DISCARD
> #else
> #undef LIBRBD_SUPPORTS_DISCARD
> @@ -73,7 +73,12 @@ typedef struct RBDAIOCB {
> BlockAIOCB common;
> int64_t ret;
> QEMUIOVector *qiov;
> +/* Note:
> + * The LIBRBD_SUPPORTS_IOVEC is defined in librbd.h.
> + */
I understand that since this feature relies on new symbols in the library,
the ifdef can't be entirely avoided. However, there are a few changes that
can make the code much more readable, and greatly reduce the use of ifdefs
through the code.
For instance, you could have helper constants:
#ifdef LIBRBD_SUPPORTS_IOVEC
#define LIBRBD_USE_IOVEC 1
#else
#define LIBRBD_USE_IOVEC 0
#endif
Now that can be used for a more natural code, with minimal ifdefs. The
compiler optimizations should still remove the code, as well.
A helper function for memset will also keep things simpler:
static void qemu_rbd_memset(RADOSCB *rcb, int64_t offs)
{
if (LIBRBD_USE_IOVEC) {
RBDAIOCB *acb = rcb->acb;
iov_memset(acb->qiov->iov, acb->qiov->niov, offs, 0,
acb->qiov->size - offs);
} else {
memset(rcb->buf + offs, 0, rcb->size - offs);
}
}
> +#ifndef LIBRBD_SUPPORTS_IOVEC
> char *bounce;
> +#endif
This conditional can go away (see [1]).
> RBDAIOCmd cmd;
> int error;
> struct BDRVRBDState *s;
> @@ -83,7 +88,9 @@ typedef struct RADOSCB {
> RBDAIOCB *acb;
> struct BDRVRBDState *s;
> int64_t size;
> +#ifndef LIBRBD_SUPPORTS_IOVEC
> char *buf;
> +#endif
As can this.
> int64_t ret;
> } RADOSCB;
>
> @@ -426,11 +433,21 @@ static void qemu_rbd_complete_aio(RADOSCB *rcb)
> }
> } else {
> if (r < 0) {
> +#ifndef LIBRBD_SUPPORTS_IOVEC
> memset(rcb->buf, 0, rcb->size);
> +#else
> + iov_memset(acb->qiov->iov, acb->qiov->niov, 0, 0, acb->qiov->size);
> +#endif
This just becomes:
qemu_rbd_memset(rcb, 0);
> acb->ret = r;
> acb->error = 1;
> } else if (r < rcb->size) {
> +#ifndef LIBRBD_SUPPORTS_IOVEC
> memset(rcb->buf + r, 0, rcb->size - r);
> +#else
> + iov_memset(acb->qiov->iov, acb->qiov->niov,
> + r, 0, acb->qiov->size - r);
> +#endif
> +
Same here:
qemu_rbd_memset(rcb, r);
> if (!acb->error) {
> acb->ret = rcb->size;
> }
> @@ -441,10 +458,12 @@ static void qemu_rbd_complete_aio(RADOSCB *rcb)
>
> g_free(rcb);
>
> +#ifndef LIBRBD_SUPPORTS_IOVEC
> if (acb->cmd == RBD_AIO_READ) {
> qemu_iovec_from_buf(acb->qiov, 0, acb->bounce, acb->qiov->size);
> }
> qemu_vfree(acb->bounce);
> +#endif
[1]
Instead of a conditional, you can now use the constant with an if statement:
if (!LIBRBD_USE_IOVEC) {
if (acb->cmd == RBD_AIO_READ) {
qemu_iovec_from_buf(acb->qiov, 0, acb->bounce, acb->qiov->size);
}
qemu_vfree(acb->bounce);
}
> acb->common.cb(acb->common.opaque, (acb->ret > 0 ? 0 : acb->ret));
>
> qemu_aio_unref(acb);
> @@ -655,8 +674,10 @@ static BlockAIOCB *rbd_start_aio(BlockDriverState *bs,
> RBDAIOCB *acb;
> RADOSCB *rcb = NULL;
> rbd_completion_t c;
> - char *buf;
> int r;
> +#ifndef LIBRBD_SUPPORTS_IOVEC
> + char *buf = NULL;
> +#endif
This variable can completely go away with some code re-arrangement (below)
>
> BDRVRBDState *s = bs->opaque;
>
> @@ -664,6 +685,8 @@ static BlockAIOCB *rbd_start_aio(BlockDriverState *bs,
> acb->cmd = cmd;
> acb->qiov = qiov;
> assert(!qiov || qiov->size == size);
[2]
Allocate rcb here
> +#ifndef LIBRBD_SUPPORTS_IOVEC
> +
You can use if(!LIBRBD_USE_IOVEC) here then.
> if (cmd == RBD_AIO_DISCARD || cmd == RBD_AIO_FLUSH) {
> acb->bounce = NULL;
> } else {
> @@ -672,19 +695,21 @@ static BlockAIOCB *rbd_start_aio(BlockDriverState *bs,
> goto failed;
> }
> }
> - acb->ret = 0;
> - acb->error = 0;
> - acb->s = s;
> -
> if (cmd == RBD_AIO_WRITE) {
> qemu_iovec_to_buf(acb->qiov, 0, acb->bounce, qiov->size);
> }
> -
> buf = acb->bounce;
This can just become rcb->buf = acb->bounce
> +#endif
> + acb->ret = 0;
> + acb->error = 0;
> + acb->s = s;
>
> rcb = g_new(RADOSCB, 1);
Move this to [2]
> +
> rcb->acb = acb;
> +#ifndef LIBRBD_SUPPORTS_IOVEC
> rcb->buf = buf;
> +#endif
These 3 lines can then go away
> rcb->s = acb->s;
> rcb->size = size;
> r = rbd_aio_create_completion(rcb, (rbd_callback_t) rbd_finish_aiocb, &c);
> @@ -694,10 +719,18 @@ static BlockAIOCB *rbd_start_aio(BlockDriverState *bs,
>
> switch (cmd) {
> case RBD_AIO_WRITE:
> +#ifndef LIBRBD_SUPPORTS_IOVEC
> r = rbd_aio_write(s->image, off, size, buf, c);
If you use rcb->buf here, that allows buf to go away completely.
> +#else
> + r = rbd_aio_writev(s->image, qiov->iov, qiov->niov, off, c);
> +#endif
> break;
> case RBD_AIO_READ:
> +#ifndef LIBRBD_SUPPORTS_IOVEC
> r = rbd_aio_read(s->image, off, size, buf, c);
Same
> +#else
> + r = rbd_aio_readv(s->image, qiov->iov, qiov->niov, off, c);
> +#endif
> break;
> case RBD_AIO_DISCARD:
> r = rbd_aio_discard_wrapper(s->image, off, size, c);
> @@ -719,7 +752,9 @@ failed_completion:
> rbd_aio_release(c);
> failed:
> g_free(rcb);
> +#ifndef LIBRBD_SUPPORTS_IOVEC
And use the if(!LIBRBD_USE_IOVEC) here too.
> qemu_vfree(acb->bounce);
> +#endif
> qemu_aio_unref(acb);
> return NULL;
> }
> --
> 2.10.2
>
-Jeff
prev parent reply other threads:[~2017-02-16 15:52 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-21 10:59 [Qemu-devel] [RFC v3] RBD: Add support readv,writev for rbd jazeltq
2017-01-21 11:13 ` no-reply
2017-01-21 13:19 ` [Qemu-devel] [RFC v4] " jazeltq
2017-02-16 8:43 ` jazeltq
2017-02-16 9:00 ` [Qemu-devel] [RFC v5] " jazeltq
2017-02-16 12:07 ` Tiger Hu
2017-02-16 14:03 ` Jaze Lee
2017-02-16 15:13 ` Alexandre DERUMIER
2017-02-16 15:26 ` Jason Dillaman
2017-02-16 14:14 ` Jason Dillaman
2017-02-16 14:22 ` Jaze Lee
2017-02-16 15:45 ` Eric Blake
2017-02-16 15:51 ` Jeff Cody [this message]
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