From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: virtio-fs@redhat.com, qemu-devel@nongnu.org
Subject: Re: [PATCH 5/7] virtiofsd: Simplify skip byte logic
Date: Tue, 18 May 2021 13:26:45 +0100 [thread overview]
Message-ID: <YKOyhfMDmahKOxsj@work-vm> (raw)
In-Reply-To: <20210511213736.281016-6-vgoyal@redhat.com>
* Vivek Goyal (vgoyal@redhat.com) wrote:
> We need to skip bytes in two cases.
>
> a. Before we start reading into in_sg, we need to skip iov_len bytes
> in the beginning which typically will have fuse_out_header.
>
> b. If preadv() does a short read, then we need to retry preadv() with
> remainig bytes and skip the bytes preadv() read in short read.
>
> For case a, there is no reason that skipping logic be inside the while
> loop. Move it outside. And only retain logic "b" inside while loop.
>
> Also get rid of variable "skip_size". Looks like we can do without it.
>
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Yep, now iov_discard_front makes it easy to skip.
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
> tools/virtiofsd/fuse_virtio.c | 14 ++++----------
> 1 file changed, 4 insertions(+), 10 deletions(-)
>
> diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c
> index ccad2b3f8a..434fe401cf 100644
> --- a/tools/virtiofsd/fuse_virtio.c
> +++ b/tools/virtiofsd/fuse_virtio.c
> @@ -392,17 +392,11 @@ int virtio_send_data_iov(struct fuse_session *se, struct fuse_chan *ch,
> unsigned int in_sg_cpy_count = in_num;
>
> /* skip over parts of in_sg that contained the header iov */
> - size_t skip_size = iov_len;
> + iov_discard_front(&in_sg_ptr, &in_sg_cpy_count, iov_len);
>
> do {
> - if (skip_size != 0) {
> - iov_discard_front(&in_sg_ptr, &in_sg_cpy_count, skip_size);
> - }
> -
> - fuse_log(FUSE_LOG_DEBUG,
> - "%s: after skip skip_size=%zd in_sg_cpy_count=%d "
> - "len remaining=%zd\n", __func__, skip_size, in_sg_cpy_count,
> - len);
> + fuse_log(FUSE_LOG_DEBUG, "%s: in_sg_cpy_count=%d len remaining=%zd\n",
> + __func__, in_sg_cpy_count, len);
>
> ret = preadv(buf->buf[0].fd, in_sg_ptr, in_sg_cpy_count,
> buf->buf[0].pos);
> @@ -421,7 +415,7 @@ int virtio_send_data_iov(struct fuse_session *se, struct fuse_chan *ch,
> if (ret < len && ret) {
> fuse_log(FUSE_LOG_DEBUG, "%s: ret < len\n", __func__);
> /* Skip over this much next time around */
> - skip_size = ret;
> + iov_discard_front(&in_sg_ptr, &in_sg_cpy_count, ret);
> buf->buf[0].pos += ret;
> len -= ret;
>
> --
> 2.25.4
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
next prev parent reply other threads:[~2021-05-18 12:36 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-11 21:37 [PATCH 0/7] virtiofsd: Few cleanups in virtio_send_data_iov() Vivek Goyal
2021-05-11 21:37 ` [PATCH 1/7] virtiofsd: Check for EINTR in preadv() and retry Vivek Goyal
2021-05-18 11:59 ` Dr. David Alan Gilbert
2021-05-11 21:37 ` [PATCH 2/7] virtiofsd: Get rid of unreachable code in read Vivek Goyal
2021-05-18 12:01 ` Dr. David Alan Gilbert
2021-05-11 21:37 ` [PATCH 3/7] virtiofsd: Use iov_discard_front() to skip bytes Vivek Goyal
2021-05-18 12:10 ` Dr. David Alan Gilbert
2021-05-11 21:37 ` [PATCH 4/7] virtiofsd: get rid of in_sg_left variable Vivek Goyal
2021-05-18 12:19 ` Dr. David Alan Gilbert
2021-05-11 21:37 ` [PATCH 5/7] virtiofsd: Simplify skip byte logic Vivek Goyal
2021-05-18 12:26 ` Dr. David Alan Gilbert [this message]
2021-05-11 21:37 ` [PATCH 6/7] virtiofsd: Check EOF before short read Vivek Goyal
2021-05-18 12:31 ` Dr. David Alan Gilbert
2021-05-11 21:37 ` [PATCH 7/7] virtiofsd: Set req->reply_sent right after sending reply Vivek Goyal
2021-05-13 20:50 ` [Virtio-fs] " Connor Kuehl
2021-05-17 13:08 ` Vivek Goyal
2021-05-18 12:34 ` Dr. David Alan Gilbert
2021-05-18 12:32 ` Dr. David Alan Gilbert
2021-05-11 21:48 ` [PATCH 0/7] virtiofsd: Few cleanups in virtio_send_data_iov() no-reply
2021-05-13 20:50 ` [Virtio-fs] " Connor Kuehl
2021-05-17 13:08 ` Vivek Goyal
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