| Message ID | 166949612452.106845.16079864294324208424.stgit@klimt.1015granger.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | quick NFSD-related clean-ups for 6.2 | expand |
On Sat, 2022-11-26 at 15:55 -0500, Chuck Lever wrote: > Make it more evident how xdr_write_pages() updates the tail buffer > by using the convention of naming the iov pointer variable "tail". > I spent more than a couple of hours chasing through code to > understand this, so someone is likely to find this useful later. > > Signed-off-by: Chuck Lever <chuck.lever@oracle.com> > --- > net/sunrpc/xdr.c | 22 +++++++++++++--------- > 1 file changed, 13 insertions(+), 9 deletions(-) > > diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c > index 336a7c7833e4..f7767bf22406 100644 > --- a/net/sunrpc/xdr.c > +++ b/net/sunrpc/xdr.c > @@ -1224,30 +1224,34 @@ EXPORT_SYMBOL(xdr_restrict_buflen); > /** > * xdr_write_pages - Insert a list of pages into an XDR buffer for sending > * @xdr: pointer to xdr_stream > - * @pages: list of pages > - * @base: offset of first byte > - * @len: length of data in bytes > + * @pages: array of pages to insert > + * @base: starting offset of first data byte in @pages > + * @len: number of data bytes in @pages to insert > * > + * After the @pages are added, the tail iovec is instantiated pointing to > + * end of the head buffer, and the stream is set up to encode subsequent > + * items into the tail. > */ > void xdr_write_pages(struct xdr_stream *xdr, struct page **pages, unsigned int base, > unsigned int len) > { > struct xdr_buf *buf = xdr->buf; > - struct kvec *iov = buf->tail; > + struct kvec *tail = buf->tail; > + > buf->pages = pages; > buf->page_base = base; > buf->page_len = len; > > - iov->iov_base = (char *)xdr->p; > - iov->iov_len = 0; > - xdr->iov = iov; > + tail->iov_base = xdr->p; > + tail->iov_len = 0; > + xdr->iov = tail; > > if (len & 3) { > unsigned int pad = 4 - (len & 3); > > BUG_ON(xdr->p >= xdr->end); > - iov->iov_base = (char *)xdr->p + (len & 3); > - iov->iov_len += pad; > + tail->iov_base = (char *)xdr->p + (len & 3); > + tail->iov_len += pad; > len += pad; > *xdr->p++ = 0; > } > > Reviewed-by: Jeff Layton <jlayton@kernel.org>
diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c index 336a7c7833e4..f7767bf22406 100644 --- a/net/sunrpc/xdr.c +++ b/net/sunrpc/xdr.c @@ -1224,30 +1224,34 @@ EXPORT_SYMBOL(xdr_restrict_buflen); /** * xdr_write_pages - Insert a list of pages into an XDR buffer for sending * @xdr: pointer to xdr_stream - * @pages: list of pages - * @base: offset of first byte - * @len: length of data in bytes + * @pages: array of pages to insert + * @base: starting offset of first data byte in @pages + * @len: number of data bytes in @pages to insert * + * After the @pages are added, the tail iovec is instantiated pointing to + * end of the head buffer, and the stream is set up to encode subsequent + * items into the tail. */ void xdr_write_pages(struct xdr_stream *xdr, struct page **pages, unsigned int base, unsigned int len) { struct xdr_buf *buf = xdr->buf; - struct kvec *iov = buf->tail; + struct kvec *tail = buf->tail; + buf->pages = pages; buf->page_base = base; buf->page_len = len; - iov->iov_base = (char *)xdr->p; - iov->iov_len = 0; - xdr->iov = iov; + tail->iov_base = xdr->p; + tail->iov_len = 0; + xdr->iov = tail; if (len & 3) { unsigned int pad = 4 - (len & 3); BUG_ON(xdr->p >= xdr->end); - iov->iov_base = (char *)xdr->p + (len & 3); - iov->iov_len += pad; + tail->iov_base = (char *)xdr->p + (len & 3); + tail->iov_len += pad; len += pad; *xdr->p++ = 0; }
Make it more evident how xdr_write_pages() updates the tail buffer by using the convention of naming the iov pointer variable "tail". I spent more than a couple of hours chasing through code to understand this, so someone is likely to find this useful later. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> --- net/sunrpc/xdr.c | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-)