[PATCH 17/27] afs: Use a bvec rather than a kvec in afs_send_pages()

From: David Howells
Date: Thu Mar 09 2017 - 14:00:40 EST


Use a bvec rather than a kvec in afs_send_pages() as we don't then have to
call kmap() in advance. This allows us to pass the array of contiguous
pages that we extracted through to rxrpc in one go rather than passing a
single page at a time.

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---

fs/afs/rxrpc.c | 97 ++++++++++++++++++++++++++++++--------------------------
1 file changed, 52 insertions(+), 45 deletions(-)

diff --git a/fs/afs/rxrpc.c b/fs/afs/rxrpc.c
index 419ef05dcb5e..bf45307ff201 100644
--- a/fs/afs/rxrpc.c
+++ b/fs/afs/rxrpc.c
@@ -259,67 +259,74 @@ void afs_flat_call_destructor(struct afs_call *call)
call->buffer = NULL;
}

+#define AFS_BVEC_MAX 8
+
+/*
+ * Load the given bvec with the next few pages.
+ */
+static void afs_load_bvec(struct afs_call *call, struct msghdr *msg,
+ struct bio_vec *bv, pgoff_t first, pgoff_t last,
+ unsigned offset)
+{
+ struct page *pages[AFS_BVEC_MAX];
+ unsigned int nr, n, i, to, bytes = 0;
+
+ nr = min_t(pgoff_t, last - first + 1, AFS_BVEC_MAX);
+ n = find_get_pages_contig(call->mapping, first, nr, pages);
+ ASSERTCMP(n, ==, nr);
+
+ msg->msg_flags |= MSG_MORE;
+ for (i = 0; i < nr; i++) {
+ to = PAGE_SIZE;
+ if (first + i >= last) {
+ to = call->last_to;
+ msg->msg_flags &= ~MSG_MORE;
+ }
+ bv[i].bv_page = pages[i];
+ bv[i].bv_len = to - offset;
+ bv[i].bv_offset = offset;
+ bytes += to - offset;
+ offset = 0;
+ }
+
+ iov_iter_bvec(&msg->msg_iter, WRITE | ITER_BVEC, bv, nr, bytes);
+}
+
/*
* attach the data from a bunch of pages on an inode to a call
*/
static int afs_send_pages(struct afs_call *call, struct msghdr *msg)
{
- struct page *pages[8];
- unsigned count, n, loop, offset, to;
+ struct bio_vec bv[AFS_BVEC_MAX];
+ unsigned int bytes, nr, loop, offset;
pgoff_t first = call->first, last = call->last;
int ret;

- _enter("");
-
offset = call->first_offset;
call->first_offset = 0;

do {
- _debug("attach %lx-%lx", first, last);
-
- count = last - first + 1;
- if (count > ARRAY_SIZE(pages))
- count = ARRAY_SIZE(pages);
- n = find_get_pages_contig(call->mapping, first, count, pages);
- ASSERTCMP(n, ==, count);
-
- loop = 0;
- do {
- struct bio_vec bvec = {.bv_page = pages[loop],
- .bv_offset = offset};
- msg->msg_flags = 0;
- to = PAGE_SIZE;
- if (first + loop >= last)
- to = call->last_to;
- else
- msg->msg_flags = MSG_MORE;
- bvec.bv_len = to - offset;
- offset = 0;
-
- _debug("- range %u-%u%s",
- offset, to, msg->msg_flags ? " [more]" : "");
- iov_iter_bvec(&msg->msg_iter, WRITE | ITER_BVEC,
- &bvec, 1, to - offset);
-
- /* have to change the state *before* sending the last
- * packet as RxRPC might give us the reply before it
- * returns from sending the request */
- if (first + loop >= last)
- call->state = AFS_CALL_AWAIT_REPLY;
- ret = rxrpc_kernel_send_data(afs_socket, call->rxcall,
- msg, to - offset);
- if (ret < 0)
- break;
- } while (++loop < count);
- first += count;
-
- for (loop = 0; loop < count; loop++)
- put_page(pages[loop]);
+ afs_load_bvec(call, msg, bv, first, last, offset);
+ offset = 0;
+ bytes = msg->msg_iter.count;
+ nr = msg->msg_iter.nr_segs;
+
+ /* Have to change the state *before* sending the last
+ * packet as RxRPC might give us the reply before it
+ * returns from sending the request.
+ */
+ if (first + nr >= last)
+ call->state = AFS_CALL_AWAIT_REPLY;
+ ret = rxrpc_kernel_send_data(afs_socket, call->rxcall,
+ msg, bytes);
+ for (loop = 0; loop < nr; loop++)
+ put_page(bv[loop].bv_page);
if (ret < 0)
break;
+
+ first += nr;
} while (first <= last);

- _leave(" = %d", ret);
return ret;
}