File 0113-xen_disk-use-a-single-entry-iovec.patch of Package qemu.20395
From: Paul Durrant <paul.durrant@citrix.com>
Date: Thu, 17 May 2018 16:35:57 +0100
Subject: xen_disk: use a single entry iovec
Since xen_disk now always copies data to and from a guest there is no need
to maintain a vector entry corresponding to every page of a request.
This means there is less per-request state to maintain so the ioreq
structure can shrink significantly.
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Anthony Perard <anthony.perard@citrix.com>
Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>
(cherry picked from commit 5ebf96265244e720d56367703a752f05010b7d55)
[LD: BSC#1100408]
Signed-off-by: Larry Dewey <ldewey@suse.com>
---
hw/block/xen_disk.c | 76 +++++++++++++--------------------------------
1 file changed, 21 insertions(+), 55 deletions(-)
diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c
index 31aabafb6633ed384d174b4af346..e6786fa24c8b59a132d59c7efab6 100644
--- a/hw/block/xen_disk.c
+++ b/hw/block/xen_disk.c
@@ -44,13 +44,10 @@ struct ioreq {
/* parsed request */
off_t start;
QEMUIOVector v;
+ void *buf;
+ size_t size;
int presync;
- /* grant mapping */
- uint32_t refs[BLKIF_MAX_SEGMENTS_PER_REQUEST];
- void *page[BLKIF_MAX_SEGMENTS_PER_REQUEST];
- void *pages;
-
/* aio status */
int aio_inflight;
int aio_errors;
@@ -106,12 +103,10 @@ static void ioreq_reset(struct ioreq *ioreq)
memset(&ioreq->req, 0, sizeof(ioreq->req));
ioreq->status = 0;
ioreq->start = 0;
+ ioreq->buf = NULL;
+ ioreq->size = 0;
ioreq->presync = 0;
- memset(ioreq->refs, 0, sizeof(ioreq->refs));
- memset(ioreq->page, 0, sizeof(ioreq->page));
- ioreq->pages = NULL;
-
ioreq->aio_inflight = 0;
ioreq->aio_errors = 0;
@@ -134,7 +129,7 @@ static struct ioreq *ioreq_start(struct XenBlkDev *blkdev)
ioreq = g_malloc0(sizeof(*ioreq));
ioreq->blkdev = blkdev;
blkdev->requests_total++;
- qemu_iovec_init(&ioreq->v, BLKIF_MAX_SEGMENTS_PER_REQUEST);
+ qemu_iovec_init(&ioreq->v, 1);
} else {
/* get one from freelist */
ioreq = QLIST_FIRST(&blkdev->freelist);
@@ -179,7 +174,6 @@ static void ioreq_release(struct ioreq *ioreq, bool finish)
static int ioreq_parse(struct ioreq *ioreq)
{
struct XenBlkDev *blkdev = ioreq->blkdev;
- uintptr_t mem;
size_t len;
int i;
@@ -226,13 +220,10 @@ static int ioreq_parse(struct ioreq *ioreq)
goto err;
}
- ioreq->refs[i] = ioreq->req.seg[i].gref;
-
- mem = ioreq->req.seg[i].first_sect * blkdev->file_blk;
len = (ioreq->req.seg[i].last_sect - ioreq->req.seg[i].first_sect + 1) * blkdev->file_blk;
- qemu_iovec_add(&ioreq->v, (void*)mem, len);
+ ioreq->size += len;
}
- if (ioreq->start + ioreq->v.size > blkdev->file_size) {
+ if (ioreq->start + ioreq->size > blkdev->file_size) {
xen_pv_printf(&blkdev->xendev, 0, "error: access beyond end of file\n");
goto err;
}
@@ -243,35 +234,6 @@ err:
return -1;
}
-static void ioreq_free_copy_buffers(struct ioreq *ioreq)
-{
- int i;
-
- for (i = 0; i < ioreq->v.niov; i++) {
- ioreq->page[i] = NULL;
- }
-
- qemu_vfree(ioreq->pages);
-}
-
-static int ioreq_init_copy_buffers(struct ioreq *ioreq)
-{
- int i;
-
- if (ioreq->v.niov == 0) {
- return 0;
- }
-
- ioreq->pages = qemu_memalign(XC_PAGE_SIZE, ioreq->v.niov * XC_PAGE_SIZE);
-
- for (i = 0; i < ioreq->v.niov; i++) {
- ioreq->page[i] = ioreq->pages + i * XC_PAGE_SIZE;
- ioreq->v.iov[i].iov_base = ioreq->page[i];
- }
-
- return 0;
-}
-
static int ioreq_grant_copy(struct ioreq *ioreq)
{
struct XenBlkDev *blkdev = ioreq->blkdev;
@@ -280,25 +242,27 @@ static int ioreq_grant_copy(struct ioreq *ioreq)
int i, count, rc;
int64_t file_blk = ioreq->blkdev->file_blk;
bool to_domain = (ioreq->req.operation == BLKIF_OP_READ);
+ void *virt = ioreq->buf;
- if (ioreq->v.niov == 0) {
+ if (ioreq->req.nr_segments == 0) {
return 0;
}
- count = ioreq->v.niov;
+ count = ioreq->req.nr_segments;
for (i = 0; i < count; i++) {
if (to_domain) {
- segs[i].dest.foreign.ref = ioreq->refs[i];
+ segs[i].dest.foreign.ref = ioreq->req.seg[i].gref;
segs[i].dest.foreign.offset = ioreq->req.seg[i].first_sect * file_blk;
- segs[i].source.virt = ioreq->v.iov[i].iov_base;
+ segs[i].source.virt = virt;
} else {
- segs[i].source.foreign.ref = ioreq->refs[i];
+ segs[i].source.foreign.ref = ioreq->req.seg[i].gref;
segs[i].source.foreign.offset = ioreq->req.seg[i].first_sect * file_blk;
- segs[i].dest.virt = ioreq->v.iov[i].iov_base;
+ segs[i].dest.virt = virt;
}
segs[i].len = (ioreq->req.seg[i].last_sect
- ioreq->req.seg[i].first_sect + 1) * file_blk;
+ virt += segs[i].len;
}
rc = xen_be_copy_grant_refs(xendev, to_domain, segs, count);
@@ -341,14 +305,14 @@ static void qemu_aio_complete(void *opaque, int ret)
if (ret == 0) {
ioreq_grant_copy(ioreq);
}
- ioreq_free_copy_buffers(ioreq);
+ qemu_vfree(ioreq->buf);
break;
case BLKIF_OP_WRITE:
case BLKIF_OP_FLUSH_DISKCACHE:
if (!ioreq->req.nr_segments) {
break;
}
- ioreq_free_copy_buffers(ioreq);
+ qemu_vfree(ioreq->buf);
break;
default:
break;
@@ -413,12 +377,12 @@ static int ioreq_runio_qemu_aio(struct ioreq *ioreq)
{
struct XenBlkDev *blkdev = ioreq->blkdev;
- ioreq_init_copy_buffers(ioreq);
+ ioreq->buf = qemu_memalign(XC_PAGE_SIZE, ioreq->size);
if (ioreq->req.nr_segments &&
(ioreq->req.operation == BLKIF_OP_WRITE ||
ioreq->req.operation == BLKIF_OP_FLUSH_DISKCACHE) &&
ioreq_grant_copy(ioreq)) {
- ioreq_free_copy_buffers(ioreq);
+ qemu_vfree(ioreq->buf);
goto err;
}
@@ -430,6 +394,7 @@ static int ioreq_runio_qemu_aio(struct ioreq *ioreq)
switch (ioreq->req.operation) {
case BLKIF_OP_READ:
+ qemu_iovec_add(&ioreq->v, ioreq->buf, ioreq->size);
block_acct_start(blk_get_stats(blkdev->blk), &ioreq->acct,
ioreq->v.size, BLOCK_ACCT_READ);
ioreq->aio_inflight++;
@@ -442,6 +407,7 @@ static int ioreq_runio_qemu_aio(struct ioreq *ioreq)
break;
}
+ qemu_iovec_add(&ioreq->v, ioreq->buf, ioreq->size);
block_acct_start(blk_get_stats(blkdev->blk), &ioreq->acct,
ioreq->v.size,
ioreq->req.operation == BLKIF_OP_WRITE ?
