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qemu.12241
0103-xen_disk-use-a-single-entry-iovec.patch
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File 0103-xen_disk-use-a-single-entry-iovec.patch of Package qemu.12241
From 9c0ae3dece64a5274a2551743bf95e140413df5e Mon Sep 17 00:00:00 2001 From: Paul Durrant <paul.durrant@citrix.com> Date: Thu, 17 May 2018 16:35:57 +0100 Subject: [PATCH] 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 31aabafb66..e6786fa24c 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 ?
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