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From fb4f98330be87d3272d91c354843eadc6db8fc73 Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Thu, 12 Jul 2018 14:42:57 +0200
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Subject: [PATCH 212/268] block: Use tracked request for truncate
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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Message-id: <20180712144258.17303-6-kwolf@redhat.com>
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Patchwork-id: 81326
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O-Subject: [RHV-7.6 qemu-kvm-rhev PATCH 5/6] block: Use tracked request for truncate
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Bugzilla: 1595173
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RH-Acked-by: Max Reitz <mreitz@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: John Snow <jsnow@redhat.com>
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When growing an image, block drivers (especially protocol drivers) may
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initialise the newly added area. I/O requests to the same area need to
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wait for this initialisation to be completed so that data writes don't
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get overwritten and reads don't read uninitialised data.
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To avoid overhead in the fast I/O path by adding new locking in the
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protocol drivers and to restrict the impact to requests that actually
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touch the new area, reuse the existing tracked request infrastructure in
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block/io.c and mark all discard requests as serialising.
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With this change, it is safe for protocol drivers to make
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.bdrv_co_truncate actually asynchronous.
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit 1bc5f09f2e1b2be8f6f737b8d5352b438fc41492)
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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block/io.c | 25 +++++++++++++++++++++++++
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include/block/block_int.h | 1 +
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2 files changed, 26 insertions(+)
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diff --git a/block/io.c b/block/io.c
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index 32a82e3..ad8afc0 100644
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--- a/block/io.c
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+++ b/block/io.c
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@@ -2948,6 +2948,8 @@ int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset,
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{
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BlockDriverState *bs = child->bs;
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BlockDriver *drv = bs->drv;
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+ BdrvTrackedRequest req;
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+ int64_t old_size, new_bytes;
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int ret;
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assert(child->perm & BLK_PERM_RESIZE);
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@@ -2962,7 +2964,28 @@ int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset,
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return -EINVAL;
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}
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+ old_size = bdrv_getlength(bs);
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+ if (old_size < 0) {
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+ error_setg_errno(errp, -old_size, "Failed to get old image size");
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+ return old_size;
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+ }
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+
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+ if (offset > old_size) {
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+ new_bytes = offset - old_size;
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+ } else {
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+ new_bytes = 0;
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+ }
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+
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bdrv_inc_in_flight(bs);
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+ tracked_request_begin(&req, bs, offset, new_bytes, BDRV_TRACKED_TRUNCATE);
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+
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+ /* If we are growing the image and potentially using preallocation for the
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+ * new area, we need to make sure that no write requests are made to it
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+ * concurrently or they might be overwritten by preallocation. */
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+ if (new_bytes) {
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+ mark_request_serialising(&req, 1);
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+ wait_serialising_requests(&req;;
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+ }
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if (!drv->bdrv_co_truncate) {
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if (bs->file && drv->is_filter) {
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@@ -2996,7 +3019,9 @@ int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset,
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atomic_inc(&bs->write_gen);
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out:
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+ tracked_request_end(&req;;
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bdrv_dec_in_flight(bs);
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+
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return ret;
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}
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diff --git a/include/block/block_int.h b/include/block/block_int.h
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index 6a844ec..27e168f 100644
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--- a/include/block/block_int.h
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+++ b/include/block/block_int.h
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@@ -63,6 +63,7 @@ enum BdrvTrackedRequestType {
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BDRV_TRACKED_READ,
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BDRV_TRACKED_WRITE,
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BDRV_TRACKED_DISCARD,
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+ BDRV_TRACKED_TRUNCATE,
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};
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typedef struct BdrvTrackedRequest {
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--
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1.8.3.1
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