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From 6b97fd0b69ecf0e1bebafa6bc607ae60b9ab252e Mon Sep 17 00:00:00 2001
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From: John Snow <jsnow@redhat.com>
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Date: Tue, 25 Sep 2018 22:34:21 +0100
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Subject: [PATCH 18/28] block/mirror: conservative mirror_exit refactor
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RH-Author: John Snow <jsnow@redhat.com>
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Message-id: <20180925223431.24791-16-jsnow@redhat.com>
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Patchwork-id: 82270
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O-Subject: [RHEL8/rhel qemu-kvm PATCH 15/25] block/mirror: conservative mirror_exit refactor
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Bugzilla: 1632939
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RH-Acked-by: Jeffrey Cody <jcody@redhat.com>
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RH-Acked-by: Max Reitz <mreitz@redhat.com>
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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For purposes of minimum code movement, refactor the mirror_exit
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callback to use the post-finalization callbacks in a trivial way.
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Signed-off-by: John Snow <jsnow@redhat.com>
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Message-id: 20180906130225.5118-7-jsnow@redhat.com
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Reviewed-by: Jeff Cody <jcody@redhat.com>
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Reviewed-by: Max Reitz <mreitz@redhat.com>
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[mreitz: Added comment for the mirror_exit() function]
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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(cherry picked from commit 737efc1eda23b904fbe0e66b37715fb0e5c3e58b)
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Signed-off-by: John Snow <jsnow@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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Conflicts:
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    block/mirror.c: context conflict on job properties
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---
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 block/mirror.c | 44 +++++++++++++++++++++++++++++++++-----------
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 1 file changed, 33 insertions(+), 11 deletions(-)
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diff --git a/block/mirror.c b/block/mirror.c
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index 057db7c..163b1d4 100644
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--- a/block/mirror.c
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+++ b/block/mirror.c
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@@ -71,6 +71,7 @@ typedef struct MirrorBlockJob {
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     int target_cluster_size;
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     int max_iov;
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     bool initial_zeroing_ongoing;
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+    bool prepared;
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 } MirrorBlockJob;
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 typedef struct MirrorOp {
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@@ -480,7 +481,12 @@ static void mirror_wait_for_all_io(MirrorBlockJob *s)
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     }
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 }
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-static void mirror_exit(Job *job)
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+/**
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+ * mirror_exit_common: handle both abort() and prepare() cases.
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+ * for .prepare, returns 0 on success and -errno on failure.
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+ * for .abort cases, denoted by abort = true, MUST return 0.
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+ */
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+static int mirror_exit_common(Job *job)
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 {
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     MirrorBlockJob *s = container_of(job, MirrorBlockJob, common.job);
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     BlockJob *bjob = &s->common;
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@@ -489,7 +495,13 @@ static void mirror_exit(Job *job)
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     BlockDriverState *target_bs = blk_bs(s->target);
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     BlockDriverState *mirror_top_bs = s->mirror_top_bs;
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     Error *local_err = NULL;
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-    int ret = job->ret;
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+    bool abort = job->ret < 0;
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+    int ret = 0;
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+
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+    if (s->prepared) {
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+        return 0;
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+    }
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+    s->prepared = true;
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     bdrv_release_dirty_bitmap(src, s->dirty_bitmap);
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@@ -514,7 +526,7 @@ static void mirror_exit(Job *job)
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      * required before it could become a backing file of target_bs. */
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     bdrv_child_try_set_perm(mirror_top_bs->backing, 0, BLK_PERM_ALL,
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                             &error_abort);
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-    if (ret == 0 && s->backing_mode == MIRROR_SOURCE_BACKING_CHAIN) {
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+    if (!abort && s->backing_mode == MIRROR_SOURCE_BACKING_CHAIN) {
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         BlockDriverState *backing = s->is_none_mode ? src : s->base;
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         if (backing_bs(target_bs) != backing) {
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             bdrv_set_backing_hd(target_bs, backing, &local_err);
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@@ -530,11 +542,8 @@ static void mirror_exit(Job *job)
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         aio_context_acquire(replace_aio_context);
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     }
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-    if (s->should_complete && ret == 0) {
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-        BlockDriverState *to_replace = src;
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-        if (s->to_replace) {
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-            to_replace = s->to_replace;
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-        }
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+    if (s->should_complete && !abort) {
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+        BlockDriverState *to_replace = s->to_replace ?: src;
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         if (bdrv_get_flags(target_bs) != bdrv_get_flags(to_replace)) {
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             bdrv_reopen(target_bs, bdrv_get_flags(to_replace), NULL);
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@@ -581,7 +590,18 @@ static void mirror_exit(Job *job)
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     bdrv_unref(mirror_top_bs);
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     bdrv_unref(src);
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-    job->ret = ret;
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+    return ret;
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+}
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+
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+static int mirror_prepare(Job *job)
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+{
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+    return mirror_exit_common(job);
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+}
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+
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+static void mirror_abort(Job *job)
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+{
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+    int ret = mirror_exit_common(job);
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+    assert(ret == 0);
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 }
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 static void mirror_throttle(MirrorBlockJob *s)
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@@ -986,7 +1006,8 @@ static const BlockJobDriver mirror_job_driver = {
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         .user_resume            = block_job_user_resume,
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         .drain                  = block_job_drain,
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         .run                    = mirror_run,
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-        .exit                   = mirror_exit,
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+        .prepare                = mirror_prepare,
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+        .abort                  = mirror_abort,
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         .pause                  = mirror_pause,
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         .complete               = mirror_complete,
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     },
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@@ -1002,7 +1023,8 @@ static const BlockJobDriver commit_active_job_driver = {
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         .user_resume            = block_job_user_resume,
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         .drain                  = block_job_drain,
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         .run                    = mirror_run,
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-        .exit                   = mirror_exit,
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+        .prepare                = mirror_prepare,
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+        .abort                  = mirror_abort,
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         .pause                  = mirror_pause,
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         .complete               = mirror_complete,
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     },
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-- 
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1.8.3.1
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