blkdebug: Implement suspend/resume of AIO requests

This allows more systematic AIO testing. The patch adds three new
operations to blkdebug:

 * Setting a "breakpoint" on a blkdebug event. The next request that
   triggers this breakpoint is suspended and is tagged with a name.
   The breakpoint is removed after a request has triggered it.

 * A suspended request (identified by it's tag) can be resumed

 * It's possible to check whether a suspended request with a given
   tag exists. This can be used for waiting for an event.

Ideally, we would instead tag requests right when they are created and
set breakpoints for individual requests. However, at this point the
block layer doesn't allow this easily, and breakpoints that trigger for
any request already allow a lot of useful testing.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 105 insertions, 3 deletions

diff --git a/block/blkdebug.c b/block/blkdebug.c
index 859792b647..294e983306 100644
--- a/block/blkdebug.c
+++ b/block/blkdebug.c
@@ -29,8 +29,10 @@
 typedef struct BDRVBlkdebugState {
     int state;
     int new_state;
+
     QLIST_HEAD(, BlkdebugRule) rules[BLKDBG_EVENT_MAX];
     QSIMPLEQ_HEAD(, BlkdebugRule) active_rules;
+    QLIST_HEAD(, BlkdebugSuspendedReq) suspended_reqs;
 } BDRVBlkdebugState;
 
 typedef struct BlkdebugAIOCB {
@@ -39,6 +41,12 @@ typedef struct BlkdebugAIOCB {
     int ret;
 } BlkdebugAIOCB;
 
+typedef struct BlkdebugSuspendedReq {
+    Coroutine *co;
+    char *tag;
+    QLIST_ENTRY(BlkdebugSuspendedReq) next;
+} BlkdebugSuspendedReq;
+
 static void blkdebug_aio_cancel(BlockDriverAIOCB *blockacb);
 
 static const AIOCBInfo blkdebug_aiocb_info = {
@@ -49,6 +57,7 @@ static const AIOCBInfo blkdebug_aiocb_info = {
 enum {
     ACTION_INJECT_ERROR,
     ACTION_SET_STATE,
+    ACTION_SUSPEND,
 };
 
 typedef struct BlkdebugRule {
@@ -65,6 +74,9 @@ typedef struct BlkdebugRule {
         struct {
             int new_state;
         } set_state;
+        struct {
+            char *tag;
+        } suspend;
     } options;
     QLIST_ENTRY(BlkdebugRule) next;
     QSIMPLEQ_ENTRY(BlkdebugRule) active_next;
@@ -226,6 +238,11 @@ static int add_rule(QemuOpts *opts, void *opaque)
         rule->options.set_state.new_state =
             qemu_opt_get_number(opts, "new_state", 0);
         break;
+
+    case ACTION_SUSPEND:
+        rule->options.suspend.tag =
+            g_strdup(qemu_opt_get(opts, "tag"));
+        break;
     };
 
     /* Add the rule */
@@ -240,6 +257,9 @@ static void remove_rule(BlkdebugRule *rule)
     case ACTION_INJECT_ERROR:
     case ACTION_SET_STATE:
         break;
+    case ACTION_SUSPEND:
+        g_free(rule->options.suspend.tag);
+        break;
     }
 
     QLIST_REMOVE(rule, next);
@@ -406,6 +426,7 @@ static BlockDriverAIOCB *blkdebug_aio_writev(BlockDriverState *bs,
     return bdrv_aio_writev(bs->file, sector_num, qiov, nb_sectors, cb, opaque);
 }
 
+
 static void blkdebug_close(BlockDriverState *bs)
 {
     BDRVBlkdebugState *s = bs->opaque;
@@ -419,6 +440,27 @@ static void blkdebug_close(BlockDriverState *bs)
     }
 }
 
+static void suspend_request(BlockDriverState *bs, BlkdebugRule *rule)
+{
+    BDRVBlkdebugState *s = bs->opaque;
+    BlkdebugSuspendedReq r;
+
+    r = (BlkdebugSuspendedReq) {
+        .co         = qemu_coroutine_self(),
+        .tag        = g_strdup(rule->options.suspend.tag),
+    };
+
+    remove_rule(rule);
+    QLIST_INSERT_HEAD(&s->suspended_reqs, &r, next);
+
+    printf("blkdebug: Suspended request '%s'\n", r.tag);
+    qemu_coroutine_yield();
+    printf("blkdebug: Resuming request '%s'\n", r.tag);
+
+    QLIST_REMOVE(&r, next);
+    g_free(r.tag);
+}
+
 static bool process_rule(BlockDriverState *bs, struct BlkdebugRule *rule,
     bool injected)
 {
@@ -442,6 +484,10 @@ static bool process_rule(BlockDriverState *bs, struct BlkdebugRule *rule,
     case ACTION_SET_STATE:
         s->new_state = rule->options.set_state.new_state;
         break;
+
+    case ACTION_SUSPEND:
+        suspend_request(bs, rule);
+        break;
     }
     return injected;
 }
@@ -449,19 +495,72 @@ static bool process_rule(BlockDriverState *bs, struct BlkdebugRule *rule,
 static void blkdebug_debug_event(BlockDriverState *bs, BlkDebugEvent event)
 {
     BDRVBlkdebugState *s = bs->opaque;
-    struct BlkdebugRule *rule;
+    struct BlkdebugRule *rule, *next;
     bool injected;
 
     assert((int)event >= 0 && event < BLKDBG_EVENT_MAX);
 
     injected = false;
     s->new_state = s->state;
-    QLIST_FOREACH(rule, &s->rules[event], next) {
+    QLIST_FOREACH_SAFE(rule, &s->rules[event], next, next) {
         injected = process_rule(bs, rule, injected);
     }
     s->state = s->new_state;
 }
 
+static int blkdebug_debug_breakpoint(BlockDriverState *bs, const char *event,
+                                     const char *tag)
+{
+    BDRVBlkdebugState *s = bs->opaque;
+    struct BlkdebugRule *rule;
+    BlkDebugEvent blkdebug_event;
+
+    if (get_event_by_name(event, &blkdebug_event) < 0) {
+        return -ENOENT;
+    }
+
+
+    rule = g_malloc(sizeof(*rule));
+    *rule = (struct BlkdebugRule) {
+        .event  = blkdebug_event,
+        .action = ACTION_SUSPEND,
+        .state  = 0,
+        .options.suspend.tag = g_strdup(tag),
+    };
+
+    QLIST_INSERT_HEAD(&s->rules[blkdebug_event], rule, next);
+
+    return 0;
+}
+
+static int blkdebug_debug_resume(BlockDriverState *bs, const char *tag)
+{
+    BDRVBlkdebugState *s = bs->opaque;
+    BlkdebugSuspendedReq *r;
+
+    QLIST_FOREACH(r, &s->suspended_reqs, next) {
+        if (!strcmp(r->tag, tag)) {
+            qemu_coroutine_enter(r->co, NULL);
+            return 0;
+        }
+    }
+    return -ENOENT;
+}
+
+
+static bool blkdebug_debug_is_suspended(BlockDriverState *bs, const char *tag)
+{
+    BDRVBlkdebugState *s = bs->opaque;
+    BlkdebugSuspendedReq *r;
+
+    QLIST_FOREACH(r, &s->suspended_reqs, next) {
+        if (!strcmp(r->tag, tag)) {
+            return true;
+        }
+    }
+    return false;
+}
+
 static int64_t blkdebug_getlength(BlockDriverState *bs)
 {
     return bdrv_getlength(bs->file);
@@ -480,7 +579,10 @@ static BlockDriver bdrv_blkdebug = {
     .bdrv_aio_readv     = blkdebug_aio_readv,
     .bdrv_aio_writev    = blkdebug_aio_writev,
 
-    .bdrv_debug_event   = blkdebug_debug_event,
+    .bdrv_debug_event           = blkdebug_debug_event,
+    .bdrv_debug_breakpoint      = blkdebug_debug_breakpoint,
+    .bdrv_debug_resume          = blkdebug_debug_resume,
+    .bdrv_debug_is_suspended    = blkdebug_debug_is_suspended,
 };
 
 static void bdrv_blkdebug_init(void)