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[Qemu-devel] [RFC 4/5] block: Add AIO followers
From: |
Max Reitz |
Subject: |
[Qemu-devel] [RFC 4/5] block: Add AIO followers |
Date: |
Sat, 31 May 2014 20:43:11 +0200 |
If a long-running operation on a BDS wants to always remain in the same
AIO context, it somehow needs to keep track of the BDS changing its
context. This adds a function for registering callbacks on a BDS which
are called whenever the BDS is attached or detached from an AIO context.
Signed-off-by: Max Reitz <address@hidden>
---
block.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++
include/block/block_int.h | 40 ++++++++++++++++++++++++++++++++++
2 files changed, 95 insertions(+)
diff --git a/block.c b/block.c
index fe85d78..9c8dd5b 100644
--- a/block.c
+++ b/block.c
@@ -1775,6 +1775,8 @@ void bdrv_reopen_abort(BDRVReopenState *reopen_state)
void bdrv_close(BlockDriverState *bs)
{
+ BdrvAioFollower *baf, *baf_next;
+
if (bs->job) {
block_job_cancel_sync(bs->job);
}
@@ -1816,6 +1818,11 @@ void bdrv_close(BlockDriverState *bs)
if (bs->io_limits_enabled) {
bdrv_io_limits_disable(bs);
}
+
+ QLIST_FOREACH_SAFE(baf, &bs->aio_followers, list, baf_next) {
+ g_free(baf);
+ }
+ QLIST_INIT(&bs->aio_followers);
}
void bdrv_close_all(void)
@@ -5580,10 +5587,16 @@ AioContext *bdrv_get_aio_context(BlockDriverState *bs)
void bdrv_detach_aio_context(BlockDriverState *bs)
{
+ BdrvAioFollower *baf;
+
if (!bs->drv) {
return;
}
+ QLIST_FOREACH(baf, &bs->aio_followers, list) {
+ baf->aio_context_detached(baf->opaque);
+ }
+
if (bs->drv->bdrv_detach_aio_context) {
bs->drv->bdrv_detach_aio_context(bs);
}
@@ -5600,6 +5613,8 @@ void bdrv_detach_aio_context(BlockDriverState *bs)
void bdrv_attach_aio_context(BlockDriverState *bs,
AioContext *new_context)
{
+ BdrvAioFollower *baf;
+
if (!bs->drv) {
return;
}
@@ -5615,6 +5630,10 @@ void bdrv_attach_aio_context(BlockDriverState *bs,
if (bs->drv->bdrv_attach_aio_context) {
bs->drv->bdrv_attach_aio_context(bs, new_context);
}
+
+ QLIST_FOREACH(baf, &bs->aio_followers, list) {
+ baf->aio_context_attached(new_context, baf->opaque);
+ }
}
void bdrv_set_aio_context(BlockDriverState *bs, AioContext *new_context)
@@ -5631,6 +5650,42 @@ void bdrv_set_aio_context(BlockDriverState *bs,
AioContext *new_context)
aio_context_release(new_context);
}
+void bdrv_follow_aio(BlockDriverState *bs,
+ void (*aio_context_attached)(AioContext *new_context,
+ void *opaque),
+ void (*aio_context_detached)(void *opaque), void *opaque)
+{
+ BdrvAioFollower *baf = g_new(BdrvAioFollower, 1);
+ *baf = (BdrvAioFollower){
+ .aio_context_attached = aio_context_attached,
+ .aio_context_detached = aio_context_detached,
+ .opaque = opaque
+ };
+
+ QLIST_INSERT_HEAD(&bs->aio_followers, baf, list);
+}
+
+void bdrv_unfollow_aio(BlockDriverState *bs,
+ void (*aio_context_attached)(AioContext *, void *),
+ void (*aio_context_detached)(void *), void *opaque)
+{
+ BdrvAioFollower *baf, *baf_next;
+
+ QLIST_FOREACH_SAFE(baf, &bs->aio_followers, list, baf_next) {
+ if (baf->aio_context_attached == aio_context_attached &&
+ baf->aio_context_detached == aio_context_detached &&
+ baf->opaque == opaque)
+ {
+ QLIST_REMOVE(baf, list);
+ g_free(baf);
+
+ return;
+ }
+ }
+
+ abort();
+}
+
void bdrv_add_before_write_notifier(BlockDriverState *bs,
NotifierWithReturn *notifier)
{
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 7d156e3..aacc22f 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -283,6 +283,15 @@ typedef struct BlockLimits {
size_t opt_mem_alignment;
} BlockLimits;
+typedef struct BdrvAioFollower {
+ void (*aio_context_attached)(AioContext *new_context, void *opaque);
+ void (*aio_context_detached)(void *opaque);
+
+ void *opaque;
+
+ QLIST_ENTRY(BdrvAioFollower) list;
+} BdrvAioFollower;
+
/*
* Note: the function bdrv_append() copies and swaps contents of
* BlockDriverStates, so if you add new fields to this struct, please
@@ -309,6 +318,10 @@ struct BlockDriverState {
void *dev_opaque;
AioContext *aio_context; /* event loop used for fd handlers, timers, etc */
+ /* long-running tasks intended to always use the same AioContext as this
+ * BDS may register themselves in this list to be notified of changes
+ * regarding this BDS's context */
+ QLIST_HEAD(, BdrvAioFollower) aio_followers;
char filename[1024];
char backing_file[1024]; /* if non zero, the image is a diff of
@@ -425,6 +438,33 @@ void bdrv_detach_aio_context(BlockDriverState *bs);
void bdrv_attach_aio_context(BlockDriverState *bs,
AioContext *new_context);
+/**
+ * bdrv_follow_aio:
+ *
+ * If a long-running job intends to be always run in the same AioContext as a
+ * certain BDS, it may use this function to be notified of changes regarding
the
+ * association of the BDS to an AioContext.
+ *
+ * aio_context_attached() is called after the target BDS has been attached to a
+ * new AioContext; aio_context_detached() is called before the target BDS is
+ * being detached from its old AioContext.
+ */
+void bdrv_follow_aio(BlockDriverState *bs,
+ void (*aio_context_attached)(AioContext *new_context,
+ void *opaque),
+ void (*aio_context_detached)(void *opaque), void *opaque);
+
+/**
+ * bdrv_unfollow_aio:
+ *
+ * Unsubscribe of change notifications regarding the BDS's AioContext. The
+ * parameters given here have to be the same as those given to
+ * bdrv_follow_aio().
+ */
+void bdrv_unfollow_aio(BlockDriverState *bs,
+ void (*aio_context_attached)(AioContext *, void *),
+ void (*aio_context_detached)(void *), void *opaque);
+
#ifdef _WIN32
int is_windows_drive(const char *filename);
#endif
--
1.9.3
- [Qemu-devel] [RFC 0/5] nbd: Adapt for dataplane, Max Reitz, 2014/05/31
- [Qemu-devel] [RFC 1/5] nbd: Correct name comparison for export_set_name(), Max Reitz, 2014/05/31
- [Qemu-devel] [RFC 2/5] aio: Add io_read_poll() callback, Max Reitz, 2014/05/31
- [Qemu-devel] [RFC 3/5] nbd: Use aio_set_fd_handler2(), Max Reitz, 2014/05/31
- [Qemu-devel] [RFC 4/5] block: Add AIO followers,
Max Reitz <=
- [Qemu-devel] [RFC 5/5] nbd: Follow the BDS' AIO context, Max Reitz, 2014/05/31
- Re: [Qemu-devel] [RFC 0/5] nbd: Adapt for dataplane, Max Reitz, 2014/05/31