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[PULL 16/37] nbd/server: Simplify export shutdown
From: |
Kevin Wolf |
Subject: |
[PULL 16/37] nbd/server: Simplify export shutdown |
Date: |
Fri, 2 Oct 2020 16:43:24 +0200 |
Closing export is somewhat convoluted because nbd_export_close() and
nbd_export_put() call each other and the ways they actually end up being
nested is not necessarily obvious.
However, it is not really necessary to call nbd_export_close() from
nbd_export_put() when putting the last reference because it only does
three things:
1. Close all clients. We're going to refcount 0 and all clients hold a
reference, so we know there is no active client any more.
2. Close the user reference (represented by exp->name being non-NULL).
The same argument applies: If the export were still named, we would
still have a reference.
3. Freeing exp->description. This is really cleanup work to be done when
the export is finally freed. There is no reason to already clear it
while clients are still in the process of shutting down.
So after moving the cleanup of exp->description, the code can be
simplified so that only nbd_export_close() calls nbd_export_put(), but
never the other way around.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200924152717.287415-13-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
nbd/server.c | 17 ++++-------------
1 file changed, 4 insertions(+), 13 deletions(-)
diff --git a/nbd/server.c b/nbd/server.c
index 1cc915f01d..fb70374df5 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -1678,8 +1678,6 @@ void nbd_export_close(NBDExport *exp)
QTAILQ_REMOVE(&exports, exp, next);
QTAILQ_INSERT_TAIL(&closed_exports, exp, next);
}
- g_free(exp->description);
- exp->description = NULL;
nbd_export_put(exp);
}
@@ -1706,19 +1704,12 @@ void nbd_export_get(NBDExport *exp)
void nbd_export_put(NBDExport *exp)
{
assert(exp->refcount > 0);
- if (exp->refcount == 1) {
- nbd_export_close(exp);
- }
-
- /* nbd_export_close() may theoretically reduce refcount to 0. It may happen
- * if someone calls nbd_export_put() on named export not through
- * nbd_export_set_name() when refcount is 1. So, let's assert that
- * it is > 0.
- */
- assert(exp->refcount > 0);
if (--exp->refcount == 0) {
assert(exp->name == NULL);
- assert(exp->description == NULL);
+ assert(QTAILQ_EMPTY(&exp->clients));
+
+ g_free(exp->description);
+ exp->description = NULL;
if (exp->blk) {
if (exp->eject_notifier_blk) {
--
2.25.4
- [PULL 03/37] docs: Document the throttle block filter, (continued)
- [PULL 03/37] docs: Document the throttle block filter, Kevin Wolf, 2020/10/02
- [PULL 05/37] nbd: Remove unused nbd_export_get_blockdev(), Kevin Wolf, 2020/10/02
- [PULL 08/37] block/export: Add BlockExport infrastructure and block-export-add, Kevin Wolf, 2020/10/02
- [PULL 06/37] qapi: Create block-export module, Kevin Wolf, 2020/10/02
- [PULL 09/37] qemu-storage-daemon: Use qmp_block_export_add(), Kevin Wolf, 2020/10/02
- [PULL 07/37] qapi: Rename BlockExport to BlockExportOptions, Kevin Wolf, 2020/10/02
- [PULL 11/37] block/export: Remove magic from block-export-add, Kevin Wolf, 2020/10/02
- [PULL 10/37] qemu-nbd: Use raw block driver for --offset, Kevin Wolf, 2020/10/02
- [PULL 12/37] nbd: Add max-connections to nbd-server-start, Kevin Wolf, 2020/10/02
- [PULL 13/37] nbd: Add writethrough to block-export-add, Kevin Wolf, 2020/10/02
- [PULL 16/37] nbd/server: Simplify export shutdown,
Kevin Wolf <=
- [PULL 14/37] nbd: Remove NBDExport.close callback, Kevin Wolf, 2020/10/02
- [PULL 17/37] block/export: Move refcount from NBDExport to BlockExport, Kevin Wolf, 2020/10/02
- [PULL 15/37] qemu-nbd: Use blk_exp_add() to create the export, Kevin Wolf, 2020/10/02
- [PULL 18/37] block/export: Move AioContext from NBDExport to BlockExport, Kevin Wolf, 2020/10/02
- [PULL 19/37] block/export: Add node-name to BlockExportOptions, Kevin Wolf, 2020/10/02
- [PULL 21/37] block/export: Add blk_exp_close_all(_type), Kevin Wolf, 2020/10/02
- [PULL 20/37] block/export: Allocate BlockExport in blk_exp_add(), Kevin Wolf, 2020/10/02
- [PULL 22/37] block/export: Add 'id' option to block-export-add, Kevin Wolf, 2020/10/02
- [PULL 24/37] block/export: Add block-export-del, Kevin Wolf, 2020/10/02
- [PULL 23/37] block/export: Move strong user reference to block_exports, Kevin Wolf, 2020/10/02