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[Qemu-block] [PATCH] blockdev: avoid acquiring AioContext lock twice at
From: |
Sergio Lopez |
Subject: |
[Qemu-block] [PATCH] blockdev: avoid acquiring AioContext lock twice at do_drive_backup() |
Date: |
Thu, 12 Sep 2019 18:16:25 +0200 |
do_drive_backup() acquires the AioContext lock of the corresponding
BlockDriverState. This is not a problem when it's called from
qmp_drive_backup(), but drive_backup_prepare() also acquires the lock
before calling it.
This change adds a BlockDriverState argument to do_drive_backup(),
which is used to signal that the context lock is already acquired and
to save a couple of redundant calls.
Signed-off-by: Sergio Lopez <address@hidden>
---
blockdev.c | 54 ++++++++++++++++++++++++++++++++++++++----------------
1 file changed, 38 insertions(+), 16 deletions(-)
diff --git a/blockdev.c b/blockdev.c
index fbef6845c8..0cc6c69ceb 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1762,8 +1762,10 @@ typedef struct DriveBackupState {
BlockJob *job;
} DriveBackupState;
-static BlockJob *do_drive_backup(DriveBackup *backup, JobTxn *txn,
- Error **errp);
+static BlockJob *do_drive_backup(DriveBackup *backup,
+ BlockDriverState *backup_bs,
+ JobTxn *txn,
+ Error **errp);
static void drive_backup_prepare(BlkActionState *common, Error **errp)
{
@@ -1781,6 +1783,11 @@ static void drive_backup_prepare(BlkActionState *common,
Error **errp)
return;
}
+ if (!bs->drv) {
+ error_setg(errp, "Device has no medium");
+ return;
+ }
+
aio_context = bdrv_get_aio_context(bs);
aio_context_acquire(aio_context);
@@ -1789,7 +1796,9 @@ static void drive_backup_prepare(BlkActionState *common,
Error **errp)
state->bs = bs;
- state->job = do_drive_backup(backup, common->block_job_txn, &local_err);
+ state->job = do_drive_backup(backup, bs,
+ common->block_job_txn,
+ &local_err);
if (local_err) {
error_propagate(errp, local_err);
goto out;
@@ -3607,7 +3616,9 @@ static BlockJob *do_backup_common(BackupCommon *backup,
return job;
}
-static BlockJob *do_drive_backup(DriveBackup *backup, JobTxn *txn,
+static BlockJob *do_drive_backup(DriveBackup *backup,
+ BlockDriverState *backup_bs,
+ JobTxn *txn,
Error **errp)
{
BlockDriverState *bs;
@@ -3625,18 +3636,27 @@ static BlockJob *do_drive_backup(DriveBackup *backup,
JobTxn *txn,
backup->mode = NEW_IMAGE_MODE_ABSOLUTE_PATHS;
}
- bs = bdrv_lookup_bs(backup->device, backup->device, errp);
- if (!bs) {
- return NULL;
- }
+ if (backup_bs) {
+ bs = backup_bs;
+ /*
+ * If the caller passes us a BDS, we assume it has already
+ * acquired the context lock.
+ */
+ aio_context = bdrv_get_aio_context(bs);
+ } else {
+ bs = bdrv_lookup_bs(backup->device, backup->device, errp);
+ if (!bs) {
+ return NULL;
+ }
- if (!bs->drv) {
- error_setg(errp, "Device has no medium");
- return NULL;
- }
+ if (!bs->drv) {
+ error_setg(errp, "Device has no medium");
+ return NULL;
+ }
- aio_context = bdrv_get_aio_context(bs);
- aio_context_acquire(aio_context);
+ aio_context = bdrv_get_aio_context(bs);
+ aio_context_acquire(aio_context);
+ }
if (!backup->has_format) {
backup->format = backup->mode == NEW_IMAGE_MODE_EXISTING ?
@@ -3713,7 +3733,9 @@ static BlockJob *do_drive_backup(DriveBackup *backup,
JobTxn *txn,
unref:
bdrv_unref(target_bs);
out:
- aio_context_release(aio_context);
+ if (!backup_bs) {
+ aio_context_release(aio_context);
+ }
return job;
}
@@ -3721,7 +3743,7 @@ void qmp_drive_backup(DriveBackup *arg, Error **errp)
{
BlockJob *job;
- job = do_drive_backup(arg, NULL, errp);
+ job = do_drive_backup(arg, NULL, NULL, errp);
if (job) {
job_start(&job->job);
}
--
2.21.0
- [Qemu-block] [PATCH] blockdev: avoid acquiring AioContext lock twice at do_drive_backup(),
Sergio Lopez <=