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iscsi: fix races between task completion and abort
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This patch fixes two main issues with block/iscsi.c:

1) iscsi_task_mgmt_abort_task_async calls iscsi_scsi_task_cancel which
was also directly called in iscsi_aio_cancel

2) a race between task completion and task abortion could happen cause
the scsi_free_scsi_task were done before iscsi_schedule_bh has finished.
To fix this, all the freeing of IscsiTasks and releasing of the AIOCBs
is centralized in iscsi_bh_cb, independent of whether the SCSI command
has completed or was cancelled.

3) iscsi_aio_cancel was not synchronously waiting for the end of the
command.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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@bonzini
bonzini committed Aug 20, 2012
1 parent cfb3f50 commit 1bd075f
Showing 1 changed file with 30 additions and 29 deletions.
59 changes: 30 additions & 29 deletions block/iscsi.c
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Expand Up @@ -83,12 +83,20 @@ iscsi_bh_cb(void *p)
acb->common.cb(acb->common.opaque, acb->status);
}

if (acb->task != NULL) {
scsi_free_scsi_task(acb->task);
acb->task = NULL;
}

qemu_aio_release(acb);
}

static void
iscsi_schedule_bh(IscsiAIOCB *acb)
{
if (acb->bh) {
return;
}
acb->bh = qemu_bh_new(iscsi_bh_cb, acb);
qemu_bh_schedule(acb->bh);
}
Expand All @@ -98,6 +106,10 @@ static void
iscsi_abort_task_cb(struct iscsi_context *iscsi, int status, void *command_data,
void *private_data)
{
IscsiAIOCB *acb = private_data;

acb->status = -ECANCELED;
iscsi_schedule_bh(acb);
}

static void
Expand All @@ -106,15 +118,19 @@ iscsi_aio_cancel(BlockDriverAIOCB *blockacb)
IscsiAIOCB *acb = (IscsiAIOCB *)blockacb;
IscsiLun *iscsilun = acb->iscsilun;

acb->common.cb(acb->common.opaque, -ECANCELED);
if (acb->status != -EINPROGRESS) {
return;
}

acb->canceled = 1;

/* send a task mgmt call to the target to cancel the task on the target */
iscsi_task_mgmt_abort_task_async(iscsilun->iscsi, acb->task,
iscsi_abort_task_cb, NULL);
iscsi_abort_task_cb, acb);

/* then also cancel the task locally in libiscsi */
iscsi_scsi_task_cancel(iscsilun->iscsi, acb->task);
while (acb->status == -EINPROGRESS) {
qemu_aio_wait();
}
}

static AIOPool iscsi_aio_pool = {
Expand Down Expand Up @@ -192,9 +208,6 @@ iscsi_aio_write16_cb(struct iscsi_context *iscsi, int status,
g_free(acb->buf);

if (acb->canceled != 0) {
qemu_aio_release(acb);
scsi_free_scsi_task(acb->task);
acb->task = NULL;
return;
}

Expand All @@ -206,8 +219,6 @@ iscsi_aio_write16_cb(struct iscsi_context *iscsi, int status,
}

iscsi_schedule_bh(acb);
scsi_free_scsi_task(acb->task);
acb->task = NULL;
}

static int64_t sector_qemu2lun(int64_t sector, IscsiLun *iscsilun)
Expand Down Expand Up @@ -236,6 +247,8 @@ iscsi_aio_writev(BlockDriverState *bs, int64_t sector_num,
acb->qiov = qiov;

acb->canceled = 0;
acb->bh = NULL;
acb->status = -EINPROGRESS;

/* XXX we should pass the iovec to write16 to avoid the extra copy */
/* this will allow us to get rid of 'buf' completely */
Expand Down Expand Up @@ -293,9 +306,6 @@ iscsi_aio_read16_cb(struct iscsi_context *iscsi, int status,
trace_iscsi_aio_read16_cb(iscsi, status, acb, acb->canceled);

if (acb->canceled != 0) {
qemu_aio_release(acb);
scsi_free_scsi_task(acb->task);
acb->task = NULL;
return;
}

Expand All @@ -307,8 +317,6 @@ iscsi_aio_read16_cb(struct iscsi_context *iscsi, int status,
}

iscsi_schedule_bh(acb);
scsi_free_scsi_task(acb->task);
acb->task = NULL;
}

static BlockDriverAIOCB *
Expand All @@ -334,6 +342,8 @@ iscsi_aio_readv(BlockDriverState *bs, int64_t sector_num,
acb->qiov = qiov;

acb->canceled = 0;
acb->bh = NULL;
acb->status = -EINPROGRESS;
acb->read_size = qemu_read_size;
acb->buf = NULL;

Expand Down Expand Up @@ -409,9 +419,6 @@ iscsi_synccache10_cb(struct iscsi_context *iscsi, int status,
IscsiAIOCB *acb = opaque;

if (acb->canceled != 0) {
qemu_aio_release(acb);
scsi_free_scsi_task(acb->task);
acb->task = NULL;
return;
}

Expand All @@ -423,8 +430,6 @@ iscsi_synccache10_cb(struct iscsi_context *iscsi, int status,
}

iscsi_schedule_bh(acb);
scsi_free_scsi_task(acb->task);
acb->task = NULL;
}

static BlockDriverAIOCB *
Expand All @@ -439,6 +444,8 @@ iscsi_aio_flush(BlockDriverState *bs,

acb->iscsilun = iscsilun;
acb->canceled = 0;
acb->bh = NULL;
acb->status = -EINPROGRESS;

acb->task = iscsi_synchronizecache10_task(iscsi, iscsilun->lun,
0, 0, 0, 0,
Expand All @@ -463,9 +470,6 @@ iscsi_unmap_cb(struct iscsi_context *iscsi, int status,
IscsiAIOCB *acb = opaque;

if (acb->canceled != 0) {
qemu_aio_release(acb);
scsi_free_scsi_task(acb->task);
acb->task = NULL;
return;
}

Expand All @@ -477,8 +481,6 @@ iscsi_unmap_cb(struct iscsi_context *iscsi, int status,
}

iscsi_schedule_bh(acb);
scsi_free_scsi_task(acb->task);
acb->task = NULL;
}

static BlockDriverAIOCB *
Expand All @@ -495,6 +497,8 @@ iscsi_aio_discard(BlockDriverState *bs,

acb->iscsilun = iscsilun;
acb->canceled = 0;
acb->bh = NULL;
acb->status = -EINPROGRESS;

list[0].lba = sector_qemu2lun(sector_num, iscsilun);
list[0].num = nb_sectors * BDRV_SECTOR_SIZE / iscsilun->block_size;
Expand Down Expand Up @@ -523,9 +527,6 @@ iscsi_aio_ioctl_cb(struct iscsi_context *iscsi, int status,
IscsiAIOCB *acb = opaque;

if (acb->canceled != 0) {
qemu_aio_release(acb);
scsi_free_scsi_task(acb->task);
acb->task = NULL;
return;
}

Expand Down Expand Up @@ -554,8 +555,6 @@ iscsi_aio_ioctl_cb(struct iscsi_context *iscsi, int status,
}

iscsi_schedule_bh(acb);
scsi_free_scsi_task(acb->task);
acb->task = NULL;
}

static BlockDriverAIOCB *iscsi_aio_ioctl(BlockDriverState *bs,
Expand All @@ -573,6 +572,8 @@ static BlockDriverAIOCB *iscsi_aio_ioctl(BlockDriverState *bs,

acb->iscsilun = iscsilun;
acb->canceled = 0;
acb->bh = NULL;
acb->status = -EINPROGRESS;
acb->buf = NULL;
acb->ioh = buf;

Expand Down

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