Patchwork [PATCHv6] rbd block driver fix race between aio completition and aio cancel

login
register
mail settings
Submitter Stefan Priebe - Profihost AG
Date Nov. 30, 2012, 8:55 a.m.
Message ID <1354265746-8390-1-git-send-email-s.priebe@profihost.ag>
Download mbox | patch
Permalink /patch/202891/
State New
Headers show

Comments

Stefan Priebe - Profihost AG - Nov. 30, 2012, 8:55 a.m.
This one fixes a race which qemu had also in iscsi block driver
between cancellation and io completition.

qemu_rbd_aio_cancel was not synchronously waiting for the end of
the command.

To archieve this it introduces a new status flag which uses
-EINPROGRESS.

Changes since PATCHv5:
- qemu_aio_release has to be done in qemu_rbd_aio_cancel if I/O
  was cancelled

Changes since PATCHv4:
- removed unnecessary qemu_vfree of acb->bounce as BH will always
  run

Changes since PATCHv3:
- removed unnecessary if condition in rbd_start_aio as we
  haven't start io yet
- moved acb->status = 0 to rbd_aio_bh_cb so qemu_aio_wait always
  waits until BH was executed

Changes since PATCHv2:
- fixed missing braces
- added vfree for bounce

Signed-off-by: Stefan Priebe <s.priebe@profihost.ag>

---
 block/rbd.c |   20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)
Stefan Hajnoczi - Nov. 30, 2012, 1:50 p.m.
On Fri, Nov 30, 2012 at 9:55 AM, Stefan Priebe <s.priebe@profihost.ag> wrote:
> This one fixes a race which qemu had also in iscsi block driver
> between cancellation and io completition.
>
> qemu_rbd_aio_cancel was not synchronously waiting for the end of
> the command.
>
> To archieve this it introduces a new status flag which uses
> -EINPROGRESS.
>
> Changes since PATCHv5:
> - qemu_aio_release has to be done in qemu_rbd_aio_cancel if I/O
>   was cancelled
>
> Changes since PATCHv4:
> - removed unnecessary qemu_vfree of acb->bounce as BH will always
>   run
>
> Changes since PATCHv3:
> - removed unnecessary if condition in rbd_start_aio as we
>   haven't start io yet
> - moved acb->status = 0 to rbd_aio_bh_cb so qemu_aio_wait always
>   waits until BH was executed
>
> Changes since PATCHv2:
> - fixed missing braces
> - added vfree for bounce
>
> Signed-off-by: Stefan Priebe <s.priebe@profihost.ag>
>
> ---
>  block/rbd.c |   20 ++++++++++++--------
>  1 file changed, 12 insertions(+), 8 deletions(-)

Reviewed-by: Stefan Hajnoczi <stefanha@gmail.com>
Kevin Wolf - Dec. 10, 2012, 1:09 p.m.
Am 30.11.2012 14:50, schrieb Stefan Hajnoczi:
> On Fri, Nov 30, 2012 at 9:55 AM, Stefan Priebe <s.priebe@profihost.ag> wrote:
>> This one fixes a race which qemu had also in iscsi block driver
>> between cancellation and io completition.
>>
>> qemu_rbd_aio_cancel was not synchronously waiting for the end of
>> the command.
>>
>> To archieve this it introduces a new status flag which uses
>> -EINPROGRESS.
>>
>> Changes since PATCHv5:
>> - qemu_aio_release has to be done in qemu_rbd_aio_cancel if I/O
>>   was cancelled
>>
>> Changes since PATCHv4:
>> - removed unnecessary qemu_vfree of acb->bounce as BH will always
>>   run
>>
>> Changes since PATCHv3:
>> - removed unnecessary if condition in rbd_start_aio as we
>>   haven't start io yet
>> - moved acb->status = 0 to rbd_aio_bh_cb so qemu_aio_wait always
>>   waits until BH was executed
>>
>> Changes since PATCHv2:
>> - fixed missing braces
>> - added vfree for bounce
>>
>> Signed-off-by: Stefan Priebe <s.priebe@profihost.ag>
>>
>> ---
>>  block/rbd.c |   20 ++++++++++++--------
>>  1 file changed, 12 insertions(+), 8 deletions(-)
> 
> Reviewed-by: Stefan Hajnoczi <stefanha@gmail.com>

Thanks, applied to the block branch.

For future patches, please put a "---" line between the real commit
message (including the SoB, of course) and the changelog so that git am
automatically removes the changelog.

Kevin

Patch

diff --git a/block/rbd.c b/block/rbd.c
index f3becc7..737bab1 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -77,6 +77,7 @@  typedef struct RBDAIOCB {
     int error;
     struct BDRVRBDState *s;
     int cancelled;
+    int status;
 } RBDAIOCB;
 
 typedef struct RADOSCB {
@@ -376,12 +377,6 @@  static void qemu_rbd_complete_aio(RADOSCB *rcb)
     RBDAIOCB *acb = rcb->acb;
     int64_t r;
 
-    if (acb->cancelled) {
-        qemu_vfree(acb->bounce);
-        qemu_aio_release(acb);
-        goto done;
-    }
-
     r = rcb->ret;
 
     if (acb->cmd == RBD_AIO_WRITE ||
@@ -409,7 +404,6 @@  static void qemu_rbd_complete_aio(RADOSCB *rcb)
     /* Note that acb->bh can be NULL in case where the aio was cancelled */
     acb->bh = qemu_bh_new(rbd_aio_bh_cb, acb);
     qemu_bh_schedule(acb->bh);
-done:
     g_free(rcb);
 }
 
@@ -568,6 +562,12 @@  static void qemu_rbd_aio_cancel(BlockDriverAIOCB *blockacb)
 {
     RBDAIOCB *acb = (RBDAIOCB *) blockacb;
     acb->cancelled = 1;
+
+    while (acb->status == -EINPROGRESS) {
+        qemu_aio_wait();
+    }
+
+    qemu_aio_release(acb);
 }
 
 static const AIOCBInfo rbd_aiocb_info = {
@@ -639,8 +639,11 @@  static void rbd_aio_bh_cb(void *opaque)
     acb->common.cb(acb->common.opaque, (acb->ret > 0 ? 0 : acb->ret));
     qemu_bh_delete(acb->bh);
     acb->bh = NULL;
+    acb->status = 0;
 
-    qemu_aio_release(acb);
+    if (!acb->cancelled) {
+        qemu_aio_release(acb);
+    }
 }
 
 static int rbd_aio_discard_wrapper(rbd_image_t image,
@@ -685,6 +688,7 @@  static BlockDriverAIOCB *rbd_start_aio(BlockDriverState *bs,
     acb->s = s;
     acb->cancelled = 0;
     acb->bh = NULL;
+    acb->status = -EINPROGRESS;
 
     if (cmd == RBD_AIO_WRITE) {
         qemu_iovec_to_buf(acb->qiov, 0, acb->bounce, qiov->size);