[Qemu-devel] [PATCH 04/21] block/commit: utilize job_exit shim

John Snow posted 21 patches 7 years, 2 months ago
[Qemu-devel] [PATCH 04/21] block/commit: utilize job_exit shim
Posted by John Snow 7 years, 2 months ago
Change the manual deferment to commit_complete into the implicit
callback to job_exit.

Signed-off-by: John Snow <jsnow@redhat.com>
---
 block/commit.c | 19 +++++--------------
 1 file changed, 5 insertions(+), 14 deletions(-)

diff --git a/block/commit.c b/block/commit.c
index 620666161b..5bed098d5f 100644
--- a/block/commit.c
+++ b/block/commit.c
@@ -68,19 +68,14 @@ static int coroutine_fn commit_populate(BlockBackend *bs, BlockBackend *base,
     return 0;
 }
 
-typedef struct {
-    int ret;
-} CommitCompleteData;
-
-static void commit_complete(Job *job, void *opaque)
+static void commit_exit(Job *job)
 {
     CommitBlockJob *s = container_of(job, CommitBlockJob, common.job);
     BlockJob *bjob = &s->common;
-    CommitCompleteData *data = opaque;
     BlockDriverState *top = blk_bs(s->top);
     BlockDriverState *base = blk_bs(s->base);
     BlockDriverState *commit_top_bs = s->commit_top_bs;
-    int ret = data->ret;
+    int ret = job->ret;
     bool remove_commit_top_bs = false;
 
     /* Make sure commit_top_bs and top stay around until bdrv_replace_node() */
@@ -117,9 +112,6 @@ static void commit_complete(Job *job, void *opaque)
      * bdrv_set_backing_hd() to fail. */
     block_job_remove_all_bdrv(bjob);
 
-    job_completed(job, ret);
-    g_free(data);
-
     /* If bdrv_drop_intermediate() didn't already do that, remove the commit
      * filter driver from the backing chain. Do this as the final step so that
      * the 'consistent read' permission can be granted.  */
@@ -132,12 +124,12 @@ static void commit_complete(Job *job, void *opaque)
 
     bdrv_unref(commit_top_bs);
     bdrv_unref(top);
+    job->ret = ret;
 }
 
 static void coroutine_fn commit_run(void *opaque)
 {
     CommitBlockJob *s = opaque;
-    CommitCompleteData *data;
     int64_t offset;
     uint64_t delay_ns = 0;
     int ret = 0;
@@ -210,9 +202,7 @@ static void coroutine_fn commit_run(void *opaque)
 out:
     qemu_vfree(buf);
 
-    data = g_malloc(sizeof(*data));
-    data->ret = ret;
-    job_defer_to_main_loop(&s->common.job, commit_complete, data);
+    s->common.job.ret = ret;
 }
 
 static const BlockJobDriver commit_job_driver = {
@@ -223,6 +213,7 @@ static const BlockJobDriver commit_job_driver = {
         .user_resume   = block_job_user_resume,
         .drain         = block_job_drain,
         .start         = commit_run,
+        .exit          = commit_exit,
     },
 };
 
-- 
2.14.4


Re: [Qemu-devel] [PATCH 04/21] block/commit: utilize job_exit shim
Posted by Jeff Cody 7 years, 2 months ago
On Tue, Aug 07, 2018 at 12:33:32AM -0400, John Snow wrote:
> Change the manual deferment to commit_complete into the implicit
> callback to job_exit.
> 
> Signed-off-by: John Snow <jsnow@redhat.com>
> ---
>  block/commit.c | 19 +++++--------------
>  1 file changed, 5 insertions(+), 14 deletions(-)
> 
> diff --git a/block/commit.c b/block/commit.c
> index 620666161b..5bed098d5f 100644
> --- a/block/commit.c
> +++ b/block/commit.c
> @@ -68,19 +68,14 @@ static int coroutine_fn commit_populate(BlockBackend *bs, BlockBackend *base,
>      return 0;
>  }
>  
> -typedef struct {
> -    int ret;
> -} CommitCompleteData;
> -
> -static void commit_complete(Job *job, void *opaque)
> +static void commit_exit(Job *job)
>  {
>      CommitBlockJob *s = container_of(job, CommitBlockJob, common.job);
>      BlockJob *bjob = &s->common;
> -    CommitCompleteData *data = opaque;
>      BlockDriverState *top = blk_bs(s->top);
>      BlockDriverState *base = blk_bs(s->base);
>      BlockDriverState *commit_top_bs = s->commit_top_bs;
> -    int ret = data->ret;
> +    int ret = job->ret;
>      bool remove_commit_top_bs = false;
>  
>      /* Make sure commit_top_bs and top stay around until bdrv_replace_node() */

Since 'ret' is only assigned to 'job->ret' outside of this line, we could
drop the local 'ret' and assign job->ret to the output of
brdrv_drop_intermediate() in this code below:

    if (!job_is_cancelled(job) && ret == 0) {
        /* success */
        ret = bdrv_drop_intermediate(s->commit_top_bs, base,
                                     s->backing_file_str);
    }

> @@ -117,9 +112,6 @@ static void commit_complete(Job *job, void *opaque)
>       * bdrv_set_backing_hd() to fail. */
>      block_job_remove_all_bdrv(bjob);
>  
> -    job_completed(job, ret);
> -    g_free(data);
> -
>      /* If bdrv_drop_intermediate() didn't already do that, remove the commit
>       * filter driver from the backing chain. Do this as the final step so that
>       * the 'consistent read' permission can be granted.  */
> @@ -132,12 +124,12 @@ static void commit_complete(Job *job, void *opaque)
>  
>      bdrv_unref(commit_top_bs);
>      bdrv_unref(top);
> +    job->ret = ret;

We could then drop this line as well.

(This may fall under bike shedding, so I don't feel strongly about it):

Reviewed-by: Jeff Cody <jcody@redhat.com>

>  }
>  
>  static void coroutine_fn commit_run(void *opaque)
>  {
>      CommitBlockJob *s = opaque;
> -    CommitCompleteData *data;
>      int64_t offset;
>      uint64_t delay_ns = 0;
>      int ret = 0;
> @@ -210,9 +202,7 @@ static void coroutine_fn commit_run(void *opaque)
>  out:
>      qemu_vfree(buf);
>  
> -    data = g_malloc(sizeof(*data));
> -    data->ret = ret;
> -    job_defer_to_main_loop(&s->common.job, commit_complete, data);
> +    s->common.job.ret = ret;
>  }
>  
>  static const BlockJobDriver commit_job_driver = {
> @@ -223,6 +213,7 @@ static const BlockJobDriver commit_job_driver = {
>          .user_resume   = block_job_user_resume,
>          .drain         = block_job_drain,
>          .start         = commit_run,
> +        .exit          = commit_exit,
>      },
>  };
>  
> -- 
> 2.14.4
> 

Re: [Qemu-devel] [PATCH 04/21] block/commit: utilize job_exit shim
Posted by John Snow 7 years, 2 months ago

On 08/07/2018 11:41 PM, Jeff Cody wrote:
> On Tue, Aug 07, 2018 at 12:33:32AM -0400, John Snow wrote:
>> Change the manual deferment to commit_complete into the implicit
>> callback to job_exit.
>>
>> Signed-off-by: John Snow <jsnow@redhat.com>
>> ---
>>  block/commit.c | 19 +++++--------------
>>  1 file changed, 5 insertions(+), 14 deletions(-)
>>
>> diff --git a/block/commit.c b/block/commit.c
>> index 620666161b..5bed098d5f 100644
>> --- a/block/commit.c
>> +++ b/block/commit.c
>> @@ -68,19 +68,14 @@ static int coroutine_fn commit_populate(BlockBackend *bs, BlockBackend *base,
>>      return 0;
>>  }
>>  
>> -typedef struct {
>> -    int ret;
>> -} CommitCompleteData;
>> -
>> -static void commit_complete(Job *job, void *opaque)
>> +static void commit_exit(Job *job)
>>  {
>>      CommitBlockJob *s = container_of(job, CommitBlockJob, common.job);
>>      BlockJob *bjob = &s->common;
>> -    CommitCompleteData *data = opaque;
>>      BlockDriverState *top = blk_bs(s->top);
>>      BlockDriverState *base = blk_bs(s->base);
>>      BlockDriverState *commit_top_bs = s->commit_top_bs;
>> -    int ret = data->ret;
>> +    int ret = job->ret;
>>      bool remove_commit_top_bs = false;
>>  
>>      /* Make sure commit_top_bs and top stay around until bdrv_replace_node() */
> 
> Since 'ret' is only assigned to 'job->ret' outside of this line, we could
> drop the local 'ret' and assign job->ret to the output of
> brdrv_drop_intermediate() in this code below:
> 
>     if (!job_is_cancelled(job) && ret == 0) {
>         /* success */
>         ret = bdrv_drop_intermediate(s->commit_top_bs, base,
>                                      s->backing_file_str);
>     }
> 
>> @@ -117,9 +112,6 @@ static void commit_complete(Job *job, void *opaque)
>>       * bdrv_set_backing_hd() to fail. */
>>      block_job_remove_all_bdrv(bjob);
>>  
>> -    job_completed(job, ret);
>> -    g_free(data);
>> -
>>      /* If bdrv_drop_intermediate() didn't already do that, remove the commit
>>       * filter driver from the backing chain. Do this as the final step so that
>>       * the 'consistent read' permission can be granted.  */
>> @@ -132,12 +124,12 @@ static void commit_complete(Job *job, void *opaque)
>>  
>>      bdrv_unref(commit_top_bs);
>>      bdrv_unref(top);
>> +    job->ret = ret;
> 
> We could then drop this line as well.
> 
> (This may fall under bike shedding, so I don't feel strongly about it):

You're right; though most of it gets blown out of the water in #16
anyway, so it doesn't stay a problem for long.

--js

> 
> Reviewed-by: Jeff Cody <jcody@redhat.com>
> 

Thanks!

>>  }
>>  
>>  static void coroutine_fn commit_run(void *opaque)
>>  {
>>      CommitBlockJob *s = opaque;
>> -    CommitCompleteData *data;
>>      int64_t offset;
>>      uint64_t delay_ns = 0;
>>      int ret = 0;
>> @@ -210,9 +202,7 @@ static void coroutine_fn commit_run(void *opaque)
>>  out:
>>      qemu_vfree(buf);
>>  
>> -    data = g_malloc(sizeof(*data));
>> -    data->ret = ret;
>> -    job_defer_to_main_loop(&s->common.job, commit_complete, data);
>> +    s->common.job.ret = ret;
>>  }
>>  
>>  static const BlockJobDriver commit_job_driver = {
>> @@ -223,6 +213,7 @@ static const BlockJobDriver commit_job_driver = {
>>          .user_resume   = block_job_user_resume,
>>          .drain         = block_job_drain,
>>          .start         = commit_run,
>> +        .exit          = commit_exit,
>>      },
>>  };
>>  
>> -- 
>> 2.14.4
>>



Re: [Qemu-devel] [PATCH 04/21] block/commit: utilize job_exit shim
Posted by Kevin Wolf 7 years, 2 months ago
Am 07.08.2018 um 06:33 hat John Snow geschrieben:
> Change the manual deferment to commit_complete into the implicit
> callback to job_exit.
> 
> Signed-off-by: John Snow <jsnow@redhat.com>

There is one tricky thing in this patch that the commit message could be
a bit more explicit about, which is moving job_completed() to a later
point.

This is the code that happens between the old call of job_completed()
and the new one:

    /* If bdrv_drop_intermediate() didn't already do that, remove the commit
     * filter driver from the backing chain. Do this as the final step so that
     * the 'consistent read' permission can be granted.  */
    if (remove_commit_top_bs) {
        bdrv_child_try_set_perm(commit_top_bs->backing, 0, BLK_PERM_ALL,
                                &error_abort);
        bdrv_replace_node(commit_top_bs, backing_bs(commit_top_bs),
                          &error_abort);
    }

    bdrv_unref(commit_top_bs);
    bdrv_unref(top);

As the comment states, bdrv_replace_node() requires that the permission
restrictions that the commit job made are already lifted. The most
important part is done by the explicit block_job_remove_all_bdrv() call
right before this hunk. It still leaves bjob->blk around, which could
have implications, but luckily we didn't take any permissions for that
one:

    s = block_job_create(job_id, &commit_job_driver, NULL, bs, 0, BLK_PERM_ALL,
                         speed, JOB_DEFAULT, NULL, NULL, errp);

So I think we got everything out of the way and bdrv_replace_node() can
do what it wants to do.

Kevin

Re: [Qemu-devel] [PATCH 04/21] block/commit: utilize job_exit shim
Posted by John Snow 7 years, 2 months ago

On 08/08/2018 12:29 PM, Kevin Wolf wrote:
> Am 07.08.2018 um 06:33 hat John Snow geschrieben:
>> Change the manual deferment to commit_complete into the implicit
>> callback to job_exit.
>>
>> Signed-off-by: John Snow <jsnow@redhat.com>
> 
> There is one tricky thing in this patch that the commit message could be
> a bit more explicit about, which is moving job_completed() to a later
> point.
> 
> This is the code that happens between the old call of job_completed()
> and the new one:
> 
>     /* If bdrv_drop_intermediate() didn't already do that, remove the commit
>      * filter driver from the backing chain. Do this as the final step so that
>      * the 'consistent read' permission can be granted.  */
>     if (remove_commit_top_bs) {
>         bdrv_child_try_set_perm(commit_top_bs->backing, 0, BLK_PERM_ALL,
>                                 &error_abort);
>         bdrv_replace_node(commit_top_bs, backing_bs(commit_top_bs),
>                           &error_abort);
>     }
> 
>     bdrv_unref(commit_top_bs);
>     bdrv_unref(top);
> 
> As the comment states, bdrv_replace_node() requires that the permission
> restrictions that the commit job made are already lifted. The most
> important part is done by the explicit block_job_remove_all_bdrv() call
> right before this hunk. It still leaves bjob->blk around, which could
> have implications, but luckily we didn't take any permissions for that
> one:
> 
>     s = block_job_create(job_id, &commit_job_driver, NULL, bs, 0, BLK_PERM_ALL,
>                          speed, JOB_DEFAULT, NULL, NULL, errp);
> 
> So I think we got everything out of the way and bdrv_replace_node() can
> do what it wants to do.
> 
> Kevin
> 

I suppose it will be up to the author of a job to be aware of any
permissions they pick up at creation time that might have an effect on
the cleanup they wish to do during completion time.

--js

Re: [Qemu-devel] [PATCH 04/21] block/commit: utilize job_exit shim
Posted by Kevin Wolf 7 years, 2 months ago
Am 15.08.2018 um 22:52 hat John Snow geschrieben:
> On 08/08/2018 12:29 PM, Kevin Wolf wrote:
> > Am 07.08.2018 um 06:33 hat John Snow geschrieben:
> >> Change the manual deferment to commit_complete into the implicit
> >> callback to job_exit.
> >>
> >> Signed-off-by: John Snow <jsnow@redhat.com>
> > 
> > There is one tricky thing in this patch that the commit message could be
> > a bit more explicit about, which is moving job_completed() to a later
> > point.
> > 
> > This is the code that happens between the old call of job_completed()
> > and the new one:
> > 
> >     /* If bdrv_drop_intermediate() didn't already do that, remove the commit
> >      * filter driver from the backing chain. Do this as the final step so that
> >      * the 'consistent read' permission can be granted.  */
> >     if (remove_commit_top_bs) {
> >         bdrv_child_try_set_perm(commit_top_bs->backing, 0, BLK_PERM_ALL,
> >                                 &error_abort);
> >         bdrv_replace_node(commit_top_bs, backing_bs(commit_top_bs),
> >                           &error_abort);
> >     }
> > 
> >     bdrv_unref(commit_top_bs);
> >     bdrv_unref(top);
> > 
> > As the comment states, bdrv_replace_node() requires that the permission
> > restrictions that the commit job made are already lifted. The most
> > important part is done by the explicit block_job_remove_all_bdrv() call
> > right before this hunk. It still leaves bjob->blk around, which could
> > have implications, but luckily we didn't take any permissions for that
> > one:
> > 
> >     s = block_job_create(job_id, &commit_job_driver, NULL, bs, 0, BLK_PERM_ALL,
> >                          speed, JOB_DEFAULT, NULL, NULL, errp);
> > 
> > So I think we got everything out of the way and bdrv_replace_node() can
> > do what it wants to do.
> > 
> > Kevin
> > 
> 
> I suppose it will be up to the author of a job to be aware of any
> permissions they pick up at creation time that might have an effect on
> the cleanup they wish to do during completion time.

I'm really only talking about the commit job, the specific conversion
in this patch and the terse commit message.

Kevin