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KVM: PPC: Book3S HV: Drop prepare_done from struct kvm_resize_hpt

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Currently the kvm_resize_hpt structure has two fields relevant to the
state of an ongoing resize: 'prepare_done', which indicates whether
the worker thread has completed or not, and 'error' which indicates
whether it was successful or not.

Since the success/failure isn't known until completion, this is
confusingly redundant.  This patch consolidates the information into
just the 'error' value: -EBUSY indicates the worked is still in
progress, other negative values indicate (completed) failure, 0
indicates successful completion.

As a bonus this reduces size of struct kvm_resize_hpt by
__alignof__(struct kvm_hpt_info) and saves few bytes of code.

While there correct comment in struct kvm_resize_hpt which references
a non-existent semaphore (leftover from an early draft).

Assert with WARN_ON() in case of HPT allocation thread work runs more
than once for resize request or resize_hpt_allocate() returns -EBUSY
that is treated specially.

Change comparison against zero to make checkpatch.pl happy.

Cc: stable@vger.kernel.org # v4.10+
Signed-off-by: Serhii Popovych <spopovyc@redhat.com>
[dwg: Changed BUG_ON()s to WARN_ON()s and altered commit message for
 clarity]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
This commit is contained in:
Serhii Popovych 2017-12-04 09:36:41 -05:00 committed by Paul Mackerras
parent a63dd7480d
commit 3073774e63
1 changed files with 28 additions and 18 deletions
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46
arch/powerpc/kvm/book3s_64_mmu_hv.c
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@ -65,11 +65,17 @@ struct kvm_resize_hpt {
u32 order;
/* These fields protected by kvm->lock */
int error;
bool prepare_done;
/* Private to the work thread, until prepare_done is true,
* then protected by kvm->resize_hpt_sem */
/* Possible values and their usage:
* <0 an error occurred during allocation,
* -EBUSY allocation is in the progress,
* 0 allocation made successfuly.
*/
int error;
/* Private to the work thread, until error != -EBUSY,
* then protected by kvm->lock.
*/
struct kvm_hpt_info hpt;
};
@ -1433,15 +1439,23 @@ static void resize_hpt_prepare_work(struct work_struct *work)
struct kvm *kvm = resize->kvm;
int err;
if (WARN_ON(resize->error != -EBUSY))
return;
resize_hpt_debug(resize, "resize_hpt_prepare_work(): order = %d\n",
resize->order);
err = resize_hpt_allocate(resize);
/* We have strict assumption about -EBUSY
* when preparing for HPT resize.
*/
if (WARN_ON(err == -EBUSY))
err = -EINPROGRESS;
mutex_lock(&kvm->lock);
resize->error = err;
resize->prepare_done = true;
mutex_unlock(&kvm->lock);
}
@ -1466,14 +1480,12 @@ long kvm_vm_ioctl_resize_hpt_prepare(struct kvm *kvm,
if (resize) {
if (resize->order == shift) {
/* Suitable resize in progress */
if (resize->prepare_done) {
ret = resize->error;
if (ret != 0)
resize_hpt_release(kvm, resize);
} else {
/* Suitable resize in progress? */
ret = resize->error;
if (ret == -EBUSY)
ret = 100; /* estimated time in ms */
}
else if (ret)
resize_hpt_release(kvm, resize);
goto out;
}
@ -1493,6 +1505,8 @@ long kvm_vm_ioctl_resize_hpt_prepare(struct kvm *kvm,
ret = -ENOMEM;
goto out;
}
resize->error = -EBUSY;
resize->order = shift;
resize->kvm = kvm;
INIT_WORK(&resize->work, resize_hpt_prepare_work);
@ -1547,16 +1561,12 @@ long kvm_vm_ioctl_resize_hpt_commit(struct kvm *kvm,
if (!resize || (resize->order != shift))
goto out;
ret = -EBUSY;
if (!resize->prepare_done)
goto out;
ret = resize->error;
if (ret != 0)
if (ret)
goto out;
ret = resize_hpt_rehash(resize);
if (ret != 0)
if (ret)
goto out;
resize_hpt_pivot(resize);