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SubjectRe: [PATCH] lightnvm: pblk: use vfree_atomic when freeing line metadata
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> On 3 Oct 2017, at 16.07, Andrey Ryabinin <aryabinin@virtuozzo.com> wrote:
>
>
>
> On 10/03/2017 04:48 PM, Hans Holmberg wrote:
>> From: Hans Holmberg <hans.holmberg@cnexlabs.com>
>>
>> The commit bf22e37a6413 ("mm: add vfree_atomic()") made vfree unsafe to
>> call in atomic context (unless the call came from an interrupt) and
>> introduced vfree_atomic that is safe to call in atomic context.
>>
>> So, since we're holding locks when freeing line metadata, we need to
>> use the atomic version of vfree.
>>
>> Fix this by introducing an atomic variant of pblk_mfree and
>> switching to that in pblk_line_meta_free.
>>
>> Signed-off-by: Hans Holmberg <hans.holmberg@cnexlabs.com>
>> ---
>>
>> The patch is for:
>> https://github.com/OpenChannelSSD/linux branch for-4.15/pblk
>>
>> drivers/lightnvm/pblk-init.c | 3 ++-
>> drivers/lightnvm/pblk.h | 8 ++++++++
>> 2 files changed, 10 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/lightnvm/pblk-init.c b/drivers/lightnvm/pblk-init.c
>> index c452478..3a191a6 100644
>> --- a/drivers/lightnvm/pblk-init.c
>> +++ b/drivers/lightnvm/pblk-init.c
>> @@ -396,7 +396,8 @@ static void pblk_line_meta_free(struct pblk *pblk)
>> spin_lock(&l_mg->free_lock);
>
> What's the point in holding ->free_lock here? It seems like it could be just dropped.
>

This lock can indeed be dropped, but the general pblk semaphore, which
serializes initialization and tear down cannot. This is taken on
pblk_exit().

Javier
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