[PATCH] f2fs: no need to scan nat bitmap if it's not enable

[PATCH] f2fs: no need to scan nat bitmap if it's not enable

[Yunlei He]

Now, nat bitmap will get lost after sudden power off,
when we build free nids, it's better to judge nat bitmap
enable or not before scan nat bitmap.

Signed-off-by: Yunlei He <heyunlei@huawei.com>
---
 fs/f2fs/node.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index fca8783..482f424 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -1937,6 +1937,9 @@ static void scan_free_nid_bits(struct f2fs_sb_info *sbi)
 	struct f2fs_journal *journal = curseg->journal;
 	unsigned int i, idx;
 
+	if (!enabled_nat_bits(sbi, NULL))
+		return;
+
 	down_read(&nm_i->nat_tree_lock);
 
 	for (i = 0; i < nm_i->nat_blocks; i++) {
-- 
1.9.1


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Re: [PATCH] f2fs: no need to scan nat bitmap if it's not enable

[Chao Yu]

On 2017/9/7 10:55, Yunlei He wrote:
> Now, nat bitmap will get lost after sudden power off,
> when we build free nids, it's better to judge nat bitmap
> enable or not before scan nat bitmap.

We will load uptodate nit_bits map in last valid checkpoint after SPOR, is there
any problem here?

Thanks,

> 
> Signed-off-by: Yunlei He <heyunlei@huawei.com>
> ---
>  fs/f2fs/node.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index fca8783..482f424 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -1937,6 +1937,9 @@ static void scan_free_nid_bits(struct f2fs_sb_info *sbi)
>  	struct f2fs_journal *journal = curseg->journal;
>  	unsigned int i, idx;
>  
> +	if (!enabled_nat_bits(sbi, NULL))
> +		return;
> +
>  	down_read(&nm_i->nat_tree_lock);
>  
>  	for (i = 0; i < nm_i->nat_blocks; i++) {
> 


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答复: [PATCH] f2fs: no need to scan nat bitmap if it's not enable

[heyunlei]

Hi Chao，
On 2017/9/7 10:55, Yunlei He wrote:
> Now, nat bitmap will get lost after sudden power off, when we build 
> free nids, it's better to judge nat bitmap enable or not before scan 
> nat bitmap.

We will load uptodate nit_bits map in last valid checkpoint after SPOR, is there any problem here?

Thanks,

 We write nat bits only when CP_UMOUNT is set, is something else I missing? 

Thanks，

> 
> Signed-off-by: Yunlei He <heyunlei@huawei.com>
> ---
>  fs/f2fs/node.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c index fca8783..482f424 
> 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -1937,6 +1937,9 @@ static void scan_free_nid_bits(struct f2fs_sb_info *sbi)
>  	struct f2fs_journal *journal = curseg->journal;
>  	unsigned int i, idx;
>  
> +	if (!enabled_nat_bits(sbi, NULL))
> +		return;
> +
>  	down_read(&nm_i->nat_tree_lock);
>  
>  	for (i = 0; i < nm_i->nat_blocks; i++) {
> 

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Re: 答复: [PATCH] f2fs: no need to scan nat bitmap if it's not enable

[Chao Yu]

Hi Yunlei,

On 2017/9/7 11:44, heyunlei wrote:
> Hi Chao，
> On 2017/9/7 10:55, Yunlei He wrote:
>> Now, nat bitmap will get lost after sudden power off, when we build 
>> free nids, it's better to judge nat bitmap enable or not before scan 
>> nat bitmap.
> 
> We will load uptodate nit_bits map in last valid checkpoint after SPOR, is there any problem here?
> 
> Thanks,
> 
>  We write nat bits only when CP_UMOUNT is set, is something else I missing? 

Yup, if nat_bits map is out of update, we have already skipped loading it in
load_free_nid_bitmap.

You're trying to shut down free nide bitmap cache which is just pure
intermediate cache, the cache will be initialized with nat_bits map and be
updated during free nid allocation/releasing, for SPOR case, we will skip
initialization step, but still the cache can run well due to other updating
mechanism. So I don't think we have to disable the cache for that case.

Below patches can help you understand well about history and implementation of
the cache, please check them:

f2fs: add bitmaps for empty or full NAT blocks
f2fs: introduce free nid bitmap
f2fs: combine nat_bits and free_nid_bitmap cache

Thanks,

> 
> Thanks，
> 
>>
>> Signed-off-by: Yunlei He <heyunlei@huawei.com>
>> ---
>>  fs/f2fs/node.c | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c index fca8783..482f424 
>> 100644
>> --- a/fs/f2fs/node.c
>> +++ b/fs/f2fs/node.c
>> @@ -1937,6 +1937,9 @@ static void scan_free_nid_bits(struct f2fs_sb_info *sbi)
>>  	struct f2fs_journal *journal = curseg->journal;
>>  	unsigned int i, idx;
>>  
>> +	if (!enabled_nat_bits(sbi, NULL))
>> +		return;
>> +
>>  	down_read(&nm_i->nat_tree_lock);
>>  
>>  	for (i = 0; i < nm_i->nat_blocks; i++) {
>>
> 


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