[PATCH] f2fs: adjust the way of calculating nat block

[PATCH] f2fs: adjust the way of calculating nat block

[Fan Li]

use a slightly simpler expression to calculate nat block with nid.

Signed-off-by: Fan Li <fanofcode.li@samsung.com>
---
 fs/f2fs/node.h | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/fs/f2fs/node.h b/fs/f2fs/node.h
index 2f9603f..f9fb5b8 100644
--- a/fs/f2fs/node.h
+++ b/fs/f2fs/node.h
@@ -200,13 +200,11 @@ static inline pgoff_t current_nat_addr(struct f2fs_sb_info *sbi, nid_t start)
        struct f2fs_nm_info *nm_i = NM_I(sbi);
        pgoff_t block_off;
        pgoff_t block_addr;
-       int seg_off;

        block_off = NAT_BLOCK_OFFSET(start);
-       seg_off = block_off >> sbi->log_blocks_per_seg;

        block_addr = (pgoff_t)(nm_i->nat_blkaddr +
-               (seg_off << sbi->log_blocks_per_seg << 1) +
+               (block_off << 1) -
                (block_off & (sbi->blocks_per_seg - 1)));

        if (f2fs_test_bit(block_off, nm_i->nat_bitmap))
--
2.7.4


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Re: [PATCH] f2fs: adjust the way of calculating nat block

[Jaegeuk Kim]

On 03/08, Fan Li wrote:
> use a slightly simpler expression to calculate nat block with nid.
> 
> Signed-off-by: Fan Li <fanofcode.li@samsung.com>
> ---
>  fs/f2fs/node.h | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/fs/f2fs/node.h b/fs/f2fs/node.h
> index 2f9603f..f9fb5b8 100644
> --- a/fs/f2fs/node.h
> +++ b/fs/f2fs/node.h
> @@ -200,13 +200,11 @@ static inline pgoff_t current_nat_addr(struct f2fs_sb_info *sbi, nid_t start)
>         struct f2fs_nm_info *nm_i = NM_I(sbi);
>         pgoff_t block_off;
>         pgoff_t block_addr;
> -       int seg_off;
> 
>         block_off = NAT_BLOCK_OFFSET(start);
> -       seg_off = block_off >> sbi->log_blocks_per_seg;
> 
>         block_addr = (pgoff_t)(nm_i->nat_blkaddr +
> -               (seg_off << sbi->log_blocks_per_seg << 1) +
> +               (block_off << 1) -

NAK. This breaks the behavior.

Thanks,

>                 (block_off & (sbi->blocks_per_seg - 1)));
> 
>         if (f2fs_test_bit(block_off, nm_i->nat_bitmap))
> --
> 2.7.4

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Re: [PATCH] f2fs: adjust the way of calculating nat block

[Fan Li]

> -----Original Message-----
> From: Jaegeuk Kim [mailto:jaegeuk@kernel.org]
> Sent: Thursday, March 09, 2017 5:56 AM
> To: Fan Li
> Cc: linux-f2fs-devel@lists.sourceforge.net
> Subject: Re: [f2fs-dev] [PATCH] f2fs: adjust the way of calculating nat block
> 
> On 03/08, Fan Li wrote:
> > use a slightly simpler expression to calculate nat block with nid.
> >
> > Signed-off-by: Fan Li <fanofcode.li@samsung.com>
> > ---
> >  fs/f2fs/node.h | 4 +---
> >  1 file changed, 1 insertion(+), 3 deletions(-)
> >
> > diff --git a/fs/f2fs/node.h b/fs/f2fs/node.h index 2f9603f..f9fb5b8
> > 100644
> > --- a/fs/f2fs/node.h
> > +++ b/fs/f2fs/node.h
> > @@ -200,13 +200,11 @@ static inline pgoff_t current_nat_addr(struct f2fs_sb_info *sbi, nid_t start)
> >         struct f2fs_nm_info *nm_i = NM_I(sbi);
> >         pgoff_t block_off;
> >         pgoff_t block_addr;
> > -       int seg_off;
> >
> >         block_off = NAT_BLOCK_OFFSET(start);
> > -       seg_off = block_off >> sbi->log_blocks_per_seg;
> >
> >         block_addr = (pgoff_t)(nm_i->nat_blkaddr +
> > -               (seg_off << sbi->log_blocks_per_seg << 1) +
> > +               (block_off << 1) -
> 
> NAK. This breaks the behavior.

OK, I'm guessing by "breaks the behavior", you mean make the code hard to understand?
I was concerned the same thing, but with the context, I think most people will be able to
 see right through it, and it saves some calculation, makes code as simple as possible, I
just think maybe it's worthy.


> 
> Thanks,
> 
> >                 (block_off & (sbi->blocks_per_seg - 1)));
> >
> >         if (f2fs_test_bit(block_off, nm_i->nat_bitmap))
> > --
> > 2.7.4



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Re: [PATCH] f2fs: adjust the way of calculating nat block

[Chao Yu]

On 2017/3/9 13:37, Fan Li wrote:
> 
> 
>> -----Original Message-----
>> From: Jaegeuk Kim [mailto:jaegeuk@kernel.org]
>> Sent: Thursday, March 09, 2017 5:56 AM
>> To: Fan Li
>> Cc: linux-f2fs-devel@lists.sourceforge.net
>> Subject: Re: [f2fs-dev] [PATCH] f2fs: adjust the way of calculating nat block
>>
>> On 03/08, Fan Li wrote:
>>> use a slightly simpler expression to calculate nat block with nid.
>>>
>>> Signed-off-by: Fan Li <fanofcode.li@samsung.com>
>>> ---
>>>  fs/f2fs/node.h | 4 +---
>>>  1 file changed, 1 insertion(+), 3 deletions(-)
>>>
>>> diff --git a/fs/f2fs/node.h b/fs/f2fs/node.h index 2f9603f..f9fb5b8
>>> 100644
>>> --- a/fs/f2fs/node.h
>>> +++ b/fs/f2fs/node.h
>>> @@ -200,13 +200,11 @@ static inline pgoff_t current_nat_addr(struct f2fs_sb_info *sbi, nid_t start)
>>>         struct f2fs_nm_info *nm_i = NM_I(sbi);
>>>         pgoff_t block_off;
>>>         pgoff_t block_addr;
>>> -       int seg_off;
>>>
>>>         block_off = NAT_BLOCK_OFFSET(start);
>>> -       seg_off = block_off >> sbi->log_blocks_per_seg;
>>>
>>>         block_addr = (pgoff_t)(nm_i->nat_blkaddr +
>>> -               (seg_off << sbi->log_blocks_per_seg << 1) +
>>> +               (block_off << 1) -
>>
>> NAK. This breaks the behavior.
> 
> OK, I'm guessing by "breaks the behavior", you mean make the code hard to understand?
> I was concerned the same thing, but with the context, I think most people will be able to
>  see right through it, and it saves some calculation, makes code as simple as possible, I
> just think maybe it's worthy.

I know both calculation are right, assume:
block_off = segment_off * 512 + off_in_segment
a) origin: (segment_off * 512) * 2 + off_in_segment
b) yours: 2 * (segment_off * 512 + off_in_segment) - off_in_segment

Seem calculation of yours is more simple, but from my side, readability is also
important, it's a bit hard to understand your calculation approach without comments.

Thanks,

> 
> 
>>
>> Thanks,
>>
>>>                 (block_off & (sbi->blocks_per_seg - 1)));
>>>
>>>         if (f2fs_test_bit(block_off, nm_i->nat_bitmap))
>>> --
>>> 2.7.4
> 
> 
> 
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> account today to start using our lexical data to power your apps and
> projects. Get started today and enter our developer competition.
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> 
> 


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Re: [PATCH] f2fs: adjust the way of calculating nat block

[Jaegeuk Kim]

On 03/09, Chao Yu wrote:
> On 2017/3/9 13:37, Fan Li wrote:
> > 
> > 
> >> -----Original Message-----
> >> From: Jaegeuk Kim [mailto:jaegeuk@kernel.org]
> >> Sent: Thursday, March 09, 2017 5:56 AM
> >> To: Fan Li
> >> Cc: linux-f2fs-devel@lists.sourceforge.net
> >> Subject: Re: [f2fs-dev] [PATCH] f2fs: adjust the way of calculating nat block
> >>
> >> On 03/08, Fan Li wrote:
> >>> use a slightly simpler expression to calculate nat block with nid.
> >>>
> >>> Signed-off-by: Fan Li <fanofcode.li@samsung.com>
> >>> ---
> >>>  fs/f2fs/node.h | 4 +---
> >>>  1 file changed, 1 insertion(+), 3 deletions(-)
> >>>
> >>> diff --git a/fs/f2fs/node.h b/fs/f2fs/node.h index 2f9603f..f9fb5b8
> >>> 100644
> >>> --- a/fs/f2fs/node.h
> >>> +++ b/fs/f2fs/node.h
> >>> @@ -200,13 +200,11 @@ static inline pgoff_t current_nat_addr(struct f2fs_sb_info *sbi, nid_t start)
> >>>         struct f2fs_nm_info *nm_i = NM_I(sbi);
> >>>         pgoff_t block_off;
> >>>         pgoff_t block_addr;
> >>> -       int seg_off;
> >>>
> >>>         block_off = NAT_BLOCK_OFFSET(start);
> >>> -       seg_off = block_off >> sbi->log_blocks_per_seg;
> >>>
> >>>         block_addr = (pgoff_t)(nm_i->nat_blkaddr +
> >>> -               (seg_off << sbi->log_blocks_per_seg << 1) +
> >>> +               (block_off << 1) -
> >>
> >> NAK. This breaks the behavior.
> > 
> > OK, I'm guessing by "breaks the behavior", you mean make the code hard to understand?
> > I was concerned the same thing, but with the context, I think most people will be able to
> >  see right through it, and it saves some calculation, makes code as simple as possible, I
> > just think maybe it's worthy.
> 
> I know both calculation are right, assume:
> block_off = segment_off * 512 + off_in_segment
> a) origin: (segment_off * 512) * 2 + off_in_segment
> b) yours: 2 * (segment_off * 512 + off_in_segment) - off_in_segment

Oh, I missed '-' in the end of the line.
Let me add Chao's explanation in the patch. :)

Thanks,

> 
> Seem calculation of yours is more simple, but from my side, readability is also
> important, it's a bit hard to understand your calculation approach without comments.
> 
> Thanks,
> 
> > 
> > 
> >>
> >> Thanks,
> >>
> >>>                 (block_off & (sbi->blocks_per_seg - 1)));
> >>>
> >>>         if (f2fs_test_bit(block_off, nm_i->nat_bitmap))
> >>> --
> >>> 2.7.4
> > 
> > 
> > 
> > ------------------------------------------------------------------------------
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> > dictionary content that is easy and intuitive to access. Sign up for an
> > account today to start using our lexical data to power your apps and
> > projects. Get started today and enter our developer competition.
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> > _______________________________________________
> > Linux-f2fs-devel mailing list
> > Linux-f2fs-devel@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
> > 
> > 
> 
> 
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