[PATCH][next] f2fs: Replace one-element array with flexible-array member

[PATCH][next] f2fs: Replace one-element array with flexible-array member

[Gustavo A. R. Silva]

There is a regular need in the kernel to provide a way to declare having
a dynamically sized set of trailing elements in a structure. Kernel code
should always use “flexible array members”[1] for these cases. The older
style of one-element or zero-length arrays should no longer be used[2].

Refactor the code according to the use of a flexible-array member in
struct f2fs_checkpoint, instead of a one-element arrays.

Notice that a temporary pointer to void '*tmp_ptr' was used in order to
fix the following errors when using a flexible array instead of a one
element array in struct f2fs_checkpoint:

  CC [M]  fs/f2fs/dir.o
In file included from fs/f2fs/dir.c:13:
fs/f2fs/f2fs.h: In function ‘__bitmap_ptr’:
fs/f2fs/f2fs.h:2227:40: error: invalid use of flexible array member
 2227 |   return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
      |                                        ^
fs/f2fs/f2fs.h:2227:49: error: invalid use of flexible array member
 2227 |   return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
      |                                                 ^
fs/f2fs/f2fs.h:2238:40: error: invalid use of flexible array member
 2238 |   return &ckpt->sit_nat_version_bitmap + offset;
      |                                        ^
make[2]: *** [scripts/Makefile.build:287: fs/f2fs/dir.o] Error 1
make[1]: *** [scripts/Makefile.build:530: fs/f2fs] Error 2
make: *** [Makefile:1819: fs] Error 2

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.9/process/deprecated.html#zero-length-and-one-element-arrays

Link: https://github.com/KSPP/linux/issues/79
Build-tested-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/lkml/603647e4.DeEFbl4eqljuwAUe%25lkp@intel.com/
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 fs/f2fs/f2fs.h          | 5 +++--
 include/linux/f2fs_fs.h | 2 +-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index e2d302ae3a46..3f5cb097c30f 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -2215,6 +2215,7 @@ static inline block_t __cp_payload(struct f2fs_sb_info *sbi)
 static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
 {
 	struct f2fs_checkpoint *ckpt = F2FS_CKPT(sbi);
+	void *tmp_ptr = &ckpt->sit_nat_version_bitmap;
 	int offset;
 
 	if (is_set_ckpt_flags(sbi, CP_LARGE_NAT_BITMAP_FLAG)) {
@@ -2224,7 +2225,7 @@ static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
 		 * if large_nat_bitmap feature is enabled, leave checksum
 		 * protection for all nat/sit bitmaps.
 		 */
-		return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
+		return tmp_ptr + offset + sizeof(__le32);
 	}
 
 	if (__cp_payload(sbi) > 0) {
@@ -2235,7 +2236,7 @@ static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
 	} else {
 		offset = (flag == NAT_BITMAP) ?
 			le32_to_cpu(ckpt->sit_ver_bitmap_bytesize) : 0;
-		return &ckpt->sit_nat_version_bitmap + offset;
+		return tmp_ptr + offset;
 	}
 }
 
diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
index c6cc0a566ef5..5487a80617a3 100644
--- a/include/linux/f2fs_fs.h
+++ b/include/linux/f2fs_fs.h
@@ -168,7 +168,7 @@ struct f2fs_checkpoint {
 	unsigned char alloc_type[MAX_ACTIVE_LOGS];
 
 	/* SIT and NAT version bitmap */
-	unsigned char sit_nat_version_bitmap[1];
+	unsigned char sit_nat_version_bitmap[];
 } __packed;
 
 #define CP_CHKSUM_OFFSET	4092	/* default chksum offset in checkpoint */
-- 
2.27.0

[f2fs-dev] [PATCH][next] f2fs: Replace one-element array with flexible-array member

[Gustavo A. R. Silva]

There is a regular need in the kernel to provide a way to declare having
a dynamically sized set of trailing elements in a structure. Kernel code
should always use “flexible array members”[1] for these cases. The older
style of one-element or zero-length arrays should no longer be used[2].

Refactor the code according to the use of a flexible-array member in
struct f2fs_checkpoint, instead of a one-element arrays.

Notice that a temporary pointer to void '*tmp_ptr' was used in order to
fix the following errors when using a flexible array instead of a one
element array in struct f2fs_checkpoint:

  CC [M]  fs/f2fs/dir.o
In file included from fs/f2fs/dir.c:13:
fs/f2fs/f2fs.h: In function ‘__bitmap_ptr’:
fs/f2fs/f2fs.h:2227:40: error: invalid use of flexible array member
 2227 |   return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
      |                                        ^
fs/f2fs/f2fs.h:2227:49: error: invalid use of flexible array member
 2227 |   return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
      |                                                 ^
fs/f2fs/f2fs.h:2238:40: error: invalid use of flexible array member
 2238 |   return &ckpt->sit_nat_version_bitmap + offset;
      |                                        ^
make[2]: *** [scripts/Makefile.build:287: fs/f2fs/dir.o] Error 1
make[1]: *** [scripts/Makefile.build:530: fs/f2fs] Error 2
make: *** [Makefile:1819: fs] Error 2

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.9/process/deprecated.html#zero-length-and-one-element-arrays

Link: https://github.com/KSPP/linux/issues/79
Build-tested-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/lkml/603647e4.DeEFbl4eqljuwAUe%25lkp@intel.com/
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 fs/f2fs/f2fs.h          | 5 +++--
 include/linux/f2fs_fs.h | 2 +-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index e2d302ae3a46..3f5cb097c30f 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -2215,6 +2215,7 @@ static inline block_t __cp_payload(struct f2fs_sb_info *sbi)
 static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
 {
 	struct f2fs_checkpoint *ckpt = F2FS_CKPT(sbi);
+	void *tmp_ptr = &ckpt->sit_nat_version_bitmap;
 	int offset;
 
 	if (is_set_ckpt_flags(sbi, CP_LARGE_NAT_BITMAP_FLAG)) {
@@ -2224,7 +2225,7 @@ static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
 		 * if large_nat_bitmap feature is enabled, leave checksum
 		 * protection for all nat/sit bitmaps.
 		 */
-		return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
+		return tmp_ptr + offset + sizeof(__le32);
 	}
 
 	if (__cp_payload(sbi) > 0) {
@@ -2235,7 +2236,7 @@ static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
 	} else {
 		offset = (flag == NAT_BITMAP) ?
 			le32_to_cpu(ckpt->sit_ver_bitmap_bytesize) : 0;
-		return &ckpt->sit_nat_version_bitmap + offset;
+		return tmp_ptr + offset;
 	}
 }
 
diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
index c6cc0a566ef5..5487a80617a3 100644
--- a/include/linux/f2fs_fs.h
+++ b/include/linux/f2fs_fs.h
@@ -168,7 +168,7 @@ struct f2fs_checkpoint {
 	unsigned char alloc_type[MAX_ACTIVE_LOGS];
 
 	/* SIT and NAT version bitmap */
-	unsigned char sit_nat_version_bitmap[1];
+	unsigned char sit_nat_version_bitmap[];
 } __packed;
 
 #define CP_CHKSUM_OFFSET	4092	/* default chksum offset in checkpoint */
-- 
2.27.0



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Re: [f2fs-dev] [PATCH][next] f2fs: Replace one-element array with flexible-array member

[Chao Yu]

Hello, Gustavo,

On 2021/2/25 3:03, Gustavo A. R. Silva wrote:
> There is a regular need in the kernel to provide a way to declare having
> a dynamically sized set of trailing elements in a structure. Kernel code
> should always use “flexible array members”[1] for these cases. The older
> style of one-element or zero-length arrays should no longer be used[2].

I proposal to do the similar cleanup, and I've no objection on doing this.

https://lore.kernel.org/patchwork/patch/869440/

Let's ask for Jaegeuk' opinion.

> 
> Refactor the code according to the use of a flexible-array member in
> struct f2fs_checkpoint, instead of a one-element arrays.
> 
> Notice that a temporary pointer to void '*tmp_ptr' was used in order to
> fix the following errors when using a flexible array instead of a one
> element array in struct f2fs_checkpoint:
> 
>    CC [M]  fs/f2fs/dir.o
> In file included from fs/f2fs/dir.c:13:
> fs/f2fs/f2fs.h: In function ‘__bitmap_ptr’:
> fs/f2fs/f2fs.h:2227:40: error: invalid use of flexible array member
>   2227 |   return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
>        |                                        ^
> fs/f2fs/f2fs.h:2227:49: error: invalid use of flexible array member
>   2227 |   return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
>        |                                                 ^
> fs/f2fs/f2fs.h:2238:40: error: invalid use of flexible array member
>   2238 |   return &ckpt->sit_nat_version_bitmap + offset;
>        |                                        ^
> make[2]: *** [scripts/Makefile.build:287: fs/f2fs/dir.o] Error 1
> make[1]: *** [scripts/Makefile.build:530: fs/f2fs] Error 2
> make: *** [Makefile:1819: fs] Error 2
> 
> [1] https://en.wikipedia.org/wiki/Flexible_array_member
> [2] https://www.kernel.org/doc/html/v5.9/process/deprecated.html#zero-length-and-one-element-arrays
> 
> Link: https://github.com/KSPP/linux/issues/79
> Build-tested-by: kernel test robot <lkp@intel.com>
> Link: https://lore.kernel.org/lkml/603647e4.DeEFbl4eqljuwAUe%25lkp@intel.com/
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
>   fs/f2fs/f2fs.h          | 5 +++--
>   include/linux/f2fs_fs.h | 2 +-
>   2 files changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index e2d302ae3a46..3f5cb097c30f 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -2215,6 +2215,7 @@ static inline block_t __cp_payload(struct f2fs_sb_info *sbi)
>   static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
>   {
>   	struct f2fs_checkpoint *ckpt = F2FS_CKPT(sbi);
> +	void *tmp_ptr = &ckpt->sit_nat_version_bitmap;
>   	int offset;
>   
>   	if (is_set_ckpt_flags(sbi, CP_LARGE_NAT_BITMAP_FLAG)) {
> @@ -2224,7 +2225,7 @@ static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
>   		 * if large_nat_bitmap feature is enabled, leave checksum
>   		 * protection for all nat/sit bitmaps.
>   		 */
> -		return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
> +		return tmp_ptr + offset + sizeof(__le32);
>   	}
>   
>   	if (__cp_payload(sbi) > 0) {
> @@ -2235,7 +2236,7 @@ static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
>   	} else {
>   		offset = (flag == NAT_BITMAP) ?
>   			le32_to_cpu(ckpt->sit_ver_bitmap_bytesize) : 0;
> -		return &ckpt->sit_nat_version_bitmap + offset;
> +		return tmp_ptr + offset;
>   	}
>   }
>   
> diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
> index c6cc0a566ef5..5487a80617a3 100644
> --- a/include/linux/f2fs_fs.h
> +++ b/include/linux/f2fs_fs.h
> @@ -168,7 +168,7 @@ struct f2fs_checkpoint {
>   	unsigned char alloc_type[MAX_ACTIVE_LOGS];
>   
>   	/* SIT and NAT version bitmap */
> -	unsigned char sit_nat_version_bitmap[1];
> +	unsigned char sit_nat_version_bitmap[];
>   } __packed;
>   
>   #define CP_CHKSUM_OFFSET	4092	/* default chksum offset in checkpoint */
> 

Re: [f2fs-dev] [PATCH][next] f2fs: Replace one-element array with flexible-array member

[Chao Yu]

Hello, Gustavo,

On 2021/2/25 3:03, Gustavo A. R. Silva wrote:
> There is a regular need in the kernel to provide a way to declare having
> a dynamically sized set of trailing elements in a structure. Kernel code
> should always use “flexible array members”[1] for these cases. The older
> style of one-element or zero-length arrays should no longer be used[2].

I proposal to do the similar cleanup, and I've no objection on doing this.

https://lore.kernel.org/patchwork/patch/869440/

Let's ask for Jaegeuk' opinion.

> 
> Refactor the code according to the use of a flexible-array member in
> struct f2fs_checkpoint, instead of a one-element arrays.
> 
> Notice that a temporary pointer to void '*tmp_ptr' was used in order to
> fix the following errors when using a flexible array instead of a one
> element array in struct f2fs_checkpoint:
> 
>    CC [M]  fs/f2fs/dir.o
> In file included from fs/f2fs/dir.c:13:
> fs/f2fs/f2fs.h: In function ‘__bitmap_ptr’:
> fs/f2fs/f2fs.h:2227:40: error: invalid use of flexible array member
>   2227 |   return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
>        |                                        ^
> fs/f2fs/f2fs.h:2227:49: error: invalid use of flexible array member
>   2227 |   return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
>        |                                                 ^
> fs/f2fs/f2fs.h:2238:40: error: invalid use of flexible array member
>   2238 |   return &ckpt->sit_nat_version_bitmap + offset;
>        |                                        ^
> make[2]: *** [scripts/Makefile.build:287: fs/f2fs/dir.o] Error 1
> make[1]: *** [scripts/Makefile.build:530: fs/f2fs] Error 2
> make: *** [Makefile:1819: fs] Error 2
> 
> [1] https://en.wikipedia.org/wiki/Flexible_array_member
> [2] https://www.kernel.org/doc/html/v5.9/process/deprecated.html#zero-length-and-one-element-arrays
> 
> Link: https://github.com/KSPP/linux/issues/79
> Build-tested-by: kernel test robot <lkp@intel.com>
> Link: https://lore.kernel.org/lkml/603647e4.DeEFbl4eqljuwAUe%25lkp@intel.com/
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
>   fs/f2fs/f2fs.h          | 5 +++--
>   include/linux/f2fs_fs.h | 2 +-
>   2 files changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index e2d302ae3a46..3f5cb097c30f 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -2215,6 +2215,7 @@ static inline block_t __cp_payload(struct f2fs_sb_info *sbi)
>   static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
>   {
>   	struct f2fs_checkpoint *ckpt = F2FS_CKPT(sbi);
> +	void *tmp_ptr = &ckpt->sit_nat_version_bitmap;
>   	int offset;
>   
>   	if (is_set_ckpt_flags(sbi, CP_LARGE_NAT_BITMAP_FLAG)) {
> @@ -2224,7 +2225,7 @@ static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
>   		 * if large_nat_bitmap feature is enabled, leave checksum
>   		 * protection for all nat/sit bitmaps.
>   		 */
> -		return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
> +		return tmp_ptr + offset + sizeof(__le32);
>   	}
>   
>   	if (__cp_payload(sbi) > 0) {
> @@ -2235,7 +2236,7 @@ static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
>   	} else {
>   		offset = (flag == NAT_BITMAP) ?
>   			le32_to_cpu(ckpt->sit_ver_bitmap_bytesize) : 0;
> -		return &ckpt->sit_nat_version_bitmap + offset;
> +		return tmp_ptr + offset;
>   	}
>   }
>   
> diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
> index c6cc0a566ef5..5487a80617a3 100644
> --- a/include/linux/f2fs_fs.h
> +++ b/include/linux/f2fs_fs.h
> @@ -168,7 +168,7 @@ struct f2fs_checkpoint {
>   	unsigned char alloc_type[MAX_ACTIVE_LOGS];
>   
>   	/* SIT and NAT version bitmap */
> -	unsigned char sit_nat_version_bitmap[1];
> +	unsigned char sit_nat_version_bitmap[];
>   } __packed;
>   
>   #define CP_CHKSUM_OFFSET	4092	/* default chksum offset in checkpoint */
> 


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Re: [f2fs-dev] [PATCH][next] f2fs: Replace one-element array with flexible-array member

[Jaegeuk Kim]

On 02/25, Chao Yu wrote:
> Hello, Gustavo,
> 
> On 2021/2/25 3:03, Gustavo A. R. Silva wrote:
> > There is a regular need in the kernel to provide a way to declare having
> > a dynamically sized set of trailing elements in a structure. Kernel code
> > should always use “flexible array members”[1] for these cases. The older
> > style of one-element or zero-length arrays should no longer be used[2].
> 
> I proposal to do the similar cleanup, and I've no objection on doing this.
> 
> https://lore.kernel.org/patchwork/patch/869440/
> 
> Let's ask for Jaegeuk' opinion.

Merged, thanks.
This looks better reason than code readability. :)

> 
> > 
> > Refactor the code according to the use of a flexible-array member in
> > struct f2fs_checkpoint, instead of a one-element arrays.
> > 
> > Notice that a temporary pointer to void '*tmp_ptr' was used in order to
> > fix the following errors when using a flexible array instead of a one
> > element array in struct f2fs_checkpoint:
> > 
> >    CC [M]  fs/f2fs/dir.o
> > In file included from fs/f2fs/dir.c:13:
> > fs/f2fs/f2fs.h: In function ‘__bitmap_ptr’:
> > fs/f2fs/f2fs.h:2227:40: error: invalid use of flexible array member
> >   2227 |   return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
> >        |                                        ^
> > fs/f2fs/f2fs.h:2227:49: error: invalid use of flexible array member
> >   2227 |   return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
> >        |                                                 ^
> > fs/f2fs/f2fs.h:2238:40: error: invalid use of flexible array member
> >   2238 |   return &ckpt->sit_nat_version_bitmap + offset;
> >        |                                        ^
> > make[2]: *** [scripts/Makefile.build:287: fs/f2fs/dir.o] Error 1
> > make[1]: *** [scripts/Makefile.build:530: fs/f2fs] Error 2
> > make: *** [Makefile:1819: fs] Error 2
> > 
> > [1] https://en.wikipedia.org/wiki/Flexible_array_member
> > [2] https://www.kernel.org/doc/html/v5.9/process/deprecated.html#zero-length-and-one-element-arrays
> > 
> > Link: https://github.com/KSPP/linux/issues/79
> > Build-tested-by: kernel test robot <lkp@intel.com>
> > Link: https://lore.kernel.org/lkml/603647e4.DeEFbl4eqljuwAUe%25lkp@intel.com/
> > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> > ---
> >   fs/f2fs/f2fs.h          | 5 +++--
> >   include/linux/f2fs_fs.h | 2 +-
> >   2 files changed, 4 insertions(+), 3 deletions(-)
> > 
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index e2d302ae3a46..3f5cb097c30f 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -2215,6 +2215,7 @@ static inline block_t __cp_payload(struct f2fs_sb_info *sbi)
> >   static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
> >   {
> >   	struct f2fs_checkpoint *ckpt = F2FS_CKPT(sbi);
> > +	void *tmp_ptr = &ckpt->sit_nat_version_bitmap;
> >   	int offset;
> >   	if (is_set_ckpt_flags(sbi, CP_LARGE_NAT_BITMAP_FLAG)) {
> > @@ -2224,7 +2225,7 @@ static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
> >   		 * if large_nat_bitmap feature is enabled, leave checksum
> >   		 * protection for all nat/sit bitmaps.
> >   		 */
> > -		return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
> > +		return tmp_ptr + offset + sizeof(__le32);
> >   	}
> >   	if (__cp_payload(sbi) > 0) {
> > @@ -2235,7 +2236,7 @@ static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
> >   	} else {
> >   		offset = (flag == NAT_BITMAP) ?
> >   			le32_to_cpu(ckpt->sit_ver_bitmap_bytesize) : 0;
> > -		return &ckpt->sit_nat_version_bitmap + offset;
> > +		return tmp_ptr + offset;
> >   	}
> >   }
> > diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
> > index c6cc0a566ef5..5487a80617a3 100644
> > --- a/include/linux/f2fs_fs.h
> > +++ b/include/linux/f2fs_fs.h
> > @@ -168,7 +168,7 @@ struct f2fs_checkpoint {
> >   	unsigned char alloc_type[MAX_ACTIVE_LOGS];
> >   	/* SIT and NAT version bitmap */
> > -	unsigned char sit_nat_version_bitmap[1];
> > +	unsigned char sit_nat_version_bitmap[];
> >   } __packed;
> >   #define CP_CHKSUM_OFFSET	4092	/* default chksum offset in checkpoint */
> > 

Re: [f2fs-dev] [PATCH][next] f2fs: Replace one-element array with flexible-array member

[Jaegeuk Kim]

On 02/25, Chao Yu wrote:
> Hello, Gustavo,
> 
> On 2021/2/25 3:03, Gustavo A. R. Silva wrote:
> > There is a regular need in the kernel to provide a way to declare having
> > a dynamically sized set of trailing elements in a structure. Kernel code
> > should always use “flexible array members”[1] for these cases. The older
> > style of one-element or zero-length arrays should no longer be used[2].
> 
> I proposal to do the similar cleanup, and I've no objection on doing this.
> 
> https://lore.kernel.org/patchwork/patch/869440/
> 
> Let's ask for Jaegeuk' opinion.

Merged, thanks.
This looks better reason than code readability. :)

> 
> > 
> > Refactor the code according to the use of a flexible-array member in
> > struct f2fs_checkpoint, instead of a one-element arrays.
> > 
> > Notice that a temporary pointer to void '*tmp_ptr' was used in order to
> > fix the following errors when using a flexible array instead of a one
> > element array in struct f2fs_checkpoint:
> > 
> >    CC [M]  fs/f2fs/dir.o
> > In file included from fs/f2fs/dir.c:13:
> > fs/f2fs/f2fs.h: In function ‘__bitmap_ptr’:
> > fs/f2fs/f2fs.h:2227:40: error: invalid use of flexible array member
> >   2227 |   return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
> >        |                                        ^
> > fs/f2fs/f2fs.h:2227:49: error: invalid use of flexible array member
> >   2227 |   return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
> >        |                                                 ^
> > fs/f2fs/f2fs.h:2238:40: error: invalid use of flexible array member
> >   2238 |   return &ckpt->sit_nat_version_bitmap + offset;
> >        |                                        ^
> > make[2]: *** [scripts/Makefile.build:287: fs/f2fs/dir.o] Error 1
> > make[1]: *** [scripts/Makefile.build:530: fs/f2fs] Error 2
> > make: *** [Makefile:1819: fs] Error 2
> > 
> > [1] https://en.wikipedia.org/wiki/Flexible_array_member
> > [2] https://www.kernel.org/doc/html/v5.9/process/deprecated.html#zero-length-and-one-element-arrays
> > 
> > Link: https://github.com/KSPP/linux/issues/79
> > Build-tested-by: kernel test robot <lkp@intel.com>
> > Link: https://lore.kernel.org/lkml/603647e4.DeEFbl4eqljuwAUe%25lkp@intel.com/
> > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> > ---
> >   fs/f2fs/f2fs.h          | 5 +++--
> >   include/linux/f2fs_fs.h | 2 +-
> >   2 files changed, 4 insertions(+), 3 deletions(-)
> > 
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index e2d302ae3a46..3f5cb097c30f 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -2215,6 +2215,7 @@ static inline block_t __cp_payload(struct f2fs_sb_info *sbi)
> >   static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
> >   {
> >   	struct f2fs_checkpoint *ckpt = F2FS_CKPT(sbi);
> > +	void *tmp_ptr = &ckpt->sit_nat_version_bitmap;
> >   	int offset;
> >   	if (is_set_ckpt_flags(sbi, CP_LARGE_NAT_BITMAP_FLAG)) {
> > @@ -2224,7 +2225,7 @@ static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
> >   		 * if large_nat_bitmap feature is enabled, leave checksum
> >   		 * protection for all nat/sit bitmaps.
> >   		 */
> > -		return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
> > +		return tmp_ptr + offset + sizeof(__le32);
> >   	}
> >   	if (__cp_payload(sbi) > 0) {
> > @@ -2235,7 +2236,7 @@ static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
> >   	} else {
> >   		offset = (flag == NAT_BITMAP) ?
> >   			le32_to_cpu(ckpt->sit_ver_bitmap_bytesize) : 0;
> > -		return &ckpt->sit_nat_version_bitmap + offset;
> > +		return tmp_ptr + offset;
> >   	}
> >   }
> > diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
> > index c6cc0a566ef5..5487a80617a3 100644
> > --- a/include/linux/f2fs_fs.h
> > +++ b/include/linux/f2fs_fs.h
> > @@ -168,7 +168,7 @@ struct f2fs_checkpoint {
> >   	unsigned char alloc_type[MAX_ACTIVE_LOGS];
> >   	/* SIT and NAT version bitmap */
> > -	unsigned char sit_nat_version_bitmap[1];
> > +	unsigned char sit_nat_version_bitmap[];
> >   } __packed;
> >   #define CP_CHKSUM_OFFSET	4092	/* default chksum offset in checkpoint */
> > 


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Re: [f2fs-dev] [PATCH][next] f2fs: Replace one-element array with flexible-array member

[Chao Yu]

On 2021/2/28 13:00, Jaegeuk Kim wrote:
> On 02/25, Chao Yu wrote:
>> Hello, Gustavo,
>>
>> On 2021/2/25 3:03, Gustavo A. R. Silva wrote:
>>> There is a regular need in the kernel to provide a way to declare having
>>> a dynamically sized set of trailing elements in a structure. Kernel code
>>> should always use “flexible array members”[1] for these cases. The older
>>> style of one-element or zero-length arrays should no longer be used[2].
>>
>> I proposal to do the similar cleanup, and I've no objection on doing this.
>>
>> https://lore.kernel.org/patchwork/patch/869440/
>>
>> Let's ask for Jaegeuk' opinion.
> 
> Merged, thanks.
> This looks better reason than code readability. :)

Agreed.

Reviewed-by: Chao Yu <yuchao0@huawei.com>

Thanks,

> 
>>
>>>
>>> Refactor the code according to the use of a flexible-array member in
>>> struct f2fs_checkpoint, instead of a one-element arrays.
>>>
>>> Notice that a temporary pointer to void '*tmp_ptr' was used in order to
>>> fix the following errors when using a flexible array instead of a one
>>> element array in struct f2fs_checkpoint:
>>>
>>>     CC [M]  fs/f2fs/dir.o
>>> In file included from fs/f2fs/dir.c:13:
>>> fs/f2fs/f2fs.h: In function ‘__bitmap_ptr’:
>>> fs/f2fs/f2fs.h:2227:40: error: invalid use of flexible array member
>>>    2227 |   return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
>>>         |                                        ^
>>> fs/f2fs/f2fs.h:2227:49: error: invalid use of flexible array member
>>>    2227 |   return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
>>>         |                                                 ^
>>> fs/f2fs/f2fs.h:2238:40: error: invalid use of flexible array member
>>>    2238 |   return &ckpt->sit_nat_version_bitmap + offset;
>>>         |                                        ^
>>> make[2]: *** [scripts/Makefile.build:287: fs/f2fs/dir.o] Error 1
>>> make[1]: *** [scripts/Makefile.build:530: fs/f2fs] Error 2
>>> make: *** [Makefile:1819: fs] Error 2
>>>
>>> [1] https://en.wikipedia.org/wiki/Flexible_array_member
>>> [2] https://www.kernel.org/doc/html/v5.9/process/deprecated.html#zero-length-and-one-element-arrays
>>>
>>> Link: https://github.com/KSPP/linux/issues/79
>>> Build-tested-by: kernel test robot <lkp@intel.com>
>>> Link: https://lore.kernel.org/lkml/603647e4.DeEFbl4eqljuwAUe%25lkp@intel.com/
>>> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
>>> ---
>>>    fs/f2fs/f2fs.h          | 5 +++--
>>>    include/linux/f2fs_fs.h | 2 +-
>>>    2 files changed, 4 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>> index e2d302ae3a46..3f5cb097c30f 100644
>>> --- a/fs/f2fs/f2fs.h
>>> +++ b/fs/f2fs/f2fs.h
>>> @@ -2215,6 +2215,7 @@ static inline block_t __cp_payload(struct f2fs_sb_info *sbi)
>>>    static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
>>>    {
>>>    	struct f2fs_checkpoint *ckpt = F2FS_CKPT(sbi);
>>> +	void *tmp_ptr = &ckpt->sit_nat_version_bitmap;
>>>    	int offset;
>>>    	if (is_set_ckpt_flags(sbi, CP_LARGE_NAT_BITMAP_FLAG)) {
>>> @@ -2224,7 +2225,7 @@ static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
>>>    		 * if large_nat_bitmap feature is enabled, leave checksum
>>>    		 * protection for all nat/sit bitmaps.
>>>    		 */
>>> -		return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
>>> +		return tmp_ptr + offset + sizeof(__le32);
>>>    	}
>>>    	if (__cp_payload(sbi) > 0) {
>>> @@ -2235,7 +2236,7 @@ static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
>>>    	} else {
>>>    		offset = (flag == NAT_BITMAP) ?
>>>    			le32_to_cpu(ckpt->sit_ver_bitmap_bytesize) : 0;
>>> -		return &ckpt->sit_nat_version_bitmap + offset;
>>> +		return tmp_ptr + offset;
>>>    	}
>>>    }
>>> diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
>>> index c6cc0a566ef5..5487a80617a3 100644
>>> --- a/include/linux/f2fs_fs.h
>>> +++ b/include/linux/f2fs_fs.h
>>> @@ -168,7 +168,7 @@ struct f2fs_checkpoint {
>>>    	unsigned char alloc_type[MAX_ACTIVE_LOGS];
>>>    	/* SIT and NAT version bitmap */
>>> -	unsigned char sit_nat_version_bitmap[1];
>>> +	unsigned char sit_nat_version_bitmap[];
>>>    } __packed;
>>>    #define CP_CHKSUM_OFFSET	4092	/* default chksum offset in checkpoint */
>>>
> .
> 

Re: [f2fs-dev] [PATCH][next] f2fs: Replace one-element array with flexible-array member

[Chao Yu]

On 2021/2/28 13:00, Jaegeuk Kim wrote:
> On 02/25, Chao Yu wrote:
>> Hello, Gustavo,
>>
>> On 2021/2/25 3:03, Gustavo A. R. Silva wrote:
>>> There is a regular need in the kernel to provide a way to declare having
>>> a dynamically sized set of trailing elements in a structure. Kernel code
>>> should always use “flexible array members”[1] for these cases. The older
>>> style of one-element or zero-length arrays should no longer be used[2].
>>
>> I proposal to do the similar cleanup, and I've no objection on doing this.
>>
>> https://lore.kernel.org/patchwork/patch/869440/
>>
>> Let's ask for Jaegeuk' opinion.
> 
> Merged, thanks.
> This looks better reason than code readability. :)

Agreed.

Reviewed-by: Chao Yu <yuchao0@huawei.com>

Thanks,

> 
>>
>>>
>>> Refactor the code according to the use of a flexible-array member in
>>> struct f2fs_checkpoint, instead of a one-element arrays.
>>>
>>> Notice that a temporary pointer to void '*tmp_ptr' was used in order to
>>> fix the following errors when using a flexible array instead of a one
>>> element array in struct f2fs_checkpoint:
>>>
>>>     CC [M]  fs/f2fs/dir.o
>>> In file included from fs/f2fs/dir.c:13:
>>> fs/f2fs/f2fs.h: In function ‘__bitmap_ptr’:
>>> fs/f2fs/f2fs.h:2227:40: error: invalid use of flexible array member
>>>    2227 |   return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
>>>         |                                        ^
>>> fs/f2fs/f2fs.h:2227:49: error: invalid use of flexible array member
>>>    2227 |   return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
>>>         |                                                 ^
>>> fs/f2fs/f2fs.h:2238:40: error: invalid use of flexible array member
>>>    2238 |   return &ckpt->sit_nat_version_bitmap + offset;
>>>         |                                        ^
>>> make[2]: *** [scripts/Makefile.build:287: fs/f2fs/dir.o] Error 1
>>> make[1]: *** [scripts/Makefile.build:530: fs/f2fs] Error 2
>>> make: *** [Makefile:1819: fs] Error 2
>>>
>>> [1] https://en.wikipedia.org/wiki/Flexible_array_member
>>> [2] https://www.kernel.org/doc/html/v5.9/process/deprecated.html#zero-length-and-one-element-arrays
>>>
>>> Link: https://github.com/KSPP/linux/issues/79
>>> Build-tested-by: kernel test robot <lkp@intel.com>
>>> Link: https://lore.kernel.org/lkml/603647e4.DeEFbl4eqljuwAUe%25lkp@intel.com/
>>> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
>>> ---
>>>    fs/f2fs/f2fs.h          | 5 +++--
>>>    include/linux/f2fs_fs.h | 2 +-
>>>    2 files changed, 4 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>> index e2d302ae3a46..3f5cb097c30f 100644
>>> --- a/fs/f2fs/f2fs.h
>>> +++ b/fs/f2fs/f2fs.h
>>> @@ -2215,6 +2215,7 @@ static inline block_t __cp_payload(struct f2fs_sb_info *sbi)
>>>    static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
>>>    {
>>>    	struct f2fs_checkpoint *ckpt = F2FS_CKPT(sbi);
>>> +	void *tmp_ptr = &ckpt->sit_nat_version_bitmap;
>>>    	int offset;
>>>    	if (is_set_ckpt_flags(sbi, CP_LARGE_NAT_BITMAP_FLAG)) {
>>> @@ -2224,7 +2225,7 @@ static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
>>>    		 * if large_nat_bitmap feature is enabled, leave checksum
>>>    		 * protection for all nat/sit bitmaps.
>>>    		 */
>>> -		return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
>>> +		return tmp_ptr + offset + sizeof(__le32);
>>>    	}
>>>    	if (__cp_payload(sbi) > 0) {
>>> @@ -2235,7 +2236,7 @@ static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
>>>    	} else {
>>>    		offset = (flag == NAT_BITMAP) ?
>>>    			le32_to_cpu(ckpt->sit_ver_bitmap_bytesize) : 0;
>>> -		return &ckpt->sit_nat_version_bitmap + offset;
>>> +		return tmp_ptr + offset;
>>>    	}
>>>    }
>>> diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
>>> index c6cc0a566ef5..5487a80617a3 100644
>>> --- a/include/linux/f2fs_fs.h
>>> +++ b/include/linux/f2fs_fs.h
>>> @@ -168,7 +168,7 @@ struct f2fs_checkpoint {
>>>    	unsigned char alloc_type[MAX_ACTIVE_LOGS];
>>>    	/* SIT and NAT version bitmap */
>>> -	unsigned char sit_nat_version_bitmap[1];
>>> +	unsigned char sit_nat_version_bitmap[];
>>>    } __packed;
>>>    #define CP_CHKSUM_OFFSET	4092	/* default chksum offset in checkpoint */
>>>
> .
> 


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