Re: [PATCH] fs: ufs: Convert ufs_set_de_type to use lookup table

[Phillip Potter]

On Tue, Oct 02, 2018 at 03:28:14AM +0100, Al Viro wrote:
> On Mon, Oct 01, 2018 at 04:33:10PM +0100, Phillip Potter wrote:
> > Modify ufs_set_de_type function in fs/ufs/util.h to use a lookup
> > table rather than a switch statement, as per the TODO comment.
> 
> Brittle, that...   Something like fs/ext2/dir.c approach (that is,
> #define S_SHIFT 12
> static unsigned char ext2_type_by_mode[S_IFMT >> S_SHIFT] = {
> [S_IFREG >> S_SHIFT]= EXT2_FT_REG_FILE,
> [S_IFDIR >> S_SHIFT]= EXT2_FT_DIR,
> [S_IFCHR >> S_SHIFT]= EXT2_FT_CHRDEV,
> [S_IFBLK >> S_SHIFT]= EXT2_FT_BLKDEV,
> [S_IFIFO >> S_SHIFT]= EXT2_FT_FIFO,
> [S_IFSOCK >> S_SHIFT]   = EXT2_FT_SOCK,
> [S_IFLNK >> S_SHIFT]= EXT2_FT_SYMLINK,
> };
> in there) would be saner, IMO.  Note that DT_UNKNOWN is zero, so the
> array elements lacking an explicit initializer will end up with that.
> 
> What's more, the values are ->i_mode >> 12 or 0, depending upon the
> value being valid.  And since the upper layers do validate the type,
> I'd consider simply using (inode->i_mode & S_IFMT) >> 12 there.
> Unlike ext2, ufs stores straight bits 12..15 there (ext2 uses an
> enum with sequential values instead; e.g. regular files are encoded
> as 1 there, not 8 as on ufs)...

Dear Al,

Thank you for taking time to offer your feedback, I really appreciate
it. I will rework this patch this evening and resubmit.

Regards,
Phil

Re: [PATCH] fs: ufs: Convert ufs_set_de_type to use lookup table

[Phillip Potter]

On Tue, Oct 02, 2018 at 03:28:14AM +0100, Al Viro wrote:
> On Mon, Oct 01, 2018 at 04:33:10PM +0100, Phillip Potter wrote:
> > Modify ufs_set_de_type function in fs/ufs/util.h to use a lookup
> > table rather than a switch statement, as per the TODO comment.
> 
> Brittle, that...   Something like fs/ext2/dir.c approach (that is,
> #define S_SHIFT 12
> static unsigned char ext2_type_by_mode[S_IFMT >> S_SHIFT] = {
> [S_IFREG >> S_SHIFT]= EXT2_FT_REG_FILE,
> [S_IFDIR >> S_SHIFT]= EXT2_FT_DIR,
> [S_IFCHR >> S_SHIFT]= EXT2_FT_CHRDEV,
> [S_IFBLK >> S_SHIFT]= EXT2_FT_BLKDEV,
> [S_IFIFO >> S_SHIFT]= EXT2_FT_FIFO,
> [S_IFSOCK >> S_SHIFT]   = EXT2_FT_SOCK,
> [S_IFLNK >> S_SHIFT]= EXT2_FT_SYMLINK,
> };
> in there) would be saner, IMO.  Note that DT_UNKNOWN is zero, so the
> array elements lacking an explicit initializer will end up with that.
> 
> What's more, the values are ->i_mode >> 12 or 0, depending upon the
> value being valid.  And since the upper layers do validate the type,
> I'd consider simply using (inode->i_mode & S_IFMT) >> 12 there.
> Unlike ext2, ufs stores straight bits 12..15 there (ext2 uses an
> enum with sequential values instead; e.g. regular files are encoded
> as 1 there, not 8 as on ufs)...

Dear Al,

Thank you for taking time to offer your feedback, I really appreciate
it. I will rework this patch this evening and resubmit.

Regards,
Phil

Re: [PATCH] fs: ufs: Convert ufs_set_de_type to use lookup table

[Al Viro]

On Mon, Oct 01, 2018 at 04:33:10PM +0100, Phillip Potter wrote:
> Modify ufs_set_de_type function in fs/ufs/util.h to use a lookup
> table rather than a switch statement, as per the TODO comment.

Brittle, that...   Something like fs/ext2/dir.c approach (that is,
#define S_SHIFT 12
static unsigned char ext2_type_by_mode[S_IFMT >> S_SHIFT] = {
[S_IFREG >> S_SHIFT]= EXT2_FT_REG_FILE,
[S_IFDIR >> S_SHIFT]= EXT2_FT_DIR,
[S_IFCHR >> S_SHIFT]= EXT2_FT_CHRDEV,
[S_IFBLK >> S_SHIFT]= EXT2_FT_BLKDEV,
[S_IFIFO >> S_SHIFT]= EXT2_FT_FIFO,
[S_IFSOCK >> S_SHIFT]   = EXT2_FT_SOCK,
[S_IFLNK >> S_SHIFT]= EXT2_FT_SYMLINK,
};
in there) would be saner, IMO.  Note that DT_UNKNOWN is zero, so the
array elements lacking an explicit initializer will end up with that.

What's more, the values are ->i_mode >> 12 or 0, depending upon the
value being valid.  And since the upper layers do validate the type,
I'd consider simply using (inode->i_mode & S_IFMT) >> 12 there.
Unlike ext2, ufs stores straight bits 12..15 there (ext2 uses an
enum with sequential values instead; e.g. regular files are encoded
as 1 there, not 8 as on ufs)...

Re: [PATCH] fs: ufs: Convert ufs_set_de_type to use lookup table

[Al Viro]

On Mon, Oct 01, 2018 at 04:33:10PM +0100, Phillip Potter wrote:
> Modify ufs_set_de_type function in fs/ufs/util.h to use a lookup
> table rather than a switch statement, as per the TODO comment.

Brittle, that...   Something like fs/ext2/dir.c approach (that is,
#define S_SHIFT 12
static unsigned char ext2_type_by_mode[S_IFMT >> S_SHIFT] = {
[S_IFREG >> S_SHIFT]= EXT2_FT_REG_FILE,
[S_IFDIR >> S_SHIFT]= EXT2_FT_DIR,
[S_IFCHR >> S_SHIFT]= EXT2_FT_CHRDEV,
[S_IFBLK >> S_SHIFT]= EXT2_FT_BLKDEV,
[S_IFIFO >> S_SHIFT]= EXT2_FT_FIFO,
[S_IFSOCK >> S_SHIFT]   = EXT2_FT_SOCK,
[S_IFLNK >> S_SHIFT]= EXT2_FT_SYMLINK,
};
in there) would be saner, IMO.  Note that DT_UNKNOWN is zero, so the
array elements lacking an explicit initializer will end up with that.

What's more, the values are ->i_mode >> 12 or 0, depending upon the
value being valid.  And since the upper layers do validate the type,
I'd consider simply using (inode->i_mode & S_IFMT) >> 12 there.
Unlike ext2, ufs stores straight bits 12..15 there (ext2 uses an
enum with sequential values instead; e.g. regular files are encoded
as 1 there, not 8 as on ufs)...

[PATCH] fs: ufs: Convert ufs_set_de_type to use lookup table

[Phillip Potter]

Modify ufs_set_de_type function in fs/ufs/util.h to use a lookup
table rather than a switch statement, as per the TODO comment.

Signed-off-by: Phillip Potter 
---
diff --git a/fs/ufs/util.h b/fs/ufs/util.h
index 1907be6d5808..1edf4c6454e3 100644
--- a/fs/ufs/util.h
+++ b/fs/ufs/util.h
@@ -155,37 +155,31 @@ ufs_set_de_namlen(struct super_block *sb, struct 
ufs_dir_entry *de, u16 value)
 static inline void
 ufs_set_de_type(struct super_block *sb, struct ufs_dir_entry *de, int mode)
 {
+   /* type lookup table, DT_UNKNOWN is default type if no case holds */
+   const int mode_table[] = {
+   DT_UNKNOWN,
+   DT_FIFO,/* mode & S_IFMT == S_IFIFO case */
+   DT_CHR, /* mode & S_IFMT == S_IFCHR case */
+   DT_UNKNOWN,
+   DT_DIR, /* mode & S_IFMT == S_IFDIR case */
+   DT_UNKNOWN,
+   DT_BLK, /* mode & S_IFMT == S_IFBLK case */
+   DT_UNKNOWN,
+   DT_REG, /* mode & S_IFMT == S_IFREG case */
+   DT_UNKNOWN,
+   DT_LNK, /* mode & S_IFMT == S_IFLNK case */
+   DT_UNKNOWN,
+   DT_SOCK,/* mode & S_IFMT == S_IFSOCK case */
+   DT_UNKNOWN,
+   DT_UNKNOWN,
+   DT_UNKNOWN
+   };
+
if ((UFS_SB(sb)->s_flags & UFS_DE_MASK) != UFS_DE_44BSD)
return;
 
-   /*
-* TODO turn this into a table lookup
-*/
-   switch (mode & S_IFMT) {
-   case S_IFSOCK:
-   de->d_u.d_44.d_type = DT_SOCK;
-   break;
-   case S_IFLNK:
-   de->d_u.d_44.d_type = DT_LNK;
-   break;
-   case S_IFREG:
-   de->d_u.d_44.d_type = DT_REG;
-   break;
-   case S_IFBLK:
-   de->d_u.d_44.d_type = DT_BLK;
-   break;
-   case S_IFDIR:
-   de->d_u.d_44.d_type = DT_DIR;
-   break;
-   case S_IFCHR:
-   de->d_u.d_44.d_type = DT_CHR;
-   break;
-   case S_IFIFO:
-   de->d_u.d_44.d_type = DT_FIFO;
-   break;
-   default:
-   de->d_u.d_44.d_type = DT_UNKNOWN;
-   }
+   /* shift (mode & S_IFMT) right 12 bits to index into table */
+   de->d_u.d_44.d_type = mode_table[(mode & S_IFMT) >> 12];
 }
 
 static inline u32

[PATCH] fs: ufs: Convert ufs_set_de_type to use lookup table

[Phillip Potter]

Modify ufs_set_de_type function in fs/ufs/util.h to use a lookup
table rather than a switch statement, as per the TODO comment.

Signed-off-by: Phillip Potter 
---
diff --git a/fs/ufs/util.h b/fs/ufs/util.h
index 1907be6d5808..1edf4c6454e3 100644
--- a/fs/ufs/util.h
+++ b/fs/ufs/util.h
@@ -155,37 +155,31 @@ ufs_set_de_namlen(struct super_block *sb, struct 
ufs_dir_entry *de, u16 value)
 static inline void
 ufs_set_de_type(struct super_block *sb, struct ufs_dir_entry *de, int mode)
 {
+   /* type lookup table, DT_UNKNOWN is default type if no case holds */
+   const int mode_table[] = {
+   DT_UNKNOWN,
+   DT_FIFO,/* mode & S_IFMT == S_IFIFO case */
+   DT_CHR, /* mode & S_IFMT == S_IFCHR case */
+   DT_UNKNOWN,
+   DT_DIR, /* mode & S_IFMT == S_IFDIR case */
+   DT_UNKNOWN,
+   DT_BLK, /* mode & S_IFMT == S_IFBLK case */
+   DT_UNKNOWN,
+   DT_REG, /* mode & S_IFMT == S_IFREG case */
+   DT_UNKNOWN,
+   DT_LNK, /* mode & S_IFMT == S_IFLNK case */
+   DT_UNKNOWN,
+   DT_SOCK,/* mode & S_IFMT == S_IFSOCK case */
+   DT_UNKNOWN,
+   DT_UNKNOWN,
+   DT_UNKNOWN
+   };
+
if ((UFS_SB(sb)->s_flags & UFS_DE_MASK) != UFS_DE_44BSD)
return;
 
-   /*
-* TODO turn this into a table lookup
-*/
-   switch (mode & S_IFMT) {
-   case S_IFSOCK:
-   de->d_u.d_44.d_type = DT_SOCK;
-   break;
-   case S_IFLNK:
-   de->d_u.d_44.d_type = DT_LNK;
-   break;
-   case S_IFREG:
-   de->d_u.d_44.d_type = DT_REG;
-   break;
-   case S_IFBLK:
-   de->d_u.d_44.d_type = DT_BLK;
-   break;
-   case S_IFDIR:
-   de->d_u.d_44.d_type = DT_DIR;
-   break;
-   case S_IFCHR:
-   de->d_u.d_44.d_type = DT_CHR;
-   break;
-   case S_IFIFO:
-   de->d_u.d_44.d_type = DT_FIFO;
-   break;
-   default:
-   de->d_u.d_44.d_type = DT_UNKNOWN;
-   }
+   /* shift (mode & S_IFMT) right 12 bits to index into table */
+   de->d_u.d_44.d_type = mode_table[(mode & S_IFMT) >> 12];
 }
 
 static inline u32

[PATCH] fs: ufs: Convert ufs_set_de_type to use lookup table

[Phillip Potter]

Modify ufs_set_de_type function in fs/ufs/util.h to use a lookup
table rather than a switch statement, as per the TODO comment.

Signed-off-by: Phillip Potter 
---
 fs/ufs/util.h | 50 ++
 1 file changed, 22 insertions(+), 28 deletions(-)

diff --git a/fs/ufs/util.h b/fs/ufs/util.h
index 1907be6d5808..1edf4c6454e3 100644
--- a/fs/ufs/util.h
+++ b/fs/ufs/util.h
@@ -155,37 +155,31 @@ ufs_set_de_namlen(struct super_block *sb, struct 
ufs_dir_entry *de, u16 value)
 static inline void
 ufs_set_de_type(struct super_block *sb, struct ufs_dir_entry *de, int mode)
 {
+   /* type lookup table, DT_UNKNOWN is default type if no case holds */
+   const int mode_table[] = {
+   DT_UNKNOWN,
+   DT_FIFO,/* mode & S_IFMT == S_IFIFO case */
+   DT_CHR, /* mode & S_IFMT == S_IFCHR case */
+   DT_UNKNOWN,
+   DT_DIR, /* mode & S_IFMT == S_IFDIR case */
+   DT_UNKNOWN,
+   DT_BLK, /* mode & S_IFMT == S_IFBLK case */
+   DT_UNKNOWN,
+   DT_REG, /* mode & S_IFMT == S_IFREG case */
+   DT_UNKNOWN,
+   DT_LNK, /* mode & S_IFMT == S_IFLNK case */
+   DT_UNKNOWN,
+   DT_SOCK,/* mode & S_IFMT == S_IFSOCK case */
+   DT_UNKNOWN,
+   DT_UNKNOWN,
+   DT_UNKNOWN
+   };
+
if ((UFS_SB(sb)->s_flags & UFS_DE_MASK) != UFS_DE_44BSD)
return;
 
-   /*
-* TODO turn this into a table lookup
-*/
-   switch (mode & S_IFMT) {
-   case S_IFSOCK:
-   de->d_u.d_44.d_type = DT_SOCK;
-   break;
-   case S_IFLNK:
-   de->d_u.d_44.d_type = DT_LNK;
-   break;
-   case S_IFREG:
-   de->d_u.d_44.d_type = DT_REG;
-   break;
-   case S_IFBLK:
-   de->d_u.d_44.d_type = DT_BLK;
-   break;
-   case S_IFDIR:
-   de->d_u.d_44.d_type = DT_DIR;
-   break;
-   case S_IFCHR:
-   de->d_u.d_44.d_type = DT_CHR;
-   break;
-   case S_IFIFO:
-   de->d_u.d_44.d_type = DT_FIFO;
-   break;
-   default:
-   de->d_u.d_44.d_type = DT_UNKNOWN;
-   }
+   /* shift (mode & S_IFMT) right 12 bits to index into table */
+   de->d_u.d_44.d_type = mode_table[(mode & S_IFMT) >> 12];
 }
 
 static inline u32
-- 
2.14.3

[PATCH] fs: ufs: Convert ufs_set_de_type to use lookup table

[Phillip Potter]

Modify ufs_set_de_type function in fs/ufs/util.h to use a lookup
table rather than a switch statement, as per the TODO comment.

Signed-off-by: Phillip Potter 
---
 fs/ufs/util.h | 50 ++
 1 file changed, 22 insertions(+), 28 deletions(-)

diff --git a/fs/ufs/util.h b/fs/ufs/util.h
index 1907be6d5808..1edf4c6454e3 100644
--- a/fs/ufs/util.h
+++ b/fs/ufs/util.h
@@ -155,37 +155,31 @@ ufs_set_de_namlen(struct super_block *sb, struct 
ufs_dir_entry *de, u16 value)
 static inline void
 ufs_set_de_type(struct super_block *sb, struct ufs_dir_entry *de, int mode)
 {
+   /* type lookup table, DT_UNKNOWN is default type if no case holds */
+   const int mode_table[] = {
+   DT_UNKNOWN,
+   DT_FIFO,/* mode & S_IFMT == S_IFIFO case */
+   DT_CHR, /* mode & S_IFMT == S_IFCHR case */
+   DT_UNKNOWN,
+   DT_DIR, /* mode & S_IFMT == S_IFDIR case */
+   DT_UNKNOWN,
+   DT_BLK, /* mode & S_IFMT == S_IFBLK case */
+   DT_UNKNOWN,
+   DT_REG, /* mode & S_IFMT == S_IFREG case */
+   DT_UNKNOWN,
+   DT_LNK, /* mode & S_IFMT == S_IFLNK case */
+   DT_UNKNOWN,
+   DT_SOCK,/* mode & S_IFMT == S_IFSOCK case */
+   DT_UNKNOWN,
+   DT_UNKNOWN,
+   DT_UNKNOWN
+   };
+
if ((UFS_SB(sb)->s_flags & UFS_DE_MASK) != UFS_DE_44BSD)
return;
 
-   /*
-* TODO turn this into a table lookup
-*/
-   switch (mode & S_IFMT) {
-   case S_IFSOCK:
-   de->d_u.d_44.d_type = DT_SOCK;
-   break;
-   case S_IFLNK:
-   de->d_u.d_44.d_type = DT_LNK;
-   break;
-   case S_IFREG:
-   de->d_u.d_44.d_type = DT_REG;
-   break;
-   case S_IFBLK:
-   de->d_u.d_44.d_type = DT_BLK;
-   break;
-   case S_IFDIR:
-   de->d_u.d_44.d_type = DT_DIR;
-   break;
-   case S_IFCHR:
-   de->d_u.d_44.d_type = DT_CHR;
-   break;
-   case S_IFIFO:
-   de->d_u.d_44.d_type = DT_FIFO;
-   break;
-   default:
-   de->d_u.d_44.d_type = DT_UNKNOWN;
-   }
+   /* shift (mode & S_IFMT) right 12 bits to index into table */
+   de->d_u.d_44.d_type = mode_table[(mode & S_IFMT) >> 12];
 }
 
 static inline u32
-- 
2.14.3

[PATCH] fs: ufs: Convert ufs_set_de_type to use lookup table

[Phillip Potter]

Modify ufs_set_de_type function in fs/ufs/util.h to use a lookup
table rather than a switch statement, as per the TODO comment.

Signed-off-by: Phillip Potter 
---
 fs/ufs/util.h | 50 ++
 1 file changed, 22 insertions(+), 28 deletions(-)

diff --git a/fs/ufs/util.h b/fs/ufs/util.h
index 1907be6d5808..1edf4c6454e3 100644
--- a/fs/ufs/util.h
+++ b/fs/ufs/util.h
@@ -155,37 +155,31 @@ ufs_set_de_namlen(struct super_block *sb, struct 
ufs_dir_entry *de, u16 value)
 static inline void
 ufs_set_de_type(struct super_block *sb, struct ufs_dir_entry *de, int mode)
 {
+   /* type lookup table, DT_UNKNOWN is default type if no case holds */
+   const int mode_table[] = {
+   DT_UNKNOWN,
+   DT_FIFO,/* mode & S_IFMT == S_IFIFO case */
+   DT_CHR, /* mode & S_IFMT == S_IFCHR case */
+   DT_UNKNOWN,
+   DT_DIR, /* mode & S_IFMT == S_IFDIR case */
+   DT_UNKNOWN,
+   DT_BLK, /* mode & S_IFMT == S_IFBLK case */
+   DT_UNKNOWN,
+   DT_REG, /* mode & S_IFMT == S_IFREG case */
+   DT_UNKNOWN,
+   DT_LNK, /* mode & S_IFMT == S_IFLNK case */
+   DT_UNKNOWN,
+   DT_SOCK,/* mode & S_IFMT == S_IFSOCK case */
+   DT_UNKNOWN,
+   DT_UNKNOWN,
+   DT_UNKNOWN
+   };
+
if ((UFS_SB(sb)->s_flags & UFS_DE_MASK) != UFS_DE_44BSD)
return;
 
-   /*
-* TODO turn this into a table lookup
-*/
-   switch (mode & S_IFMT) {
-   case S_IFSOCK:
-   de->d_u.d_44.d_type = DT_SOCK;
-   break;
-   case S_IFLNK:
-   de->d_u.d_44.d_type = DT_LNK;
-   break;
-   case S_IFREG:
-   de->d_u.d_44.d_type = DT_REG;
-   break;
-   case S_IFBLK:
-   de->d_u.d_44.d_type = DT_BLK;
-   break;
-   case S_IFDIR:
-   de->d_u.d_44.d_type = DT_DIR;
-   break;
-   case S_IFCHR:
-   de->d_u.d_44.d_type = DT_CHR;
-   break;
-   case S_IFIFO:
-   de->d_u.d_44.d_type = DT_FIFO;
-   break;
-   default:
-   de->d_u.d_44.d_type = DT_UNKNOWN;
-   }
+   /* shift (mode & S_IFMT) right 12 bits to index into table */
+   de->d_u.d_44.d_type = mode_table[(mode & S_IFMT) >> 12];
 }
 
 static inline u32
-- 
2.14.3

[PATCH] fs: ufs: Convert ufs_set_de_type to use lookup table

[Phillip Potter]

Modify ufs_set_de_type function in fs/ufs/util.h to use a lookup
table rather than a switch statement, as per the TODO comment.

Signed-off-by: Phillip Potter 
---
 fs/ufs/util.h | 50 ++
 1 file changed, 22 insertions(+), 28 deletions(-)

diff --git a/fs/ufs/util.h b/fs/ufs/util.h
index 1907be6d5808..1edf4c6454e3 100644
--- a/fs/ufs/util.h
+++ b/fs/ufs/util.h
@@ -155,37 +155,31 @@ ufs_set_de_namlen(struct super_block *sb, struct 
ufs_dir_entry *de, u16 value)
 static inline void
 ufs_set_de_type(struct super_block *sb, struct ufs_dir_entry *de, int mode)
 {
+   /* type lookup table, DT_UNKNOWN is default type if no case holds */
+   const int mode_table[] = {
+   DT_UNKNOWN,
+   DT_FIFO,/* mode & S_IFMT == S_IFIFO case */
+   DT_CHR, /* mode & S_IFMT == S_IFCHR case */
+   DT_UNKNOWN,
+   DT_DIR, /* mode & S_IFMT == S_IFDIR case */
+   DT_UNKNOWN,
+   DT_BLK, /* mode & S_IFMT == S_IFBLK case */
+   DT_UNKNOWN,
+   DT_REG, /* mode & S_IFMT == S_IFREG case */
+   DT_UNKNOWN,
+   DT_LNK, /* mode & S_IFMT == S_IFLNK case */
+   DT_UNKNOWN,
+   DT_SOCK,/* mode & S_IFMT == S_IFSOCK case */
+   DT_UNKNOWN,
+   DT_UNKNOWN,
+   DT_UNKNOWN
+   };
+
if ((UFS_SB(sb)->s_flags & UFS_DE_MASK) != UFS_DE_44BSD)
return;
 
-   /*
-* TODO turn this into a table lookup
-*/
-   switch (mode & S_IFMT) {
-   case S_IFSOCK:
-   de->d_u.d_44.d_type = DT_SOCK;
-   break;
-   case S_IFLNK:
-   de->d_u.d_44.d_type = DT_LNK;
-   break;
-   case S_IFREG:
-   de->d_u.d_44.d_type = DT_REG;
-   break;
-   case S_IFBLK:
-   de->d_u.d_44.d_type = DT_BLK;
-   break;
-   case S_IFDIR:
-   de->d_u.d_44.d_type = DT_DIR;
-   break;
-   case S_IFCHR:
-   de->d_u.d_44.d_type = DT_CHR;
-   break;
-   case S_IFIFO:
-   de->d_u.d_44.d_type = DT_FIFO;
-   break;
-   default:
-   de->d_u.d_44.d_type = DT_UNKNOWN;
-   }
+   /* shift (mode & S_IFMT) right 12 bits to index into table */
+   de->d_u.d_44.d_type = mode_table[(mode & S_IFMT) >> 12];
 }
 
 static inline u32
-- 
2.14.3