[01/11] btrfs: add macros for compression type and level
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Message ID 20190128212437.11597-2-dennis@kernel.org
State New
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Series
  • btrfs: add zstd compression level support
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Commit Message

Dennis Zhou Jan. 28, 2019, 9:24 p.m. UTC
It is very easy to miss places that rely on a certain bitshifting for
decyphering the type_level overloading. Make macros handle this instead.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
---
 fs/btrfs/compression.c | 2 +-
 fs/btrfs/compression.h | 3 +++
 fs/btrfs/zlib.c        | 2 +-
 3 files changed, 5 insertions(+), 2 deletions(-)

Comments

Nikolay Borisov Jan. 29, 2019, 7:26 a.m. UTC | #1
On 28.01.19 г. 23:24 ч., Dennis Zhou wrote:
> It is very easy to miss places that rely on a certain bitshifting for
> decyphering the type_level overloading. Make macros handle this instead.
> 
> Signed-off-by: Dennis Zhou <dennis@kernel.org>

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Josef Bacik Jan. 29, 2019, 5:57 p.m. UTC | #2
On Mon, Jan 28, 2019 at 04:24:27PM -0500, Dennis Zhou wrote:
> It is very easy to miss places that rely on a certain bitshifting for
> decyphering the type_level overloading. Make macros handle this instead.
> 
> Signed-off-by: Dennis Zhou <dennis@kernel.org>

Reviewed-by: Josef Bacik <josef@toxicpanda.com>

Thanks,

Josef
Omar Sandoval Jan. 29, 2019, 10:30 p.m. UTC | #3
On Mon, Jan 28, 2019 at 04:24:27PM -0500, Dennis Zhou wrote:
> It is very easy to miss places that rely on a certain bitshifting for
> decyphering the type_level overloading. Make macros handle this instead.
> 
> Signed-off-by: Dennis Zhou <dennis@kernel.org>
> ---
>  fs/btrfs/compression.c | 2 +-
>  fs/btrfs/compression.h | 3 +++
>  fs/btrfs/zlib.c        | 2 +-
>  3 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
> index 548057630b69..586f95ac0aea 100644
> --- a/fs/btrfs/compression.c
> +++ b/fs/btrfs/compression.c
> @@ -1036,9 +1036,9 @@ int btrfs_compress_pages(unsigned int type_level, struct address_space *mapping,
>  			 unsigned long *total_in,
>  			 unsigned long *total_out)
>  {
> +	int type = BTRFS_COMPRESS_TYPE(type_level);
>  	struct list_head *workspace;
>  	int ret;
> -	int type = type_level & 0xF;
>  
>  	workspace = find_workspace(type);
>  
> diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h
> index ddda9b80bf20..69a9197dadc3 100644
> --- a/fs/btrfs/compression.h
> +++ b/fs/btrfs/compression.h
> @@ -25,6 +25,9 @@
>  
>  #define	BTRFS_ZLIB_DEFAULT_LEVEL		3
>  
> +#define BTRFS_COMPRESS_TYPE(type_level)		(type_level & 0xF)
> +#define BTRFS_COMPRESS_LEVEL(type_level)	((type_level & 0xF0) >> 4)

Nit: these can be inline functions rather than macros.

>  struct compressed_bio {
>  	/* number of bios pending for this compressed extent */
>  	refcount_t pending_bios;
> diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c
> index 970ff3e35bb3..1480b3eee306 100644
> --- a/fs/btrfs/zlib.c
> +++ b/fs/btrfs/zlib.c
> @@ -393,7 +393,7 @@ static int zlib_decompress(struct list_head *ws, unsigned char *data_in,
>  static void zlib_set_level(struct list_head *ws, unsigned int type)
>  {
>  	struct workspace *workspace = list_entry(ws, struct workspace, list);
> -	unsigned level = (type & 0xF0) >> 4;
> +	unsigned int level = BTRFS_COMPRESS_LEVEL(type);
>  
>  	if (level > 9)
>  		level = 9;
> -- 
> 2.17.1
>
David Sterba Jan. 31, 2019, 4 p.m. UTC | #4
On Mon, Jan 28, 2019 at 04:24:27PM -0500, Dennis Zhou wrote:
> It is very easy to miss places that rely on a certain bitshifting for
> decyphering the type_level overloading. Make macros handle this instead.

This encoding was a simple way to introduce the combined type and level
for zlib and it could certainly be improved. Either we'll use helpers
like you suggest or add a new structure that contains type and level as
members. That way we'd see where the level still matters and where the
just the type is ok.

I haven't checked how much intrusive this would be, so that's for later
consideration. Some indirection can be removed for the .set_level
callbacks as it does not necessarily need to be a function so I'm
expecting that the code around that would be touched anyway.
Dennis Zhou Jan. 31, 2019, 4:17 p.m. UTC | #5
On Thu, Jan 31, 2019 at 05:00:10PM +0100, David Sterba wrote:
> On Mon, Jan 28, 2019 at 04:24:27PM -0500, Dennis Zhou wrote:
> > It is very easy to miss places that rely on a certain bitshifting for
> > decyphering the type_level overloading. Make macros handle this instead.
> 
> This encoding was a simple way to introduce the combined type and level
> for zlib and it could certainly be improved. Either we'll use helpers
> like you suggest or add a new structure that contains type and level as
> members. That way we'd see where the level still matters and where the
> just the type is ok.
> 
> I haven't checked how much intrusive this would be, so that's for later
> consideration. Some indirection can be removed for the .set_level
> callbacks as it does not necessarily need to be a function so I'm
> expecting that the code around that would be touched anyway.

The only user of type_level is btrfs_compress_pages(). I do make an
extra call to .set_level() there just to be safe, but that can be taken
out as it should be correctly set from when we mounted.

I envisioned .set_level() to be called when setting the compression
level of the mount. This can be used in the same place if we were to add
per-file compression levels too. I mention later, but an important part
of .set_level() is to repurpose the meaning of 0 from meaning use the
default to meaning use any workspace available.

Thanks,
Dennis

Patch
diff mbox series

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 548057630b69..586f95ac0aea 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -1036,9 +1036,9 @@  int btrfs_compress_pages(unsigned int type_level, struct address_space *mapping,
 			 unsigned long *total_in,
 			 unsigned long *total_out)
 {
+	int type = BTRFS_COMPRESS_TYPE(type_level);
 	struct list_head *workspace;
 	int ret;
-	int type = type_level & 0xF;
 
 	workspace = find_workspace(type);
 
diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h
index ddda9b80bf20..69a9197dadc3 100644
--- a/fs/btrfs/compression.h
+++ b/fs/btrfs/compression.h
@@ -25,6 +25,9 @@ 
 
 #define	BTRFS_ZLIB_DEFAULT_LEVEL		3
 
+#define BTRFS_COMPRESS_TYPE(type_level)		(type_level & 0xF)
+#define BTRFS_COMPRESS_LEVEL(type_level)	((type_level & 0xF0) >> 4)
+
 struct compressed_bio {
 	/* number of bios pending for this compressed extent */
 	refcount_t pending_bios;
diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c
index 970ff3e35bb3..1480b3eee306 100644
--- a/fs/btrfs/zlib.c
+++ b/fs/btrfs/zlib.c
@@ -393,7 +393,7 @@  static int zlib_decompress(struct list_head *ws, unsigned char *data_in,
 static void zlib_set_level(struct list_head *ws, unsigned int type)
 {
 	struct workspace *workspace = list_entry(ws, struct workspace, list);
-	unsigned level = (type & 0xF0) >> 4;
+	unsigned int level = BTRFS_COMPRESS_LEVEL(type);
 
 	if (level > 9)
 		level = 9;