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Message-ID: <20130107192016.GD13659@quack.suse.cz>
Date:	Mon, 7 Jan 2013 20:20:16 +0100
From:	Jan Kara <jack@...e.cz>
To:	Chen Gang <gang.chen@...anux.com>
Cc:	jack@...e.cz, akpm@...ux-foundation.org, adilger.kernel@...ger.ca,
	Theodore Ts'o <tytso@....edu>, jaegeuk.kim@...sung.com,
	dwmw2@...radead.org, torvalds@...ux-foundation.org,
	linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
	linux-mtd@...ts.infradead.org, reiserfs-devel@...r.kernel.org
Subject: Re: [PATCH v3] fs/ext*,f2fs,jffs2,reiserfs: give comments for acl
 size and count calculation

On Fri 04-01-13 11:26:53, Chen Gang wrote:
> 
>   give comments (by Theodore Ts'o)
> 
>     ACL_USER_OBJ ACL_USER*[1] ACL_GROUP_OBJ ACL_GROUP*[1] ACL_MASK[2] ACL_OTHER
> 
>     [1] Where * is the regexp sense of "0 or more times"
>     [2] Only if there is at least one ACL_USER or ACL_GROUP tag;
>         otherwise skip ACL_MASK.
  Note that I actually updated the entry [2] to be more precise in my
suggested comment. I wrote:
[2] If ACL_USER or ACL_GROUP is present, then ACL_MASK must be present.

  Please use this formulation because the old version suggests ACL_MASK
cannot be present if neither ACL_USER nor ACL_GROUP are present and that's
not true. Otherwise your patch looks fine. Thanks!

								Honza

> 
>   give comments (by Jan Kara)
>     posix_acl_valid() makes sure that if there are <= 4 ACL entries, then
>     all of them are short. Otherwise exactly 4 entries are short ones and
>     other have full length. See comment before that function for exact ACL
>     format.
> 
>   use macro instead of hard code number (by Chen Gang)
> 
> Signed-off-by: Theodore Ts'o <tytso@....edu>
> Signed-off-by: Jan Kara <jack@...e.cz>
> Signed-off-by: Chen Gang <gang.chen@...anux.com>
> ---
>  fs/ext2/acl.h             |   10 +++++-----
>  fs/ext3/acl.h             |   10 +++++-----
>  fs/ext4/acl.h             |   10 +++++-----
>  fs/f2fs/acl.c             |   12 +++++++-----
>  fs/jffs2/acl.c            |   15 +++++++++------
>  fs/posix_acl.c            |    8 ++++++++
>  fs/reiserfs/acl.h         |   10 +++++-----
>  include/linux/posix_acl.h |    8 ++++++++
>  8 files changed, 52 insertions(+), 31 deletions(-)
> 
> diff --git a/fs/ext2/acl.h b/fs/ext2/acl.h
> index 503bfb0..9af79d0 100644
> --- a/fs/ext2/acl.h
> +++ b/fs/ext2/acl.h
> @@ -25,13 +25,13 @@ typedef struct {
>  
>  static inline size_t ext2_acl_size(int count)
>  {
> -	if (count <= 4) {
> +	if (count <= ACL_MAX_SHORT_ENTRY) {
>  		return sizeof(ext2_acl_header) +
>  		       count * sizeof(ext2_acl_entry_short);
>  	} else {
>  		return sizeof(ext2_acl_header) +
> -		       4 * sizeof(ext2_acl_entry_short) +
> -		       (count - 4) * sizeof(ext2_acl_entry);
> +		       ACL_MAX_SHORT_ENTRY * sizeof(ext2_acl_entry_short) +
> +		       (count - ACL_MAX_SHORT_ENTRY) * sizeof(ext2_acl_entry);
>  	}
>  }
>  
> @@ -39,7 +39,7 @@ static inline int ext2_acl_count(size_t size)
>  {
>  	ssize_t s;
>  	size -= sizeof(ext2_acl_header);
> -	s = size - 4 * sizeof(ext2_acl_entry_short);
> +	s = size - ACL_MAX_SHORT_ENTRY * sizeof(ext2_acl_entry_short);
>  	if (s < 0) {
>  		if (size % sizeof(ext2_acl_entry_short))
>  			return -1;
> @@ -47,7 +47,7 @@ static inline int ext2_acl_count(size_t size)
>  	} else {
>  		if (s % sizeof(ext2_acl_entry))
>  			return -1;
> -		return s / sizeof(ext2_acl_entry) + 4;
> +		return s / sizeof(ext2_acl_entry) + ACL_MAX_SHORT_ENTRY;
>  	}
>  }
>  
> diff --git a/fs/ext3/acl.h b/fs/ext3/acl.h
> index dbc921e..b1cf2c0 100644
> --- a/fs/ext3/acl.h
> +++ b/fs/ext3/acl.h
> @@ -25,13 +25,13 @@ typedef struct {
>  
>  static inline size_t ext3_acl_size(int count)
>  {
> -	if (count <= 4) {
> +	if (count <= ACL_MAX_SHORT_ENTRY) {
>  		return sizeof(ext3_acl_header) +
>  		       count * sizeof(ext3_acl_entry_short);
>  	} else {
>  		return sizeof(ext3_acl_header) +
> -		       4 * sizeof(ext3_acl_entry_short) +
> -		       (count - 4) * sizeof(ext3_acl_entry);
> +		       ACL_MAX_SHORT_ENTRY * sizeof(ext3_acl_entry_short) +
> +		       (count - ACL_MAX_SHORT_ENTRY) * sizeof(ext3_acl_entry);
>  	}
>  }
>  
> @@ -39,7 +39,7 @@ static inline int ext3_acl_count(size_t size)
>  {
>  	ssize_t s;
>  	size -= sizeof(ext3_acl_header);
> -	s = size - 4 * sizeof(ext3_acl_entry_short);
> +	s = size - ACL_MAX_SHORT_ENTRY * sizeof(ext3_acl_entry_short);
>  	if (s < 0) {
>  		if (size % sizeof(ext3_acl_entry_short))
>  			return -1;
> @@ -47,7 +47,7 @@ static inline int ext3_acl_count(size_t size)
>  	} else {
>  		if (s % sizeof(ext3_acl_entry))
>  			return -1;
> -		return s / sizeof(ext3_acl_entry) + 4;
> +		return s / sizeof(ext3_acl_entry) + ACL_MAX_SHORT_ENTRY;
>  	}
>  }
>  
> diff --git a/fs/ext4/acl.h b/fs/ext4/acl.h
> index 18cb39e..66d1fa3 100644
> --- a/fs/ext4/acl.h
> +++ b/fs/ext4/acl.h
> @@ -25,13 +25,13 @@ typedef struct {
>  
>  static inline size_t ext4_acl_size(int count)
>  {
> -	if (count <= 4) {
> +	if (count <= ACL_MAX_SHORT_ENTRY) {
>  		return sizeof(ext4_acl_header) +
>  		       count * sizeof(ext4_acl_entry_short);
>  	} else {
>  		return sizeof(ext4_acl_header) +
> -		       4 * sizeof(ext4_acl_entry_short) +
> -		       (count - 4) * sizeof(ext4_acl_entry);
> +		       ACL_MAX_SHORT_ENTRY * sizeof(ext4_acl_entry_short) +
> +		       (count - ACL_MAX_SHORT_ENTRY) * sizeof(ext4_acl_entry);
>  	}
>  }
>  
> @@ -39,7 +39,7 @@ static inline int ext4_acl_count(size_t size)
>  {
>  	ssize_t s;
>  	size -= sizeof(ext4_acl_header);
> -	s = size - 4 * sizeof(ext4_acl_entry_short);
> +	s = size - ACL_MAX_SHORT_ENTRY * sizeof(ext4_acl_entry_short);
>  	if (s < 0) {
>  		if (size % sizeof(ext4_acl_entry_short))
>  			return -1;
> @@ -47,7 +47,7 @@ static inline int ext4_acl_count(size_t size)
>  	} else {
>  		if (s % sizeof(ext4_acl_entry))
>  			return -1;
> -		return s / sizeof(ext4_acl_entry) + 4;
> +		return s / sizeof(ext4_acl_entry) + ACL_MAX_SHORT_ENTRY;
>  	}
>  }
>  
> diff --git a/fs/f2fs/acl.c b/fs/f2fs/acl.c
> index fed74d1..42e0070 100644
> --- a/fs/f2fs/acl.c
> +++ b/fs/f2fs/acl.c
> @@ -22,13 +22,15 @@
>  
>  static inline size_t f2fs_acl_size(int count)
>  {
> -	if (count <= 4) {
> +	if (count <= ACL_MAX_SHORT_ENTRY) {
>  		return sizeof(struct f2fs_acl_header) +
>  			count * sizeof(struct f2fs_acl_entry_short);
>  	} else {
>  		return sizeof(struct f2fs_acl_header) +
> -			4 * sizeof(struct f2fs_acl_entry_short) +
> -			(count - 4) * sizeof(struct f2fs_acl_entry);
> +			ACL_MAX_SHORT_ENTRY
> +			 * sizeof(struct f2fs_acl_entry_short) +
> +			(count - ACL_MAX_SHORT_ENTRY)
> +			 * sizeof(struct f2fs_acl_entry);
>  	}
>  }
>  
> @@ -36,7 +38,7 @@ static inline int f2fs_acl_count(size_t size)
>  {
>  	ssize_t s;
>  	size -= sizeof(struct f2fs_acl_header);
> -	s = size - 4 * sizeof(struct f2fs_acl_entry_short);
> +	s = size - ACL_MAX_SHORT_ENTRY * sizeof(struct f2fs_acl_entry_short);
>  	if (s < 0) {
>  		if (size % sizeof(struct f2fs_acl_entry_short))
>  			return -1;
> @@ -44,7 +46,7 @@ static inline int f2fs_acl_count(size_t size)
>  	} else {
>  		if (s % sizeof(struct f2fs_acl_entry))
>  			return -1;
> -		return s / sizeof(struct f2fs_acl_entry) + 4;
> +		return s / sizeof(struct f2fs_acl_entry) + ACL_MAX_SHORT_ENTRY;
>  	}
>  }
>  
> diff --git a/fs/jffs2/acl.c b/fs/jffs2/acl.c
> index 223283c..48ef4b8 100644
> --- a/fs/jffs2/acl.c
> +++ b/fs/jffs2/acl.c
> @@ -25,13 +25,15 @@
>  
>  static size_t jffs2_acl_size(int count)
>  {
> -	if (count <= 4) {
> +	if (count <= ACL_MAX_SHORT_ENTRY) {
>  		return sizeof(struct jffs2_acl_header)
>  		       + count * sizeof(struct jffs2_acl_entry_short);
>  	} else {
>  		return sizeof(struct jffs2_acl_header)
> -		       + 4 * sizeof(struct jffs2_acl_entry_short)
> -		       + (count - 4) * sizeof(struct jffs2_acl_entry);
> +		       + ACL_MAX_SHORT_ENTRY
> +				 * sizeof(struct jffs2_acl_entry_short)
> +		       + (count - ACL_MAX_SHORT_ENTRY)
> +				 * sizeof(struct jffs2_acl_entry);
>  	}
>  }
>  
> @@ -40,15 +42,16 @@ static int jffs2_acl_count(size_t size)
>  	size_t s;
>  
>  	size -= sizeof(struct jffs2_acl_header);
> -	if (size < 4 * sizeof(struct jffs2_acl_entry_short)) {
> +	if (size < ACL_MAX_SHORT_ENTRY * sizeof(struct jffs2_acl_entry_short)) {
>  		if (size % sizeof(struct jffs2_acl_entry_short))
>  			return -1;
>  		return size / sizeof(struct jffs2_acl_entry_short);
>  	} else {
> -		s = size - 4 * sizeof(struct jffs2_acl_entry_short);
> +		s = size - ACL_MAX_SHORT_ENTRY
> +				 * sizeof(struct jffs2_acl_entry_short);
>  		if (s % sizeof(struct jffs2_acl_entry))
>  			return -1;
> -		return s / sizeof(struct jffs2_acl_entry) + 4;
> +		return s / sizeof(struct jffs2_acl_entry) + ACL_MAX_SHORT_ENTRY;
>  	}
>  }
>  
> diff --git a/fs/posix_acl.c b/fs/posix_acl.c
> index 8bd2135..8cfdebe 100644
> --- a/fs/posix_acl.c
> +++ b/fs/posix_acl.c
> @@ -72,6 +72,14 @@ posix_acl_clone(const struct posix_acl *acl, gfp_t flags)
>  
>  /*
>   * Check if an acl is valid. Returns 0 if it is, or -E... otherwise.
> + *
> + * make sure ACL format is the following:
> + *
> + *   ACL_USER_OBJ ACL_USER*[1] ACL_GROUP_OBJ ACL_GROUP*[1] ACL_MASK[2] ACL_OTHER
> + *
> + *   [1] Where * is the regexp sense of "0 or more times"
> + *   [2] Only if there is at least one ACL_USER or ACL_GROUP tag;
> + *       otherwise skip ACL_MASK.
>   */
>  int
>  posix_acl_valid(const struct posix_acl *acl)
> diff --git a/fs/reiserfs/acl.h b/fs/reiserfs/acl.h
> index f096b80..cb967a3 100644
> --- a/fs/reiserfs/acl.h
> +++ b/fs/reiserfs/acl.h
> @@ -20,13 +20,13 @@ typedef struct {
>  
>  static inline size_t reiserfs_acl_size(int count)
>  {
> -	if (count <= 4) {
> +	if (count <= ACL_MAX_SHORT_ENTRY) {
>  		return sizeof(reiserfs_acl_header) +
>  		    count * sizeof(reiserfs_acl_entry_short);
>  	} else {
>  		return sizeof(reiserfs_acl_header) +
> -		    4 * sizeof(reiserfs_acl_entry_short) +
> -		    (count - 4) * sizeof(reiserfs_acl_entry);
> +		    ACL_MAX_SHORT_ENTRY * sizeof(reiserfs_acl_entry_short) +
> +		    (count - ACL_MAX_SHORT_ENTRY) * sizeof(reiserfs_acl_entry);
>  	}
>  }
>  
> @@ -34,7 +34,7 @@ static inline int reiserfs_acl_count(size_t size)
>  {
>  	ssize_t s;
>  	size -= sizeof(reiserfs_acl_header);
> -	s = size - 4 * sizeof(reiserfs_acl_entry_short);
> +	s = size - ACL_MAX_SHORT_ENTRY * sizeof(reiserfs_acl_entry_short);
>  	if (s < 0) {
>  		if (size % sizeof(reiserfs_acl_entry_short))
>  			return -1;
> @@ -42,7 +42,7 @@ static inline int reiserfs_acl_count(size_t size)
>  	} else {
>  		if (s % sizeof(reiserfs_acl_entry))
>  			return -1;
> -		return s / sizeof(reiserfs_acl_entry) + 4;
> +		return s / sizeof(reiserfs_acl_entry) + ACL_MAX_SHORT_ENTRY;
>  	}
>  }
>  
> diff --git a/include/linux/posix_acl.h b/include/linux/posix_acl.h
> index 7931efe..2c5609c 100644
> --- a/include/linux/posix_acl.h
> +++ b/include/linux/posix_acl.h
> @@ -26,6 +26,14 @@
>  #define ACL_MASK		(0x10)
>  #define ACL_OTHER		(0x20)
>  
> +/*
> + * posix_acl_valid() makes sure that if there are <= 4 ACL entries, then
> + * all of them are short. Otherwise exactly 4 entries are short ones and
> + * other have full length. See comment before that function for exact ACL
> + * format.
> + */
> +#define ACL_MAX_SHORT_ENTRY	4
> +
>  /* permissions in the e_perm field */
>  #define ACL_READ		(0x04)
>  #define ACL_WRITE		(0x02)
> -- 
> 1.7.10.4
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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