linux-ext4 - Re: [Patch 2/4] Controlling block allocation of a file with respect to grading information

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Date:   Fri, 6 Apr 2018 10:14:42 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Sayan Ghosh <sgdgp.2014@...il.com>, linux-ext4@...r.kernel.org
Cc:     linux-fsdevel@...r.kernel.org,
        "Bhattacharya, Suparna" <suparna.bhattacharya@....com>,
        niloy ganguly <ganguly.niloy@...il.com>,
        Madhumita Mallick <madhu.cse.ju@...il.com>,
        "Bharde, Madhumita" <madhumita.bharde@....com>
Subject: Re: [Patch 2/4] Controlling block allocation of a file with respect
 to grading information

On 04/06/2018 04:41 AM, Sayan Ghosh wrote:

> The patch is on top of Linux Kernel 4.7.2.
> 
> Signed-off-by: Sayan Ghosh <sgdgp.2014@...il.com>
> ---
>  fs/ext4/ext4.h    |   1 +
>  fs/ext4/extents.c | 116 ++++++++++++++++++++++++++++++++++++++++++++++++++++--
>  2 files changed, 114 insertions(+), 3 deletions(-)
> 

> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index de9194f..aaff3a3 100755
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -58,6 +58,12 @@
>  #define EXT4_EXT_DATA_VALID2    0x10 /* second half contains valid data */
> 
>  /*
> + * Starting block numbers for low and high grades
> + */
> +#define LOW_GRADE_STARTING_BLOCK 0
> +#define HIGH_GRADE_STARTING_BLOCK 1249280
> +
> +/*
>   * read_grade_xattr() is used to read the grade array from the
> extended attribute.
>   */
>  void read_grade_xattr(struct inode *inode,struct grade_struct *grade_array)
> @@ -92,6 +98,43 @@ unsigned long long read_count_xattr(struct inode *inode)
>      return total;
>  }
> 
> +/*
> + * find_grade() is to find the grade of a logical block.
> + * This also returns the length of graded or ungraded portion
> + * starting from that logical block number (gets stored in the variable
> + * req_len). The return value is 1 for high grade and 0 otherwise.
> + */

Lots of style issues:

> +int find_grade(struct grade_struct* grade_array, unsigned long long
> total, ext4_fsblk_t val, unsigned long long *req_len)

line too long.

> +{
> +    if (val >= (grade_array[total -1].block_num + grade_array[total -1].len) ){
> +        if (req_len != NULL)
> +            (*req_len) = 0;
> +        return 0;
> +    }

use tabs, not spaces. and indentation should be 8, not 4. (many places)

> +    unsigned long long beg, end, mid;

Don't declare variables after code.

> +    beg = 0;
> +    end = total-1;
> +    while (beg <= end){
> +        mid = (beg + end)/2;
> +        if ((val >= grade_array[mid].block_num) && (val <=
> (grade_array[mid].block_num + grade_array[mid].len - 1)) ){

line too long.

> +            if (req_len != NULL)
> +                (*req_len) = grade_array[mid].len;
> +            return 1;
> +        }
> +        if(beg == end)

space after "if"

> +            break;
> +        if (grade_array[mid].block_num > val){
> +            end = (mid > 0) ? (mid - 1) : 0;
> +        }
> +        else{
> +            beg = mid + 1;
> +        }
> +    }
> +    if (req_len != NULL)
> +        (*req_len) = grade_array[mid].block_num - val;
> +    return 0;
> +}
> +
>  static __le32 ext4_extent_block_csum(struct inode *inode,
>                       struct ext4_extent_header *eh)
>  {


-- 
~Randy