Re: [PATCH 6/8] exofs: super_operations and file_system_type

[Andrew Morton]

On Wed, 18 Mar 2009 20:09:51 +0200 Boaz Harrosh <bharrosh@xxxxxxxxxxx> wrote:

> This patch ties all operation vectors into a file system superblock
> and registers the exofs file_system_type at module's load time.
> 
> * The file system control block (AKA on-disk superblock) resides in
>   an object with a special ID (defined in common.h).
>   Information included in the file system control block is used to
>   fill the in-memory superblock structure at mount time. This object
>   is created before the file system is used by mkexofs.c It contains
>   information such as:
> 	- The file system's magic number
> 	- The next inode number to be allocated
> 
>
> ...
>
> +static int exofs_statfs(struct dentry *dentry, struct kstatfs *buf)
> +{
> +	struct super_block *sb = dentry->d_sb;
> +	struct exofs_sb_info *sbi = sb->s_fs_info;
> +	struct osd_obj_id obj = {sbi->s_pid, 0};
> +	struct osd_attr attrs[] = {
> +		ATTR_DEF(OSD_APAGE_PARTITION_QUOTAS,
> +			OSD_ATTR_PQ_CAPACITY_QUOTA, sizeof(__be64)),
> +		ATTR_DEF(OSD_APAGE_PARTITION_INFORMATION,
> +			OSD_ATTR_PI_USED_CAPACITY, sizeof(__be64)),
> +	};
> +	uint64_t capacity = ~0;
> +	uint64_t used = ~0;

My brain hurts.

~0 is signed 0xffffffff.

When assigning to a u64 it gets signed extended to signed
0xffffffffffffffff and then converted to unsigned 0xffffffffffffffff.

I think.  Just as with plain old "-1".  Perhaps using plain old "-1"
would be clearer here.

>
> ...
>
> +const struct super_operations exofs_sops = {

This can in fact be made static, I believe.

>
> ...
>

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