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    SubjectRe: Re: [PATCH] btrfs: Simplify offset calculation method for ctree.h
    sniper wrote:
    > No, many pointers in btrfs function arguments are not pointing to an
    > absolute address, but relative to the start address of extent.
    > Take following function as example, argument inode_item is an offset
    > value to the beginning of leaf. So we can't reach its member with
    > &inode_item->xxx

    Notice that we are not reach its member, we are getting pointer of its
    member with &inode_item->mtime.
    This operation have same effect as old one.


    >> static inline struct btrfs_timespec *
    >> btrfs_inode_mtime(struct btrfs_inode_item *inode_item)
    >> {
    >> - unsigned long ptr = (unsigned long)inode_item;
    >> - ptr += offsetof(struct btrfs_inode_item, mtime);
    >> - return (struct btrfs_timespec *)ptr;
    >> + return &inode_item->mtime;
    >> }

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      Last update: 2009-12-18 06:51    [W:0.022 / U:68.812 seconds]
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