Hi,
Recently I was reading some code about filesystems, and I found
the usage of struct blockgroup_lock is confusing. I have 3 questions
about it, and please help give me some instuctions on them.
http://lxr.linux.no/#linux+v2.6.32/include/linux/blockgroup_lock.h
1) What is the relationship between NR_CPUS and NR_BG_LOCKS ?
2) And how to understand the usage of struct blockgroup_lock?
3) What is the relationship between block_group and NR_BG_LOCKS, e.g.
in blk_lock_ptr?
56static inline spinlock_t *
57bgl_lock_ptr(struct blockgroup_lock *bgl, unsigned int block_group)
58{
59 return &bgl->locks[(block_group) & (NR_BG_LOCKS-1)].lock;
60}
thanks,
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