blk_cgroup_congested

Name:blk_cgroup_congested

Proto:static inline bool blk_cgroup_congested(void)

Type:bool

Parameter:Nothing

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bool ret = false

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_read_lock() - mark the beginning of an RCU read-side critical section* When synchronize_rcu() is invoked on one CPU while other CPUs* are within RCU read-side critical sections, then the* synchronize_rcu() is guaranteed to block until after all the other

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css = kthread_blkcg - get associated blkcg css of current kthread* Current thread must be a kthread.

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If Not css Then css = ask_css - obtain css for (task, subsys)*@task: the target task*@subsys_id: the target subsystem ID* See task_css_check().

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When css cycle

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If atomic_read( & If there is block congestion on this cgroup. ) Then

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ret = true

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Break

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css = PI: the parent css. Placed here for cache proximity to following* fields of the containing structure.

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_read_unlock() - marks the end of an RCU read-side critical section.* In most situations, rcu_read_unlock() is immune from deadlock.* However, in kernels built with CONFIG_RCU_BOOST, rcu_read_unlock()

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Return ret

**Caller**
Name	Describe
page_cache_sync_readahead	page_cache_sync_readahead - generic file readahead@mapping: address_space which holds the pagecache and I/O vectors@ra: file_ra_state which holds the readahead state@filp: passed on to ->readpage() and ->readpages()@offset: start offset into @mapping,
page_cache_async_readahead	page_cache_async_readahead - file readahead for marked pages@mapping: address_space which holds the pagecache and I/O vectors@ra: file_ra_state which holds the readahead state@filp: passed on to ->readpage() and ->readpages()@page: the page at @offset
mem_cgroup_throttle_swaprate

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