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a13f35e871
52ebea749a
("writeback: make backing_dev_info host cgroup-specific
bdi_writebacks") made bdi (backing_dev_info) host per-cgroup wb's
(bdi_writeback's). As the congested state needs to be per-wb and
referenced from blkcg side and multiple wbs, the patch made all
non-root cong's (bdi_writeback_congested's) reference counted and
indexed on bdi.
When a bdi is destroyed, cgwb_bdi_destroy() tries to drain all
non-root cong's; however, this can hang indefinitely because wb's can
also be referenced from blkcg_gq's which are destroyed after bdi
destruction is complete.
To fix the bug, bdi destruction will be updated to not wait for cong's
to drain, which naturally means that cong's may outlive the associated
bdi. This is fine for non-root cong's but is problematic for the root
cong's which are embedded in their bdi's as they may end up getting
dereferenced after the containing bdi's are freed.
This patch makes root cong's behave the same as non-root cong's. They
are no longer embedded in their bdi's but allocated separately during
bdi initialization, indexed and reference counted the same way.
* As cong handling is the same for all wb's, wb->congested
initialization is moved into wb_init().
* When !CONFIG_CGROUP_WRITEBACK, there was no indexing or refcnting.
bdi->wb_congested is now a pointer pointing to the root cong
allocated during bdi init and minimal refcnting operations are
implemented.
* The above makes root wb init paths diverge depending on
CONFIG_CGROUP_WRITEBACK. root wb init is moved to cgwb_bdi_init().
This patch in itself shouldn't cause any consequential behavior
differences but prepares for the actual fix.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Jon Christopherson <jon@jons.org>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=100681
Tested-by: Jon Christopherson <jon@jons.org>
Added <linux/slab.h> include to backing-dev.h for kfree() definition.
Signed-off-by: Jens Axboe <axboe@fb.com>
571 lines
15 KiB
C
571 lines
15 KiB
C
/*
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* include/linux/backing-dev.h
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*
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* low-level device information and state which is propagated up through
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* to high-level code.
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*/
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#ifndef _LINUX_BACKING_DEV_H
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#define _LINUX_BACKING_DEV_H
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#include <linux/kernel.h>
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#include <linux/fs.h>
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#include <linux/sched.h>
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#include <linux/blkdev.h>
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#include <linux/writeback.h>
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#include <linux/blk-cgroup.h>
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#include <linux/backing-dev-defs.h>
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#include <linux/slab.h>
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int __must_check bdi_init(struct backing_dev_info *bdi);
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void bdi_destroy(struct backing_dev_info *bdi);
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__printf(3, 4)
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int bdi_register(struct backing_dev_info *bdi, struct device *parent,
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const char *fmt, ...);
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int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
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int __must_check bdi_setup_and_register(struct backing_dev_info *, char *);
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void wb_start_writeback(struct bdi_writeback *wb, long nr_pages,
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bool range_cyclic, enum wb_reason reason);
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void wb_start_background_writeback(struct bdi_writeback *wb);
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void wb_workfn(struct work_struct *work);
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void wb_wakeup_delayed(struct bdi_writeback *wb);
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extern spinlock_t bdi_lock;
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extern struct list_head bdi_list;
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extern struct workqueue_struct *bdi_wq;
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static inline bool wb_has_dirty_io(struct bdi_writeback *wb)
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{
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return test_bit(WB_has_dirty_io, &wb->state);
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}
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static inline bool bdi_has_dirty_io(struct backing_dev_info *bdi)
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{
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/*
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* @bdi->tot_write_bandwidth is guaranteed to be > 0 if there are
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* any dirty wbs. See wb_update_write_bandwidth().
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*/
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return atomic_long_read(&bdi->tot_write_bandwidth);
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}
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static inline void __add_wb_stat(struct bdi_writeback *wb,
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enum wb_stat_item item, s64 amount)
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{
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__percpu_counter_add(&wb->stat[item], amount, WB_STAT_BATCH);
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}
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static inline void __inc_wb_stat(struct bdi_writeback *wb,
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enum wb_stat_item item)
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{
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__add_wb_stat(wb, item, 1);
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}
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static inline void inc_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
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{
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unsigned long flags;
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local_irq_save(flags);
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__inc_wb_stat(wb, item);
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local_irq_restore(flags);
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}
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static inline void __dec_wb_stat(struct bdi_writeback *wb,
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enum wb_stat_item item)
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{
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__add_wb_stat(wb, item, -1);
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}
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static inline void dec_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
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{
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unsigned long flags;
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local_irq_save(flags);
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__dec_wb_stat(wb, item);
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local_irq_restore(flags);
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}
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static inline s64 wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
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{
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return percpu_counter_read_positive(&wb->stat[item]);
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}
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static inline s64 __wb_stat_sum(struct bdi_writeback *wb,
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enum wb_stat_item item)
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{
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return percpu_counter_sum_positive(&wb->stat[item]);
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}
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static inline s64 wb_stat_sum(struct bdi_writeback *wb, enum wb_stat_item item)
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{
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s64 sum;
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unsigned long flags;
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local_irq_save(flags);
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sum = __wb_stat_sum(wb, item);
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local_irq_restore(flags);
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return sum;
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}
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extern void wb_writeout_inc(struct bdi_writeback *wb);
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/*
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* maximal error of a stat counter.
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*/
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static inline unsigned long wb_stat_error(struct bdi_writeback *wb)
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{
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#ifdef CONFIG_SMP
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return nr_cpu_ids * WB_STAT_BATCH;
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#else
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return 1;
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#endif
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}
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int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio);
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int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
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/*
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* Flags in backing_dev_info::capability
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*
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* The first three flags control whether dirty pages will contribute to the
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* VM's accounting and whether writepages() should be called for dirty pages
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* (something that would not, for example, be appropriate for ramfs)
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*
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* WARNING: these flags are closely related and should not normally be
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* used separately. The BDI_CAP_NO_ACCT_AND_WRITEBACK combines these
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* three flags into a single convenience macro.
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*
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* BDI_CAP_NO_ACCT_DIRTY: Dirty pages shouldn't contribute to accounting
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* BDI_CAP_NO_WRITEBACK: Don't write pages back
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* BDI_CAP_NO_ACCT_WB: Don't automatically account writeback pages
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* BDI_CAP_STRICTLIMIT: Keep number of dirty pages below bdi threshold.
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*
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* BDI_CAP_CGROUP_WRITEBACK: Supports cgroup-aware writeback.
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*/
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#define BDI_CAP_NO_ACCT_DIRTY 0x00000001
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#define BDI_CAP_NO_WRITEBACK 0x00000002
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#define BDI_CAP_NO_ACCT_WB 0x00000004
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#define BDI_CAP_STABLE_WRITES 0x00000008
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#define BDI_CAP_STRICTLIMIT 0x00000010
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#define BDI_CAP_CGROUP_WRITEBACK 0x00000020
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#define BDI_CAP_NO_ACCT_AND_WRITEBACK \
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(BDI_CAP_NO_WRITEBACK | BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_ACCT_WB)
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extern struct backing_dev_info noop_backing_dev_info;
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/**
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* writeback_in_progress - determine whether there is writeback in progress
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* @wb: bdi_writeback of interest
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*
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* Determine whether there is writeback waiting to be handled against a
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* bdi_writeback.
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*/
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static inline bool writeback_in_progress(struct bdi_writeback *wb)
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{
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return test_bit(WB_writeback_running, &wb->state);
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}
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static inline struct backing_dev_info *inode_to_bdi(struct inode *inode)
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{
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struct super_block *sb;
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if (!inode)
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return &noop_backing_dev_info;
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sb = inode->i_sb;
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#ifdef CONFIG_BLOCK
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if (sb_is_blkdev_sb(sb))
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return blk_get_backing_dev_info(I_BDEV(inode));
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#endif
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return sb->s_bdi;
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}
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static inline int wb_congested(struct bdi_writeback *wb, int cong_bits)
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{
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struct backing_dev_info *bdi = wb->bdi;
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if (bdi->congested_fn)
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return bdi->congested_fn(bdi->congested_data, cong_bits);
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return wb->congested->state & cong_bits;
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}
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long congestion_wait(int sync, long timeout);
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long wait_iff_congested(struct zone *zone, int sync, long timeout);
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int pdflush_proc_obsolete(struct ctl_table *table, int write,
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void __user *buffer, size_t *lenp, loff_t *ppos);
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static inline bool bdi_cap_stable_pages_required(struct backing_dev_info *bdi)
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{
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return bdi->capabilities & BDI_CAP_STABLE_WRITES;
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}
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static inline bool bdi_cap_writeback_dirty(struct backing_dev_info *bdi)
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{
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return !(bdi->capabilities & BDI_CAP_NO_WRITEBACK);
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}
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static inline bool bdi_cap_account_dirty(struct backing_dev_info *bdi)
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{
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return !(bdi->capabilities & BDI_CAP_NO_ACCT_DIRTY);
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}
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static inline bool bdi_cap_account_writeback(struct backing_dev_info *bdi)
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{
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/* Paranoia: BDI_CAP_NO_WRITEBACK implies BDI_CAP_NO_ACCT_WB */
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return !(bdi->capabilities & (BDI_CAP_NO_ACCT_WB |
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BDI_CAP_NO_WRITEBACK));
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}
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static inline bool mapping_cap_writeback_dirty(struct address_space *mapping)
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{
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return bdi_cap_writeback_dirty(inode_to_bdi(mapping->host));
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}
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static inline bool mapping_cap_account_dirty(struct address_space *mapping)
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{
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return bdi_cap_account_dirty(inode_to_bdi(mapping->host));
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}
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static inline int bdi_sched_wait(void *word)
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{
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schedule();
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return 0;
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}
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#ifdef CONFIG_CGROUP_WRITEBACK
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struct bdi_writeback_congested *
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wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp);
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void wb_congested_put(struct bdi_writeback_congested *congested);
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struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
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struct cgroup_subsys_state *memcg_css,
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gfp_t gfp);
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void wb_memcg_offline(struct mem_cgroup *memcg);
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void wb_blkcg_offline(struct blkcg *blkcg);
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int inode_congested(struct inode *inode, int cong_bits);
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/**
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* inode_cgwb_enabled - test whether cgroup writeback is enabled on an inode
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* @inode: inode of interest
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*
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* cgroup writeback requires support from both the bdi and filesystem.
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* Test whether @inode has both.
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*/
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static inline bool inode_cgwb_enabled(struct inode *inode)
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{
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struct backing_dev_info *bdi = inode_to_bdi(inode);
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return bdi_cap_account_dirty(bdi) &&
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(bdi->capabilities & BDI_CAP_CGROUP_WRITEBACK) &&
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(inode->i_sb->s_iflags & SB_I_CGROUPWB);
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}
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/**
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* wb_find_current - find wb for %current on a bdi
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* @bdi: bdi of interest
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*
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* Find the wb of @bdi which matches both the memcg and blkcg of %current.
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* Must be called under rcu_read_lock() which protects the returend wb.
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* NULL if not found.
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*/
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static inline struct bdi_writeback *wb_find_current(struct backing_dev_info *bdi)
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{
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struct cgroup_subsys_state *memcg_css;
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struct bdi_writeback *wb;
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memcg_css = task_css(current, memory_cgrp_id);
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if (!memcg_css->parent)
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return &bdi->wb;
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wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
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/*
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* %current's blkcg equals the effective blkcg of its memcg. No
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* need to use the relatively expensive cgroup_get_e_css().
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*/
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if (likely(wb && wb->blkcg_css == task_css(current, blkio_cgrp_id)))
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return wb;
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return NULL;
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}
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/**
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* wb_get_create_current - get or create wb for %current on a bdi
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* @bdi: bdi of interest
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* @gfp: allocation mask
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*
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* Equivalent to wb_get_create() on %current's memcg. This function is
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* called from a relatively hot path and optimizes the common cases using
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* wb_find_current().
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*/
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static inline struct bdi_writeback *
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wb_get_create_current(struct backing_dev_info *bdi, gfp_t gfp)
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{
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struct bdi_writeback *wb;
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rcu_read_lock();
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wb = wb_find_current(bdi);
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if (wb && unlikely(!wb_tryget(wb)))
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wb = NULL;
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rcu_read_unlock();
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if (unlikely(!wb)) {
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struct cgroup_subsys_state *memcg_css;
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memcg_css = task_get_css(current, memory_cgrp_id);
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wb = wb_get_create(bdi, memcg_css, gfp);
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css_put(memcg_css);
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}
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return wb;
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}
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/**
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* inode_to_wb_is_valid - test whether an inode has a wb associated
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* @inode: inode of interest
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*
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* Returns %true if @inode has a wb associated. May be called without any
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* locking.
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*/
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static inline bool inode_to_wb_is_valid(struct inode *inode)
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{
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return inode->i_wb;
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}
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/**
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* inode_to_wb - determine the wb of an inode
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* @inode: inode of interest
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*
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* Returns the wb @inode is currently associated with. The caller must be
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* holding either @inode->i_lock, @inode->i_mapping->tree_lock, or the
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* associated wb's list_lock.
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*/
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static inline struct bdi_writeback *inode_to_wb(struct inode *inode)
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{
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#ifdef CONFIG_LOCKDEP
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WARN_ON_ONCE(debug_locks &&
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(!lockdep_is_held(&inode->i_lock) &&
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!lockdep_is_held(&inode->i_mapping->tree_lock) &&
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!lockdep_is_held(&inode->i_wb->list_lock)));
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#endif
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return inode->i_wb;
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}
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/**
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* unlocked_inode_to_wb_begin - begin unlocked inode wb access transaction
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* @inode: target inode
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* @lockedp: temp bool output param, to be passed to the end function
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*
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* The caller wants to access the wb associated with @inode but isn't
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* holding inode->i_lock, mapping->tree_lock or wb->list_lock. This
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* function determines the wb associated with @inode and ensures that the
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* association doesn't change until the transaction is finished with
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* unlocked_inode_to_wb_end().
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*
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* The caller must call unlocked_inode_to_wb_end() with *@lockdep
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* afterwards and can't sleep during transaction. IRQ may or may not be
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* disabled on return.
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*/
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static inline struct bdi_writeback *
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unlocked_inode_to_wb_begin(struct inode *inode, bool *lockedp)
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{
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rcu_read_lock();
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/*
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* Paired with store_release in inode_switch_wb_work_fn() and
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* ensures that we see the new wb if we see cleared I_WB_SWITCH.
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*/
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*lockedp = smp_load_acquire(&inode->i_state) & I_WB_SWITCH;
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if (unlikely(*lockedp))
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spin_lock_irq(&inode->i_mapping->tree_lock);
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/*
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* Protected by either !I_WB_SWITCH + rcu_read_lock() or tree_lock.
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* inode_to_wb() will bark. Deref directly.
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*/
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return inode->i_wb;
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}
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/**
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* unlocked_inode_to_wb_end - end inode wb access transaction
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* @inode: target inode
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* @locked: *@lockedp from unlocked_inode_to_wb_begin()
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*/
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static inline void unlocked_inode_to_wb_end(struct inode *inode, bool locked)
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{
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if (unlikely(locked))
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spin_unlock_irq(&inode->i_mapping->tree_lock);
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rcu_read_unlock();
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}
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struct wb_iter {
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int start_blkcg_id;
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struct radix_tree_iter tree_iter;
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void **slot;
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};
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static inline struct bdi_writeback *__wb_iter_next(struct wb_iter *iter,
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struct backing_dev_info *bdi)
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{
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struct radix_tree_iter *titer = &iter->tree_iter;
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WARN_ON_ONCE(!rcu_read_lock_held());
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if (iter->start_blkcg_id >= 0) {
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iter->slot = radix_tree_iter_init(titer, iter->start_blkcg_id);
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iter->start_blkcg_id = -1;
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} else {
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iter->slot = radix_tree_next_slot(iter->slot, titer, 0);
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}
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if (!iter->slot)
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iter->slot = radix_tree_next_chunk(&bdi->cgwb_tree, titer, 0);
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if (iter->slot)
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return *iter->slot;
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return NULL;
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}
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static inline struct bdi_writeback *__wb_iter_init(struct wb_iter *iter,
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struct backing_dev_info *bdi,
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int start_blkcg_id)
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{
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iter->start_blkcg_id = start_blkcg_id;
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if (start_blkcg_id)
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return __wb_iter_next(iter, bdi);
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else
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return &bdi->wb;
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}
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/**
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* bdi_for_each_wb - walk all wb's of a bdi in ascending blkcg ID order
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* @wb_cur: cursor struct bdi_writeback pointer
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* @bdi: bdi to walk wb's of
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* @iter: pointer to struct wb_iter to be used as iteration buffer
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* @start_blkcg_id: blkcg ID to start iteration from
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*
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* Iterate @wb_cur through the wb's (bdi_writeback's) of @bdi in ascending
|
|
* blkcg ID order starting from @start_blkcg_id. @iter is struct wb_iter
|
|
* to be used as temp storage during iteration. rcu_read_lock() must be
|
|
* held throughout iteration.
|
|
*/
|
|
#define bdi_for_each_wb(wb_cur, bdi, iter, start_blkcg_id) \
|
|
for ((wb_cur) = __wb_iter_init(iter, bdi, start_blkcg_id); \
|
|
(wb_cur); (wb_cur) = __wb_iter_next(iter, bdi))
|
|
|
|
#else /* CONFIG_CGROUP_WRITEBACK */
|
|
|
|
static inline bool inode_cgwb_enabled(struct inode *inode)
|
|
{
|
|
return false;
|
|
}
|
|
|
|
static inline struct bdi_writeback_congested *
|
|
wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp)
|
|
{
|
|
atomic_inc(&bdi->wb_congested->refcnt);
|
|
return bdi->wb_congested;
|
|
}
|
|
|
|
static inline void wb_congested_put(struct bdi_writeback_congested *congested)
|
|
{
|
|
if (atomic_dec_and_test(&congested->refcnt))
|
|
kfree(congested);
|
|
}
|
|
|
|
static inline struct bdi_writeback *wb_find_current(struct backing_dev_info *bdi)
|
|
{
|
|
return &bdi->wb;
|
|
}
|
|
|
|
static inline struct bdi_writeback *
|
|
wb_get_create_current(struct backing_dev_info *bdi, gfp_t gfp)
|
|
{
|
|
return &bdi->wb;
|
|
}
|
|
|
|
static inline bool inode_to_wb_is_valid(struct inode *inode)
|
|
{
|
|
return true;
|
|
}
|
|
|
|
static inline struct bdi_writeback *inode_to_wb(struct inode *inode)
|
|
{
|
|
return &inode_to_bdi(inode)->wb;
|
|
}
|
|
|
|
static inline struct bdi_writeback *
|
|
unlocked_inode_to_wb_begin(struct inode *inode, bool *lockedp)
|
|
{
|
|
return inode_to_wb(inode);
|
|
}
|
|
|
|
static inline void unlocked_inode_to_wb_end(struct inode *inode, bool locked)
|
|
{
|
|
}
|
|
|
|
static inline void wb_memcg_offline(struct mem_cgroup *memcg)
|
|
{
|
|
}
|
|
|
|
static inline void wb_blkcg_offline(struct blkcg *blkcg)
|
|
{
|
|
}
|
|
|
|
struct wb_iter {
|
|
int next_id;
|
|
};
|
|
|
|
#define bdi_for_each_wb(wb_cur, bdi, iter, start_blkcg_id) \
|
|
for ((iter)->next_id = (start_blkcg_id); \
|
|
({ (wb_cur) = !(iter)->next_id++ ? &(bdi)->wb : NULL; }); )
|
|
|
|
static inline int inode_congested(struct inode *inode, int cong_bits)
|
|
{
|
|
return wb_congested(&inode_to_bdi(inode)->wb, cong_bits);
|
|
}
|
|
|
|
#endif /* CONFIG_CGROUP_WRITEBACK */
|
|
|
|
static inline int inode_read_congested(struct inode *inode)
|
|
{
|
|
return inode_congested(inode, 1 << WB_sync_congested);
|
|
}
|
|
|
|
static inline int inode_write_congested(struct inode *inode)
|
|
{
|
|
return inode_congested(inode, 1 << WB_async_congested);
|
|
}
|
|
|
|
static inline int inode_rw_congested(struct inode *inode)
|
|
{
|
|
return inode_congested(inode, (1 << WB_sync_congested) |
|
|
(1 << WB_async_congested));
|
|
}
|
|
|
|
static inline int bdi_congested(struct backing_dev_info *bdi, int cong_bits)
|
|
{
|
|
return wb_congested(&bdi->wb, cong_bits);
|
|
}
|
|
|
|
static inline int bdi_read_congested(struct backing_dev_info *bdi)
|
|
{
|
|
return bdi_congested(bdi, 1 << WB_sync_congested);
|
|
}
|
|
|
|
static inline int bdi_write_congested(struct backing_dev_info *bdi)
|
|
{
|
|
return bdi_congested(bdi, 1 << WB_async_congested);
|
|
}
|
|
|
|
static inline int bdi_rw_congested(struct backing_dev_info *bdi)
|
|
{
|
|
return bdi_congested(bdi, (1 << WB_sync_congested) |
|
|
(1 << WB_async_congested));
|
|
}
|
|
|
|
#endif /* _LINUX_BACKING_DEV_H */
|