include/linux/backing-dev-defs.h

   1 #ifndef __LINUX_BACKING_DEV_DEFS_H
   2 #define __LINUX_BACKING_DEV_DEFS_H
   3
   4 #include <linux/list.h>
   5 #include <linux/radix-tree.h>
   6 #include <linux/rbtree.h>
   7 #include <linux/spinlock.h>
   8 #include <linux/percpu_counter.h>
   9 #include <linux/percpu-refcount.h>
  10 #include <linux/flex_proportions.h>
  11 #include <linux/timer.h>
  12 #include <linux/workqueue.h>
  13 #include <linux/kref.h>
  14
  15 struct page;
  16 struct device;
  17 struct dentry;
  18
  19 /*
  20  * Bits in bdi_writeback.state
  21  */
  22 enum wb_state {
  23         WB_registered,          /* bdi_register() was done */
  24         WB_shutting_down,       /* wb_shutdown() in progress */
  25         WB_writeback_running,   /* Writeback is in progress */
  26         WB_has_dirty_io,        /* Dirty inodes on ->b_{dirty|io|more_io} */
  27 };
  28
  29 enum wb_congested_state {
  30         WB_async_congested,     /* The async (write) queue is getting full */
  31         WB_sync_congested,      /* The sync queue is getting full */
  32 };
  33
  34 typedef int (congested_fn)(void *, int);
  35
  36 enum wb_stat_item {
  37         WB_RECLAIMABLE,
  38         WB_WRITEBACK,
  39         WB_DIRTIED,
  40         WB_WRITTEN,
  41         NR_WB_STAT_ITEMS
  42 };
  43
  44 #define WB_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
  45
  46 /*
  47  * For cgroup writeback, multiple wb's may map to the same blkcg.  Those
  48  * wb's can operate mostly independently but should share the congested
  49  * state.  To facilitate such sharing, the congested state is tracked using
  50  * the following struct which is created on demand, indexed by blkcg ID on
  51  * its bdi, and refcounted.
  52  */
  53 struct bdi_writeback_congested {
  54         unsigned long state;            /* WB_[a]sync_congested flags */
  55         atomic_t refcnt;                /* nr of attached wb's and blkg */
  56
  57 #ifdef CONFIG_CGROUP_WRITEBACK
  58         struct backing_dev_info *__bdi; /* the associated bdi, set to NULL
  59                                          * on bdi unregistration. For memcg-wb
  60                                          * internal use only! */
  61         int blkcg_id;                   /* ID of the associated blkcg */
  62         struct rb_node rb_node;         /* on bdi->cgwb_congestion_tree */
  63 #endif
  64 };
  65
  66 /*
  67  * Each wb (bdi_writeback) can perform writeback operations, is measured
  68  * and throttled, independently.  Without cgroup writeback, each bdi
  69  * (bdi_writeback) is served by its embedded bdi->wb.
  70  *
  71  * On the default hierarchy, blkcg implicitly enables memcg.  This allows
  72  * using memcg's page ownership for attributing writeback IOs, and every
  73  * memcg - blkcg combination can be served by its own wb by assigning a
  74  * dedicated wb to each memcg, which enables isolation across different
  75  * cgroups and propagation of IO back pressure down from the IO layer upto
  76  * the tasks which are generating the dirty pages to be written back.
  77  *
  78  * A cgroup wb is indexed on its bdi by the ID of the associated memcg,
  79  * refcounted with the number of inodes attached to it, and pins the memcg
  80  * and the corresponding blkcg.  As the corresponding blkcg for a memcg may
  81  * change as blkcg is disabled and enabled higher up in the hierarchy, a wb
  82  * is tested for blkcg after lookup and removed from index on mismatch so
  83  * that a new wb for the combination can be created.
  84  */
  85 struct bdi_writeback {
  86         struct backing_dev_info *bdi;   /* our parent bdi */
  87
  88         unsigned long state;            /* Always use atomic bitops on this */
  89         unsigned long last_old_flush;   /* last old data flush */
  90
  91         struct list_head b_dirty;       /* dirty inodes */
  92         struct list_head b_io;          /* parked for writeback */
  93         struct list_head b_more_io;     /* parked for more writeback */
  94         struct list_head b_dirty_time;  /* time stamps are dirty */
  95         spinlock_t list_lock;           /* protects the b_* lists */
  96
  97         struct percpu_counter stat[NR_WB_STAT_ITEMS];
  98
  99         struct bdi_writeback_congested *congested;
 100
 101         unsigned long bw_time_stamp;    /* last time write bw is updated */
 102         unsigned long dirtied_stamp;
 103         unsigned long written_stamp;    /* pages written at bw_time_stamp */
 104         unsigned long write_bandwidth;  /* the estimated write bandwidth */
 105         unsigned long avg_write_bandwidth; /* further smoothed write bw, > 0 */
 106
 107         /*
 108          * The base dirty throttle rate, re-calculated on every 200ms.
 109          * All the bdi tasks' dirty rate will be curbed under it.
 110          * @dirty_ratelimit tracks the estimated @balanced_dirty_ratelimit
 111          * in small steps and is much more smooth/stable than the latter.
 112          */
 113         unsigned long dirty_ratelimit;
 114         unsigned long balanced_dirty_ratelimit;
 115
 116         struct fprop_local_percpu completions;
 117         int dirty_exceeded;
 118
 119         spinlock_t work_lock;           /* protects work_list & dwork scheduling */
 120         struct list_head work_list;
 121         struct delayed_work dwork;      /* work item used for writeback */
 122
 123         unsigned long dirty_sleep;      /* last wait */
 124
 125         struct list_head bdi_node;      /* anchored at bdi->wb_list */
 126
 127 #ifdef CONFIG_CGROUP_WRITEBACK
 128         struct percpu_ref refcnt;       /* used only for !root wb's */
 129         struct fprop_local_percpu memcg_completions;
 130         struct cgroup_subsys_state *memcg_css; /* the associated memcg */
 131         struct cgroup_subsys_state *blkcg_css; /* and blkcg */
 132         struct list_head memcg_node;    /* anchored at memcg->cgwb_list */
 133         struct list_head blkcg_node;    /* anchored at blkcg->cgwb_list */
 134
 135         union {
 136                 struct work_struct release_work;
 137                 struct rcu_head rcu;
 138         };
 139 #endif
 140 };
 141
 142 struct backing_dev_info {
 143         struct list_head bdi_list;
 144         unsigned long ra_pages; /* max readahead in PAGE_SIZE units */
 145         unsigned long io_pages; /* max allowed IO size */
 146         congested_fn *congested_fn; /* Function pointer if device is md/dm */
 147         void *congested_data;   /* Pointer to aux data for congested func */
 148
 149         const char *name;
 150
 151         struct kref refcnt;     /* Reference counter for the structure */
 152         unsigned int capabilities; /* Device capabilities */
 153         unsigned int min_ratio;
 154         unsigned int max_ratio, max_prop_frac;
 155
 156         /*
 157          * Sum of avg_write_bw of wbs with dirty inodes.  > 0 if there are
 158          * any dirty wbs, which is depended upon by bdi_has_dirty().
 159          */
 160         atomic_long_t tot_write_bandwidth;
 161
 162         struct bdi_writeback wb;  /* the root writeback info for this bdi */
 163         struct list_head wb_list; /* list of all wbs */
 164 #ifdef CONFIG_CGROUP_WRITEBACK
 165         struct radix_tree_root cgwb_tree; /* radix tree of active cgroup wbs */
 166         struct rb_root cgwb_congested_tree; /* their congested states */
 167 #else
 168         struct bdi_writeback_congested *wb_congested;
 169 #endif
 170         wait_queue_head_t wb_waitq;
 171
 172         struct device *dev;
 173         struct device *owner;
 174
 175         struct timer_list laptop_mode_wb_timer;
 176
 177 #ifdef CONFIG_DEBUG_FS
 178         struct dentry *debug_dir;
 179         struct dentry *debug_stats;
 180 #endif
 181 };
 182
 183 enum {
 184         BLK_RW_ASYNC    = 0,
 185         BLK_RW_SYNC     = 1,
 186 };
 187
 188 void clear_wb_congested(struct bdi_writeback_congested *congested, int sync);
 189 void set_wb_congested(struct bdi_writeback_congested *congested, int sync);
 190
 191 static inline void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
 192 {
 193         clear_wb_congested(bdi->wb.congested, sync);
 194 }
 195
 196 static inline void set_bdi_congested(struct backing_dev_info *bdi, int sync)
 197 {
 198         set_wb_congested(bdi->wb.congested, sync);
 199 }
 200
 201 #ifdef CONFIG_CGROUP_WRITEBACK
 202
 203 /**
 204  * wb_tryget - try to increment a wb's refcount
 205  * @wb: bdi_writeback to get
 206  */
 207 static inline bool wb_tryget(struct bdi_writeback *wb)
 208 {
 209         if (wb != &wb->bdi->wb)
 210                 return percpu_ref_tryget(&wb->refcnt);
 211         return true;
 212 }
 213
 214 /**
 215  * wb_get - increment a wb's refcount
 216  * @wb: bdi_writeback to get
 217  */
 218 static inline void wb_get(struct bdi_writeback *wb)
 219 {
 220         if (wb != &wb->bdi->wb)
 221                 percpu_ref_get(&wb->refcnt);
 222 }
 223
 224 /**
 225  * wb_put - decrement a wb's refcount
 226  * @wb: bdi_writeback to put
 227  */
 228 static inline void wb_put(struct bdi_writeback *wb)
 229 {
 230         if (wb != &wb->bdi->wb)
 231                 percpu_ref_put(&wb->refcnt);
 232 }
 233
 234 /**
 235  * wb_dying - is a wb dying?
 236  * @wb: bdi_writeback of interest
 237  *
 238  * Returns whether @wb is unlinked and being drained.
 239  */
 240 static inline bool wb_dying(struct bdi_writeback *wb)
 241 {
 242         return percpu_ref_is_dying(&wb->refcnt);
 243 }
 244
 245 #else   /* CONFIG_CGROUP_WRITEBACK */
 246
 247 static inline bool wb_tryget(struct bdi_writeback *wb)
 248 {
 249         return true;
 250 }
 251
 252 static inline void wb_get(struct bdi_writeback *wb)
 253 {
 254 }
 255
 256 static inline void wb_put(struct bdi_writeback *wb)
 257 {
 258 }
 259
 260 static inline bool wb_dying(struct bdi_writeback *wb)
 261 {
 262         return false;
 263 }
 264
 265 #endif  /* CONFIG_CGROUP_WRITEBACK */
 266
 267 #endif  /* __LINUX_BACKING_DEV_DEFS_H */