include/linux/backing-dev-defs.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef __LINUX_BACKING_DEV_DEFS_H
   3 #define __LINUX_BACKING_DEV_DEFS_H
   4
   5 #include <linux/list.h>
   6 #include <linux/radix-tree.h>
   7 #include <linux/rbtree.h>
   8 #include <linux/spinlock.h>
   9 #include <linux/percpu_counter.h>
  10 #include <linux/percpu-refcount.h>
  11 #include <linux/flex_proportions.h>
  12 #include <linux/timer.h>
  13 #include <linux/workqueue.h>
  14 #include <linux/kref.h>
  15 #include <linux/refcount.h>
  16
  17 struct page;
  18 struct device;
  19 struct dentry;
  20
  21 /*
  22  * Bits in bdi_writeback.state
  23  */
  24 enum wb_state {
  25         WB_registered,          /* bdi_register() was done */
  26         WB_writeback_running,   /* Writeback is in progress */
  27         WB_has_dirty_io,        /* Dirty inodes on ->b_{dirty|io|more_io} */
  28         WB_start_all,           /* nr_pages == 0 (all) work pending */
  29 };
  30
  31 enum wb_congested_state {
  32         WB_async_congested,     /* The async (write) queue is getting full */
  33         WB_sync_congested,      /* The sync queue is getting full */
  34 };
  35
  36 typedef int (congested_fn)(void *, int);
  37
  38 enum wb_stat_item {
  39         WB_RECLAIMABLE,
  40         WB_WRITEBACK,
  41         WB_DIRTIED,
  42         WB_WRITTEN,
  43         NR_WB_STAT_ITEMS
  44 };
  45
  46 #define WB_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
  47
  48 /*
  49  * why some writeback work was initiated
  50  */
  51 enum wb_reason {
  52         WB_REASON_BACKGROUND,
  53         WB_REASON_VMSCAN,
  54         WB_REASON_SYNC,
  55         WB_REASON_PERIODIC,
  56         WB_REASON_LAPTOP_TIMER,
  57         WB_REASON_FREE_MORE_MEM,
  58         WB_REASON_FS_FREE_SPACE,
  59         /*
  60          * There is no bdi forker thread any more and works are done
  61          * by emergency worker, however, this is TPs userland visible
  62          * and we'll be exposing exactly the same information,
  63          * so it has a mismatch name.
  64          */
  65         WB_REASON_FORKER_THREAD,
  66
  67         WB_REASON_MAX,
  68 };
  69
  70 /*
  71  * For cgroup writeback, multiple wb's may map to the same blkcg.  Those
  72  * wb's can operate mostly independently but should share the congested
  73  * state.  To facilitate such sharing, the congested state is tracked using
  74  * the following struct which is created on demand, indexed by blkcg ID on
  75  * its bdi, and refcounted.
  76  */
  77 struct bdi_writeback_congested {
  78         unsigned long state;            /* WB_[a]sync_congested flags */
  79         refcount_t refcnt;              /* nr of attached wb's and blkg */
  80
  81 #ifdef CONFIG_CGROUP_WRITEBACK
  82         struct backing_dev_info *__bdi; /* the associated bdi, set to NULL
  83                                          * on bdi unregistration. For memcg-wb
  84                                          * internal use only! */
  85         int blkcg_id;                   /* ID of the associated blkcg */
  86         struct rb_node rb_node;         /* on bdi->cgwb_congestion_tree */
  87 #endif
  88 };
  89
  90 /*
  91  * Each wb (bdi_writeback) can perform writeback operations, is measured
  92  * and throttled, independently.  Without cgroup writeback, each bdi
  93  * (bdi_writeback) is served by its embedded bdi->wb.
  94  *
  95  * On the default hierarchy, blkcg implicitly enables memcg.  This allows
  96  * using memcg's page ownership for attributing writeback IOs, and every
  97  * memcg - blkcg combination can be served by its own wb by assigning a
  98  * dedicated wb to each memcg, which enables isolation across different
  99  * cgroups and propagation of IO back pressure down from the IO layer upto
 100  * the tasks which are generating the dirty pages to be written back.
 101  *
 102  * A cgroup wb is indexed on its bdi by the ID of the associated memcg,
 103  * refcounted with the number of inodes attached to it, and pins the memcg
 104  * and the corresponding blkcg.  As the corresponding blkcg for a memcg may
 105  * change as blkcg is disabled and enabled higher up in the hierarchy, a wb
 106  * is tested for blkcg after lookup and removed from index on mismatch so
 107  * that a new wb for the combination can be created.
 108  */
 109 struct bdi_writeback {
 110         struct backing_dev_info *bdi;   /* our parent bdi */
 111
 112         unsigned long state;            /* Always use atomic bitops on this */
 113         unsigned long last_old_flush;   /* last old data flush */
 114
 115         struct list_head b_dirty;       /* dirty inodes */
 116         struct list_head b_io;          /* parked for writeback */
 117         struct list_head b_more_io;     /* parked for more writeback */
 118         struct list_head b_dirty_time;  /* time stamps are dirty */
 119         spinlock_t list_lock;           /* protects the b_* lists */
 120
 121         struct percpu_counter stat[NR_WB_STAT_ITEMS];
 122
 123         struct bdi_writeback_congested *congested;
 124
 125         unsigned long bw_time_stamp;    /* last time write bw is updated */
 126         unsigned long dirtied_stamp;
 127         unsigned long written_stamp;    /* pages written at bw_time_stamp */
 128         unsigned long write_bandwidth;  /* the estimated write bandwidth */
 129         unsigned long avg_write_bandwidth; /* further smoothed write bw, > 0 */
 130
 131         /*
 132          * The base dirty throttle rate, re-calculated on every 200ms.
 133          * All the bdi tasks' dirty rate will be curbed under it.
 134          * @dirty_ratelimit tracks the estimated @balanced_dirty_ratelimit
 135          * in small steps and is much more smooth/stable than the latter.
 136          */
 137         unsigned long dirty_ratelimit;
 138         unsigned long balanced_dirty_ratelimit;
 139
 140         struct fprop_local_percpu completions;
 141         int dirty_exceeded;
 142         enum wb_reason start_all_reason;
 143
 144         spinlock_t work_lock;           /* protects work_list & dwork scheduling */
 145         struct list_head work_list;
 146         struct delayed_work dwork;      /* work item used for writeback */
 147
 148         unsigned long dirty_sleep;      /* last wait */
 149
 150         struct list_head bdi_node;      /* anchored at bdi->wb_list */
 151
 152 #ifdef CONFIG_CGROUP_WRITEBACK
 153         struct percpu_ref refcnt;       /* used only for !root wb's */
 154         struct fprop_local_percpu memcg_completions;
 155         struct cgroup_subsys_state *memcg_css; /* the associated memcg */
 156         struct cgroup_subsys_state *blkcg_css; /* and blkcg */
 157         struct list_head memcg_node;    /* anchored at memcg->cgwb_list */
 158         struct list_head blkcg_node;    /* anchored at blkcg->cgwb_list */
 159
 160         union {
 161                 struct work_struct release_work;
 162                 struct rcu_head rcu;
 163         };
 164 #endif
 165 };
 166
 167 struct backing_dev_info {
 168         struct list_head bdi_list;
 169         unsigned long ra_pages; /* max readahead in PAGE_SIZE units */
 170         unsigned long io_pages; /* max allowed IO size */
 171         congested_fn *congested_fn; /* Function pointer if device is md/dm */
 172         void *congested_data;   /* Pointer to aux data for congested func */
 173
 174         const char *name;
 175
 176         struct kref refcnt;     /* Reference counter for the structure */
 177         unsigned int capabilities; /* Device capabilities */
 178         unsigned int min_ratio;
 179         unsigned int max_ratio, max_prop_frac;
 180
 181         /*
 182          * Sum of avg_write_bw of wbs with dirty inodes.  > 0 if there are
 183          * any dirty wbs, which is depended upon by bdi_has_dirty().
 184          */
 185         atomic_long_t tot_write_bandwidth;
 186
 187         struct bdi_writeback wb;  /* the root writeback info for this bdi */
 188         struct list_head wb_list; /* list of all wbs */
 189 #ifdef CONFIG_CGROUP_WRITEBACK
 190         struct radix_tree_root cgwb_tree; /* radix tree of active cgroup wbs */
 191         struct rb_root cgwb_congested_tree; /* their congested states */
 192         struct mutex cgwb_release_mutex;  /* protect shutdown of wb structs */
 193 #else
 194         struct bdi_writeback_congested *wb_congested;
 195 #endif
 196         wait_queue_head_t wb_waitq;
 197
 198         struct device *dev;
 199         struct device *owner;
 200
 201         struct timer_list laptop_mode_wb_timer;
 202
 203 #ifdef CONFIG_DEBUG_FS
 204         struct dentry *debug_dir;
 205         struct dentry *debug_stats;
 206 #endif
 207 };
 208
 209 enum {
 210         BLK_RW_ASYNC    = 0,
 211         BLK_RW_SYNC     = 1,
 212 };
 213
 214 void clear_wb_congested(struct bdi_writeback_congested *congested, int sync);
 215 void set_wb_congested(struct bdi_writeback_congested *congested, int sync);
 216
 217 static inline void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
 218 {
 219         clear_wb_congested(bdi->wb.congested, sync);
 220 }
 221
 222 static inline void set_bdi_congested(struct backing_dev_info *bdi, int sync)
 223 {
 224         set_wb_congested(bdi->wb.congested, sync);
 225 }
 226
 227 struct wb_lock_cookie {
 228         bool locked;
 229         unsigned long flags;
 230 };
 231
 232 #ifdef CONFIG_CGROUP_WRITEBACK
 233
 234 /**
 235  * wb_tryget - try to increment a wb's refcount
 236  * @wb: bdi_writeback to get
 237  */
 238 static inline bool wb_tryget(struct bdi_writeback *wb)
 239 {
 240         if (wb != &wb->bdi->wb)
 241                 return percpu_ref_tryget(&wb->refcnt);
 242         return true;
 243 }
 244
 245 /**
 246  * wb_get - increment a wb's refcount
 247  * @wb: bdi_writeback to get
 248  */
 249 static inline void wb_get(struct bdi_writeback *wb)
 250 {
 251         if (wb != &wb->bdi->wb)
 252                 percpu_ref_get(&wb->refcnt);
 253 }
 254
 255 /**
 256  * wb_put - decrement a wb's refcount
 257  * @wb: bdi_writeback to put
 258  */
 259 static inline void wb_put(struct bdi_writeback *wb)
 260 {
 261         if (WARN_ON_ONCE(!wb->bdi)) {
 262                 /*
 263                  * A driver bug might cause a file to be removed before bdi was
 264                  * initialized.
 265                  */
 266                 return;
 267         }
 268
 269         if (wb != &wb->bdi->wb)
 270                 percpu_ref_put(&wb->refcnt);
 271 }
 272
 273 /**
 274  * wb_dying - is a wb dying?
 275  * @wb: bdi_writeback of interest
 276  *
 277  * Returns whether @wb is unlinked and being drained.
 278  */
 279 static inline bool wb_dying(struct bdi_writeback *wb)
 280 {
 281         return percpu_ref_is_dying(&wb->refcnt);
 282 }
 283
 284 #else   /* CONFIG_CGROUP_WRITEBACK */
 285
 286 static inline bool wb_tryget(struct bdi_writeback *wb)
 287 {
 288         return true;
 289 }
 290
 291 static inline void wb_get(struct bdi_writeback *wb)
 292 {
 293 }
 294
 295 static inline void wb_put(struct bdi_writeback *wb)
 296 {
 297 }
 298
 299 static inline bool wb_dying(struct bdi_writeback *wb)
 300 {
 301         return false;
 302 }
 303
 304 #endif  /* CONFIG_CGROUP_WRITEBACK */
 305
 306 #endif  /* __LINUX_BACKING_DEV_DEFS_H */