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         WB_REASON_FOREIGN_FLUSH,
  67
  68         WB_REASON_MAX,
  69 };
  70
  71 struct wb_completion {
  72         atomic_t                cnt;
  73         wait_queue_head_t       *waitq;
  74 };
  75
  76 #define __WB_COMPLETION_INIT(_waitq)    \
  77         (struct wb_completion){ .cnt = ATOMIC_INIT(1), .waitq = (_waitq) }
  78
  79 /*
  80  * If one wants to wait for one or more wb_writeback_works, each work's
  81  * ->done should be set to a wb_completion defined using the following
  82  * macro.  Once all work items are issued with wb_queue_work(), the caller
  83  * can wait for the completion of all using wb_wait_for_completion().  Work
  84  * items which are waited upon aren't freed automatically on completion.
  85  */
  86 #define WB_COMPLETION_INIT(bdi)         __WB_COMPLETION_INIT(&(bdi)->wb_waitq)
  87
  88 #define DEFINE_WB_COMPLETION(cmpl, bdi) \
  89         struct wb_completion cmpl = WB_COMPLETION_INIT(bdi)
  90
  91 /*
  92  * For cgroup writeback, multiple wb's may map to the same blkcg.  Those
  93  * wb's can operate mostly independently but should share the congested
  94  * state.  To facilitate such sharing, the congested state is tracked using
  95  * the following struct which is created on demand, indexed by blkcg ID on
  96  * its bdi, and refcounted.
  97  */
  98 struct bdi_writeback_congested {
  99         unsigned long state;            /* WB_[a]sync_congested flags */
 100         refcount_t refcnt;              /* nr of attached wb's and blkg */
 101
 102 #ifdef CONFIG_CGROUP_WRITEBACK
 103         struct backing_dev_info *__bdi; /* the associated bdi, set to NULL
 104                                          * on bdi unregistration. For memcg-wb
 105                                          * internal use only! */
 106         int blkcg_id;                   /* ID of the associated blkcg */
 107         struct rb_node rb_node;         /* on bdi->cgwb_congestion_tree */
 108 #endif
 109 };
 110
 111 /*
 112  * Each wb (bdi_writeback) can perform writeback operations, is measured
 113  * and throttled, independently.  Without cgroup writeback, each bdi
 114  * (bdi_writeback) is served by its embedded bdi->wb.
 115  *
 116  * On the default hierarchy, blkcg implicitly enables memcg.  This allows
 117  * using memcg's page ownership for attributing writeback IOs, and every
 118  * memcg - blkcg combination can be served by its own wb by assigning a
 119  * dedicated wb to each memcg, which enables isolation across different
 120  * cgroups and propagation of IO back pressure down from the IO layer upto
 121  * the tasks which are generating the dirty pages to be written back.
 122  *
 123  * A cgroup wb is indexed on its bdi by the ID of the associated memcg,
 124  * refcounted with the number of inodes attached to it, and pins the memcg
 125  * and the corresponding blkcg.  As the corresponding blkcg for a memcg may
 126  * change as blkcg is disabled and enabled higher up in the hierarchy, a wb
 127  * is tested for blkcg after lookup and removed from index on mismatch so
 128  * that a new wb for the combination can be created.
 129  */
 130 struct bdi_writeback {
 131         struct backing_dev_info *bdi;   /* our parent bdi */
 132
 133         unsigned long state;            /* Always use atomic bitops on this */
 134         unsigned long last_old_flush;   /* last old data flush */
 135
 136         struct list_head b_dirty;       /* dirty inodes */
 137         struct list_head b_io;          /* parked for writeback */
 138         struct list_head b_more_io;     /* parked for more writeback */
 139         struct list_head b_dirty_time;  /* time stamps are dirty */
 140         spinlock_t list_lock;           /* protects the b_* lists */
 141
 142         struct percpu_counter stat[NR_WB_STAT_ITEMS];
 143
 144         struct bdi_writeback_congested *congested;
 145
 146         unsigned long bw_time_stamp;    /* last time write bw is updated */
 147         unsigned long dirtied_stamp;
 148         unsigned long written_stamp;    /* pages written at bw_time_stamp */
 149         unsigned long write_bandwidth;  /* the estimated write bandwidth */
 150         unsigned long avg_write_bandwidth; /* further smoothed write bw, > 0 */
 151
 152         /*
 153          * The base dirty throttle rate, re-calculated on every 200ms.
 154          * All the bdi tasks' dirty rate will be curbed under it.
 155          * @dirty_ratelimit tracks the estimated @balanced_dirty_ratelimit
 156          * in small steps and is much more smooth/stable than the latter.
 157          */
 158         unsigned long dirty_ratelimit;
 159         unsigned long balanced_dirty_ratelimit;
 160
 161         struct fprop_local_percpu completions;
 162         int dirty_exceeded;
 163         enum wb_reason start_all_reason;
 164
 165         spinlock_t work_lock;           /* protects work_list & dwork scheduling */
 166         struct list_head work_list;
 167         struct delayed_work dwork;      /* work item used for writeback */
 168
 169         unsigned long dirty_sleep;      /* last wait */
 170
 171         struct list_head bdi_node;      /* anchored at bdi->wb_list */
 172
 173 #ifdef CONFIG_CGROUP_WRITEBACK
 174         struct percpu_ref refcnt;       /* used only for !root wb's */
 175         struct fprop_local_percpu memcg_completions;
 176         struct cgroup_subsys_state *memcg_css; /* the associated memcg */
 177         struct cgroup_subsys_state *blkcg_css; /* and blkcg */
 178         struct list_head memcg_node;    /* anchored at memcg->cgwb_list */
 179         struct list_head blkcg_node;    /* anchored at blkcg->cgwb_list */
 180
 181         union {
 182                 struct work_struct release_work;
 183                 struct rcu_head rcu;
 184         };
 185 #endif
 186 };
 187
 188 struct backing_dev_info {
 189         u64 id;
 190         struct rb_node rb_node; /* keyed by ->id */
 191         struct list_head bdi_list;
 192         unsigned long ra_pages; /* max readahead in PAGE_SIZE units */
 193         unsigned long io_pages; /* max allowed IO size */
 194         congested_fn *congested_fn; /* Function pointer if device is md/dm */
 195         void *congested_data;   /* Pointer to aux data for congested func */
 196
 197         const char *name;
 198
 199         struct kref refcnt;     /* Reference counter for the structure */
 200         unsigned int capabilities; /* Device capabilities */
 201         unsigned int min_ratio;
 202         unsigned int max_ratio, max_prop_frac;
 203
 204         /*
 205          * Sum of avg_write_bw of wbs with dirty inodes.  > 0 if there are
 206          * any dirty wbs, which is depended upon by bdi_has_dirty().
 207          */
 208         atomic_long_t tot_write_bandwidth;
 209
 210         struct bdi_writeback wb;  /* the root writeback info for this bdi */
 211         struct list_head wb_list; /* list of all wbs */
 212 #ifdef CONFIG_CGROUP_WRITEBACK
 213         struct radix_tree_root cgwb_tree; /* radix tree of active cgroup wbs */
 214         struct rb_root cgwb_congested_tree; /* their congested states */
 215         struct mutex cgwb_release_mutex;  /* protect shutdown of wb structs */
 216         struct rw_semaphore wb_switch_rwsem; /* no cgwb switch while syncing */
 217 #else
 218         struct bdi_writeback_congested *wb_congested;
 219 #endif
 220         wait_queue_head_t wb_waitq;
 221
 222         struct device *dev;
 223         struct device *owner;
 224
 225         struct timer_list laptop_mode_wb_timer;
 226
 227 #ifdef CONFIG_DEBUG_FS
 228         struct dentry *debug_dir;
 229 #endif
 230 };
 231
 232 enum {
 233         BLK_RW_ASYNC    = 0,
 234         BLK_RW_SYNC     = 1,
 235 };
 236
 237 void clear_wb_congested(struct bdi_writeback_congested *congested, int sync);
 238 void set_wb_congested(struct bdi_writeback_congested *congested, int sync);
 239
 240 static inline void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
 241 {
 242         clear_wb_congested(bdi->wb.congested, sync);
 243 }
 244
 245 static inline void set_bdi_congested(struct backing_dev_info *bdi, int sync)
 246 {
 247         set_wb_congested(bdi->wb.congested, sync);
 248 }
 249
 250 struct wb_lock_cookie {
 251         bool locked;
 252         unsigned long flags;
 253 };
 254
 255 #ifdef CONFIG_CGROUP_WRITEBACK
 256
 257 /**
 258  * wb_tryget - try to increment a wb's refcount
 259  * @wb: bdi_writeback to get
 260  */
 261 static inline bool wb_tryget(struct bdi_writeback *wb)
 262 {
 263         if (wb != &wb->bdi->wb)
 264                 return percpu_ref_tryget(&wb->refcnt);
 265         return true;
 266 }
 267
 268 /**
 269  * wb_get - increment a wb's refcount
 270  * @wb: bdi_writeback to get
 271  */
 272 static inline void wb_get(struct bdi_writeback *wb)
 273 {
 274         if (wb != &wb->bdi->wb)
 275                 percpu_ref_get(&wb->refcnt);
 276 }
 277
 278 /**
 279  * wb_put - decrement a wb's refcount
 280  * @wb: bdi_writeback to put
 281  */
 282 static inline void wb_put(struct bdi_writeback *wb)
 283 {
 284         if (WARN_ON_ONCE(!wb->bdi)) {
 285                 /*
 286                  * A driver bug might cause a file to be removed before bdi was
 287                  * initialized.
 288                  */
 289                 return;
 290         }
 291
 292         if (wb != &wb->bdi->wb)
 293                 percpu_ref_put(&wb->refcnt);
 294 }
 295
 296 /**
 297  * wb_dying - is a wb dying?
 298  * @wb: bdi_writeback of interest
 299  *
 300  * Returns whether @wb is unlinked and being drained.
 301  */
 302 static inline bool wb_dying(struct bdi_writeback *wb)
 303 {
 304         return percpu_ref_is_dying(&wb->refcnt);
 305 }
 306
 307 #else   /* CONFIG_CGROUP_WRITEBACK */
 308
 309 static inline bool wb_tryget(struct bdi_writeback *wb)
 310 {
 311         return true;
 312 }
 313
 314 static inline void wb_get(struct bdi_writeback *wb)
 315 {
 316 }
 317
 318 static inline void wb_put(struct bdi_writeback *wb)
 319 {
 320 }
 321
 322 static inline bool wb_dying(struct bdi_writeback *wb)
 323 {
 324         return false;
 325 }
 326
 327 #endif  /* CONFIG_CGROUP_WRITEBACK */
 328
 329 #endif  /* __LINUX_BACKING_DEV_DEFS_H */