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
  16 struct page;
  17 struct device;
  18 struct dentry;
  19
  20 /*
  21  * Bits in bdi_writeback.state
  22  */
  23 enum wb_state {
  24         WB_registered,          /* bdi_register() was done */
  25         WB_shutting_down,       /* wb_shutdown() in progress */
  26         WB_writeback_running,   /* Writeback is in progress */
  27         WB_has_dirty_io,        /* Dirty inodes on ->b_{dirty|io|more_io} */
  28 };
  29
  30 enum wb_congested_state {
  31         WB_async_congested,     /* The async (write) queue is getting full */
  32         WB_sync_congested,      /* The sync queue is getting full */
  33 };
  34
  35 typedef int (congested_fn)(void *, int);
  36
  37 enum wb_stat_item {
  38         WB_RECLAIMABLE,
  39         WB_WRITEBACK,
  40         WB_DIRTIED,
  41         WB_WRITTEN,
  42         NR_WB_STAT_ITEMS
  43 };
  44
  45 #define WB_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
  46
  47 /*
  48  * For cgroup writeback, multiple wb's may map to the same blkcg.  Those
  49  * wb's can operate mostly independently but should share the congested
  50  * state.  To facilitate such sharing, the congested state is tracked using
  51  * the following struct which is created on demand, indexed by blkcg ID on
  52  * its bdi, and refcounted.
  53  */
  54 struct bdi_writeback_congested {
  55         unsigned long state;            /* WB_[a]sync_congested flags */
  56         atomic_t refcnt;                /* nr of attached wb's and blkg */
  57
  58 #ifdef CONFIG_CGROUP_WRITEBACK
  59         struct backing_dev_info *__bdi; /* the associated bdi, set to NULL
  60                                          * on bdi unregistration. For memcg-wb
  61                                          * internal use only! */
  62         int blkcg_id;                   /* ID of the associated blkcg */
  63         struct rb_node rb_node;         /* on bdi->cgwb_congestion_tree */
  64 #endif
  65 };
  66
  67 /*
  68  * Each wb (bdi_writeback) can perform writeback operations, is measured
  69  * and throttled, independently.  Without cgroup writeback, each bdi
  70  * (bdi_writeback) is served by its embedded bdi->wb.
  71  *
  72  * On the default hierarchy, blkcg implicitly enables memcg.  This allows
  73  * using memcg's page ownership for attributing writeback IOs, and every
  74  * memcg - blkcg combination can be served by its own wb by assigning a
  75  * dedicated wb to each memcg, which enables isolation across different
  76  * cgroups and propagation of IO back pressure down from the IO layer upto
  77  * the tasks which are generating the dirty pages to be written back.
  78  *
  79  * A cgroup wb is indexed on its bdi by the ID of the associated memcg,
  80  * refcounted with the number of inodes attached to it, and pins the memcg
  81  * and the corresponding blkcg.  As the corresponding blkcg for a memcg may
  82  * change as blkcg is disabled and enabled higher up in the hierarchy, a wb
  83  * is tested for blkcg after lookup and removed from index on mismatch so
  84  * that a new wb for the combination can be created.
  85  */
  86 struct bdi_writeback {
  87         struct backing_dev_info *bdi;   /* our parent bdi */
  88
  89         unsigned long state;            /* Always use atomic bitops on this */
  90         unsigned long last_old_flush;   /* last old data flush */
  91
  92         struct list_head b_dirty;       /* dirty inodes */
  93         struct list_head b_io;          /* parked for writeback */
  94         struct list_head b_more_io;     /* parked for more writeback */
  95         struct list_head b_dirty_time;  /* time stamps are dirty */
  96         spinlock_t list_lock;           /* protects the b_* lists */
  97
  98         struct percpu_counter stat[NR_WB_STAT_ITEMS];
  99
 100         struct bdi_writeback_congested *congested;
 101
 102         unsigned long bw_time_stamp;    /* last time write bw is updated */
 103         unsigned long dirtied_stamp;
 104         unsigned long written_stamp;    /* pages written at bw_time_stamp */
 105         unsigned long write_bandwidth;  /* the estimated write bandwidth */
 106         unsigned long avg_write_bandwidth; /* further smoothed write bw, > 0 */
 107
 108         /*
 109          * The base dirty throttle rate, re-calculated on every 200ms.
 110          * All the bdi tasks' dirty rate will be curbed under it.
 111          * @dirty_ratelimit tracks the estimated @balanced_dirty_ratelimit
 112          * in small steps and is much more smooth/stable than the latter.
 113          */
 114         unsigned long dirty_ratelimit;
 115         unsigned long balanced_dirty_ratelimit;
 116
 117         struct fprop_local_percpu completions;
 118         int dirty_exceeded;
 119
 120         spinlock_t work_lock;           /* protects work_list & dwork scheduling */
 121         struct list_head work_list;
 122         struct delayed_work dwork;      /* work item used for writeback */
 123
 124         unsigned long dirty_sleep;      /* last wait */
 125
 126         struct list_head bdi_node;      /* anchored at bdi->wb_list */
 127
 128 #ifdef CONFIG_CGROUP_WRITEBACK
 129         struct percpu_ref refcnt;       /* used only for !root wb's */
 130         struct fprop_local_percpu memcg_completions;
 131         struct cgroup_subsys_state *memcg_css; /* the associated memcg */
 132         struct cgroup_subsys_state *blkcg_css; /* and blkcg */
 133         struct list_head memcg_node;    /* anchored at memcg->cgwb_list */
 134         struct list_head blkcg_node;    /* anchored at blkcg->cgwb_list */
 135
 136         union {
 137                 struct work_struct release_work;
 138                 struct rcu_head rcu;
 139         };
 140 #endif
 141 };
 142
 143 struct backing_dev_info {
 144         struct list_head bdi_list;
 145         unsigned long ra_pages; /* max readahead in PAGE_SIZE units */
 146         unsigned long io_pages; /* max allowed IO size */
 147         congested_fn *congested_fn; /* Function pointer if device is md/dm */
 148         void *congested_data;   /* Pointer to aux data for congested func */
 149
 150         const char *name;
 151
 152         struct kref refcnt;     /* Reference counter for the structure */
 153         unsigned int capabilities; /* Device capabilities */
 154         unsigned int min_ratio;
 155         unsigned int max_ratio, max_prop_frac;
 156
 157         /*
 158          * Sum of avg_write_bw of wbs with dirty inodes.  > 0 if there are
 159          * any dirty wbs, which is depended upon by bdi_has_dirty().
 160          */
 161         atomic_long_t tot_write_bandwidth;
 162
 163         struct bdi_writeback wb;  /* the root writeback info for this bdi */
 164         struct list_head wb_list; /* list of all wbs */
 165 #ifdef CONFIG_CGROUP_WRITEBACK
 166         struct radix_tree_root cgwb_tree; /* radix tree of active cgroup wbs */
 167         struct rb_root cgwb_congested_tree; /* their congested states */
 168 #else
 169         struct bdi_writeback_congested *wb_congested;
 170 #endif
 171         wait_queue_head_t wb_waitq;
 172
 173         struct device *dev;
 174         struct device *owner;
 175
 176         struct timer_list laptop_mode_wb_timer;
 177
 178 #ifdef CONFIG_DEBUG_FS
 179         struct dentry *debug_dir;
 180         struct dentry *debug_stats;
 181 #endif
 182 };
 183
 184 enum {
 185         BLK_RW_ASYNC    = 0,
 186         BLK_RW_SYNC     = 1,
 187 };
 188
 189 void clear_wb_congested(struct bdi_writeback_congested *congested, int sync);
 190 void set_wb_congested(struct bdi_writeback_congested *congested, int sync);
 191
 192 static inline void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
 193 {
 194         clear_wb_congested(bdi->wb.congested, sync);
 195 }
 196
 197 static inline void set_bdi_congested(struct backing_dev_info *bdi, int sync)
 198 {
 199         set_wb_congested(bdi->wb.congested, sync);
 200 }
 201
 202 struct wb_lock_cookie {
 203         bool locked;
 204         unsigned long flags;
 205 };
 206
 207 #ifdef CONFIG_CGROUP_WRITEBACK
 208
 209 /**
 210  * wb_tryget - try to increment a wb's refcount
 211  * @wb: bdi_writeback to get
 212  */
 213 static inline bool wb_tryget(struct bdi_writeback *wb)
 214 {
 215         if (wb != &wb->bdi->wb)
 216                 return percpu_ref_tryget(&wb->refcnt);
 217         return true;
 218 }
 219
 220 /**
 221  * wb_get - increment a wb's refcount
 222  * @wb: bdi_writeback to get
 223  */
 224 static inline void wb_get(struct bdi_writeback *wb)
 225 {
 226         if (wb != &wb->bdi->wb)
 227                 percpu_ref_get(&wb->refcnt);
 228 }
 229
 230 /**
 231  * wb_put - decrement a wb's refcount
 232  * @wb: bdi_writeback to put
 233  */
 234 static inline void wb_put(struct bdi_writeback *wb)
 235 {
 236         if (wb != &wb->bdi->wb)
 237                 percpu_ref_put(&wb->refcnt);
 238 }
 239
 240 /**
 241  * wb_dying - is a wb dying?
 242  * @wb: bdi_writeback of interest
 243  *
 244  * Returns whether @wb is unlinked and being drained.
 245  */
 246 static inline bool wb_dying(struct bdi_writeback *wb)
 247 {
 248         return percpu_ref_is_dying(&wb->refcnt);
 249 }
 250
 251 #else   /* CONFIG_CGROUP_WRITEBACK */
 252
 253 static inline bool wb_tryget(struct bdi_writeback *wb)
 254 {
 255         return true;
 256 }
 257
 258 static inline void wb_get(struct bdi_writeback *wb)
 259 {
 260 }
 261
 262 static inline void wb_put(struct bdi_writeback *wb)
 263 {
 264 }
 265
 266 static inline bool wb_dying(struct bdi_writeback *wb)
 267 {
 268         return false;
 269 }
 270
 271 #endif  /* CONFIG_CGROUP_WRITEBACK */
 272
 273 #endif  /* __LINUX_BACKING_DEV_DEFS_H */