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_stat_item {
  32         WB_RECLAIMABLE,
  33         WB_WRITEBACK,
  34         WB_DIRTIED,
  35         WB_WRITTEN,
  36         NR_WB_STAT_ITEMS
  37 };
  38
  39 #define WB_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
  40
  41 /*
  42  * why some writeback work was initiated
  43  */
  44 enum wb_reason {
  45         WB_REASON_BACKGROUND,
  46         WB_REASON_VMSCAN,
  47         WB_REASON_SYNC,
  48         WB_REASON_PERIODIC,
  49         WB_REASON_LAPTOP_TIMER,
  50         WB_REASON_FS_FREE_SPACE,
  51         /*
  52          * There is no bdi forker thread any more and works are done
  53          * by emergency worker, however, this is TPs userland visible
  54          * and we'll be exposing exactly the same information,
  55          * so it has a mismatch name.
  56          */
  57         WB_REASON_FORKER_THREAD,
  58         WB_REASON_FOREIGN_FLUSH,
  59
  60         WB_REASON_MAX,
  61 };
  62
  63 struct wb_completion {
  64         atomic_t                cnt;
  65         wait_queue_head_t       *waitq;
  66 };
  67
  68 #define __WB_COMPLETION_INIT(_waitq)    \
  69         (struct wb_completion){ .cnt = ATOMIC_INIT(1), .waitq = (_waitq) }
  70
  71 /*
  72  * If one wants to wait for one or more wb_writeback_works, each work's
  73  * ->done should be set to a wb_completion defined using the following
  74  * macro.  Once all work items are issued with wb_queue_work(), the caller
  75  * can wait for the completion of all using wb_wait_for_completion().  Work
  76  * items which are waited upon aren't freed automatically on completion.
  77  */
  78 #define WB_COMPLETION_INIT(bdi)         __WB_COMPLETION_INIT(&(bdi)->wb_waitq)
  79
  80 #define DEFINE_WB_COMPLETION(cmpl, bdi) \
  81         struct wb_completion cmpl = WB_COMPLETION_INIT(bdi)
  82
  83 /*
  84  * Each wb (bdi_writeback) can perform writeback operations, is measured
  85  * and throttled, independently.  Without cgroup writeback, each bdi
  86  * (bdi_writeback) is served by its embedded bdi->wb.
  87  *
  88  * On the default hierarchy, blkcg implicitly enables memcg.  This allows
  89  * using memcg's page ownership for attributing writeback IOs, and every
  90  * memcg - blkcg combination can be served by its own wb by assigning a
  91  * dedicated wb to each memcg, which enables isolation across different
  92  * cgroups and propagation of IO back pressure down from the IO layer upto
  93  * the tasks which are generating the dirty pages to be written back.
  94  *
  95  * A cgroup wb is indexed on its bdi by the ID of the associated memcg,
  96  * refcounted with the number of inodes attached to it, and pins the memcg
  97  * and the corresponding blkcg.  As the corresponding blkcg for a memcg may
  98  * change as blkcg is disabled and enabled higher up in the hierarchy, a wb
  99  * is tested for blkcg after lookup and removed from index on mismatch so
 100  * that a new wb for the combination can be created.
 101  *
 102  * Each bdi_writeback that is not embedded into the backing_dev_info must hold
 103  * a reference to the parent backing_dev_info.  See cgwb_create() for details.
 104  */
 105 struct bdi_writeback {
 106         struct backing_dev_info *bdi;   /* our parent bdi */
 107
 108         unsigned long state;            /* Always use atomic bitops on this */
 109         unsigned long last_old_flush;   /* last old data flush */
 110
 111         struct list_head b_dirty;       /* dirty inodes */
 112         struct list_head b_io;          /* parked for writeback */
 113         struct list_head b_more_io;     /* parked for more writeback */
 114         struct list_head b_dirty_time;  /* time stamps are dirty */
 115         spinlock_t list_lock;           /* protects the b_* lists */
 116
 117         atomic_t writeback_inodes;      /* number of inodes under writeback */
 118         struct percpu_counter stat[NR_WB_STAT_ITEMS];
 119
 120         unsigned long bw_time_stamp;    /* last time write bw is updated */
 121         unsigned long dirtied_stamp;
 122         unsigned long written_stamp;    /* pages written at bw_time_stamp */
 123         unsigned long write_bandwidth;  /* the estimated write bandwidth */
 124         unsigned long avg_write_bandwidth; /* further smoothed write bw, > 0 */
 125
 126         /*
 127          * The base dirty throttle rate, re-calculated on every 200ms.
 128          * All the bdi tasks' dirty rate will be curbed under it.
 129          * @dirty_ratelimit tracks the estimated @balanced_dirty_ratelimit
 130          * in small steps and is much more smooth/stable than the latter.
 131          */
 132         unsigned long dirty_ratelimit;
 133         unsigned long balanced_dirty_ratelimit;
 134
 135         struct fprop_local_percpu completions;
 136         int dirty_exceeded;
 137         enum wb_reason start_all_reason;
 138
 139         spinlock_t work_lock;           /* protects work_list & dwork scheduling */
 140         struct list_head work_list;
 141         struct delayed_work dwork;      /* work item used for writeback */
 142         struct delayed_work bw_dwork;   /* work item used for bandwidth estimate */
 143
 144         struct list_head bdi_node;      /* anchored at bdi->wb_list */
 145
 146 #ifdef CONFIG_CGROUP_WRITEBACK
 147         struct percpu_ref refcnt;       /* used only for !root wb's */
 148         struct fprop_local_percpu memcg_completions;
 149         struct cgroup_subsys_state *memcg_css; /* the associated memcg */
 150         struct cgroup_subsys_state *blkcg_css; /* and blkcg */
 151         struct list_head memcg_node;    /* anchored at memcg->cgwb_list */
 152         struct list_head blkcg_node;    /* anchored at blkcg->cgwb_list */
 153         struct list_head b_attached;    /* attached inodes, protected by list_lock */
 154         struct list_head offline_node;  /* anchored at offline_cgwbs */
 155
 156         union {
 157                 struct work_struct release_work;
 158                 struct rcu_head rcu;
 159         };
 160 #endif
 161 };
 162
 163 struct backing_dev_info {
 164         u64 id;
 165         struct rb_node rb_node; /* keyed by ->id */
 166         struct list_head bdi_list;
 167         unsigned long ra_pages; /* max readahead in PAGE_SIZE units */
 168         unsigned long io_pages; /* max allowed IO size */
 169
 170         struct kref refcnt;     /* Reference counter for the structure */
 171         unsigned int capabilities; /* Device capabilities */
 172         unsigned int min_ratio;
 173         unsigned int max_ratio, max_prop_frac;
 174
 175         /*
 176          * Sum of avg_write_bw of wbs with dirty inodes.  > 0 if there are
 177          * any dirty wbs, which is depended upon by bdi_has_dirty().
 178          */
 179         atomic_long_t tot_write_bandwidth;
 180         /*
 181          * Jiffies when last process was dirty throttled on this bdi. Used by
 182          * blk-wbt.
 183          */
 184         unsigned long last_bdp_sleep;
 185
 186         struct bdi_writeback wb;  /* the root writeback info for this bdi */
 187         struct list_head wb_list; /* list of all wbs */
 188 #ifdef CONFIG_CGROUP_WRITEBACK
 189         struct radix_tree_root cgwb_tree; /* radix tree of active cgroup wbs */
 190         struct mutex cgwb_release_mutex;  /* protect shutdown of wb structs */
 191         struct rw_semaphore wb_switch_rwsem; /* no cgwb switch while syncing */
 192 #endif
 193         wait_queue_head_t wb_waitq;
 194
 195         struct device *dev;
 196         char dev_name[64];
 197         struct device *owner;
 198
 199         struct timer_list laptop_mode_wb_timer;
 200
 201 #ifdef CONFIG_DEBUG_FS
 202         struct dentry *debug_dir;
 203 #endif
 204 };
 205
 206 struct wb_lock_cookie {
 207         bool locked;
 208         unsigned long flags;
 209 };
 210
 211 #ifdef CONFIG_CGROUP_WRITEBACK
 212
 213 /**
 214  * wb_tryget - try to increment a wb's refcount
 215  * @wb: bdi_writeback to get
 216  */
 217 static inline bool wb_tryget(struct bdi_writeback *wb)
 218 {
 219         if (wb != &wb->bdi->wb)
 220                 return percpu_ref_tryget(&wb->refcnt);
 221         return true;
 222 }
 223
 224 /**
 225  * wb_get - increment a wb's refcount
 226  * @wb: bdi_writeback to get
 227  */
 228 static inline void wb_get(struct bdi_writeback *wb)
 229 {
 230         if (wb != &wb->bdi->wb)
 231                 percpu_ref_get(&wb->refcnt);
 232 }
 233
 234 /**
 235  * wb_put - decrement a wb's refcount
 236  * @wb: bdi_writeback to put
 237  * @nr: number of references to put
 238  */
 239 static inline void wb_put_many(struct bdi_writeback *wb, unsigned long nr)
 240 {
 241         if (WARN_ON_ONCE(!wb->bdi)) {
 242                 /*
 243                  * A driver bug might cause a file to be removed before bdi was
 244                  * initialized.
 245                  */
 246                 return;
 247         }
 248
 249         if (wb != &wb->bdi->wb)
 250                 percpu_ref_put_many(&wb->refcnt, nr);
 251 }
 252
 253 /**
 254  * wb_put - decrement a wb's refcount
 255  * @wb: bdi_writeback to put
 256  */
 257 static inline void wb_put(struct bdi_writeback *wb)
 258 {
 259         wb_put_many(wb, 1);
 260 }
 261
 262 /**
 263  * wb_dying - is a wb dying?
 264  * @wb: bdi_writeback of interest
 265  *
 266  * Returns whether @wb is unlinked and being drained.
 267  */
 268 static inline bool wb_dying(struct bdi_writeback *wb)
 269 {
 270         return percpu_ref_is_dying(&wb->refcnt);
 271 }
 272
 273 #else   /* CONFIG_CGROUP_WRITEBACK */
 274
 275 static inline bool wb_tryget(struct bdi_writeback *wb)
 276 {
 277         return true;
 278 }
 279
 280 static inline void wb_get(struct bdi_writeback *wb)
 281 {
 282 }
 283
 284 static inline void wb_put(struct bdi_writeback *wb)
 285 {
 286 }
 287
 288 static inline void wb_put_many(struct bdi_writeback *wb, unsigned long nr)
 289 {
 290 }
 291
 292 static inline bool wb_dying(struct bdi_writeback *wb)
 293 {
 294         return false;
 295 }
 296
 297 #endif  /* CONFIG_CGROUP_WRITEBACK */
 298
 299 #endif  /* __LINUX_BACKING_DEV_DEFS_H */