OSCL-LXR linux-6.0.1/​drivers/​md/​bcache/​request.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Main bcache entry point - handle a read or a write request and decide what to
  * do with it; the make_request functions are called by the block layer.
  *
  * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
  * Copyright 2012 Google, Inc.
  */
 
 #include "bcache.h"
 #include "btree.h"
 #include "debug.h"
 #include "request.h"
 #include "writeback.h"
 
 #include <linux/module.h>
 #include <linux/hash.h>
 #include <linux/random.h>
 #include <linux/backing-dev.h>
 
 #include <trace/events/bcache.h>
 
 #define CUTOFF_CACHE_ADD    95
 #define CUTOFF_CACHE_READA  90
 
 struct kmem_cache *bch_search_cache;
 
 static void bch_data_insert_start(struct closure *cl);
 
 static unsigned int cache_mode(struct cached_dev *dc)
 {
     return BDEV_CACHE_MODE(&dc->sb);
 }
 
 static bool verify(struct cached_dev *dc)
 {
     return dc->verify;
 }
 
 static void bio_csum(struct bio *bio, struct bkey *k)
 {
     struct bio_vec bv;
     struct bvec_iter iter;
     uint64_t csum = 0;
 
     bio_for_each_segment(bv, bio, iter) {
         void *d = bvec_kmap_local(&bv);
 
         csum = crc64_be(csum, d, bv.bv_len);
         kunmap_local(d);
     }
 
     k->ptr[KEY_PTRS(k)] = csum & (~0ULL >> 1);
 }
 
 /* Insert data into cache */
 
 static void bch_data_insert_keys(struct closure *cl)
 {
     struct data_insert_op *op = container_of(cl, struct data_insert_op, cl);
     atomic_t *journal_ref = NULL;
     struct bkey *replace_key = op->replace ? &op->replace_key : NULL;
     int ret;
 
     if (!op->replace)
         journal_ref = bch_journal(op->c, &op->insert_keys,
                       op->flush_journal ? cl : NULL);
 
     ret = bch_btree_insert(op->c, &op->insert_keys,
                    journal_ref, replace_key);
     if (ret == -ESRCH) {
         op->replace_collision = true;
     } else if (ret) {
         op->status      = BLK_STS_RESOURCE;
         op->insert_data_done    = true;
     }
 
     if (journal_ref)
         atomic_dec_bug(journal_ref);
 
     if (!op->insert_data_done) {
         continue_at(cl, bch_data_insert_start, op->wq);
         return;
     }
 
     bch_keylist_free(&op->insert_keys);
     closure_return(cl);
 }
 
 static int bch_keylist_realloc(struct keylist *l, unsigned int u64s,
                    struct cache_set *c)
 {
     size_t oldsize = bch_keylist_nkeys(l);
     size_t newsize = oldsize + u64s;
 
     /*
      * The journalling code doesn't handle the case where the keys to insert
      * is bigger than an empty write: If we just return -ENOMEM here,
      * bch_data_insert_keys() will insert the keys created so far
      * and finish the rest when the keylist is empty.
      */
     if (newsize * sizeof(uint64_t) > block_bytes(c->cache) - sizeof(struct jset))
         return -ENOMEM;
 
     return __bch_keylist_realloc(l, u64s);
 }
 
 static void bch_data_invalidate(struct closure *cl)
 {
     struct data_insert_op *op = container_of(cl, struct data_insert_op, cl);
     struct bio *bio = op->bio;
 
     pr_debug("invalidating %i sectors from %llu\n",
          bio_sectors(bio), (uint64_t) bio->bi_iter.bi_sector);
 
     while (bio_sectors(bio)) {
         unsigned int sectors = min(bio_sectors(bio),
                        1U << (KEY_SIZE_BITS - 1));
 
         if (bch_keylist_realloc(&op->insert_keys, 2, op->c))
             goto out;
 
         bio->bi_iter.bi_sector  += sectors;
         bio->bi_iter.bi_size    -= sectors << 9;
 
         bch_keylist_add(&op->insert_keys,
                 &KEY(op->inode,
                      bio->bi_iter.bi_sector,
                      sectors));
     }
 
     op->insert_data_done = true;
     /* get in bch_data_insert() */
     bio_put(bio);
 out:
     continue_at(cl, bch_data_insert_keys, op->wq);
 }
 
 static void bch_data_insert_error(struct closure *cl)
 {
     struct data_insert_op *op = container_of(cl, struct data_insert_op, cl);
 
     /*
      * Our data write just errored, which means we've got a bunch of keys to
      * insert that point to data that wasn't successfully written.
      *
      * We don't have to insert those keys but we still have to invalidate
      * that region of the cache - so, if we just strip off all the pointers
      * from the keys we'll accomplish just that.
      */
 
     struct bkey *src = op->insert_keys.keys, *dst = op->insert_keys.keys;
 
     while (src != op->insert_keys.top) {
         struct bkey *n = bkey_next(src);
 
         SET_KEY_PTRS(src, 0);
         memmove(dst, src, bkey_bytes(src));
 
         dst = bkey_next(dst);
         src = n;
     }
 
     op->insert_keys.top = dst;
 
     bch_data_insert_keys(cl);
 }
 
 static void bch_data_insert_endio(struct bio *bio)
 {
     struct closure *cl = bio->bi_private;
     struct data_insert_op *op = container_of(cl, struct data_insert_op, cl);
 
     if (bio->bi_status) {
         /* TODO: We could try to recover from this. */
         if (op->writeback)
             op->status = bio->bi_status;
         else if (!op->replace)
             set_closure_fn(cl, bch_data_insert_error, op->wq);
         else
             set_closure_fn(cl, NULL, NULL);
     }
 
     bch_bbio_endio(op->c, bio, bio->bi_status, "writing data to cache");
 }
 
 static void bch_data_insert_start(struct closure *cl)
 {
     struct data_insert_op *op = container_of(cl, struct data_insert_op, cl);
     struct bio *bio = op->bio, *n;
 
     if (op->bypass)
         return bch_data_invalidate(cl);
 
     if (atomic_sub_return(bio_sectors(bio), &op->c->sectors_to_gc) < 0)
         wake_up_gc(op->c);
 
     /*
      * Journal writes are marked REQ_PREFLUSH; if the original write was a
      * flush, it'll wait on the journal write.
      */
     bio->bi_opf &= ~(REQ_PREFLUSH|REQ_FUA);
 
     do {
         unsigned int i;
         struct bkey *k;
         struct bio_set *split = &op->c->bio_split;
 
         /* 1 for the device pointer and 1 for the chksum */
         if (bch_keylist_realloc(&op->insert_keys,
                     3 + (op->csum ? 1 : 0),
                     op->c)) {
             continue_at(cl, bch_data_insert_keys, op->wq);
             return;
         }
 
         k = op->insert_keys.top;
         bkey_init(k);
         SET_KEY_INODE(k, op->inode);
         SET_KEY_OFFSET(k, bio->bi_iter.bi_sector);
 
         if (!bch_alloc_sectors(op->c, k, bio_sectors(bio),
                        op->write_point, op->write_prio,
                        op->writeback))
             goto err;
 
         n = bio_next_split(bio, KEY_SIZE(k), GFP_NOIO, split);
 
         n->bi_end_io    = bch_data_insert_endio;
         n->bi_private   = cl;
 
         if (op->writeback) {
             SET_KEY_DIRTY(k, true);
 
             for (i = 0; i < KEY_PTRS(k); i++)
                 SET_GC_MARK(PTR_BUCKET(op->c, k, i),
                         GC_MARK_DIRTY);
         }
 
         SET_KEY_CSUM(k, op->csum);
         if (KEY_CSUM(k))
             bio_csum(n, k);
 
         trace_bcache_cache_insert(k);
         bch_keylist_push(&op->insert_keys);
 
         bio_set_op_attrs(n, REQ_OP_WRITE, 0);
         bch_submit_bbio(n, op->c, k, 0);
     } while (n != bio);
 
     op->insert_data_done = true;
     continue_at(cl, bch_data_insert_keys, op->wq);
     return;
 err:
     /* bch_alloc_sectors() blocks if s->writeback = true */
     BUG_ON(op->writeback);
 
     /*
      * But if it's not a writeback write we'd rather just bail out if
      * there aren't any buckets ready to write to - it might take awhile and
      * we might be starving btree writes for gc or something.
      */
 
     if (!op->replace) {
         /*
          * Writethrough write: We can't complete the write until we've
          * updated the index. But we don't want to delay the write while
          * we wait for buckets to be freed up, so just invalidate the
          * rest of the write.
          */
         op->bypass = true;
         return bch_data_invalidate(cl);
     } else {
         /*
          * From a cache miss, we can just insert the keys for the data
          * we have written or bail out if we didn't do anything.
          */
         op->insert_data_done = true;
         bio_put(bio);
 
         if (!bch_keylist_empty(&op->insert_keys))
             continue_at(cl, bch_data_insert_keys, op->wq);
         else
             closure_return(cl);
     }
 }
 
 /**
  * bch_data_insert - stick some data in the cache
  * @cl: closure pointer.
  *
  * This is the starting point for any data to end up in a cache device; it could
  * be from a normal write, or a writeback write, or a write to a flash only
  * volume - it's also used by the moving garbage collector to compact data in
  * mostly empty buckets.
  *
  * It first writes the data to the cache, creating a list of keys to be inserted
  * (if the data had to be fragmented there will be multiple keys); after the
  * data is written it calls bch_journal, and after the keys have been added to
  * the next journal write they're inserted into the btree.
  *
  * It inserts the data in op->bio; bi_sector is used for the key offset,
  * and op->inode is used for the key inode.
  *
  * If op->bypass is true, instead of inserting the data it invalidates the
  * region of the cache represented by op->bio and op->inode.
  */
 void bch_data_insert(struct closure *cl)
 {
     struct data_insert_op *op = container_of(cl, struct data_insert_op, cl);
 
     trace_bcache_write(op->c, op->inode, op->bio,
                op->writeback, op->bypass);
 
     bch_keylist_init(&op->insert_keys);
     bio_get(op->bio);
     bch_data_insert_start(cl);
 }
 
 /*
  * Congested?  Return 0 (not congested) or the limit (in sectors)
  * beyond which we should bypass the cache due to congestion.
  */
 unsigned int bch_get_congested(const struct cache_set *c)
 {
     int i;
 
     if (!c->congested_read_threshold_us &&
         !c->congested_write_threshold_us)
         return 0;
 
     i = (local_clock_us() - c->congested_last_us) / 1024;
     if (i < 0)
         return 0;
 
     i += atomic_read(&c->congested);
     if (i >= 0)
         return 0;
 
     i += CONGESTED_MAX;
 
     if (i > 0)
         i = fract_exp_two(i, 6);
 
     i -= hweight32(get_random_u32());
 
     return i > 0 ? i : 1;
 }
 
 static void add_sequential(struct task_struct *t)
 {
     ewma_add(t->sequential_io_avg,
          t->sequential_io, 8, 0);
 
     t->sequential_io = 0;
 }
 
 static struct hlist_head *iohash(struct cached_dev *dc, uint64_t k)
 {
     return &dc->io_hash[hash_64(k, RECENT_IO_BITS)];
 }
 
 static bool check_should_bypass(struct cached_dev *dc, struct bio *bio)
 {
     struct cache_set *c = dc->disk.c;
     unsigned int mode = cache_mode(dc);
     unsigned int sectors, congested;
     struct task_struct *task = current;
     struct io *i;
 
     if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) ||
         c->gc_stats.in_use > CUTOFF_CACHE_ADD ||
         (bio_op(bio) == REQ_OP_DISCARD))
         goto skip;
 
     if (mode == CACHE_MODE_NONE ||
         (mode == CACHE_MODE_WRITEAROUND &&
          op_is_write(bio_op(bio))))
         goto skip;
 
     /*
      * If the bio is for read-ahead or background IO, bypass it or
      * not depends on the following situations,
      * - If the IO is for meta data, always cache it and no bypass
      * - If the IO is not meta data, check dc->cache_reada_policy,
      *      BCH_CACHE_READA_ALL: cache it and not bypass
      *      BCH_CACHE_READA_META_ONLY: not cache it and bypass
      * That is, read-ahead request for metadata always get cached
      * (eg, for gfs2 or xfs).
      */
     if ((bio->bi_opf & (REQ_RAHEAD|REQ_BACKGROUND))) {
         if (!(bio->bi_opf & (REQ_META|REQ_PRIO)) &&
             (dc->cache_readahead_policy != BCH_CACHE_READA_ALL))
             goto skip;
     }
 
     if (bio->bi_iter.bi_sector & (c->cache->sb.block_size - 1) ||
         bio_sectors(bio) & (c->cache->sb.block_size - 1)) {
         pr_debug("skipping unaligned io\n");
         goto skip;
     }
 
     if (bypass_torture_test(dc)) {
         if ((get_random_int() & 3) == 3)
             goto skip;
         else
             goto rescale;
     }
 
     congested = bch_get_congested(c);
     if (!congested && !dc->sequential_cutoff)
         goto rescale;
 
     spin_lock(&dc->io_lock);
 
     hlist_for_each_entry(i, iohash(dc, bio->bi_iter.bi_sector), hash)
         if (i->last == bio->bi_iter.bi_sector &&
             time_before(jiffies, i->jiffies))
             goto found;
 
     i = list_first_entry(&dc->io_lru, struct io, lru);
 
     add_sequential(task);
     i->sequential = 0;
 found:
     if (i->sequential + bio->bi_iter.bi_size > i->sequential)
         i->sequential   += bio->bi_iter.bi_size;
 
     i->last          = bio_end_sector(bio);
     i->jiffies       = jiffies + msecs_to_jiffies(5000);
     task->sequential_io  = i->sequential;
 
     hlist_del(&i->hash);
     hlist_add_head(&i->hash, iohash(dc, i->last));
     list_move_tail(&i->lru, &dc->io_lru);
 
     spin_unlock(&dc->io_lock);
 
     sectors = max(task->sequential_io,
               task->sequential_io_avg) >> 9;
 
     if (dc->sequential_cutoff &&
         sectors >= dc->sequential_cutoff >> 9) {
         trace_bcache_bypass_sequential(bio);
         goto skip;
     }
 
     if (congested && sectors >= congested) {
         trace_bcache_bypass_congested(bio);
         goto skip;
     }
 
 rescale:
     bch_rescale_priorities(c, bio_sectors(bio));
     return false;
 skip:
     bch_mark_sectors_bypassed(c, dc, bio_sectors(bio));
     return true;
 }
 
 /* Cache lookup */
 
 struct search {
     /* Stack frame for bio_complete */
     struct closure      cl;
 
     struct bbio     bio;
     struct bio      *orig_bio;
     struct bio      *cache_miss;
     struct bcache_device    *d;
 
     unsigned int        insert_bio_sectors;
     unsigned int        recoverable:1;
     unsigned int        write:1;
     unsigned int        read_dirty_data:1;
     unsigned int        cache_missed:1;
 
     struct block_device *orig_bdev;
     unsigned long       start_time;
 
     struct btree_op     op;
     struct data_insert_op   iop;
 };
 
 static void bch_cache_read_endio(struct bio *bio)
 {
     struct bbio *b = container_of(bio, struct bbio, bio);
     struct closure *cl = bio->bi_private;
     struct search *s = container_of(cl, struct search, cl);
 
     /*
      * If the bucket was reused while our bio was in flight, we might have
      * read the wrong data. Set s->error but not error so it doesn't get
      * counted against the cache device, but we'll still reread the data
      * from the backing device.
      */
 
     if (bio->bi_status)
         s->iop.status = bio->bi_status;
     else if (!KEY_DIRTY(&b->key) &&
          ptr_stale(s->iop.c, &b->key, 0)) {
         atomic_long_inc(&s->iop.c->cache_read_races);
         s->iop.status = BLK_STS_IOERR;
     }
 
     bch_bbio_endio(s->iop.c, bio, bio->bi_status, "reading from cache");
 }
 
 /*
  * Read from a single key, handling the initial cache miss if the key starts in
  * the middle of the bio
  */
 static int cache_lookup_fn(struct btree_op *op, struct btree *b, struct bkey *k)
 {
     struct search *s = container_of(op, struct search, op);
     struct bio *n, *bio = &s->bio.bio;
     struct bkey *bio_key;
     unsigned int ptr;
 
     if (bkey_cmp(k, &KEY(s->iop.inode, bio->bi_iter.bi_sector, 0)) <= 0)
         return MAP_CONTINUE;
 
     if (KEY_INODE(k) != s->iop.inode ||
         KEY_START(k) > bio->bi_iter.bi_sector) {
         unsigned int bio_sectors = bio_sectors(bio);
         unsigned int sectors = KEY_INODE(k) == s->iop.inode
             ? min_t(uint64_t, INT_MAX,
                 KEY_START(k) - bio->bi_iter.bi_sector)
             : INT_MAX;
         int ret = s->d->cache_miss(b, s, bio, sectors);
 
         if (ret != MAP_CONTINUE)
             return ret;
 
         /* if this was a complete miss we shouldn't get here */
         BUG_ON(bio_sectors <= sectors);
     }
 
     if (!KEY_SIZE(k))
         return MAP_CONTINUE;
 
     /* XXX: figure out best pointer - for multiple cache devices */
     ptr = 0;
 
     PTR_BUCKET(b->c, k, ptr)->prio = INITIAL_PRIO;
 
     if (KEY_DIRTY(k))
         s->read_dirty_data = true;
 
     n = bio_next_split(bio, min_t(uint64_t, INT_MAX,
                       KEY_OFFSET(k) - bio->bi_iter.bi_sector),
                GFP_NOIO, &s->d->bio_split);
 
     bio_key = &container_of(n, struct bbio, bio)->key;
     bch_bkey_copy_single_ptr(bio_key, k, ptr);
 
     bch_cut_front(&KEY(s->iop.inode, n->bi_iter.bi_sector, 0), bio_key);
     bch_cut_back(&KEY(s->iop.inode, bio_end_sector(n), 0), bio_key);
 
     n->bi_end_io    = bch_cache_read_endio;
     n->bi_private   = &s->cl;
 
     /*
      * The bucket we're reading from might be reused while our bio
      * is in flight, and we could then end up reading the wrong
      * data.
      *
      * We guard against this by checking (in cache_read_endio()) if
      * the pointer is stale again; if so, we treat it as an error
      * and reread from the backing device (but we don't pass that
      * error up anywhere).
      */
 
     __bch_submit_bbio(n, b->c);
     return n == bio ? MAP_DONE : MAP_CONTINUE;
 }
 
 static void cache_lookup(struct closure *cl)
 {
     struct search *s = container_of(cl, struct search, iop.cl);
     struct bio *bio = &s->bio.bio;
     struct cached_dev *dc;
     int ret;
 
     bch_btree_op_init(&s->op, -1);
 
     ret = bch_btree_map_keys(&s->op, s->iop.c,
                  &KEY(s->iop.inode, bio->bi_iter.bi_sector, 0),
                  cache_lookup_fn, MAP_END_KEY);
     if (ret == -EAGAIN) {
         continue_at(cl, cache_lookup, bcache_wq);
         return;
     }
 
     /*
      * We might meet err when searching the btree, If that happens, we will
      * get negative ret, in this scenario we should not recover data from
      * backing device (when cache device is dirty) because we don't know
      * whether bkeys the read request covered are all clean.
      *
      * And after that happened, s->iop.status is still its initial value
      * before we submit s->bio.bio
      */
     if (ret < 0) {
         BUG_ON(ret == -EINTR);
         if (s->d && s->d->c &&
                 !UUID_FLASH_ONLY(&s->d->c->uuids[s->d->id])) {
             dc = container_of(s->d, struct cached_dev, disk);
             if (dc && atomic_read(&dc->has_dirty))
                 s->recoverable = false;
         }
         if (!s->iop.status)
             s->iop.status = BLK_STS_IOERR;
     }
 
     closure_return(cl);
 }
 
 /* Common code for the make_request functions */
 
 static void request_endio(struct bio *bio)
 {
     struct closure *cl = bio->bi_private;
 
     if (bio->bi_status) {
         struct search *s = container_of(cl, struct search, cl);
 
         s->iop.status = bio->bi_status;
         /* Only cache read errors are recoverable */
         s->recoverable = false;
     }
 
     bio_put(bio);
     closure_put(cl);
 }
 
 static void backing_request_endio(struct bio *bio)
 {
     struct closure *cl = bio->bi_private;
 
     if (bio->bi_status) {
         struct search *s = container_of(cl, struct search, cl);
         struct cached_dev *dc = container_of(s->d,
                              struct cached_dev, disk);
         /*
          * If a bio has REQ_PREFLUSH for writeback mode, it is
          * speically assembled in cached_dev_write() for a non-zero
          * write request which has REQ_PREFLUSH. we don't set
          * s->iop.status by this failure, the status will be decided
          * by result of bch_data_insert() operation.
          */
         if (unlikely(s->iop.writeback &&
                  bio->bi_opf & REQ_PREFLUSH)) {
             pr_err("Can't flush %pg: returned bi_status %i\n",
                 dc->bdev, bio->bi_status);
         } else {
             /* set to orig_bio->bi_status in bio_complete() */
             s->iop.status = bio->bi_status;
         }
         s->recoverable = false;
         /* should count I/O error for backing device here */
         bch_count_backing_io_errors(dc, bio);
     }
 
     bio_put(bio);
     closure_put(cl);
 }
 
 static void bio_complete(struct search *s)
 {
     if (s->orig_bio) {
         /* Count on bcache device */
         bio_end_io_acct_remapped(s->orig_bio, s->start_time,
                      s->orig_bdev);
         trace_bcache_request_end(s->d, s->orig_bio);
         s->orig_bio->bi_status = s->iop.status;
         bio_endio(s->orig_bio);
         s->orig_bio = NULL;
     }
 }
 
 static void do_bio_hook(struct search *s,
             struct bio *orig_bio,
             bio_end_io_t *end_io_fn)
 {
     struct bio *bio = &s->bio.bio;
 
     bio_init_clone(orig_bio->bi_bdev, bio, orig_bio, GFP_NOIO);
     /*
      * bi_end_io can be set separately somewhere else, e.g. the
      * variants in,
      * - cache_bio->bi_end_io from cached_dev_cache_miss()
      * - n->bi_end_io from cache_lookup_fn()
      */
     bio->bi_end_io      = end_io_fn;
     bio->bi_private     = &s->cl;
 
     bio_cnt_set(bio, 3);
 }
 
 static void search_free(struct closure *cl)
 {
     struct search *s = container_of(cl, struct search, cl);
 
     atomic_dec(&s->iop.c->search_inflight);
 
     if (s->iop.bio)
         bio_put(s->iop.bio);
 
     bio_complete(s);
     closure_debug_destroy(cl);
     mempool_free(s, &s->iop.c->search);
 }
 
 static inline struct search *search_alloc(struct bio *bio,
         struct bcache_device *d, struct block_device *orig_bdev,
         unsigned long start_time)
 {
     struct search *s;
 
     s = mempool_alloc(&d->c->search, GFP_NOIO);
 
     closure_init(&s->cl, NULL);
     do_bio_hook(s, bio, request_endio);
     atomic_inc(&d->c->search_inflight);
 
     s->orig_bio     = bio;
     s->cache_miss       = NULL;
     s->cache_missed     = 0;
     s->d            = d;
     s->recoverable      = 1;
     s->write        = op_is_write(bio_op(bio));
     s->read_dirty_data  = 0;
     /* Count on the bcache device */
     s->orig_bdev        = orig_bdev;
     s->start_time       = start_time;
     s->iop.c        = d->c;
     s->iop.bio      = NULL;
     s->iop.inode        = d->id;
     s->iop.write_point  = hash_long((unsigned long) current, 16);
     s->iop.write_prio   = 0;
     s->iop.status       = 0;
     s->iop.flags        = 0;
     s->iop.flush_journal    = op_is_flush(bio->bi_opf);
     s->iop.wq       = bcache_wq;
 
     return s;
 }
 
 /* Cached devices */
 
 static void cached_dev_bio_complete(struct closure *cl)
 {
     struct search *s = container_of(cl, struct search, cl);
     struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
 
     cached_dev_put(dc);
     search_free(cl);
 }
 
 /* Process reads */
 
 static void cached_dev_read_error_done(struct closure *cl)
 {
     struct search *s = container_of(cl, struct search, cl);
 
     if (s->iop.replace_collision)
         bch_mark_cache_miss_collision(s->iop.c, s->d);
 
     if (s->iop.bio)
         bio_free_pages(s->iop.bio);
 
     cached_dev_bio_complete(cl);
 }
 
 static void cached_dev_read_error(struct closure *cl)
 {
     struct search *s = container_of(cl, struct search, cl);
     struct bio *bio = &s->bio.bio;
 
     /*
      * If read request hit dirty data (s->read_dirty_data is true),
      * then recovery a failed read request from cached device may
      * get a stale data back. So read failure recovery is only
      * permitted when read request hit clean data in cache device,
      * or when cache read race happened.
      */
     if (s->recoverable && !s->read_dirty_data) {
         /* Retry from the backing device: */
         trace_bcache_read_retry(s->orig_bio);
 
         s->iop.status = 0;
         do_bio_hook(s, s->orig_bio, backing_request_endio);
 
         /* XXX: invalidate cache */
 
         /* I/O request sent to backing device */
         closure_bio_submit(s->iop.c, bio, cl);
     }
 
     continue_at(cl, cached_dev_read_error_done, NULL);
 }
 
 static void cached_dev_cache_miss_done(struct closure *cl)
 {
     struct search *s = container_of(cl, struct search, cl);
     struct bcache_device *d = s->d;
 
     if (s->iop.replace_collision)
         bch_mark_cache_miss_collision(s->iop.c, s->d);
 
     if (s->iop.bio)
         bio_free_pages(s->iop.bio);
 
     cached_dev_bio_complete(cl);
     closure_put(&d->cl);
 }
 
 static void cached_dev_read_done(struct closure *cl)
 {
     struct search *s = container_of(cl, struct search, cl);
     struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
 
     /*
      * We had a cache miss; cache_bio now contains data ready to be inserted
      * into the cache.
      *
      * First, we copy the data we just read from cache_bio's bounce buffers
      * to the buffers the original bio pointed to:
      */
 
     if (s->iop.bio) {
         bio_reset(s->iop.bio, s->cache_miss->bi_bdev, REQ_OP_READ);
         s->iop.bio->bi_iter.bi_sector =
             s->cache_miss->bi_iter.bi_sector;
         s->iop.bio->bi_iter.bi_size = s->insert_bio_sectors << 9;
         bio_clone_blkg_association(s->iop.bio, s->cache_miss);
         bch_bio_map(s->iop.bio, NULL);
 
         bio_copy_data(s->cache_miss, s->iop.bio);
 
         bio_put(s->cache_miss);
         s->cache_miss = NULL;
     }
 
     if (verify(dc) && s->recoverable && !s->read_dirty_data)
         bch_data_verify(dc, s->orig_bio);
 
     closure_get(&dc->disk.cl);
     bio_complete(s);
 
     if (s->iop.bio &&
         !test_bit(CACHE_SET_STOPPING, &s->iop.c->flags)) {
         BUG_ON(!s->iop.replace);
         closure_call(&s->iop.cl, bch_data_insert, NULL, cl);
     }
 
     continue_at(cl, cached_dev_cache_miss_done, NULL);
 }
 
 static void cached_dev_read_done_bh(struct closure *cl)
 {
     struct search *s = container_of(cl, struct search, cl);
     struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
 
     bch_mark_cache_accounting(s->iop.c, s->d,
                   !s->cache_missed, s->iop.bypass);
     trace_bcache_read(s->orig_bio, !s->cache_missed, s->iop.bypass);
 
     if (s->iop.status)
         continue_at_nobarrier(cl, cached_dev_read_error, bcache_wq);
     else if (s->iop.bio || verify(dc))
         continue_at_nobarrier(cl, cached_dev_read_done, bcache_wq);
     else
         continue_at_nobarrier(cl, cached_dev_bio_complete, NULL);
 }
 
 static int cached_dev_cache_miss(struct btree *b, struct search *s,
                  struct bio *bio, unsigned int sectors)
 {
     int ret = MAP_CONTINUE;
     struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
     struct bio *miss, *cache_bio;
     unsigned int size_limit;
 
     s->cache_missed = 1;
 
     if (s->cache_miss || s->iop.bypass) {
         miss = bio_next_split(bio, sectors, GFP_NOIO, &s->d->bio_split);
         ret = miss == bio ? MAP_DONE : MAP_CONTINUE;
         goto out_submit;
     }
 
     /* Limitation for valid replace key size and cache_bio bvecs number */
     size_limit = min_t(unsigned int, BIO_MAX_VECS * PAGE_SECTORS,
                (1 << KEY_SIZE_BITS) - 1);
     s->insert_bio_sectors = min3(size_limit, sectors, bio_sectors(bio));
 
     s->iop.replace_key = KEY(s->iop.inode,
                  bio->bi_iter.bi_sector + s->insert_bio_sectors,
                  s->insert_bio_sectors);
 
     ret = bch_btree_insert_check_key(b, &s->op, &s->iop.replace_key);
     if (ret)
         return ret;
 
     s->iop.replace = true;
 
     miss = bio_next_split(bio, s->insert_bio_sectors, GFP_NOIO,
                   &s->d->bio_split);
 
     /* btree_search_recurse()'s btree iterator is no good anymore */
     ret = miss == bio ? MAP_DONE : -EINTR;
 
     cache_bio = bio_alloc_bioset(miss->bi_bdev,
             DIV_ROUND_UP(s->insert_bio_sectors, PAGE_SECTORS),
             0, GFP_NOWAIT, &dc->disk.bio_split);
     if (!cache_bio)
         goto out_submit;
 
     cache_bio->bi_iter.bi_sector    = miss->bi_iter.bi_sector;
     cache_bio->bi_iter.bi_size  = s->insert_bio_sectors << 9;
 
     cache_bio->bi_end_io    = backing_request_endio;
     cache_bio->bi_private   = &s->cl;
 
     bch_bio_map(cache_bio, NULL);
     if (bch_bio_alloc_pages(cache_bio, __GFP_NOWARN|GFP_NOIO))
         goto out_put;
 
     s->cache_miss   = miss;
     s->iop.bio  = cache_bio;
     bio_get(cache_bio);
     /* I/O request sent to backing device */
     closure_bio_submit(s->iop.c, cache_bio, &s->cl);
 
     return ret;
 out_put:
     bio_put(cache_bio);
 out_submit:
     miss->bi_end_io     = backing_request_endio;
     miss->bi_private    = &s->cl;
     /* I/O request sent to backing device */
     closure_bio_submit(s->iop.c, miss, &s->cl);
     return ret;
 }
 
 static void cached_dev_read(struct cached_dev *dc, struct search *s)
 {
     struct closure *cl = &s->cl;
 
     closure_call(&s->iop.cl, cache_lookup, NULL, cl);
     continue_at(cl, cached_dev_read_done_bh, NULL);
 }
 
 /* Process writes */
 
 static void cached_dev_write_complete(struct closure *cl)
 {
     struct search *s = container_of(cl, struct search, cl);
     struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
 
     up_read_non_owner(&dc->writeback_lock);
     cached_dev_bio_complete(cl);
 }
 
 static void cached_dev_write(struct cached_dev *dc, struct search *s)
 {
     struct closure *cl = &s->cl;
     struct bio *bio = &s->bio.bio;
     struct bkey start = KEY(dc->disk.id, bio->bi_iter.bi_sector, 0);
     struct bkey end = KEY(dc->disk.id, bio_end_sector(bio), 0);
 
     bch_keybuf_check_overlapping(&s->iop.c->moving_gc_keys, &start, &end);
 
     down_read_non_owner(&dc->writeback_lock);
     if (bch_keybuf_check_overlapping(&dc->writeback_keys, &start, &end)) {
         /*
          * We overlap with some dirty data undergoing background
          * writeback, force this write to writeback
          */
         s->iop.bypass = false;
         s->iop.writeback = true;
     }
 
     /*
      * Discards aren't _required_ to do anything, so skipping if
      * check_overlapping returned true is ok
      *
      * But check_overlapping drops dirty keys for which io hasn't started,
      * so we still want to call it.
      */
     if (bio_op(bio) == REQ_OP_DISCARD)
         s->iop.bypass = true;
 
     if (should_writeback(dc, s->orig_bio,
                  cache_mode(dc),
                  s->iop.bypass)) {
         s->iop.bypass = false;
         s->iop.writeback = true;
     }
 
     if (s->iop.bypass) {
         s->iop.bio = s->orig_bio;
         bio_get(s->iop.bio);
 
         if (bio_op(bio) == REQ_OP_DISCARD &&
             !bdev_max_discard_sectors(dc->bdev))
             goto insert_data;
 
         /* I/O request sent to backing device */
         bio->bi_end_io = backing_request_endio;
         closure_bio_submit(s->iop.c, bio, cl);
 
     } else if (s->iop.writeback) {
         bch_writeback_add(dc);
         s->iop.bio = bio;
 
         if (bio->bi_opf & REQ_PREFLUSH) {
             /*
              * Also need to send a flush to the backing
              * device.
              */
             struct bio *flush;
 
             flush = bio_alloc_bioset(bio->bi_bdev, 0,
                          REQ_OP_WRITE | REQ_PREFLUSH,
                          GFP_NOIO, &dc->disk.bio_split);
             if (!flush) {
                 s->iop.status = BLK_STS_RESOURCE;
                 goto insert_data;
             }
             flush->bi_end_io = backing_request_endio;
             flush->bi_private = cl;
             /* I/O request sent to backing device */
             closure_bio_submit(s->iop.c, flush, cl);
         }
     } else {
         s->iop.bio = bio_alloc_clone(bio->bi_bdev, bio, GFP_NOIO,
                          &dc->disk.bio_split);
         /* I/O request sent to backing device */
         bio->bi_end_io = backing_request_endio;
         closure_bio_submit(s->iop.c, bio, cl);
     }
 
 insert_data:
     closure_call(&s->iop.cl, bch_data_insert, NULL, cl);
     continue_at(cl, cached_dev_write_complete, NULL);
 }
 
 static void cached_dev_nodata(struct closure *cl)
 {
     struct search *s = container_of(cl, struct search, cl);
     struct bio *bio = &s->bio.bio;
 
     if (s->iop.flush_journal)
         bch_journal_meta(s->iop.c, cl);
 
     /* If it's a flush, we send the flush to the backing device too */
     bio->bi_end_io = backing_request_endio;
     closure_bio_submit(s->iop.c, bio, cl);
 
     continue_at(cl, cached_dev_bio_complete, NULL);
 }
 
 struct detached_dev_io_private {
     struct bcache_device    *d;
     unsigned long       start_time;
     bio_end_io_t        *bi_end_io;
     void            *bi_private;
     struct block_device *orig_bdev;
 };
 
 static void detached_dev_end_io(struct bio *bio)
 {
     struct detached_dev_io_private *ddip;
 
     ddip = bio->bi_private;
     bio->bi_end_io = ddip->bi_end_io;
     bio->bi_private = ddip->bi_private;
 
     /* Count on the bcache device */
     bio_end_io_acct_remapped(bio, ddip->start_time, ddip->orig_bdev);
 
     if (bio->bi_status) {
         struct cached_dev *dc = container_of(ddip->d,
                              struct cached_dev, disk);
         /* should count I/O error for backing device here */
         bch_count_backing_io_errors(dc, bio);
     }
 
     kfree(ddip);
     bio->bi_end_io(bio);
 }
 
 static void detached_dev_do_request(struct bcache_device *d, struct bio *bio,
         struct block_device *orig_bdev, unsigned long start_time)
 {
     struct detached_dev_io_private *ddip;
     struct cached_dev *dc = container_of(d, struct cached_dev, disk);
 
     /*
      * no need to call closure_get(&dc->disk.cl),
      * because upper layer had already opened bcache device,
      * which would call closure_get(&dc->disk.cl)
      */
     ddip = kzalloc(sizeof(struct detached_dev_io_private), GFP_NOIO);
     if (!ddip) {
         bio->bi_status = BLK_STS_RESOURCE;
         bio->bi_end_io(bio);
         return;
     }
 
     ddip->d = d;
     /* Count on the bcache device */
     ddip->orig_bdev = orig_bdev;
     ddip->start_time = start_time;
     ddip->bi_end_io = bio->bi_end_io;
     ddip->bi_private = bio->bi_private;
     bio->bi_end_io = detached_dev_end_io;
     bio->bi_private = ddip;
 
     if ((bio_op(bio) == REQ_OP_DISCARD) &&
         !bdev_max_discard_sectors(dc->bdev))
         bio->bi_end_io(bio);
     else
         submit_bio_noacct(bio);
 }
 
 static void quit_max_writeback_rate(struct cache_set *c,
                     struct cached_dev *this_dc)
 {
     int i;
     struct bcache_device *d;
     struct cached_dev *dc;
 
     /*
      * mutex bch_register_lock may compete with other parallel requesters,
      * or attach/detach operations on other backing device. Waiting to
      * the mutex lock may increase I/O request latency for seconds or more.
      * To avoid such situation, if mutext_trylock() failed, only writeback
      * rate of current cached device is set to 1, and __update_write_back()
      * will decide writeback rate of other cached devices (remember now
      * c->idle_counter is 0 already).
      */
     if (mutex_trylock(&bch_register_lock)) {
         for (i = 0; i < c->devices_max_used; i++) {
             if (!c->devices[i])
                 continue;
 
             if (UUID_FLASH_ONLY(&c->uuids[i]))
                 continue;
 
             d = c->devices[i];
             dc = container_of(d, struct cached_dev, disk);
             /*
              * set writeback rate to default minimum value,
              * then let update_writeback_rate() to decide the
              * upcoming rate.
              */
             atomic_long_set(&dc->writeback_rate.rate, 1);
         }
         mutex_unlock(&bch_register_lock);
     } else
         atomic_long_set(&this_dc->writeback_rate.rate, 1);
 }
 
 /* Cached devices - read & write stuff */
 
 void cached_dev_submit_bio(struct bio *bio)
 {
     struct search *s;
     struct block_device *orig_bdev = bio->bi_bdev;
     struct bcache_device *d = orig_bdev->bd_disk->private_data;
     struct cached_dev *dc = container_of(d, struct cached_dev, disk);
     unsigned long start_time;
     int rw = bio_data_dir(bio);
 
     if (unlikely((d->c && test_bit(CACHE_SET_IO_DISABLE, &d->c->flags)) ||
              dc->io_disable)) {
         bio->bi_status = BLK_STS_IOERR;
         bio_endio(bio);
         return;
     }
 
     if (likely(d->c)) {
         if (atomic_read(&d->c->idle_counter))
             atomic_set(&d->c->idle_counter, 0);
         /*
          * If at_max_writeback_rate of cache set is true and new I/O
          * comes, quit max writeback rate of all cached devices
          * attached to this cache set, and set at_max_writeback_rate
          * to false.
          */
         if (unlikely(atomic_read(&d->c->at_max_writeback_rate) == 1)) {
             atomic_set(&d->c->at_max_writeback_rate, 0);
             quit_max_writeback_rate(d->c, dc);
         }
     }
 
     start_time = bio_start_io_acct(bio);
 
     bio_set_dev(bio, dc->bdev);
     bio->bi_iter.bi_sector += dc->sb.data_offset;
 
     if (cached_dev_get(dc)) {
         s = search_alloc(bio, d, orig_bdev, start_time);
         trace_bcache_request_start(s->d, bio);
 
         if (!bio->bi_iter.bi_size) {
             /*
              * can't call bch_journal_meta from under
              * submit_bio_noacct
              */
             continue_at_nobarrier(&s->cl,
                           cached_dev_nodata,
                           bcache_wq);
         } else {
             s->iop.bypass = check_should_bypass(dc, bio);
 
             if (rw)
                 cached_dev_write(dc, s);
             else
                 cached_dev_read(dc, s);
         }
     } else
         /* I/O request sent to backing device */
         detached_dev_do_request(d, bio, orig_bdev, start_time);
 }
 
 static int cached_dev_ioctl(struct bcache_device *d, fmode_t mode,
                 unsigned int cmd, unsigned long arg)
 {
     struct cached_dev *dc = container_of(d, struct cached_dev, disk);
 
     if (dc->io_disable)
         return -EIO;
     if (!dc->bdev->bd_disk->fops->ioctl)
         return -ENOTTY;
     return dc->bdev->bd_disk->fops->ioctl(dc->bdev, mode, cmd, arg);
 }
 
 void bch_cached_dev_request_init(struct cached_dev *dc)
 {
     dc->disk.cache_miss         = cached_dev_cache_miss;
     dc->disk.ioctl              = cached_dev_ioctl;
 }
 
 /* Flash backed devices */
 
 static int flash_dev_cache_miss(struct btree *b, struct search *s,
                 struct bio *bio, unsigned int sectors)
 {
     unsigned int bytes = min(sectors, bio_sectors(bio)) << 9;
 
     swap(bio->bi_iter.bi_size, bytes);
     zero_fill_bio(bio);
     swap(bio->bi_iter.bi_size, bytes);
 
     bio_advance(bio, bytes);
 
     if (!bio->bi_iter.bi_size)
         return MAP_DONE;
 
     return MAP_CONTINUE;
 }
 
 static void flash_dev_nodata(struct closure *cl)
 {
     struct search *s = container_of(cl, struct search, cl);
 
     if (s->iop.flush_journal)
         bch_journal_meta(s->iop.c, cl);
 
     continue_at(cl, search_free, NULL);
 }
 
 void flash_dev_submit_bio(struct bio *bio)
 {
     struct search *s;
     struct closure *cl;
     struct bcache_device *d = bio->bi_bdev->bd_disk->private_data;
 
     if (unlikely(d->c && test_bit(CACHE_SET_IO_DISABLE, &d->c->flags))) {
         bio->bi_status = BLK_STS_IOERR;
         bio_endio(bio);
         return;
     }
 
     s = search_alloc(bio, d, bio->bi_bdev, bio_start_io_acct(bio));
     cl = &s->cl;
     bio = &s->bio.bio;
 
     trace_bcache_request_start(s->d, bio);
 
     if (!bio->bi_iter.bi_size) {
         /*
          * can't call bch_journal_meta from under submit_bio_noacct
          */
         continue_at_nobarrier(&s->cl,
                       flash_dev_nodata,
                       bcache_wq);
         return;
     } else if (bio_data_dir(bio)) {
         bch_keybuf_check_overlapping(&s->iop.c->moving_gc_keys,
                     &KEY(d->id, bio->bi_iter.bi_sector, 0),
                     &KEY(d->id, bio_end_sector(bio), 0));
 
         s->iop.bypass       = (bio_op(bio) == REQ_OP_DISCARD) != 0;
         s->iop.writeback    = true;
         s->iop.bio      = bio;
 
         closure_call(&s->iop.cl, bch_data_insert, NULL, cl);
     } else {
         closure_call(&s->iop.cl, cache_lookup, NULL, cl);
     }
 
     continue_at(cl, search_free, NULL);
 }
 
 static int flash_dev_ioctl(struct bcache_device *d, fmode_t mode,
                unsigned int cmd, unsigned long arg)
 {
     return -ENOTTY;
 }
 
 void bch_flash_dev_request_init(struct bcache_device *d)
 {
     d->cache_miss               = flash_dev_cache_miss;
     d->ioctl                = flash_dev_ioctl;
 }
 
 void bch_request_exit(void)
 {
     kmem_cache_destroy(bch_search_cache);
 }
 
 int __init bch_request_init(void)
 {
     bch_search_cache = KMEM_CACHE(search, 0);
     if (!bch_search_cache)
         return -ENOMEM;
 
     return 0;
 }

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