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bcache: remove incremental dirty sector counting for bch_sectors_dirty_init()

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commit 80db4e4707e78cb22287da7d058d7274bd4cb370 upstream.

After making bch_sectors_dirty_init() being multithreaded, the existing
incremental dirty sector counting in bch_root_node_dirty_init() doesn't
release btree occupation after iterating 500000 (INIT_KEYS_EACH_TIME)
bkeys. Because a read lock is added on btree root node to prevent the
btree to be split during the dirty sectors counting, other I/O requester
has no chance to gain the write lock even restart bcache_btree().

That is to say, the incremental dirty sectors counting is incompatible
to the multhreaded bch_sectors_dirty_init(). We have to choose one and
drop another one.

In my testing, with 512 bytes random writes, I generate 1.2T dirty data
and a btree with 400K nodes. With single thread and incremental dirty
sectors counting, it takes 30+ minites to register the backing device.
And with multithreaded dirty sectors counting, the backing device
registration can be accomplished within 2 minutes.

The 30+ minutes V.S. 2- minutes difference makes me decide to keep
multithreaded bch_sectors_dirty_init() and drop the incremental dirty
sectors counting. This is what this patch does.

But INIT_KEYS_EACH_TIME is kept, in sectors_dirty_init_fn() the CPU
will be released by cond_resched() after every INIT_KEYS_EACH_TIME keys
iterated. This is to avoid the watchdog reports a bogus soft lockup
warning.

Fixes: b144e45fc5 ("bcache: make bch_sectors_dirty_init() to be multithreaded")
Signed-off-by: Coly Li <colyli@suse.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20220524102336.10684-4-colyli@suse.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Coly Li 2022-05-24 18:23:35 +08:00 committed by Greg Kroah-Hartman
parent 3f686b249b
commit 0cf22f234e
1 changed files with 12 additions and 27 deletions
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39
drivers/md/bcache/writeback.c
View File

@ -756,13 +756,11 @@ static int bch_writeback_thread(void *arg)
/* Init */
#define INIT_KEYS_EACH_TIME 500000
#define INIT_KEYS_SLEEP_MS 100
struct sectors_dirty_init {
struct btree_op op;
unsigned int inode;
size_t count;
struct bkey start;
};
static int sectors_dirty_init_fn(struct btree_op *_op, struct btree *b,
@ -778,11 +776,8 @@ static int sectors_dirty_init_fn(struct btree_op *_op, struct btree *b,
KEY_START(k), KEY_SIZE(k));
op->count++;
if (atomic_read(&b->c->search_inflight) &&
!(op->count % INIT_KEYS_EACH_TIME)) {
bkey_copy_key(&op->start, k);
return -EAGAIN;
}
if (!(op->count % INIT_KEYS_EACH_TIME))
cond_resched();
return MAP_CONTINUE;
}
@ -797,24 +792,16 @@ static int bch_root_node_dirty_init(struct cache_set *c,
bch_btree_op_init(&op.op, -1);
op.inode = d->id;
op.count = 0;
op.start = KEY(op.inode, 0, 0);
do {
ret = bcache_btree(map_keys_recurse,
k,
c->root,
&op.op,
&op.start,
sectors_dirty_init_fn,
0);
if (ret == -EAGAIN)
schedule_timeout_interruptible(
msecs_to_jiffies(INIT_KEYS_SLEEP_MS));
else if (ret < 0) {
pr_warn("sectors dirty init failed, ret=%d!\n", ret);
break;
}
} while (ret == -EAGAIN);
ret = bcache_btree(map_keys_recurse,
k,
c->root,
&op.op,
&KEY(op.inode, 0, 0),
sectors_dirty_init_fn,
0);
if (ret < 0)
pr_warn("sectors dirty init failed, ret=%d!\n", ret);
return ret;
}
@ -858,7 +845,6 @@ static int bch_dirty_init_thread(void *arg)
goto out;
}
skip_nr--;
cond_resched();
}
if (p) {
@ -868,7 +854,6 @@ static int bch_dirty_init_thread(void *arg)
p = NULL;
prev_idx = cur_idx;
cond_resched();
}
out:
@ -907,11 +892,11 @@ void bch_sectors_dirty_init(struct bcache_device *d)
bch_btree_op_init(&op.op, -1);
op.inode = d->id;
op.count = 0;
op.start = KEY(op.inode, 0, 0);
for_each_key_filter(&c->root->keys,
k, &iter, bch_ptr_invalid)
sectors_dirty_init_fn(&op.op, c->root, k);
rw_unlock(0, c->root);
return;
}