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authorLinus Torvalds <torvalds@linux-foundation.org>2019-01-26 12:42:41 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-01-26 12:42:41 -0800
commit6b8f9159166545e576b2bc8a0c984beaeae9cc05 (patch)
tree6be248cacde030276ad7da750e71a1401d87bd51
parentba606975938179b1e893e44e190d0001de8e5262 (diff)
parent8367de2c99a13d35960a51d6084631c883e93a4d (diff)
downloadlinux-stericsson-6b8f9159166545e576b2bc8a0c984beaeae9cc05.tar.gz
Merge tag 'for-linus-20190125' of git://git.kernel.dk/linux-block
Pull block fixes from Jens Axboe: "A collection of fixes for this release. This contains: - Silence sparse rightfully complaining about non-static wbt functions (Bart) - Fixes for the zoned comments/ioctl documentation (Damien) - direct-io fix that's been lingering for a while (Ernesto) - cgroup writeback fix (Tejun) - Set of NVMe patches for nvme-rdma/tcp (Sagi, Hannes, Raju) - Block recursion tracking fix (Ming) - Fix debugfs command flag naming for a few flags (Jianchao)" * tag 'for-linus-20190125' of git://git.kernel.dk/linux-block: block: Fix comment typo uapi: fix ioctl documentation blk-wbt: Declare local functions static blk-mq: fix the cmd_flag_name array nvme-multipath: drop optimization for static ANA group IDs nvmet-rdma: fix null dereference under heavy load nvme-rdma: rework queue maps handling nvme-tcp: fix timeout handler nvme-rdma: fix timeout handler writeback: synchronize sync(2) against cgroup writeback membership switches block: cover another queue enter recursion via BIO_QUEUE_ENTERED direct-io: allow direct writes to empty inodes
-rw-r--r--block/blk-core.c11
-rw-r--r--block/blk-merge.c10
-rw-r--r--block/blk-mq-debugfs.c3
-rw-r--r--block/blk-wbt.c4
-rw-r--r--drivers/nvme/host/multipath.c3
-rw-r--r--drivers/nvme/host/rdma.c64
-rw-r--r--drivers/nvme/host/tcp.c19
-rw-r--r--drivers/nvme/target/rdma.c15
-rw-r--r--fs/direct-io.c5
-rw-r--r--fs/fs-writeback.c40
-rw-r--r--include/linux/backing-dev-defs.h1
-rw-r--r--include/linux/blk_types.h2
-rw-r--r--include/uapi/linux/blkzoned.h1
-rw-r--r--mm/backing-dev.c1
14 files changed, 129 insertions, 50 deletions
diff --git a/block/blk-core.c b/block/blk-core.c
index 3c5f61ceeb67..1ccec27d20c3 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1083,7 +1083,18 @@ blk_qc_t generic_make_request(struct bio *bio)
/* Create a fresh bio_list for all subordinate requests */
bio_list_on_stack[1] = bio_list_on_stack[0];
bio_list_init(&bio_list_on_stack[0]);
+
+ /*
+ * Since we're recursing into make_request here, ensure
+ * that we mark this bio as already having entered the queue.
+ * If not, and the queue is going away, we can get stuck
+ * forever on waiting for the queue reference to drop. But
+ * that will never happen, as we're already holding a
+ * reference to it.
+ */
+ bio_set_flag(bio, BIO_QUEUE_ENTERED);
ret = q->make_request_fn(q, bio);
+ bio_clear_flag(bio, BIO_QUEUE_ENTERED);
/* sort new bios into those for a lower level
* and those for the same level
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 71e9ac03f621..d79a22f111d1 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -272,16 +272,6 @@ void blk_queue_split(struct request_queue *q, struct bio **bio)
/* there isn't chance to merge the splitted bio */
split->bi_opf |= REQ_NOMERGE;
- /*
- * Since we're recursing into make_request here, ensure
- * that we mark this bio as already having entered the queue.
- * If not, and the queue is going away, we can get stuck
- * forever on waiting for the queue reference to drop. But
- * that will never happen, as we're already holding a
- * reference to it.
- */
- bio_set_flag(*bio, BIO_QUEUE_ENTERED);
-
bio_chain(split, *bio);
trace_block_split(q, split, (*bio)->bi_iter.bi_sector);
generic_make_request(*bio);
diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index 90d68760af08..f8120832ca7b 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -308,8 +308,9 @@ static const char *const cmd_flag_name[] = {
CMD_FLAG_NAME(PREFLUSH),
CMD_FLAG_NAME(RAHEAD),
CMD_FLAG_NAME(BACKGROUND),
- CMD_FLAG_NAME(NOUNMAP),
CMD_FLAG_NAME(NOWAIT),
+ CMD_FLAG_NAME(NOUNMAP),
+ CMD_FLAG_NAME(HIPRI),
};
#undef CMD_FLAG_NAME
diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index f0c56649775f..fd166fbb0f65 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -597,7 +597,7 @@ static void wbt_track(struct rq_qos *rqos, struct request *rq, struct bio *bio)
rq->wbt_flags |= bio_to_wbt_flags(rwb, bio);
}
-void wbt_issue(struct rq_qos *rqos, struct request *rq)
+static void wbt_issue(struct rq_qos *rqos, struct request *rq)
{
struct rq_wb *rwb = RQWB(rqos);
@@ -617,7 +617,7 @@ void wbt_issue(struct rq_qos *rqos, struct request *rq)
}
}
-void wbt_requeue(struct rq_qos *rqos, struct request *rq)
+static void wbt_requeue(struct rq_qos *rqos, struct request *rq)
{
struct rq_wb *rwb = RQWB(rqos);
if (!rwb_enabled(rwb))
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index df4b3a6db51b..b9fff3b8ed1b 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -545,8 +545,7 @@ int nvme_mpath_init(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id)
timer_setup(&ctrl->anatt_timer, nvme_anatt_timeout, 0);
ctrl->ana_log_size = sizeof(struct nvme_ana_rsp_hdr) +
ctrl->nanagrpid * sizeof(struct nvme_ana_group_desc);
- if (!(ctrl->anacap & (1 << 6)))
- ctrl->ana_log_size += ctrl->max_namespaces * sizeof(__le32);
+ ctrl->ana_log_size += ctrl->max_namespaces * sizeof(__le32);
if (ctrl->ana_log_size > ctrl->max_hw_sectors << SECTOR_SHIFT) {
dev_err(ctrl->device,
diff --git a/drivers/nvme/host/rdma.c b/drivers/nvme/host/rdma.c
index 0a2fd2949ad7..52abc3a6de12 100644
--- a/drivers/nvme/host/rdma.c
+++ b/drivers/nvme/host/rdma.c
@@ -119,6 +119,7 @@ struct nvme_rdma_ctrl {
struct nvme_ctrl ctrl;
bool use_inline_data;
+ u32 io_queues[HCTX_MAX_TYPES];
};
static inline struct nvme_rdma_ctrl *to_rdma_ctrl(struct nvme_ctrl *ctrl)
@@ -165,8 +166,8 @@ static inline int nvme_rdma_queue_idx(struct nvme_rdma_queue *queue)
static bool nvme_rdma_poll_queue(struct nvme_rdma_queue *queue)
{
return nvme_rdma_queue_idx(queue) >
- queue->ctrl->ctrl.opts->nr_io_queues +
- queue->ctrl->ctrl.opts->nr_write_queues;
+ queue->ctrl->io_queues[HCTX_TYPE_DEFAULT] +
+ queue->ctrl->io_queues[HCTX_TYPE_READ];
}
static inline size_t nvme_rdma_inline_data_size(struct nvme_rdma_queue *queue)
@@ -661,8 +662,21 @@ static int nvme_rdma_alloc_io_queues(struct nvme_rdma_ctrl *ctrl)
nr_io_queues = min_t(unsigned int, nr_io_queues,
ibdev->num_comp_vectors);
- nr_io_queues += min(opts->nr_write_queues, num_online_cpus());
- nr_io_queues += min(opts->nr_poll_queues, num_online_cpus());
+ if (opts->nr_write_queues) {
+ ctrl->io_queues[HCTX_TYPE_DEFAULT] =
+ min(opts->nr_write_queues, nr_io_queues);
+ nr_io_queues += ctrl->io_queues[HCTX_TYPE_DEFAULT];
+ } else {
+ ctrl->io_queues[HCTX_TYPE_DEFAULT] = nr_io_queues;
+ }
+
+ ctrl->io_queues[HCTX_TYPE_READ] = nr_io_queues;
+
+ if (opts->nr_poll_queues) {
+ ctrl->io_queues[HCTX_TYPE_POLL] =
+ min(opts->nr_poll_queues, num_online_cpus());
+ nr_io_queues += ctrl->io_queues[HCTX_TYPE_POLL];
+ }
ret = nvme_set_queue_count(&ctrl->ctrl, &nr_io_queues);
if (ret)
@@ -1689,18 +1703,28 @@ static enum blk_eh_timer_return
nvme_rdma_timeout(struct request *rq, bool reserved)
{
struct nvme_rdma_request *req = blk_mq_rq_to_pdu(rq);
+ struct nvme_rdma_queue *queue = req->queue;
+ struct nvme_rdma_ctrl *ctrl = queue->ctrl;
- dev_warn(req->queue->ctrl->ctrl.device,
- "I/O %d QID %d timeout, reset controller\n",
- rq->tag, nvme_rdma_queue_idx(req->queue));
+ dev_warn(ctrl->ctrl.device, "I/O %d QID %d timeout\n",
+ rq->tag, nvme_rdma_queue_idx(queue));
- /* queue error recovery */
- nvme_rdma_error_recovery(req->queue->ctrl);
+ if (ctrl->ctrl.state != NVME_CTRL_LIVE) {
+ /*
+ * Teardown immediately if controller times out while starting
+ * or we are already started error recovery. all outstanding
+ * requests are completed on shutdown, so we return BLK_EH_DONE.
+ */
+ flush_work(&ctrl->err_work);
+ nvme_rdma_teardown_io_queues(ctrl, false);
+ nvme_rdma_teardown_admin_queue(ctrl, false);
+ return BLK_EH_DONE;
+ }
- /* fail with DNR on cmd timeout */
- nvme_req(rq)->status = NVME_SC_ABORT_REQ | NVME_SC_DNR;
+ dev_warn(ctrl->ctrl.device, "starting error recovery\n");
+ nvme_rdma_error_recovery(ctrl);
- return BLK_EH_DONE;
+ return BLK_EH_RESET_TIMER;
}
static blk_status_t nvme_rdma_queue_rq(struct blk_mq_hw_ctx *hctx,
@@ -1779,17 +1803,15 @@ static int nvme_rdma_map_queues(struct blk_mq_tag_set *set)
struct nvme_rdma_ctrl *ctrl = set->driver_data;
set->map[HCTX_TYPE_DEFAULT].queue_offset = 0;
- set->map[HCTX_TYPE_READ].nr_queues = ctrl->ctrl.opts->nr_io_queues;
+ set->map[HCTX_TYPE_DEFAULT].nr_queues =
+ ctrl->io_queues[HCTX_TYPE_DEFAULT];
+ set->map[HCTX_TYPE_READ].nr_queues = ctrl->io_queues[HCTX_TYPE_READ];
if (ctrl->ctrl.opts->nr_write_queues) {
/* separate read/write queues */
- set->map[HCTX_TYPE_DEFAULT].nr_queues =
- ctrl->ctrl.opts->nr_write_queues;
set->map[HCTX_TYPE_READ].queue_offset =
- ctrl->ctrl.opts->nr_write_queues;
+ ctrl->io_queues[HCTX_TYPE_DEFAULT];
} else {
/* mixed read/write queues */
- set->map[HCTX_TYPE_DEFAULT].nr_queues =
- ctrl->ctrl.opts->nr_io_queues;
set->map[HCTX_TYPE_READ].queue_offset = 0;
}
blk_mq_rdma_map_queues(&set->map[HCTX_TYPE_DEFAULT],
@@ -1799,12 +1821,12 @@ static int nvme_rdma_map_queues(struct blk_mq_tag_set *set)
if (ctrl->ctrl.opts->nr_poll_queues) {
set->map[HCTX_TYPE_POLL].nr_queues =
- ctrl->ctrl.opts->nr_poll_queues;
+ ctrl->io_queues[HCTX_TYPE_POLL];
set->map[HCTX_TYPE_POLL].queue_offset =
- ctrl->ctrl.opts->nr_io_queues;
+ ctrl->io_queues[HCTX_TYPE_DEFAULT];
if (ctrl->ctrl.opts->nr_write_queues)
set->map[HCTX_TYPE_POLL].queue_offset +=
- ctrl->ctrl.opts->nr_write_queues;
+ ctrl->io_queues[HCTX_TYPE_READ];
blk_mq_map_queues(&set->map[HCTX_TYPE_POLL]);
}
return 0;
diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 265a0543b381..5f0a00425242 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -1948,20 +1948,23 @@ nvme_tcp_timeout(struct request *rq, bool reserved)
struct nvme_tcp_ctrl *ctrl = req->queue->ctrl;
struct nvme_tcp_cmd_pdu *pdu = req->pdu;
- dev_dbg(ctrl->ctrl.device,
+ dev_warn(ctrl->ctrl.device,
"queue %d: timeout request %#x type %d\n",
- nvme_tcp_queue_id(req->queue), rq->tag,
- pdu->hdr.type);
+ nvme_tcp_queue_id(req->queue), rq->tag, pdu->hdr.type);
if (ctrl->ctrl.state != NVME_CTRL_LIVE) {
- union nvme_result res = {};
-
- nvme_req(rq)->flags |= NVME_REQ_CANCELLED;
- nvme_end_request(rq, cpu_to_le16(NVME_SC_ABORT_REQ), res);
+ /*
+ * Teardown immediately if controller times out while starting
+ * or we are already started error recovery. all outstanding
+ * requests are completed on shutdown, so we return BLK_EH_DONE.
+ */
+ flush_work(&ctrl->err_work);
+ nvme_tcp_teardown_io_queues(&ctrl->ctrl, false);
+ nvme_tcp_teardown_admin_queue(&ctrl->ctrl, false);
return BLK_EH_DONE;
}
- /* queue error recovery */
+ dev_warn(ctrl->ctrl.device, "starting error recovery\n");
nvme_tcp_error_recovery(&ctrl->ctrl);
return BLK_EH_RESET_TIMER;
diff --git a/drivers/nvme/target/rdma.c b/drivers/nvme/target/rdma.c
index a8d23eb80192..a884e3a0e8af 100644
--- a/drivers/nvme/target/rdma.c
+++ b/drivers/nvme/target/rdma.c
@@ -139,6 +139,10 @@ static void nvmet_rdma_recv_done(struct ib_cq *cq, struct ib_wc *wc);
static void nvmet_rdma_read_data_done(struct ib_cq *cq, struct ib_wc *wc);
static void nvmet_rdma_qp_event(struct ib_event *event, void *priv);
static void nvmet_rdma_queue_disconnect(struct nvmet_rdma_queue *queue);
+static void nvmet_rdma_free_rsp(struct nvmet_rdma_device *ndev,
+ struct nvmet_rdma_rsp *r);
+static int nvmet_rdma_alloc_rsp(struct nvmet_rdma_device *ndev,
+ struct nvmet_rdma_rsp *r);
static const struct nvmet_fabrics_ops nvmet_rdma_ops;
@@ -182,9 +186,17 @@ nvmet_rdma_get_rsp(struct nvmet_rdma_queue *queue)
spin_unlock_irqrestore(&queue->rsps_lock, flags);
if (unlikely(!rsp)) {
- rsp = kmalloc(sizeof(*rsp), GFP_KERNEL);
+ int ret;
+
+ rsp = kzalloc(sizeof(*rsp), GFP_KERNEL);
if (unlikely(!rsp))
return NULL;
+ ret = nvmet_rdma_alloc_rsp(queue->dev, rsp);
+ if (unlikely(ret)) {
+ kfree(rsp);
+ return NULL;
+ }
+
rsp->allocated = true;
}
@@ -197,6 +209,7 @@ nvmet_rdma_put_rsp(struct nvmet_rdma_rsp *rsp)
unsigned long flags;
if (unlikely(rsp->allocated)) {
+ nvmet_rdma_free_rsp(rsp->queue->dev, rsp);
kfree(rsp);
return;
}
diff --git a/fs/direct-io.c b/fs/direct-io.c
index dbc1a1f080ce..ec2fb6fe6d37 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -679,6 +679,7 @@ static int get_more_blocks(struct dio *dio, struct dio_submit *sdio,
unsigned long fs_count; /* Number of filesystem-sized blocks */
int create;
unsigned int i_blkbits = sdio->blkbits + sdio->blkfactor;
+ loff_t i_size;
/*
* If there was a memory error and we've overwritten all the
@@ -708,8 +709,8 @@ static int get_more_blocks(struct dio *dio, struct dio_submit *sdio,
*/
create = dio->op == REQ_OP_WRITE;
if (dio->flags & DIO_SKIP_HOLES) {
- if (fs_startblk <= ((i_size_read(dio->inode) - 1) >>
- i_blkbits))
+ i_size = i_size_read(dio->inode);
+ if (i_size && fs_startblk <= (i_size - 1) >> i_blkbits)
create = 0;
}
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index b40168fcc94a..36855c1f8daf 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -331,11 +331,22 @@ struct inode_switch_wbs_context {
struct work_struct work;
};
+static void bdi_down_write_wb_switch_rwsem(struct backing_dev_info *bdi)
+{
+ down_write(&bdi->wb_switch_rwsem);
+}
+
+static void bdi_up_write_wb_switch_rwsem(struct backing_dev_info *bdi)
+{
+ up_write(&bdi->wb_switch_rwsem);
+}
+
static void inode_switch_wbs_work_fn(struct work_struct *work)
{
struct inode_switch_wbs_context *isw =
container_of(work, struct inode_switch_wbs_context, work);
struct inode *inode = isw->inode;
+ struct backing_dev_info *bdi = inode_to_bdi(inode);
struct address_space *mapping = inode->i_mapping;
struct bdi_writeback *old_wb = inode->i_wb;
struct bdi_writeback *new_wb = isw->new_wb;
@@ -344,6 +355,12 @@ static void inode_switch_wbs_work_fn(struct work_struct *work)
bool switched = false;
/*
+ * If @inode switches cgwb membership while sync_inodes_sb() is
+ * being issued, sync_inodes_sb() might miss it. Synchronize.
+ */
+ down_read(&bdi->wb_switch_rwsem);
+
+ /*
* By the time control reaches here, RCU grace period has passed
* since I_WB_SWITCH assertion and all wb stat update transactions
* between unlocked_inode_to_wb_begin/end() are guaranteed to be
@@ -428,6 +445,8 @@ skip_switch:
spin_unlock(&new_wb->list_lock);
spin_unlock(&old_wb->list_lock);
+ up_read(&bdi->wb_switch_rwsem);
+
if (switched) {
wb_wakeup(new_wb);
wb_put(old_wb);
@@ -468,9 +487,18 @@ static void inode_switch_wbs(struct inode *inode, int new_wb_id)
if (inode->i_state & I_WB_SWITCH)
return;
+ /*
+ * Avoid starting new switches while sync_inodes_sb() is in
+ * progress. Otherwise, if the down_write protected issue path
+ * blocks heavily, we might end up starting a large number of
+ * switches which will block on the rwsem.
+ */
+ if (!down_read_trylock(&bdi->wb_switch_rwsem))
+ return;
+
isw = kzalloc(sizeof(*isw), GFP_ATOMIC);
if (!isw)
- return;
+ goto out_unlock;
/* find and pin the new wb */
rcu_read_lock();
@@ -504,12 +532,14 @@ static void inode_switch_wbs(struct inode *inode, int new_wb_id)
* Let's continue after I_WB_SWITCH is guaranteed to be visible.
*/
call_rcu(&isw->rcu_head, inode_switch_wbs_rcu_fn);
- return;
+ goto out_unlock;
out_free:
if (isw->new_wb)
wb_put(isw->new_wb);
kfree(isw);
+out_unlock:
+ up_read(&bdi->wb_switch_rwsem);
}
/**
@@ -887,6 +917,9 @@ fs_initcall(cgroup_writeback_init);
#else /* CONFIG_CGROUP_WRITEBACK */
+static void bdi_down_write_wb_switch_rwsem(struct backing_dev_info *bdi) { }
+static void bdi_up_write_wb_switch_rwsem(struct backing_dev_info *bdi) { }
+
static struct bdi_writeback *
locked_inode_to_wb_and_lock_list(struct inode *inode)
__releases(&inode->i_lock)
@@ -2413,8 +2446,11 @@ void sync_inodes_sb(struct super_block *sb)
return;
WARN_ON(!rwsem_is_locked(&sb->s_umount));
+ /* protect against inode wb switch, see inode_switch_wbs_work_fn() */
+ bdi_down_write_wb_switch_rwsem(bdi);
bdi_split_work_to_wbs(bdi, &work, false);
wb_wait_for_completion(bdi, &done);
+ bdi_up_write_wb_switch_rwsem(bdi);
wait_sb_inodes(sb);
}
diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
index c31157135598..07e02d6df5ad 100644
--- a/include/linux/backing-dev-defs.h
+++ b/include/linux/backing-dev-defs.h
@@ -190,6 +190,7 @@ struct backing_dev_info {
struct radix_tree_root cgwb_tree; /* radix tree of active cgroup wbs */
struct rb_root cgwb_congested_tree; /* their congested states */
struct mutex cgwb_release_mutex; /* protect shutdown of wb structs */
+ struct rw_semaphore wb_switch_rwsem; /* no cgwb switch while syncing */
#else
struct bdi_writeback_congested *wb_congested;
#endif
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 5c7e7f859a24..d66bf5f32610 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -287,7 +287,7 @@ enum req_opf {
REQ_OP_DISCARD = 3,
/* securely erase sectors */
REQ_OP_SECURE_ERASE = 5,
- /* seset a zone write pointer */
+ /* reset a zone write pointer */
REQ_OP_ZONE_RESET = 6,
/* write the same sector many times */
REQ_OP_WRITE_SAME = 7,
diff --git a/include/uapi/linux/blkzoned.h b/include/uapi/linux/blkzoned.h
index 6fa38d001d84..498eec813494 100644
--- a/include/uapi/linux/blkzoned.h
+++ b/include/uapi/linux/blkzoned.h
@@ -138,6 +138,7 @@ struct blk_zone_range {
* @BLKRESETZONE: Reset the write pointer of the zones in the specified
* sector range. The sector range must be zone aligned.
* @BLKGETZONESZ: Get the device zone size in number of 512 B sectors.
+ * @BLKGETNRZONES: Get the total number of zones of the device.
*/
#define BLKREPORTZONE _IOWR(0x12, 130, struct blk_zone_report)
#define BLKRESETZONE _IOW(0x12, 131, struct blk_zone_range)
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 8a8bb8796c6c..72e6d0c55cfa 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -689,6 +689,7 @@ static int cgwb_bdi_init(struct backing_dev_info *bdi)
INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
bdi->cgwb_congested_tree = RB_ROOT;
mutex_init(&bdi->cgwb_release_mutex);
+ init_rwsem(&bdi->wb_switch_rwsem);
ret = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
if (!ret) {