[PATCH 07/16] writeback: move backing_dev_info->state into bdi_writeback

From: Tejun Heo
Date: Tue Jan 06 2015 - 14:33:25 EST

Currently, a bdi (backing_dev_info) embeds single wb (bdi_writeback)
and the role of the separation is unclear. For cgroup support for
writeback IOs, a bdi will be updated to host multiple wb's where each
wb serves writeback IOs of a different cgroup on the bdi. To achieve
that, a wb should carry all states necessary for servicing writeback
IOs for a cgroup independently.

This patch moves bdi->state into wb.

* enum bdi_state is renamed to wb_state and the prefix of all enums is
changed from BDI_ to WB_.

* Explicit zeroing of bdi->state is removed without adding zeoring of
wb->state as the whole data structure is zeroed on init anyway.

* As there's still only one bdi_writeback per backing_dev_info, all
uses of bdi->state are mechanically replaced with bdi->wb.state
introducing no behavior changes.

Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Wu Fengguang <fengguang.wu@xxxxxxxxx>
Cc: drbd-dev@xxxxxxxxxxxxxxxx
Cc: Neil Brown <neilb@xxxxxxx>
Cc: Alasdair Kergon <agk@xxxxxxxxxx>
Cc: Mike Snitzer <snitzer@xxxxxxxxxx>
---
block/blk-core.c | 1 -
drivers/block/drbd/drbd_main.c | 10 +++++-----
drivers/md/dm.c | 2 +-
drivers/md/raid1.c | 4 ++--
drivers/md/raid10.c | 2 +-
fs/aio.c | 1 -
fs/fs-writeback.c | 14 +++++++-------
include/linux/backing-dev.h | 24 ++++++++++++------------
mm/backing-dev.c | 21 ++++++++++-----------
9 files changed, 38 insertions(+), 41 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index accde9d..723e4a3 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -606,7 +606,6 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)

q->backing_dev_info.ra_pages =
(VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
- q->backing_dev_info.state = 0;
q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
q->backing_dev_info.name = "block";
q->node = node_id;
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 1fc8342..61b00aa 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -2360,7 +2360,7 @@ static void drbd_cleanup(void)
* @congested_data: User data
* @bdi_bits: Bits the BDI flusher thread is currently interested in
*
- * Returns 1<<BDI_async_congested and/or 1<<BDI_sync_congested if we are congested.
+ * Returns 1<<WB_async_congested and/or 1<<WB_sync_congested if we are congested.
*/
static int drbd_congested(void *congested_data, int bdi_bits)
{
@@ -2377,14 +2377,14 @@ static int drbd_congested(void *congested_data, int bdi_bits)
}

if (test_bit(CALLBACK_PENDING, &first_peer_device(device)->connection->flags)) {
- r |= (1 << BDI_async_congested);
+ r |= (1 << WB_async_congested);
/* Without good local data, we would need to read from remote,
* and that would need the worker thread as well, which is
* currently blocked waiting for that usermode helper to
* finish.
*/
if (!get_ldev_if_state(device, D_UP_TO_DATE))
- r |= (1 << BDI_sync_congested);
+ r |= (1 << WB_sync_congested);
else
put_ldev(device);
r &= bdi_bits;
@@ -2400,9 +2400,9 @@ static int drbd_congested(void *congested_data, int bdi_bits)
reason = 'b';
}

- if (bdi_bits & (1 << BDI_async_congested) &&
+ if (bdi_bits & (1 << WB_async_congested) &&
test_bit(NET_CONGESTED, &first_peer_device(device)->connection->flags)) {
- r |= (1 << BDI_async_congested);
+ r |= (1 << WB_async_congested);
reason = reason == 'b' ? 'a' : 'n';
}

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 549b815..92b36e5 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2036,7 +2036,7 @@ static int dm_any_congested(void *congested_data, int bdi_bits)
* the query about congestion status of request_queue
*/
if (dm_request_based(md))
- r = md->queue->backing_dev_info.state &
+ r = md->queue->backing_dev_info.wb.state &
bdi_bits;
else
r = dm_table_any_congested(map, bdi_bits);
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 40b35be..aad1482 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -739,7 +739,7 @@ int md_raid1_congested(struct mddev *mddev, int bits)
struct r1conf *conf = mddev->private;
int i, ret = 0;

- if ((bits & (1 << BDI_async_congested)) &&
+ if ((bits & (1 << WB_async_congested)) &&
conf->pending_count >= max_queued_requests)
return 1;

@@ -754,7 +754,7 @@ int md_raid1_congested(struct mddev *mddev, int bits)
/* Note the '|| 1' - when read_balance prefers
* non-congested targets, it can be removed
*/
- if ((bits & (1<<BDI_async_congested)) || 1)
+ if ((bits & (1<<WB_async_congested)) || 1)
ret |= bdi_congested(&q->backing_dev_info, bits);
else
ret &= bdi_congested(&q->backing_dev_info, bits);
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 32e282f..5180e75 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -915,7 +915,7 @@ int md_raid10_congested(struct mddev *mddev, int bits)
struct r10conf *conf = mddev->private;
int i, ret = 0;

- if ((bits & (1 << BDI_async_congested)) &&
+ if ((bits & (1 << WB_async_congested)) &&
conf->pending_count >= max_queued_requests)
return 1;

diff --git a/fs/aio.c b/fs/aio.c
index 1b7893e..a43b754 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -170,7 +170,6 @@ static const struct address_space_operations aio_ctx_aops;
*/
static struct backing_dev_info aio_fs_backing_dev_info = {
.name = "aiofs",
- .state = 0,
.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_MAP_COPY,
};

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 2d609a5..a797bda 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -62,7 +62,7 @@ struct wb_writeback_work {
*/
int writeback_in_progress(struct backing_dev_info *bdi)
{
- return test_bit(BDI_writeback_running, &bdi->state);
+ return test_bit(WB_writeback_running, &bdi->wb.state);
}
EXPORT_SYMBOL(writeback_in_progress);

@@ -94,7 +94,7 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(wbc_writepage);
static void bdi_wakeup_thread(struct backing_dev_info *bdi)
{
spin_lock_bh(&bdi->wb_lock);
- if (test_bit(BDI_registered, &bdi->state))
+ if (test_bit(WB_registered, &bdi->wb.state))
mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
spin_unlock_bh(&bdi->wb_lock);
}
@@ -105,7 +105,7 @@ static void bdi_queue_work(struct backing_dev_info *bdi,
trace_writeback_queue(bdi, work);

spin_lock_bh(&bdi->wb_lock);
- if (!test_bit(BDI_registered, &bdi->state)) {
+ if (!test_bit(WB_registered, &bdi->wb.state)) {
if (work->done)
complete(work->done);
goto out_unlock;
@@ -1007,7 +1007,7 @@ static long wb_do_writeback(struct bdi_writeback *wb)
struct wb_writeback_work *work;
long wrote = 0;

- set_bit(BDI_writeback_running, &wb->bdi->state);
+ set_bit(WB_writeback_running, &wb->state);
while ((work = get_next_work_item(bdi)) != NULL) {

trace_writeback_exec(bdi, work);
@@ -1029,7 +1029,7 @@ static long wb_do_writeback(struct bdi_writeback *wb)
*/
wrote += wb_check_old_data_flush(wb);
wrote += wb_check_background_flush(wb);
- clear_bit(BDI_writeback_running, &wb->bdi->state);
+ clear_bit(WB_writeback_running, &wb->state);

return wrote;
}
@@ -1049,7 +1049,7 @@ void bdi_writeback_workfn(struct work_struct *work)
current->flags |= PF_SWAPWRITE;

if (likely(!current_is_workqueue_rescuer() ||
- !test_bit(BDI_registered, &bdi->state))) {
+ !test_bit(WB_registered, &wb->state))) {
/*
* The normal path. Keep writing back @bdi until its
* work_list is empty. Note that this path is also taken
@@ -1211,7 +1211,7 @@ void __mark_inode_dirty(struct inode *inode, int flags)
spin_unlock(&inode->i_lock);
spin_lock(&bdi->wb.list_lock);
if (bdi_cap_writeback_dirty(bdi)) {
- WARN(!test_bit(BDI_registered, &bdi->state),
+ WARN(!test_bit(WB_registered, &bdi->wb.state),
"bdi-%s not registered\n", bdi->name);

/*
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 5da6012..a356ccd 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -25,13 +25,13 @@ struct device;
struct dentry;

/*
- * Bits in backing_dev_info.state
+ * Bits in bdi_writeback.state
*/
-enum bdi_state {
- BDI_async_congested, /* The async (write) queue is getting full */
- BDI_sync_congested, /* The sync queue is getting full */
- BDI_registered, /* bdi_register() was done */
- BDI_writeback_running, /* Writeback is in progress */
+enum wb_state {
+ WB_async_congested, /* The async (write) queue is getting full */
+ WB_sync_congested, /* The sync queue is getting full */
+ WB_registered, /* bdi_register() was done */
+ WB_writeback_running, /* Writeback is in progress */
};

typedef int (congested_fn)(void *, int);
@@ -49,6 +49,7 @@ enum bdi_stat_item {
struct bdi_writeback {
struct backing_dev_info *bdi; /* our parent bdi */

+ unsigned long state; /* Always use atomic bitops on this */
unsigned long last_old_flush; /* last old data flush */

struct delayed_work dwork; /* work item used for writeback */
@@ -61,7 +62,6 @@ struct bdi_writeback {
struct backing_dev_info {
struct list_head bdi_list;
unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
- unsigned long state; /* Always use atomic bitops on this */
unsigned int capabilities; /* Device capabilities */
congested_fn *congested_fn; /* Function pointer if device is md/dm */
void *congested_data; /* Pointer to aux data for congested func */
@@ -276,23 +276,23 @@ static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits)
{
if (bdi->congested_fn)
return bdi->congested_fn(bdi->congested_data, bdi_bits);
- return (bdi->state & bdi_bits);
+ return (bdi->wb.state & bdi_bits);
}

static inline int bdi_read_congested(struct backing_dev_info *bdi)
{
- return bdi_congested(bdi, 1 << BDI_sync_congested);
+ return bdi_congested(bdi, 1 << WB_sync_congested);
}

static inline int bdi_write_congested(struct backing_dev_info *bdi)
{
- return bdi_congested(bdi, 1 << BDI_async_congested);
+ return bdi_congested(bdi, 1 << WB_async_congested);
}

static inline int bdi_rw_congested(struct backing_dev_info *bdi)
{
- return bdi_congested(bdi, (1 << BDI_sync_congested) |
- (1 << BDI_async_congested));
+ return bdi_congested(bdi, (1 << WB_sync_congested) |
+ (1 << WB_async_congested));
}

enum {
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 06715eb..813ddd3 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -17,7 +17,6 @@ static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
struct backing_dev_info default_backing_dev_info = {
.name = "default",
.ra_pages = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE,
- .state = 0,
.capabilities = BDI_CAP_MAP_COPY,
};
EXPORT_SYMBOL_GPL(default_backing_dev_info);
@@ -111,7 +110,7 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
nr_dirty,
nr_io,
nr_more_io,
- !list_empty(&bdi->bdi_list), bdi->state);
+ !list_empty(&bdi->bdi_list), bdi->wb.state);
#undef K

return 0;
@@ -333,7 +332,7 @@ void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)

timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
spin_lock_bh(&bdi->wb_lock);
- if (test_bit(BDI_registered, &bdi->state))
+ if (test_bit(WB_registered, &bdi->wb.state))
queue_delayed_work(bdi_wq, &bdi->wb.dwork, timeout);
spin_unlock_bh(&bdi->wb_lock);
}
@@ -368,7 +367,7 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
bdi->dev = dev;

bdi_debug_register(bdi, dev_name(dev));
- set_bit(BDI_registered, &bdi->state);
+ set_bit(WB_registered, &bdi->wb.state);

spin_lock_bh(&bdi_lock);
list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
@@ -400,7 +399,7 @@ static void bdi_wb_shutdown(struct backing_dev_info *bdi)

/* Make sure nobody queues further work */
spin_lock_bh(&bdi->wb_lock);
- clear_bit(BDI_registered, &bdi->state);
+ clear_bit(WB_registered, &bdi->wb.state);
spin_unlock_bh(&bdi->wb_lock);

/*
@@ -578,11 +577,11 @@ static atomic_t nr_bdi_congested[2];

void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
{
- enum bdi_state bit;
+ enum wb_state bit;
wait_queue_head_t *wqh = &congestion_wqh[sync];

- bit = sync ? BDI_sync_congested : BDI_async_congested;
- if (test_and_clear_bit(bit, &bdi->state))
+ bit = sync ? WB_sync_congested : WB_async_congested;
+ if (test_and_clear_bit(bit, &bdi->wb.state))
atomic_dec(&nr_bdi_congested[sync]);
smp_mb__after_atomic();
if (waitqueue_active(wqh))
@@ -592,10 +591,10 @@ EXPORT_SYMBOL(clear_bdi_congested);

void set_bdi_congested(struct backing_dev_info *bdi, int sync)
{
- enum bdi_state bit;
+ enum wb_state bit;

- bit = sync ? BDI_sync_congested : BDI_async_congested;
- if (!test_and_set_bit(bit, &bdi->state))
+ bit = sync ? WB_sync_congested : WB_async_congested;
+ if (!test_and_set_bit(bit, &bdi->wb.state))
atomic_inc(&nr_bdi_congested[sync]);
}
EXPORT_SYMBOL(set_bdi_congested);
--
2.1.0

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