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block/mq-deadline: Improve compile-time argument checking
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Modern compilers complain if an out-of-range value is passed to a function
argument that has an enumeration type. Let the compiler detect out-of-range
data direction arguments instead of verifying the data_dir argument at
runtime.

Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Cc: Damien Le Moal <damien.lemoal@wdc.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20210618004456.7280-10-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Bart Van Assche authored and Jens Axboe committed Jun 21, 2021
1 parent 3e9a99e commit 004a26b
Showing 1 changed file with 49 additions and 47 deletions.
96 changes: 49 additions & 47 deletions block/mq-deadline.c
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,13 @@ static const int writes_starved = 2; /* max times reads can starve a write */
static const int fifo_batch = 16; /* # of sequential requests treated as one
by the above parameters. For throughput. */

enum dd_data_dir {
DD_READ = READ,
DD_WRITE = WRITE,
};

enum { DD_DIR_COUNT = 2 };

struct deadline_data {
/*
* run time data
Expand All @@ -43,20 +50,20 @@ struct deadline_data {
/*
* requests (deadline_rq s) are present on both sort_list and fifo_list
*/
struct rb_root sort_list[2];
struct list_head fifo_list[2];
struct rb_root sort_list[DD_DIR_COUNT];
struct list_head fifo_list[DD_DIR_COUNT];

/*
* next in sort order. read, write or both are NULL
*/
struct request *next_rq[2];
struct request *next_rq[DD_DIR_COUNT];
unsigned int batching; /* number of sequential requests made */
unsigned int starved; /* times reads have starved writes */

/*
* settings that change how the i/o scheduler behaves
*/
int fifo_expire[2];
int fifo_expire[DD_DIR_COUNT];
int fifo_batch;
int writes_starved;
int front_merges;
Expand Down Expand Up @@ -97,7 +104,7 @@ deadline_add_rq_rb(struct deadline_data *dd, struct request *rq)
static inline void
deadline_del_rq_rb(struct deadline_data *dd, struct request *rq)
{
const int data_dir = rq_data_dir(rq);
const enum dd_data_dir data_dir = rq_data_dir(rq);

if (dd->next_rq[data_dir] == rq)
dd->next_rq[data_dir] = deadline_latter_request(rq);
Expand Down Expand Up @@ -169,10 +176,10 @@ static void dd_merged_requests(struct request_queue *q, struct request *req,
static void
deadline_move_request(struct deadline_data *dd, struct request *rq)
{
const int data_dir = rq_data_dir(rq);
const enum dd_data_dir data_dir = rq_data_dir(rq);

dd->next_rq[READ] = NULL;
dd->next_rq[WRITE] = NULL;
dd->next_rq[DD_READ] = NULL;
dd->next_rq[DD_WRITE] = NULL;
dd->next_rq[data_dir] = deadline_latter_request(rq);

/*
Expand All @@ -185,9 +192,10 @@ deadline_move_request(struct deadline_data *dd, struct request *rq)
* deadline_check_fifo returns 0 if there are no expired requests on the fifo,
* 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
*/
static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
static inline int deadline_check_fifo(struct deadline_data *dd,
enum dd_data_dir data_dir)
{
struct request *rq = rq_entry_fifo(dd->fifo_list[ddir].next);
struct request *rq = rq_entry_fifo(dd->fifo_list[data_dir].next);

/*
* rq is expired!
Expand All @@ -203,27 +211,24 @@ static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
* dispatch using arrival ordered lists.
*/
static struct request *
deadline_fifo_request(struct deadline_data *dd, int data_dir)
deadline_fifo_request(struct deadline_data *dd, enum dd_data_dir data_dir)
{
struct request *rq;
unsigned long flags;

if (WARN_ON_ONCE(data_dir != READ && data_dir != WRITE))
return NULL;

if (list_empty(&dd->fifo_list[data_dir]))
return NULL;

rq = rq_entry_fifo(dd->fifo_list[data_dir].next);
if (data_dir == READ || !blk_queue_is_zoned(rq->q))
if (data_dir == DD_READ || !blk_queue_is_zoned(rq->q))
return rq;

/*
* Look for a write request that can be dispatched, that is one with
* an unlocked target zone.
*/
spin_lock_irqsave(&dd->zone_lock, flags);
list_for_each_entry(rq, &dd->fifo_list[WRITE], queuelist) {
list_for_each_entry(rq, &dd->fifo_list[DD_WRITE], queuelist) {
if (blk_req_can_dispatch_to_zone(rq))
goto out;
}
Expand All @@ -239,19 +244,16 @@ deadline_fifo_request(struct deadline_data *dd, int data_dir)
* dispatch using sector position sorted lists.
*/
static struct request *
deadline_next_request(struct deadline_data *dd, int data_dir)
deadline_next_request(struct deadline_data *dd, enum dd_data_dir data_dir)
{
struct request *rq;
unsigned long flags;

if (WARN_ON_ONCE(data_dir != READ && data_dir != WRITE))
return NULL;

rq = dd->next_rq[data_dir];
if (!rq)
return NULL;

if (data_dir == READ || !blk_queue_is_zoned(rq->q))
if (data_dir == DD_READ || !blk_queue_is_zoned(rq->q))
return rq;

/*
Expand All @@ -276,7 +278,7 @@ deadline_next_request(struct deadline_data *dd, int data_dir)
static struct request *__dd_dispatch_request(struct deadline_data *dd)
{
struct request *rq, *next_rq;
int data_dir;
enum dd_data_dir data_dir;

lockdep_assert_held(&dd->lock);

Expand All @@ -289,9 +291,9 @@ static struct request *__dd_dispatch_request(struct deadline_data *dd)
/*
* batches are currently reads XOR writes
*/
rq = deadline_next_request(dd, WRITE);
rq = deadline_next_request(dd, DD_WRITE);
if (!rq)
rq = deadline_next_request(dd, READ);
rq = deadline_next_request(dd, DD_READ);

if (rq && dd->batching < dd->fifo_batch)
/* we have a next request are still entitled to batch */
Expand All @@ -302,14 +304,14 @@ static struct request *__dd_dispatch_request(struct deadline_data *dd)
* data direction (read / write)
*/

if (!list_empty(&dd->fifo_list[READ])) {
BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[READ]));
if (!list_empty(&dd->fifo_list[DD_READ])) {
BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[DD_READ]));

if (deadline_fifo_request(dd, WRITE) &&
if (deadline_fifo_request(dd, DD_WRITE) &&
(dd->starved++ >= dd->writes_starved))
goto dispatch_writes;

data_dir = READ;
data_dir = DD_READ;

goto dispatch_find_request;
}
Expand All @@ -318,13 +320,13 @@ static struct request *__dd_dispatch_request(struct deadline_data *dd)
* there are either no reads or writes have been starved
*/

if (!list_empty(&dd->fifo_list[WRITE])) {
if (!list_empty(&dd->fifo_list[DD_WRITE])) {
dispatch_writes:
BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[WRITE]));
BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[DD_WRITE]));

dd->starved = 0;

data_dir = WRITE;
data_dir = DD_WRITE;

goto dispatch_find_request;
}
Expand Down Expand Up @@ -399,8 +401,8 @@ static void dd_exit_sched(struct elevator_queue *e)
{
struct deadline_data *dd = e->elevator_data;

BUG_ON(!list_empty(&dd->fifo_list[READ]));
BUG_ON(!list_empty(&dd->fifo_list[WRITE]));
BUG_ON(!list_empty(&dd->fifo_list[DD_READ]));
BUG_ON(!list_empty(&dd->fifo_list[DD_WRITE]));

kfree(dd);
}
Expand All @@ -424,12 +426,12 @@ static int dd_init_sched(struct request_queue *q, struct elevator_type *e)
}
eq->elevator_data = dd;

INIT_LIST_HEAD(&dd->fifo_list[READ]);
INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
dd->sort_list[READ] = RB_ROOT;
dd->sort_list[WRITE] = RB_ROOT;
dd->fifo_expire[READ] = read_expire;
dd->fifo_expire[WRITE] = write_expire;
INIT_LIST_HEAD(&dd->fifo_list[DD_READ]);
INIT_LIST_HEAD(&dd->fifo_list[DD_WRITE]);
dd->sort_list[DD_READ] = RB_ROOT;
dd->sort_list[DD_WRITE] = RB_ROOT;
dd->fifo_expire[DD_READ] = read_expire;
dd->fifo_expire[DD_WRITE] = write_expire;
dd->writes_starved = writes_starved;
dd->front_merges = 1;
dd->fifo_batch = fifo_batch;
Expand Down Expand Up @@ -497,7 +499,7 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
{
struct request_queue *q = hctx->queue;
struct deadline_data *dd = q->elevator->elevator_data;
const int data_dir = rq_data_dir(rq);
const enum dd_data_dir data_dir = rq_data_dir(rq);

lockdep_assert_held(&dd->lock);

Expand Down Expand Up @@ -585,7 +587,7 @@ static void dd_finish_request(struct request *rq)

spin_lock_irqsave(&dd->zone_lock, flags);
blk_req_zone_write_unlock(rq);
if (!list_empty(&dd->fifo_list[WRITE]))
if (!list_empty(&dd->fifo_list[DD_WRITE]))
blk_mq_sched_mark_restart_hctx(rq->mq_hctx);
spin_unlock_irqrestore(&dd->zone_lock, flags);
}
Expand Down Expand Up @@ -626,8 +628,8 @@ static ssize_t __FUNC(struct elevator_queue *e, char *page) \
__data = jiffies_to_msecs(__data); \
return deadline_var_show(__data, (page)); \
}
SHOW_FUNCTION(deadline_read_expire_show, dd->fifo_expire[READ], 1);
SHOW_FUNCTION(deadline_write_expire_show, dd->fifo_expire[WRITE], 1);
SHOW_FUNCTION(deadline_read_expire_show, dd->fifo_expire[DD_READ], 1);
SHOW_FUNCTION(deadline_write_expire_show, dd->fifo_expire[DD_WRITE], 1);
SHOW_FUNCTION(deadline_writes_starved_show, dd->writes_starved, 0);
SHOW_FUNCTION(deadline_front_merges_show, dd->front_merges, 0);
SHOW_FUNCTION(deadline_fifo_batch_show, dd->fifo_batch, 0);
Expand All @@ -649,8 +651,8 @@ static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count)
*(__PTR) = __data; \
return count; \
}
STORE_FUNCTION(deadline_read_expire_store, &dd->fifo_expire[READ], 0, INT_MAX, 1);
STORE_FUNCTION(deadline_write_expire_store, &dd->fifo_expire[WRITE], 0, INT_MAX, 1);
STORE_FUNCTION(deadline_read_expire_store, &dd->fifo_expire[DD_READ], 0, INT_MAX, 1);
STORE_FUNCTION(deadline_write_expire_store, &dd->fifo_expire[DD_WRITE], 0, INT_MAX, 1);
STORE_FUNCTION(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX, 0);
STORE_FUNCTION(deadline_front_merges_store, &dd->front_merges, 0, 1, 0);
STORE_FUNCTION(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX, 0);
Expand Down Expand Up @@ -717,8 +719,8 @@ static int deadline_##name##_next_rq_show(void *data, \
__blk_mq_debugfs_rq_show(m, rq); \
return 0; \
}
DEADLINE_DEBUGFS_DDIR_ATTRS(READ, read)
DEADLINE_DEBUGFS_DDIR_ATTRS(WRITE, write)
DEADLINE_DEBUGFS_DDIR_ATTRS(DD_READ, read)
DEADLINE_DEBUGFS_DDIR_ATTRS(DD_WRITE, write)
#undef DEADLINE_DEBUGFS_DDIR_ATTRS

static int deadline_batching_show(void *data, struct seq_file *m)
Expand Down

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