Commit 88459642 authored by Omar Sandoval's avatar Omar Sandoval Committed by Jens Axboe

blk-mq: abstract tag allocation out into sbitmap library

This is a generally useful data structure, so make it available to
anyone else who might want to use it. It's also a nice cleanup
separating the allocation logic from the rest of the tag handling logic.

The code is behind a new Kconfig option, CONFIG_SBITMAP, which is only
selected by CONFIG_BLOCK for now.

This should be a complete noop functionality-wise.
Signed-off-by: default avatarOmar Sandoval <osandov@fb.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 703fd1c0
......@@ -2451,6 +2451,7 @@ T: git git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git
S: Maintained
F: block/
F: kernel/trace/blktrace.c
F: lib/sbitmap.c
BLOCK2MTD DRIVER
M: Joern Engel <joern@lazybastard.org>
......
......@@ -4,6 +4,7 @@
menuconfig BLOCK
bool "Enable the block layer" if EXPERT
default y
select SBITMAP
help
Provide block layer support for the kernel.
......
This diff is collapsed.
......@@ -3,31 +3,6 @@
#include "blk-mq.h"
enum {
BT_WAIT_QUEUES = 8,
BT_WAIT_BATCH = 8,
};
struct bt_wait_state {
atomic_t wait_cnt;
wait_queue_head_t wait;
} ____cacheline_aligned_in_smp;
#define TAG_TO_INDEX(bt, tag) ((tag) >> (bt)->bits_per_word)
#define TAG_TO_BIT(bt, tag) ((tag) & ((1 << (bt)->bits_per_word) - 1))
struct blk_mq_bitmap_tags {
unsigned int depth;
unsigned int wake_cnt;
unsigned int bits_per_word;
unsigned int map_nr;
struct blk_align_bitmap *map;
atomic_t wake_index;
struct bt_wait_state *bs;
};
/*
* Tag address space map.
*/
......@@ -37,8 +12,8 @@ struct blk_mq_tags {
atomic_t active_queues;
struct blk_mq_bitmap_tags bitmap_tags;
struct blk_mq_bitmap_tags breserved_tags;
struct sbitmap_queue bitmap_tags;
struct sbitmap_queue breserved_tags;
struct request **rqs;
struct list_head page_list;
......@@ -61,6 +36,14 @@ extern void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool);
void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,
void *priv);
static inline struct sbq_wait_state *bt_wait_ptr(struct sbitmap_queue *bt,
struct blk_mq_hw_ctx *hctx)
{
if (!hctx)
return &bt->ws[0];
return sbq_wait_ptr(bt, &hctx->wait_index);
}
enum {
BLK_MQ_TAG_CACHE_MIN = 1,
BLK_MQ_TAG_CACHE_MAX = 64,
......
......@@ -41,42 +41,23 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx);
*/
static bool blk_mq_hctx_has_pending(struct blk_mq_hw_ctx *hctx)
{
unsigned int i;
for (i = 0; i < hctx->ctx_map.size; i++)
if (hctx->ctx_map.map[i].word)
return true;
return false;
}
static inline struct blk_align_bitmap *get_bm(struct blk_mq_hw_ctx *hctx,
struct blk_mq_ctx *ctx)
{
return &hctx->ctx_map.map[ctx->index_hw / hctx->ctx_map.bits_per_word];
return sbitmap_any_bit_set(&hctx->ctx_map);
}
#define CTX_TO_BIT(hctx, ctx) \
((ctx)->index_hw & ((hctx)->ctx_map.bits_per_word - 1))
/*
* Mark this ctx as having pending work in this hardware queue
*/
static void blk_mq_hctx_mark_pending(struct blk_mq_hw_ctx *hctx,
struct blk_mq_ctx *ctx)
{
struct blk_align_bitmap *bm = get_bm(hctx, ctx);
if (!test_bit(CTX_TO_BIT(hctx, ctx), &bm->word))
set_bit(CTX_TO_BIT(hctx, ctx), &bm->word);
if (!sbitmap_test_bit(&hctx->ctx_map, ctx->index_hw))
sbitmap_set_bit(&hctx->ctx_map, ctx->index_hw);
}
static void blk_mq_hctx_clear_pending(struct blk_mq_hw_ctx *hctx,
struct blk_mq_ctx *ctx)
{
struct blk_align_bitmap *bm = get_bm(hctx, ctx);
clear_bit(CTX_TO_BIT(hctx, ctx), &bm->word);
sbitmap_clear_bit(&hctx->ctx_map, ctx->index_hw);
}
void blk_mq_freeze_queue_start(struct request_queue *q)
......@@ -755,38 +736,36 @@ static bool blk_mq_attempt_merge(struct request_queue *q,
return false;
}
struct flush_busy_ctx_data {
struct blk_mq_hw_ctx *hctx;
struct list_head *list;
};
static bool flush_busy_ctx(struct sbitmap *sb, unsigned int bitnr, void *data)
{
struct flush_busy_ctx_data *flush_data = data;
struct blk_mq_hw_ctx *hctx = flush_data->hctx;
struct blk_mq_ctx *ctx = hctx->ctxs[bitnr];
sbitmap_clear_bit(sb, bitnr);
spin_lock(&ctx->lock);
list_splice_tail_init(&ctx->rq_list, flush_data->list);
spin_unlock(&ctx->lock);
return true;
}
/*
* Process software queues that have been marked busy, splicing them
* to the for-dispatch
*/
static void flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list)
{
struct blk_mq_ctx *ctx;
int i;
for (i = 0; i < hctx->ctx_map.size; i++) {
struct blk_align_bitmap *bm = &hctx->ctx_map.map[i];
unsigned int off, bit;
if (!bm->word)
continue;
bit = 0;
off = i * hctx->ctx_map.bits_per_word;
do {
bit = find_next_bit(&bm->word, bm->depth, bit);
if (bit >= bm->depth)
break;
ctx = hctx->ctxs[bit + off];
clear_bit(bit, &bm->word);
spin_lock(&ctx->lock);
list_splice_tail_init(&ctx->rq_list, list);
spin_unlock(&ctx->lock);
struct flush_busy_ctx_data data = {
.hctx = hctx,
.list = list,
};
bit++;
} while (1);
}
sbitmap_for_each_set(&hctx->ctx_map, flush_busy_ctx, &data);
}
static inline unsigned int queued_to_index(unsigned int queued)
......@@ -1609,32 +1588,6 @@ static struct blk_mq_tags *blk_mq_init_rq_map(struct blk_mq_tag_set *set,
return NULL;
}
static void blk_mq_free_bitmap(struct blk_mq_ctxmap *bitmap)
{
kfree(bitmap->map);
}
static int blk_mq_alloc_bitmap(struct blk_mq_ctxmap *bitmap, int node)
{
unsigned int bpw = 8, total, num_maps, i;
bitmap->bits_per_word = bpw;
num_maps = ALIGN(nr_cpu_ids, bpw) / bpw;
bitmap->map = kzalloc_node(num_maps * sizeof(struct blk_align_bitmap),
GFP_KERNEL, node);
if (!bitmap->map)
return -ENOMEM;
total = nr_cpu_ids;
for (i = 0; i < num_maps; i++) {
bitmap->map[i].depth = min(total, bitmap->bits_per_word);
total -= bitmap->map[i].depth;
}
return 0;
}
/*
* 'cpu' is going away. splice any existing rq_list entries from this
* software queue to the hw queue dispatch list, and ensure that it
......@@ -1700,7 +1653,7 @@ static void blk_mq_exit_hctx(struct request_queue *q,
blk_mq_unregister_cpu_notifier(&hctx->cpu_notifier);
blk_free_flush_queue(hctx->fq);
blk_mq_free_bitmap(&hctx->ctx_map);
sbitmap_free(&hctx->ctx_map);
}
static void blk_mq_exit_hw_queues(struct request_queue *q,
......@@ -1760,7 +1713,8 @@ static int blk_mq_init_hctx(struct request_queue *q,
if (!hctx->ctxs)
goto unregister_cpu_notifier;
if (blk_mq_alloc_bitmap(&hctx->ctx_map, node))
if (sbitmap_init_node(&hctx->ctx_map, nr_cpu_ids, ilog2(8), GFP_KERNEL,
node))
goto free_ctxs;
hctx->nr_ctx = 0;
......@@ -1787,7 +1741,7 @@ static int blk_mq_init_hctx(struct request_queue *q,
if (set->ops->exit_hctx)
set->ops->exit_hctx(hctx, hctx_idx);
free_bitmap:
blk_mq_free_bitmap(&hctx->ctx_map);
sbitmap_free(&hctx->ctx_map);
free_ctxs:
kfree(hctx->ctxs);
unregister_cpu_notifier:
......@@ -1863,8 +1817,6 @@ static void blk_mq_map_swqueue(struct request_queue *q,
mutex_unlock(&q->sysfs_lock);
queue_for_each_hw_ctx(q, hctx, i) {
struct blk_mq_ctxmap *map = &hctx->ctx_map;
/*
* If no software queues are mapped to this hardware queue,
* disable it and free the request entries.
......@@ -1890,7 +1842,7 @@ static void blk_mq_map_swqueue(struct request_queue *q,
* This is more accurate and more efficient than looping
* over all possibly mapped software queues.
*/
map->size = DIV_ROUND_UP(hctx->nr_ctx, map->bits_per_word);
sbitmap_resize(&hctx->ctx_map, hctx->nr_ctx);
/*
* Initialize batch roundrobin counts
......
......@@ -63,15 +63,6 @@ extern void blk_mq_rq_timed_out(struct request *req, bool reserved);
void blk_mq_release(struct request_queue *q);
/*
* Basic implementation of sparser bitmap, allowing the user to spread
* the bits over more cachelines.
*/
struct blk_align_bitmap {
unsigned long word;
unsigned long depth;
} ____cacheline_aligned_in_smp;
static inline struct blk_mq_ctx *__blk_mq_get_ctx(struct request_queue *q,
unsigned int cpu)
{
......
......@@ -2,6 +2,7 @@
#define BLK_MQ_H
#include <linux/blkdev.h>
#include <linux/sbitmap.h>
struct blk_mq_tags;
struct blk_flush_queue;
......@@ -12,12 +13,6 @@ struct blk_mq_cpu_notifier {
int (*notify)(void *data, unsigned long action, unsigned int cpu);
};
struct blk_mq_ctxmap {
unsigned int size;
unsigned int bits_per_word;
struct blk_align_bitmap *map;
};
struct blk_mq_hw_ctx {
struct {
spinlock_t lock;
......@@ -37,7 +32,7 @@ struct blk_mq_hw_ctx {
void *driver_data;
struct blk_mq_ctxmap ctx_map;
struct sbitmap ctx_map;
struct blk_mq_ctx **ctxs;
unsigned int nr_ctx;
......
/*
* Fast and scalable bitmaps.
*
* Copyright (C) 2016 Facebook
* Copyright (C) 2013-2014 Jens Axboe
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License v2 as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#ifndef __LINUX_SCALE_BITMAP_H
#define __LINUX_SCALE_BITMAP_H
#include <linux/kernel.h>
#include <linux/slab.h>
/**
* struct sbitmap_word - Word in a &struct sbitmap.
*/
struct sbitmap_word {
/**
* @word: The bitmap word itself.
*/
unsigned long word;
/**
* @depth: Number of bits being used in @word.
*/
unsigned long depth;
} ____cacheline_aligned_in_smp;
/**
* struct sbitmap - Scalable bitmap.
*
* A &struct sbitmap is spread over multiple cachelines to avoid ping-pong. This
* trades off higher memory usage for better scalability.
*/
struct sbitmap {
/**
* @depth: Number of bits used in the whole bitmap.
*/
unsigned int depth;
/**
* @shift: log2(number of bits used per word)
*/
unsigned int shift;
/**
* @map_nr: Number of words (cachelines) being used for the bitmap.
*/
unsigned int map_nr;
/**
* @map: Allocated bitmap.
*/
struct sbitmap_word *map;
};
#define SBQ_WAIT_QUEUES 8
#define SBQ_WAKE_BATCH 8
/**
* struct sbq_wait_state - Wait queue in a &struct sbitmap_queue.
*/
struct sbq_wait_state {
/**
* @wait_cnt: Number of frees remaining before we wake up.
*/
atomic_t wait_cnt;
/**
* @wait: Wait queue.
*/
wait_queue_head_t wait;
} ____cacheline_aligned_in_smp;
/**
* struct sbitmap_queue - Scalable bitmap with the added ability to wait on free
* bits.
*
* A &struct sbitmap_queue uses multiple wait queues and rolling wakeups to
* avoid contention on the wait queue spinlock. This ensures that we don't hit a
* scalability wall when we run out of free bits and have to start putting tasks
* to sleep.
*/
struct sbitmap_queue {
/**
* @sb: Scalable bitmap.
*/
struct sbitmap sb;
/**
* @wake_batch: Number of bits which must be freed before we wake up any
* waiters.
*/
unsigned int wake_batch;
/**
* @wake_index: Next wait queue in @ws to wake up.
*/
atomic_t wake_index;
/**
* @ws: Wait queues.
*/
struct sbq_wait_state *ws;
};
/**
* sbitmap_init_node() - Initialize a &struct sbitmap on a specific memory node.
* @sb: Bitmap to initialize.
* @depth: Number of bits to allocate.
* @shift: Use 2^@shift bits per word in the bitmap; if a negative number if
* given, a good default is chosen.
* @flags: Allocation flags.
* @node: Memory node to allocate on.
*
* Return: Zero on success or negative errno on failure.
*/
int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
gfp_t flags, int node);
/**
* sbitmap_free() - Free memory used by a &struct sbitmap.
* @sb: Bitmap to free.
*/
static inline void sbitmap_free(struct sbitmap *sb)
{
kfree(sb->map);
sb->map = NULL;
}
/**
* sbitmap_resize() - Resize a &struct sbitmap.
* @sb: Bitmap to resize.
* @depth: New number of bits to resize to.
*
* Doesn't reallocate anything. It's up to the caller to ensure that the new
* depth doesn't exceed the depth that the sb was initialized with.
*/
void sbitmap_resize(struct sbitmap *sb, unsigned int depth);
/**
* sbitmap_get() - Try to allocate a free bit from a &struct sbitmap.
* @sb: Bitmap to allocate from.
* @alloc_hint: Hint for where to start searching for a free bit.
* @round_robin: If true, be stricter about allocation order; always allocate
* starting from the last allocated bit. This is less efficient
* than the default behavior (false).
*
* Return: Non-negative allocated bit number if successful, -1 otherwise.
*/
int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin);
/**
* sbitmap_any_bit_set() - Check for a set bit in a &struct sbitmap.
* @sb: Bitmap to check.
*
* Return: true if any bit in the bitmap is set, false otherwise.
*/
bool sbitmap_any_bit_set(const struct sbitmap *sb);
/**
* sbitmap_any_bit_clear() - Check for an unset bit in a &struct
* sbitmap.
* @sb: Bitmap to check.
*
* Return: true if any bit in the bitmap is clear, false otherwise.
*/
bool sbitmap_any_bit_clear(const struct sbitmap *sb);
typedef bool (*sb_for_each_fn)(struct sbitmap *, unsigned int, void *);
/**
* sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap.
* @sb: Bitmap to iterate over.
* @fn: Callback. Should return true to continue or false to break early.
* @data: Pointer to pass to callback.
*
* This is inline even though it's non-trivial so that the function calls to the
* callback will hopefully get optimized away.
*/
static inline void sbitmap_for_each_set(struct sbitmap *sb, sb_for_each_fn fn,
void *data)
{
unsigned int i;
for (i = 0; i < sb->map_nr; i++) {
struct sbitmap_word *word = &sb->map[i];
unsigned int off, nr;
if (!word->word)
continue;
nr = 0;
off = i << sb->shift;
while (1) {
nr = find_next_bit(&word->word, word->depth, nr);
if (nr >= word->depth)
break;
if (!fn(sb, off + nr, data))
return;
nr++;
}
}
}
#define SB_NR_TO_INDEX(sb, bitnr) ((bitnr) >> (sb)->shift)
#define SB_NR_TO_BIT(sb, bitnr) ((bitnr) & ((1U << (sb)->shift) - 1U))
static inline unsigned long *__sbitmap_word(struct sbitmap *sb,
unsigned int bitnr)
{
return &sb->map[SB_NR_TO_INDEX(sb, bitnr)].word;
}
/* Helpers equivalent to the operations in asm/bitops.h and linux/bitmap.h */
static inline void sbitmap_set_bit(struct sbitmap *sb, unsigned int bitnr)
{
set_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
}
static inline void sbitmap_clear_bit(struct sbitmap *sb, unsigned int bitnr)
{
clear_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
}
static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr)
{
return test_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
}
unsigned int sbitmap_weight(const struct sbitmap *sb);
/**
* sbitmap_queue_init_node() - Initialize a &struct sbitmap_queue on a specific
* memory node.
* @sbq: Bitmap queue to initialize.
* @depth: See sbitmap_init_node().
* @shift: See sbitmap_init_node().
* @flags: Allocation flags.
* @node: Memory node to allocate on.
*
* Return: Zero on success or negative errno on failure.
*/
int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
int shift, gfp_t flags, int node);
/**
* sbitmap_queue_free() - Free memory used by a &struct sbitmap_queue.
*
* @sbq: Bitmap queue to free.
*/
static inline void sbitmap_queue_free(struct sbitmap_queue *sbq)
{
kfree(sbq->ws);
sbitmap_free(&sbq->sb);
}
/**
* sbitmap_queue_resize() - Resize a &struct sbitmap_queue.
* @sbq: Bitmap queue to resize.
* @depth: New number of bits to resize to.
*
* Like sbitmap_resize(), this doesn't reallocate anything. It has to do
* some extra work on the &struct sbitmap_queue, so it's not safe to just
* resize the underlying &struct sbitmap.
*/
void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth);
/**
* sbitmap_queue_clear() - Free an allocated bit and wake up waiters on a
* &struct sbitmap_queue.
* @sbq: Bitmap to free from.
* @nr: Bit number to free.
*/
void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr);
static inline int sbq_index_inc(int index)
{
return (index + 1) & (SBQ_WAIT_QUEUES - 1);
}
static inline void sbq_index_atomic_inc(atomic_t *index)
{
int old = atomic_read(index);
int new = sbq_index_inc(old);
atomic_cmpxchg(index, old, new);
}
/**
* sbq_wait_ptr() - Get the next wait queue to use for a &struct
* sbitmap_queue.
* @sbq: Bitmap queue to wait on.
* @wait_index: A counter per "user" of @sbq.
*/
static inline struct sbq_wait_state *sbq_wait_ptr(struct sbitmap_queue *sbq,
atomic_t *wait_index)
{
struct sbq_wait_state *ws;
ws = &sbq->ws[atomic_read(wait_index)];
sbq_index_atomic_inc(wait_index);
return ws;
}
/**
* sbitmap_queue_wake_all() - Wake up everything waiting on a &struct
* sbitmap_queue.
* @sbq: Bitmap queue to wake up.
*/
void sbitmap_queue_wake_all(struct sbitmap_queue *sbq);
#endif /* __LINUX_SCALE_BITMAP_H */
......@@ -550,4 +550,7 @@ config STACKDEPOT
bool
select STACKTRACE
config SBITMAP
bool
endmenu
......@@ -228,3 +228,5 @@ obj-$(CONFIG_UCS2_STRING) += ucs2_string.o
obj-$(CONFIG_UBSAN) += ubsan.o
UBSAN_SANITIZE_ubsan.o := n
obj-$(CONFIG_SBITMAP) += sbitmap.o
/*
* Copyright (C) 2016 Facebook
* Copyright (C) 2013-2014 Jens Axboe
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License v2 as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#include <linux/sbitmap.h>
int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
gfp_t flags, int node)
{
unsigned int bits_per_word;
unsigned int i;
if (shift < 0) {
shift = ilog2(BITS_PER_LONG);
/*
* If the bitmap is small, shrink the number of bits per word so
* we spread over a few cachelines, at least. If less than 4
* bits, just forget about it, it's not going to work optimally
* anyway.
*/
if (depth >= 4) {
while ((4U << shift) > depth)
shift--;
}
}
bits_per_word = 1U << shift;
if (bits_per_word > BITS_PER_LONG)
return -EINVAL;
sb->shift = shift;
sb->depth = depth;
sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);
if (depth == 0) {
sb->map = NULL;
return 0;
}
sb->map = kzalloc_node(sb->map_nr * sizeof(*sb->map), flags, node);
if (!sb->map)
return -ENOMEM;
for (i = 0; i < sb->map_nr; i++) {
sb->map[i].depth = min(depth, bits_per_word);
depth -= sb->map[i].depth;
}
return 0;
}
EXPORT_SYMBOL_GPL(sbitmap_init_node);
void sbitmap_resize(struct sbitmap *sb, unsigned int depth)
{
unsigned int bits_per_word = 1U << sb->shift;
unsigned int i;
sb->depth = depth;
sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);
for (i = 0; i < sb->map_nr; i++) {
sb->map[i].depth = min(depth, bits_per_word);
depth -= sb->map[i].depth;
}
}
EXPORT_SYMBOL_GPL(sbitmap_resize);
static int __sbitmap_get_word(struct sbitmap_word *word, unsigned int hint,
bool wrap)
{
unsigned int orig_hint = hint;
int nr;
while (1) {
nr = find_next_zero_bit(&word->word, word->depth, hint);
if (unlikely(nr >= word->depth)) {
/*
* We started with an offset, and we didn't reset the
* offset to 0 in a failure case, so start from 0 to
* exhaust the map.
*/
if (orig_hint && hint && wrap) {
hint = orig_hint = 0;
continue;
}
return -1;
}
if (!test_and_set_bit(nr, &word->word))
break;
hint = nr + 1;
if (hint >= word->depth - 1)
hint = 0;