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![Andrea Parri](/assets/img/avatar_default.png)
commita0934fd2b1
upstream. This barrier only applies to the read-modify-write operations; in particular, it does not apply to the atomic_set() primitive. Replace the barrier with an smp_mb(). Fixes:6c0ca7ae29
("sbitmap: fix wakeup hang after sbq resize") Cc: stable@vger.kernel.org Reported-by: "Paul E. McKenney" <paulmck@linux.ibm.com> Reported-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Omar Sandoval <osandov@fb.com> Cc: Ming Lei <ming.lei@redhat.com> Cc: linux-block@vger.kernel.org Cc: "Paul E. McKenney" <paulmck@linux.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
532 lines
12 KiB
C
532 lines
12 KiB
C
/*
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* Copyright (C) 2016 Facebook
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* Copyright (C) 2013-2014 Jens Axboe
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public
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* License v2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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#include <linux/sched.h>
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#include <linux/random.h>
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#include <linux/sbitmap.h>
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#include <linux/seq_file.h>
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int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
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gfp_t flags, int node)
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{
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unsigned int bits_per_word;
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unsigned int i;
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if (shift < 0) {
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shift = ilog2(BITS_PER_LONG);
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/*
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* If the bitmap is small, shrink the number of bits per word so
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* we spread over a few cachelines, at least. If less than 4
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* bits, just forget about it, it's not going to work optimally
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* anyway.
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*/
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if (depth >= 4) {
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while ((4U << shift) > depth)
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shift--;
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}
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}
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bits_per_word = 1U << shift;
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if (bits_per_word > BITS_PER_LONG)
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return -EINVAL;
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sb->shift = shift;
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sb->depth = depth;
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sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);
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if (depth == 0) {
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sb->map = NULL;
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return 0;
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}
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sb->map = kzalloc_node(sb->map_nr * sizeof(*sb->map), flags, node);
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if (!sb->map)
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return -ENOMEM;
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for (i = 0; i < sb->map_nr; i++) {
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sb->map[i].depth = min(depth, bits_per_word);
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depth -= sb->map[i].depth;
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}
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return 0;
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}
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EXPORT_SYMBOL_GPL(sbitmap_init_node);
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void sbitmap_resize(struct sbitmap *sb, unsigned int depth)
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{
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unsigned int bits_per_word = 1U << sb->shift;
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unsigned int i;
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sb->depth = depth;
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sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);
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for (i = 0; i < sb->map_nr; i++) {
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sb->map[i].depth = min(depth, bits_per_word);
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depth -= sb->map[i].depth;
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}
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}
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EXPORT_SYMBOL_GPL(sbitmap_resize);
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static int __sbitmap_get_word(unsigned long *word, unsigned long depth,
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unsigned int hint, bool wrap)
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{
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unsigned int orig_hint = hint;
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int nr;
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while (1) {
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nr = find_next_zero_bit(word, depth, hint);
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if (unlikely(nr >= depth)) {
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/*
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* We started with an offset, and we didn't reset the
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* offset to 0 in a failure case, so start from 0 to
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* exhaust the map.
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*/
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if (orig_hint && hint && wrap) {
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hint = orig_hint = 0;
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continue;
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}
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return -1;
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}
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if (!test_and_set_bit(nr, word))
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break;
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hint = nr + 1;
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if (hint >= depth - 1)
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hint = 0;
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}
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return nr;
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}
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int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin)
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{
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unsigned int i, index;
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int nr = -1;
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index = SB_NR_TO_INDEX(sb, alloc_hint);
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for (i = 0; i < sb->map_nr; i++) {
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nr = __sbitmap_get_word(&sb->map[index].word,
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sb->map[index].depth,
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SB_NR_TO_BIT(sb, alloc_hint),
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!round_robin);
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if (nr != -1) {
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nr += index << sb->shift;
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break;
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}
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/* Jump to next index. */
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index++;
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alloc_hint = index << sb->shift;
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if (index >= sb->map_nr) {
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index = 0;
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alloc_hint = 0;
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}
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}
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return nr;
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}
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EXPORT_SYMBOL_GPL(sbitmap_get);
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int sbitmap_get_shallow(struct sbitmap *sb, unsigned int alloc_hint,
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unsigned long shallow_depth)
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{
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unsigned int i, index;
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int nr = -1;
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index = SB_NR_TO_INDEX(sb, alloc_hint);
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for (i = 0; i < sb->map_nr; i++) {
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nr = __sbitmap_get_word(&sb->map[index].word,
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min(sb->map[index].depth, shallow_depth),
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SB_NR_TO_BIT(sb, alloc_hint), true);
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if (nr != -1) {
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nr += index << sb->shift;
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break;
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}
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/* Jump to next index. */
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index++;
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alloc_hint = index << sb->shift;
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if (index >= sb->map_nr) {
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index = 0;
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alloc_hint = 0;
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}
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}
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return nr;
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}
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EXPORT_SYMBOL_GPL(sbitmap_get_shallow);
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bool sbitmap_any_bit_set(const struct sbitmap *sb)
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{
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unsigned int i;
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for (i = 0; i < sb->map_nr; i++) {
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if (sb->map[i].word)
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return true;
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}
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return false;
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}
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EXPORT_SYMBOL_GPL(sbitmap_any_bit_set);
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bool sbitmap_any_bit_clear(const struct sbitmap *sb)
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{
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unsigned int i;
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for (i = 0; i < sb->map_nr; i++) {
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const struct sbitmap_word *word = &sb->map[i];
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unsigned long ret;
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ret = find_first_zero_bit(&word->word, word->depth);
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if (ret < word->depth)
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return true;
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}
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return false;
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}
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EXPORT_SYMBOL_GPL(sbitmap_any_bit_clear);
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unsigned int sbitmap_weight(const struct sbitmap *sb)
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{
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unsigned int i, weight = 0;
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for (i = 0; i < sb->map_nr; i++) {
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const struct sbitmap_word *word = &sb->map[i];
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weight += bitmap_weight(&word->word, word->depth);
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}
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return weight;
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}
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EXPORT_SYMBOL_GPL(sbitmap_weight);
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void sbitmap_show(struct sbitmap *sb, struct seq_file *m)
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{
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seq_printf(m, "depth=%u\n", sb->depth);
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seq_printf(m, "busy=%u\n", sbitmap_weight(sb));
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seq_printf(m, "bits_per_word=%u\n", 1U << sb->shift);
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seq_printf(m, "map_nr=%u\n", sb->map_nr);
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}
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EXPORT_SYMBOL_GPL(sbitmap_show);
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static inline void emit_byte(struct seq_file *m, unsigned int offset, u8 byte)
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{
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if ((offset & 0xf) == 0) {
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if (offset != 0)
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seq_putc(m, '\n');
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seq_printf(m, "%08x:", offset);
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}
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if ((offset & 0x1) == 0)
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seq_putc(m, ' ');
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seq_printf(m, "%02x", byte);
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}
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void sbitmap_bitmap_show(struct sbitmap *sb, struct seq_file *m)
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{
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u8 byte = 0;
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unsigned int byte_bits = 0;
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unsigned int offset = 0;
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int i;
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for (i = 0; i < sb->map_nr; i++) {
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unsigned long word = READ_ONCE(sb->map[i].word);
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unsigned int word_bits = READ_ONCE(sb->map[i].depth);
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while (word_bits > 0) {
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unsigned int bits = min(8 - byte_bits, word_bits);
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byte |= (word & (BIT(bits) - 1)) << byte_bits;
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byte_bits += bits;
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if (byte_bits == 8) {
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emit_byte(m, offset, byte);
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byte = 0;
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byte_bits = 0;
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offset++;
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}
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word >>= bits;
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word_bits -= bits;
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}
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}
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if (byte_bits) {
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emit_byte(m, offset, byte);
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offset++;
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}
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if (offset)
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seq_putc(m, '\n');
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}
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EXPORT_SYMBOL_GPL(sbitmap_bitmap_show);
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static unsigned int sbq_calc_wake_batch(unsigned int depth)
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{
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unsigned int wake_batch;
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/*
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* For each batch, we wake up one queue. We need to make sure that our
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* batch size is small enough that the full depth of the bitmap is
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* enough to wake up all of the queues.
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*/
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wake_batch = SBQ_WAKE_BATCH;
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if (wake_batch > depth / SBQ_WAIT_QUEUES)
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wake_batch = max(1U, depth / SBQ_WAIT_QUEUES);
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return wake_batch;
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}
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int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
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int shift, bool round_robin, gfp_t flags, int node)
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{
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int ret;
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int i;
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ret = sbitmap_init_node(&sbq->sb, depth, shift, flags, node);
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if (ret)
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return ret;
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sbq->alloc_hint = alloc_percpu_gfp(unsigned int, flags);
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if (!sbq->alloc_hint) {
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sbitmap_free(&sbq->sb);
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return -ENOMEM;
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}
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if (depth && !round_robin) {
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for_each_possible_cpu(i)
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*per_cpu_ptr(sbq->alloc_hint, i) = prandom_u32() % depth;
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}
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sbq->wake_batch = sbq_calc_wake_batch(depth);
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atomic_set(&sbq->wake_index, 0);
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sbq->ws = kzalloc_node(SBQ_WAIT_QUEUES * sizeof(*sbq->ws), flags, node);
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if (!sbq->ws) {
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free_percpu(sbq->alloc_hint);
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sbitmap_free(&sbq->sb);
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return -ENOMEM;
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}
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for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
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init_waitqueue_head(&sbq->ws[i].wait);
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atomic_set(&sbq->ws[i].wait_cnt, sbq->wake_batch);
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}
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sbq->round_robin = round_robin;
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return 0;
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}
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EXPORT_SYMBOL_GPL(sbitmap_queue_init_node);
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void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth)
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{
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unsigned int wake_batch = sbq_calc_wake_batch(depth);
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int i;
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if (sbq->wake_batch != wake_batch) {
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WRITE_ONCE(sbq->wake_batch, wake_batch);
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/*
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* Pairs with the memory barrier in sbq_wake_up() to ensure that
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* the batch size is updated before the wait counts.
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*/
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smp_mb();
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for (i = 0; i < SBQ_WAIT_QUEUES; i++)
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atomic_set(&sbq->ws[i].wait_cnt, 1);
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}
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sbitmap_resize(&sbq->sb, depth);
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}
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EXPORT_SYMBOL_GPL(sbitmap_queue_resize);
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int __sbitmap_queue_get(struct sbitmap_queue *sbq)
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{
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unsigned int hint, depth;
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int nr;
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hint = this_cpu_read(*sbq->alloc_hint);
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depth = READ_ONCE(sbq->sb.depth);
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if (unlikely(hint >= depth)) {
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hint = depth ? prandom_u32() % depth : 0;
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this_cpu_write(*sbq->alloc_hint, hint);
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}
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nr = sbitmap_get(&sbq->sb, hint, sbq->round_robin);
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if (nr == -1) {
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/* If the map is full, a hint won't do us much good. */
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this_cpu_write(*sbq->alloc_hint, 0);
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} else if (nr == hint || unlikely(sbq->round_robin)) {
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/* Only update the hint if we used it. */
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hint = nr + 1;
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if (hint >= depth - 1)
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hint = 0;
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this_cpu_write(*sbq->alloc_hint, hint);
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}
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return nr;
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}
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EXPORT_SYMBOL_GPL(__sbitmap_queue_get);
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int __sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
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unsigned int shallow_depth)
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{
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unsigned int hint, depth;
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int nr;
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hint = this_cpu_read(*sbq->alloc_hint);
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depth = READ_ONCE(sbq->sb.depth);
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if (unlikely(hint >= depth)) {
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hint = depth ? prandom_u32() % depth : 0;
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this_cpu_write(*sbq->alloc_hint, hint);
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}
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nr = sbitmap_get_shallow(&sbq->sb, hint, shallow_depth);
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if (nr == -1) {
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/* If the map is full, a hint won't do us much good. */
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this_cpu_write(*sbq->alloc_hint, 0);
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} else if (nr == hint || unlikely(sbq->round_robin)) {
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/* Only update the hint if we used it. */
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hint = nr + 1;
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if (hint >= depth - 1)
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hint = 0;
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this_cpu_write(*sbq->alloc_hint, hint);
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}
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return nr;
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}
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EXPORT_SYMBOL_GPL(__sbitmap_queue_get_shallow);
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static struct sbq_wait_state *sbq_wake_ptr(struct sbitmap_queue *sbq)
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{
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int i, wake_index;
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wake_index = atomic_read(&sbq->wake_index);
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for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
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struct sbq_wait_state *ws = &sbq->ws[wake_index];
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if (waitqueue_active(&ws->wait)) {
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int o = atomic_read(&sbq->wake_index);
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if (wake_index != o)
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atomic_cmpxchg(&sbq->wake_index, o, wake_index);
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return ws;
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}
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wake_index = sbq_index_inc(wake_index);
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}
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return NULL;
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}
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static void sbq_wake_up(struct sbitmap_queue *sbq)
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{
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struct sbq_wait_state *ws;
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unsigned int wake_batch;
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int wait_cnt;
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/*
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* Pairs with the memory barrier in set_current_state() to ensure the
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* proper ordering of clear_bit()/waitqueue_active() in the waker and
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* test_and_set_bit()/prepare_to_wait()/finish_wait() in the waiter. See
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* the comment on waitqueue_active(). This is __after_atomic because we
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* just did clear_bit() in the caller.
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*/
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smp_mb__after_atomic();
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ws = sbq_wake_ptr(sbq);
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if (!ws)
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return;
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wait_cnt = atomic_dec_return(&ws->wait_cnt);
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if (wait_cnt <= 0) {
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wake_batch = READ_ONCE(sbq->wake_batch);
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/*
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* Pairs with the memory barrier in sbitmap_queue_resize() to
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* ensure that we see the batch size update before the wait
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* count is reset.
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*/
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smp_mb__before_atomic();
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/*
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* If there are concurrent callers to sbq_wake_up(), the last
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* one to decrement the wait count below zero will bump it back
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* up. If there is a concurrent resize, the count reset will
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* either cause the cmpxchg to fail or overwrite after the
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* cmpxchg.
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*/
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atomic_cmpxchg(&ws->wait_cnt, wait_cnt, wait_cnt + wake_batch);
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sbq_index_atomic_inc(&sbq->wake_index);
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wake_up(&ws->wait);
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}
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}
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void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
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unsigned int cpu)
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{
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sbitmap_clear_bit(&sbq->sb, nr);
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sbq_wake_up(sbq);
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if (likely(!sbq->round_robin && nr < sbq->sb.depth))
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*per_cpu_ptr(sbq->alloc_hint, cpu) = nr;
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}
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EXPORT_SYMBOL_GPL(sbitmap_queue_clear);
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void sbitmap_queue_wake_all(struct sbitmap_queue *sbq)
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{
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int i, wake_index;
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/*
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* Pairs with the memory barrier in set_current_state() like in
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* sbq_wake_up().
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*/
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smp_mb();
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wake_index = atomic_read(&sbq->wake_index);
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for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
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struct sbq_wait_state *ws = &sbq->ws[wake_index];
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if (waitqueue_active(&ws->wait))
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wake_up(&ws->wait);
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wake_index = sbq_index_inc(wake_index);
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}
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}
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EXPORT_SYMBOL_GPL(sbitmap_queue_wake_all);
|
|
|
|
void sbitmap_queue_show(struct sbitmap_queue *sbq, struct seq_file *m)
|
|
{
|
|
bool first;
|
|
int i;
|
|
|
|
sbitmap_show(&sbq->sb, m);
|
|
|
|
seq_puts(m, "alloc_hint={");
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|
first = true;
|
|
for_each_possible_cpu(i) {
|
|
if (!first)
|
|
seq_puts(m, ", ");
|
|
first = false;
|
|
seq_printf(m, "%u", *per_cpu_ptr(sbq->alloc_hint, i));
|
|
}
|
|
seq_puts(m, "}\n");
|
|
|
|
seq_printf(m, "wake_batch=%u\n", sbq->wake_batch);
|
|
seq_printf(m, "wake_index=%d\n", atomic_read(&sbq->wake_index));
|
|
|
|
seq_puts(m, "ws={\n");
|
|
for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
|
|
struct sbq_wait_state *ws = &sbq->ws[i];
|
|
|
|
seq_printf(m, "\t{.wait_cnt=%d, .wait=%s},\n",
|
|
atomic_read(&ws->wait_cnt),
|
|
waitqueue_active(&ws->wait) ? "active" : "inactive");
|
|
}
|
|
seq_puts(m, "}\n");
|
|
|
|
seq_printf(m, "round_robin=%d\n", sbq->round_robin);
|
|
}
|
|
EXPORT_SYMBOL_GPL(sbitmap_queue_show);
|