diff options
| -rw-r--r-- | block/blklogwrites.c | 85 |
1 files changed, 77 insertions, 8 deletions
diff --git a/block/blklogwrites.c b/block/blklogwrites.c index ba717da..ed38a93 100644 --- a/block/blklogwrites.c +++ b/block/blklogwrites.c @@ -3,7 +3,7 @@ * * Copyright (c) 2017 Tuomas Tynkkynen <tuomas@tuxera.com> * Copyright (c) 2018 Aapo Vienamo <aapo@tuxera.com> - * Copyright (c) 2018 Ari Sundholm <ari@tuxera.com> + * Copyright (c) 2018-2024 Ari Sundholm <ari@tuxera.com> * * This work is licensed under the terms of the GNU GPL, version 2 or later. * See the COPYING file in the top-level directory. @@ -55,9 +55,34 @@ typedef struct { BdrvChild *log_file; uint32_t sectorsize; uint32_t sectorbits; + uint64_t update_interval; + + /* + * The mutable state of the driver, consisting of the current log sector + * and the number of log entries. + * + * May be read and/or written from multiple threads, and the mutex must be + * held when accessing these fields. + */ uint64_t cur_log_sector; uint64_t nr_entries; - uint64_t update_interval; + QemuMutex mutex; + + /* + * The super block sequence number. Non-zero if a super block update is in + * progress. + * + * The mutex must be held when accessing this field. + */ + uint64_t super_update_seq; + + /* + * A coroutine-aware queue to serialize super block updates. + * + * Used with the mutex to ensure that only one thread be updating the super + * block at a time. + */ + CoQueue super_update_queue; } BDRVBlkLogWritesState; static QemuOptsList runtime_opts = { @@ -169,6 +194,9 @@ static int blk_log_writes_open(BlockDriverState *bs, QDict *options, int flags, goto fail; } + qemu_mutex_init(&s->mutex); + qemu_co_queue_init(&s->super_update_queue); + log_append = qemu_opt_get_bool(opts, "log-append", false); if (log_append) { @@ -231,6 +259,8 @@ static int blk_log_writes_open(BlockDriverState *bs, QDict *options, int flags, s->nr_entries = 0; } + s->super_update_seq = 0; + if (!blk_log_writes_sector_size_valid(log_sector_size)) { ret = -EINVAL; error_setg(errp, "Invalid log sector size %"PRIu64, log_sector_size); @@ -255,6 +285,7 @@ fail_log: bdrv_unref_child(bs, s->log_file); bdrv_graph_wrunlock(); s->log_file = NULL; + qemu_mutex_destroy(&s->mutex); } fail: qemu_opts_del(opts); @@ -269,6 +300,7 @@ static void blk_log_writes_close(BlockDriverState *bs) bdrv_unref_child(bs, s->log_file); s->log_file = NULL; bdrv_graph_wrunlock(); + qemu_mutex_destroy(&s->mutex); } static int64_t coroutine_fn GRAPH_RDLOCK @@ -295,7 +327,7 @@ static void blk_log_writes_child_perm(BlockDriverState *bs, BdrvChild *c, static void blk_log_writes_refresh_limits(BlockDriverState *bs, Error **errp) { - BDRVBlkLogWritesState *s = bs->opaque; + const BDRVBlkLogWritesState *s = bs->opaque; bs->bl.request_alignment = s->sectorsize; } @@ -338,15 +370,18 @@ blk_log_writes_co_do_log(BlkLogWritesLogReq *lr) * driver may be modified by other driver operations while waiting for the * I/O to complete. */ + qemu_mutex_lock(&s->mutex); const uint64_t entry_start_sector = s->cur_log_sector; const uint64_t entry_offset = entry_start_sector << s->sectorbits; const uint64_t qiov_aligned_size = ROUND_UP(lr->qiov->size, s->sectorsize); const uint64_t entry_aligned_size = qiov_aligned_size + ROUND_UP(lr->zero_size, s->sectorsize); const uint64_t entry_nr_sectors = entry_aligned_size >> s->sectorbits; + const uint64_t entry_seq = s->nr_entries + 1; - s->nr_entries++; + s->nr_entries = entry_seq; s->cur_log_sector += entry_nr_sectors; + qemu_mutex_unlock(&s->mutex); /* * Write the log entry. Note that if this is a "write zeroes" operation, @@ -366,17 +401,44 @@ blk_log_writes_co_do_log(BlkLogWritesLogReq *lr) /* Update super block on flush or every update interval */ if (lr->log_ret == 0 && ((lr->entry.flags & LOG_FLUSH_FLAG) - || (s->nr_entries % s->update_interval == 0))) + || (entry_seq % s->update_interval == 0))) { struct log_write_super super = { .magic = cpu_to_le64(WRITE_LOG_MAGIC), .version = cpu_to_le64(WRITE_LOG_VERSION), - .nr_entries = cpu_to_le64(s->nr_entries), + .nr_entries = 0, /* updated below */ .sectorsize = cpu_to_le32(s->sectorsize), }; - void *zeroes = g_malloc0(s->sectorsize - sizeof(super)); + void *zeroes; QEMUIOVector qiov; + /* + * Wait if a super block update is already in progress. + * Bail out if a newer update got its turn before us. + */ + WITH_QEMU_LOCK_GUARD(&s->mutex) { + CoQueueWaitFlags wait_flags = 0; + while (s->super_update_seq) { + if (entry_seq < s->super_update_seq) { + return; + } + qemu_co_queue_wait_flags(&s->super_update_queue, + &s->mutex, wait_flags); + + /* + * In case the wait condition remains true after wakeup, + * to avoid starvation, make sure that this request is + * scheduled to rerun next by pushing it to the front of the + * queue. + */ + wait_flags = CO_QUEUE_WAIT_FRONT; + } + s->super_update_seq = entry_seq; + super.nr_entries = cpu_to_le64(s->nr_entries); + } + + zeroes = g_malloc0(s->sectorsize - sizeof(super)); + qemu_iovec_init(&qiov, 2); qemu_iovec_add(&qiov, &super, sizeof(super)); qemu_iovec_add(&qiov, zeroes, s->sectorsize - sizeof(super)); @@ -386,6 +448,13 @@ blk_log_writes_co_do_log(BlkLogWritesLogReq *lr) if (lr->log_ret == 0) { lr->log_ret = bdrv_co_flush(s->log_file->bs); } + + /* The super block has been updated. Let another request have a go. */ + qemu_mutex_lock(&s->mutex); + s->super_update_seq = 0; + (void) qemu_co_queue_next(&s->super_update_queue); + qemu_mutex_unlock(&s->mutex); + qemu_iovec_destroy(&qiov); g_free(zeroes); } @@ -405,7 +474,7 @@ blk_log_writes_co_log(BlockDriverState *bs, uint64_t offset, uint64_t bytes, { QEMUIOVector log_qiov; size_t niov = qiov ? qiov->niov : 0; - BDRVBlkLogWritesState *s = bs->opaque; + const BDRVBlkLogWritesState *s = bs->opaque; BlkLogWritesFileReq fr = { .bs = bs, .offset = offset, |