Currently, although we submit super bios in log-write thread orderly (the super.nr_entries is incremented by each logged entry), the submit_bio() cannot make sure that each super sector is written to log device in order. So the submitting bio of each super sector may be out-of-order, and then the final nr_entries maybe small than the real entries submitted.
This problem can be reproduced by the xfstests generic/455 with ext4, which may complained below after running the test: QA output created by 455 -Silence is golden +mark 'end' does not exist This patch serialize submitting super secotrs to make sure each super sectors are written to log disk in order. Signed-off-by: zhangyi (F) <[email protected]> --- drivers/md/dm-log-writes.c | 56 ++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 54 insertions(+), 2 deletions(-) diff --git a/drivers/md/dm-log-writes.c b/drivers/md/dm-log-writes.c index 9ea2b02..37088c7 100644 --- a/drivers/md/dm-log-writes.c +++ b/drivers/md/dm-log-writes.c @@ -60,6 +60,7 @@ #define WRITE_LOG_VERSION 1ULL #define WRITE_LOG_MAGIC 0x6a736677736872ULL +#define WRITE_LOG_SUPER_SECTOR 0 /* * The disk format for this is braindead simple. @@ -115,6 +116,8 @@ struct log_writes_c { struct list_head logging_blocks; wait_queue_head_t wait; struct task_struct *log_kthread; + bool submitting_super; + wait_queue_head_t wait_super; }; struct pending_block { @@ -180,6 +183,34 @@ static void log_end_io(struct bio *bio) bio_put(bio); } +static void log_end_super(struct bio *bio) +{ + struct log_writes_c *lc = bio->bi_private; + unsigned long flags; + + spin_lock_irqsave(&lc->blocks_lock, flags); + if (bio->bi_status) { + DMERR("Error writing super block, error=%d", + bio->bi_status); + lc->logging_enabled = false; + } + + WARN_ON(!lc->submitting_super); + lc->submitting_super = false; + spin_unlock_irqrestore(&lc->blocks_lock, flags); + + /* + * Wake up log-write kthread that previous super sector has + * been written to disk. + */ + if (waitqueue_active(&lc->wait_super)) + wake_up(&lc->wait_super); + + bio_free_pages(bio); + put_io_block(lc); + bio_put(bio); +} + /* * Meant to be called if there is an error, it will free all the pages * associated with the block. @@ -215,7 +246,8 @@ static int write_metadata(struct log_writes_c *lc, void *entry, bio->bi_iter.bi_size = 0; bio->bi_iter.bi_sector = sector; bio_set_dev(bio, lc->logdev->bdev); - bio->bi_end_io = log_end_io; + bio->bi_end_io = (sector == WRITE_LOG_SUPER_SECTOR) ? + log_end_super : log_end_io; bio->bi_private = lc; bio_set_op_attrs(bio, REQ_OP_WRITE, 0); @@ -418,7 +450,25 @@ static int log_super(struct log_writes_c *lc) super.nr_entries = cpu_to_le64(lc->logged_entries); super.sectorsize = cpu_to_le32(lc->sectorsize); - if (write_metadata(lc, &super, sizeof(super), NULL, 0, 0)) { + /* + * Super sector should be writen in-order, or else the + * nr_entries could be small than the real submitted entries. + * So wait previous super sector submitted here. + */ + if (!lc->submitting_super) + goto write_super; + + spin_lock_irq(&lc->blocks_lock); + if (!lc->submitting_super) { + spin_unlock_irq(&lc->blocks_lock); + goto write_super; + } + spin_unlock_irq(&lc->blocks_lock); + wait_event(lc->wait_super, !lc->submitting_super); +write_super: + lc->submitting_super = true; + if (write_metadata(lc, &super, sizeof(super), NULL, 0, + WRITE_LOG_SUPER_SECTOR)) { DMERR("Couldn't write super"); return -1; } @@ -531,6 +581,7 @@ static int log_writes_ctr(struct dm_target *ti, unsigned int argc, char **argv) INIT_LIST_HEAD(&lc->unflushed_blocks); INIT_LIST_HEAD(&lc->logging_blocks); init_waitqueue_head(&lc->wait); + init_waitqueue_head(&lc->wait_super); atomic_set(&lc->io_blocks, 0); atomic_set(&lc->pending_blocks, 0); @@ -570,6 +621,7 @@ static int log_writes_ctr(struct dm_target *ti, unsigned int argc, char **argv) lc->logging_enabled = true; lc->end_sector = logdev_last_sector(lc); lc->device_supports_discard = true; + lc->submitting_super = false; ti->num_flush_bios = 1; ti->flush_supported = true; -- 2.7.4 -- dm-devel mailing list [email protected] https://www.redhat.com/mailman/listinfo/dm-devel
