[dm-devel] [PATCH] dm log writes: make sure the log super sectors are written in order
zhangyi (F)
yi.zhang at huawei.com
Mon Jun 3 14:18:54 UTC 2019
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) <yi.zhang at huawei.com>
---
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
More information about the dm-devel
mailing list