[Devel] [PATCH vz9] ploop: add interface to request write out BAT

[Alexander Atanasov]

It is possible that BAT is corrupted on disk but
we have a good copy of it in RAM. Add dmsetup
message to write it out to file write_bat_to_file.
This is very basic interface and it must be used
as a last resort.

https://virtuozzo.atlassian.net/browse/PSBM-156501
Signed-off-by: Alexander Atanasov <alexander.atanasov at virtuozzo.com>
---
 drivers/md/dm-ploop-cmd.c | 48 +++++++++++++++++++++++++++++++++++++++
 drivers/md/dm-ploop-map.c |  4 ++--
 drivers/md/dm-ploop.h     |  3 +++
 3 files changed, 53 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm-ploop-cmd.c b/drivers/md/dm-ploop-cmd.c
index 88519f590148b..71f854c509f82 100644
--- a/drivers/md/dm-ploop-cmd.c
+++ b/drivers/md/dm-ploop-cmd.c
@@ -280,6 +280,45 @@ static void ploop_make_md_wb(struct ploop *ploop, struct md_page *md)
 	write_unlock_irq(&ploop->bat_rwlock);
 }
 
+/* write all md to disk */
+static u32 ploop_rewrite_bat_from_memory(struct ploop *ploop)
+{
+	struct rb_node *node;
+	struct md_page *md;
+	struct ploop_index_wb *piwb;
+	blk_status_t bi_status;
+	DECLARE_COMPLETION_ONSTACK(comp);
+	int err;
+
+	ploop_suspend_submitting_pios(ploop);
+	ploop_for_each_md_page(ploop, md, node) {
+		/* we have the page and want to write so prepare bat update */
+		err = ploop_prepare_bat_update(ploop, md, PIWB_TYPE_ALLOC);
+		/* does wb_init ploop_index_wb_init */
+		if (err) {
+			/* most likely no memory, notify user he may retry */
+			printk(KERN_ERR "MD prepare WB failed: %d\n", err);
+		}
+		/* mark md for writeback */
+		ploop_make_md_wb(ploop, md);
+		/* piwb is prepared in md->piwb */
+		piwb = md->piwb;
+		init_completion(&comp);
+		piwb->comp = &comp;
+		piwb->comp_bi_status = &bi_status;
+		/* Write index to disk */
+		ploop_index_wb_submit(ploop, piwb);
+		wait_for_completion(&comp);
+		/* piwb is freed on completion */
+		if (bi_status) {
+			printk(KERN_ERR "MD WB failed: %d\n", blk_status_to_errno(bi_status));
+		}
+	}
+	ploop_resume_submitting_pios(ploop);
+
+	return 0;
+}
+
 static int ploop_grow_relocate_cluster(struct ploop *ploop,
 				       struct ploop_cmd *cmd)
 {
@@ -1086,6 +1125,11 @@ static int ploop_check_delta_before_flip(struct ploop *ploop, struct file *file)
 	return ret;
 }
 
+static int ploop_write_bat_to_file(struct ploop *ploop)
+{
+	return ploop_rewrite_bat_from_memory(ploop);
+}
+
 static int ploop_flip_upper_deltas(struct ploop *ploop)
 {
 	struct file *file;
@@ -1197,6 +1241,10 @@ int ploop_message(struct dm_target *ti, unsigned int argc, char **argv,
 		if (argc != 1)
 			goto unlock;
 		ret = ploop_flip_upper_deltas(ploop);
+	} else if (!strcmp(argv[0], "write_bat_to_file")) {
+		if (argc != 1)
+			goto unlock;
+		ret = ploop_write_bat_to_file(ploop);
 	} else {
 		ret = -ENOTSUPP;
 	}
diff --git a/drivers/md/dm-ploop-map.c b/drivers/md/dm-ploop-map.c
index ea04b3e53567e..7e16005f1e5c9 100644
--- a/drivers/md/dm-ploop-map.c
+++ b/drivers/md/dm-ploop-map.c
@@ -813,7 +813,7 @@ static void ploop_advance_local_after_bat_wb(struct ploop *ploop,
 		ploop_dispatch_pios(ploop, NULL, &list);
 }
 
-static void ploop_free_piwb(struct ploop_index_wb *piwb)
+void ploop_free_piwb(struct ploop_index_wb *piwb)
 {
 	ploop_free_pio(piwb->ploop, piwb->pio);
 	put_page(piwb->bat_page);
@@ -889,7 +889,7 @@ static void ploop_bat_write_complete(struct ploop_index_wb *piwb,
 	ploop_put_piwb(piwb);
 }
 
-static int ploop_prepare_bat_update(struct ploop *ploop, struct md_page *md,
+int ploop_prepare_bat_update(struct ploop *ploop, struct md_page *md,
 				    enum piwb_type type)
 {
 	u32 i, off, last, *bat_entries;
diff --git a/drivers/md/dm-ploop.h b/drivers/md/dm-ploop.h
index db36687c81696..67dbf8abd4e41 100644
--- a/drivers/md/dm-ploop.h
+++ b/drivers/md/dm-ploop.h
@@ -559,6 +559,8 @@ extern void ploop_free_md_page(struct md_page *md);
 extern void ploop_free_md_pages_tree(struct rb_root *root);
 extern bool ploop_try_update_bat_entry(struct ploop *ploop, u32 clu,
 				       u8 level, u32 dst_clu);
+extern int ploop_prepare_bat_update(struct ploop *ploop, struct md_page *md,
+				    enum piwb_type type);
 
 extern int ploop_add_delta(struct ploop *ploop, u32 level,
 			   struct file *file, bool is_raw);
@@ -597,6 +599,7 @@ extern int ploop_read_delta_metadata(struct ploop *ploop, struct file *file,
 				     struct rb_root *md_root, u32 *delta_nr_be);
 extern void ploop_index_wb_init(struct ploop_index_wb *piwb,
 				struct ploop *ploop);
+extern void ploop_free_piwb(struct ploop_index_wb *piwb);
 extern void ploop_call_rw_iter(struct file *file, loff_t pos, unsigned rw,
 			       struct iov_iter *iter, struct pio *pio);
 extern void ploop_enospc_timer(struct timer_list *timer);
-- 
2.43.0