[Devel] [PATCH hci-8.1 v5 06/11] dm-ploop: factor out ploop_read_delta() from ploop_add_delta()

[Alexander Ivanov <alexander.ivanov@virtuozzo.com>]

Move reading of delta BAT and applying its mappings to
ploop->bat_entries into a separate function ploop_read_delta(). It
will be used to reload metadata of already added deltas.

ploop_read_delta() takes is_raw from deltas[level], so ploop_add_delta()
sets it before the call.

Replace the stale comment of ploop_add_delta(): it claimed deltas are
added from oldest to newest, while ploop_add_deltas_stack() adds them
from top to base, which ploop_read_delta() relies on.

No functional changes.

https://virtuozzo.atlassian.net/browse/VSTOR-148171
Feature: dm-ploop: ploop target driver

Signed-off-by: Alexander Ivanov <alexander.ivanov@virtuozzo.com>
Reviewed-by: Denis V. Lunev <den@openvz.org>
---
 drivers/md/dm-ploop-bat.c | 43 +++++++++++++++++++++++++++++++--------
 1 file changed, 35 insertions(+), 8 deletions(-)

diff --git a/drivers/md/dm-ploop-bat.c b/drivers/md/dm-ploop-bat.c
index 3427d1a90d81..5a89771a2e02 100644
--- a/drivers/md/dm-ploop-bat.c
+++ b/drivers/md/dm-ploop-bat.c
@@ -481,23 +481,27 @@ int ploop_check_delta_length(struct ploop *ploop, struct file *file, loff_t *fil
 ALLOW_ERROR_INJECTION(ploop_check_delta_length, ERRNO);
 
 /*
- * @fd refers to a new delta, which is placed right before top_delta.
- * So, userspace has to populate deltas stack from oldest to newest.
+ * Read BAT of delta @level and apply its mappings to ploop->bat_entries.
+ * deltas[@level].is_raw and nr_be of upper deltas must be already set.
+ *
+ * Deltas must be read from top to base: mappings of upper deltas take
+ * precedence (already populated BAT entries are not overwritten), and
+ * size of the delta is checked against nr_be of the upper one.
  */
-int ploop_add_delta(struct ploop *ploop, u32 level, struct file *file, bool is_raw)
+static int ploop_read_delta(struct ploop *ploop, u32 level, struct file *file,
+			    loff_t *file_size_ret, u32 *nr_be_ret)
 {
 	struct ploop_delta *deltas = ploop->deltas;
 	struct rb_root md_root = RB_ROOT;
-	struct file *cloned_file = NULL;
 	loff_t file_size;
 	u32 nr_be;
-	int ret, i;
+	int ret;
 
 	ret = ploop_check_delta_length(ploop, file, &file_size);
 	if (ret)
 		goto out;
 
-	if (!is_raw) {
+	if (!deltas[level].is_raw) {
 		ret = ploop_read_delta_metadata(ploop, file, &md_root, &nr_be);
 		if (ret)
 			goto out;
@@ -512,9 +516,33 @@ int ploop_add_delta(struct ploop *ploop, u32 level, struct file *file, bool is_r
 	if (level != ploop_top_level(ploop) && nr_be > deltas[level + 1].nr_be)
 		goto out;
 
-	deltas[level].is_raw = is_raw;
 	ploop_apply_delta_mappings(ploop, deltas, level, &md_root, nr_be);
 
+	*file_size_ret = file_size;
+	*nr_be_ret = nr_be;
+	ret = 0;
+out:
+	ploop_free_md_pages_tree(&md_root);
+	return ret;
+}
+
+/*
+ * Add @file as delta @level. Deltas must be added from top to base,
+ * see ploop_read_delta().
+ */
+int ploop_add_delta(struct ploop *ploop, u32 level, struct file *file, bool is_raw)
+{
+	struct ploop_delta *deltas = ploop->deltas;
+	struct file *cloned_file = NULL;
+	loff_t file_size;
+	u32 nr_be;
+	int ret, i;
+
+	deltas[level].is_raw = is_raw;
+	ret = ploop_read_delta(ploop, level, file, &file_size, &nr_be);
+	if (ret)
+		goto out;
+
 	deltas[level].file = file;
 	deltas[level].mtfile = kcalloc(ploop->nkt_runners, sizeof(*file),
 					GFP_KERNEL);
@@ -535,7 +563,6 @@ int ploop_add_delta(struct ploop *ploop, u32 level, struct file *file, bool is_r
 	deltas[level].nr_be = nr_be;
 	ret = 0;
 out:
-	ploop_free_md_pages_tree(&md_root);
 	return ret;
 }
 ALLOW_ERROR_INJECTION(ploop_add_delta, ERRNO);
-- 
2.53.0

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