[Devel] [PATCH hci-8.1 v3 2/5] dm-ploop: set delta is_raw before applying its mappings

[Alexander Ivanov]

ploop_apply_delta_mappings() takes is_raw from deltas[level], but
ploop_add_delta() sets deltas[level].is_raw only after the mappings
are applied. So a raw delta is handled as a non-raw one: its md_root
is empty, ploop_md_first_entry() returns NULL and d_md->kmpage
dereferences it.

Set is_raw before applying the mappings.

Also skip applying the mappings of empty delta (e.g. raw delta of zero
size): with nr_be == 0 the BAT iterators never reach the last entry
(nr_be - 1 wraps around), so all the clusters would be mapped to the
delta.

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

Signed-off-by: Alexander Ivanov <alexander.ivanov at virtuozzo.com>
---
 drivers/md/dm-ploop-bat.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm-ploop-bat.c b/drivers/md/dm-ploop-bat.c
index a7849de8aaa6..2cb06193eaf9 100644
--- a/drivers/md/dm-ploop-bat.c
+++ b/drivers/md/dm-ploop-bat.c
@@ -501,7 +501,10 @@ 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;
 
-	ploop_apply_delta_mappings(ploop, deltas, level, &md_root, nr_be);
+	deltas[level].is_raw = is_raw;
+	/* Empty delta has no mappings, and BAT iterators can't handle it */
+	if (nr_be)
+		ploop_apply_delta_mappings(ploop, deltas, level, &md_root, nr_be);
 
 	deltas[level].file = file;
 	deltas[level].mtfile = kcalloc(ploop->nkt_runners, sizeof(*file),
@@ -521,7 +524,6 @@ int ploop_add_delta(struct ploop *ploop, u32 level, struct file *file, bool is_r
 	deltas[level].file_size = file_size;
 	deltas[level].file_preallocated_area_start = file_size;
 	deltas[level].nr_be = nr_be;
-	deltas[level].is_raw = is_raw;
 	ret = 0;
 out:
 	ploop_free_md_pages_tree(&md_root);
-- 
2.53.0