[RFC PATCH v2] dm ioctl: fix erroneous EINVAL when signaled

[Khazhismel Kumykov <khazhy@chromium.org>]

do_resume when loading a new map first calls dm_suspend, which could
silently fail. When we proceeded to dm_swap_table, we would bail out
with EINVAL. Instead, attempt to restore new_map and return ERESTARTSYS
when signaled.

Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
---
 drivers/md/dm-ioctl.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

v2: don't leak new_map if we can't assign it back to hc.

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index c2c07bfa6471..0591455ad63c 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1181,8 +1181,27 @@ static int do_resume(struct dm_ioctl *param)
 			suspend_flags &= ~DM_SUSPEND_LOCKFS_FLAG;
 		if (param->flags & DM_NOFLUSH_FLAG)
 			suspend_flags |= DM_SUSPEND_NOFLUSH_FLAG;
-		if (!dm_suspended_md(md))
-			dm_suspend(md, suspend_flags);
+		if (!dm_suspended_md(md)) {
+			r = dm_suspend(md, suspend_flags);
+			if (r == -EINTR)
+				r = -ERESTARTSYS;
+			if (r) {
+				down_write(&_hash_lock);
+				hc = dm_get_mdptr(md);
+				if (!hc)
+					r = -ENXIO;
+				if (hc && !hc->new_map) {
+					hc->new_map = new_map;
+					up_write(&_hash_lock);
+				} else {
+					up_write(&_hash_lock);
+					dm_sync_table(md);
+					dm_table_destroy(new_map);
+				}
+				dm_put(md);
+				return r;
+			}
+		}
 
 		old_size = dm_get_size(md);
 		old_map = dm_swap_table(md, new_map);
-- 
2.45.2.993.g49e7a77208-goog