dm cache metadata: fix READ_LOCK macros and cleanup WRITE_LOCK macros

The READ_LOCK macro was incorrectly returning -EINVAL if
dm_bm_is_read_only() was true -- it will always be true once the cache
metadata transitions to read-only by dm_cache_metadata_set_read_only().

Wrap READ_LOCK and WRITE_LOCK multi-statement macros in do {} while(0).
Also, all accesses of the 'cmd' argument passed to these related macros
are now encapsulated in parenthesis.

A follow-up patch can be developed to eliminate the use of macros in
favor of pure C code.  Avoiding that now given that this needs to apply
to stable@.

Reported-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Fixes: d14fcf3dd79 ("dm cache: make sure every metadata function checks fail_io")
Cc: stable@vger.kernel.org

1 files changed, 40 insertions, 24 deletions

diff --git a/drivers/md/dm-cache-metadata.c b/drivers/md/dm-cache-metadata.c
index 27f2ef300f8b..65ce6985f87a 100644
--- a/drivers/md/dm-cache-metadata.c
+++ b/drivers/md/dm-cache-metadata.c
@@ -867,39 +867,55 @@ static int blocks_are_unmapped_or_clean(struct dm_cache_metadata *cmd,
         return 0;
 }
 
-#define WRITE_LOCK(cmd) \
-        down_write(&cmd->root_lock); \
-        if (cmd->fail_io || dm_bm_is_read_only(cmd->bm)) { \
-                up_write(&cmd->root_lock); \
-                return -EINVAL; \
+static bool cmd_write_lock(struct dm_cache_metadata *cmd)
+{
+        down_write(&cmd->root_lock);
+        if (cmd->fail_io || dm_bm_is_read_only(cmd->bm)) {
+                up_write(&cmd->root_lock);
+                return false;
         }
+        return true;
+}
 
-#define WRITE_LOCK_VOID(cmd) \
-        down_write(&cmd->root_lock); \
-        if (cmd->fail_io || dm_bm_is_read_only(cmd->bm)) { \
-                up_write(&cmd->root_lock); \
-                return; \
-        }
+#define WRITE_LOCK(cmd)                         \
+        do {                                    \
+                if (!cmd_write_lock((cmd)))     \
+                        return -EINVAL;         \
+        } while(0)
+
+#define WRITE_LOCK_VOID(cmd)                    \
+        do {                                    \
+                if (!cmd_write_lock((cmd)))     \
+                        return;                 \
+        } while(0)
 
 #define WRITE_UNLOCK(cmd) \
-        up_write(&cmd->root_lock)
+        up_write(&(cmd)->root_lock)
 
-#define READ_LOCK(cmd) \
-        down_read(&cmd->root_lock); \
-        if (cmd->fail_io || dm_bm_is_read_only(cmd->bm)) { \
-                up_read(&cmd->root_lock); \
-                return -EINVAL; \
+static bool cmd_read_lock(struct dm_cache_metadata *cmd)
+{
+        down_write(&cmd->root_lock);
+        if (cmd->fail_io) {
+                up_write(&cmd->root_lock);
+                return false;
         }
+        return true;
+}
 
-#define READ_LOCK_VOID(cmd)     \
-        down_read(&cmd->root_lock); \
-        if (cmd->fail_io || dm_bm_is_read_only(cmd->bm)) { \
-                up_read(&cmd->root_lock); \
-                return; \
-        }
+#define READ_LOCK(cmd)                          \
+        do {                                    \
+                if (!cmd_read_lock((cmd)))      \
+                        return -EINVAL;         \
+        } while(0)
+
+#define READ_LOCK_VOID(cmd)                     \
+        do {                                    \
+                if (!cmd_read_lock((cmd)))      \
+                        return;                 \
+        } while(0)
 
 #define READ_UNLOCK(cmd) \
-        up_read(&cmd->root_lock)
+        up_read(&(cmd)->root_lock)
 
 int dm_cache_resize(struct dm_cache_metadata *cmd, dm_cblock_t new_cache_size)
 {