[PATCH 4.4 017/163] dm cache metadata: fix READ_LOCK macros and cleanup WRITE_LOCK macros

Greg Kroah-Hartman
2016-05-03T01:51:52Z

From: Mike Snitzer <snitzer@redhat.com>

commit 9567366fefddeaea4ed1d713270535d93a3b3c76 upstream.

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")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/md/dm-cache-metadata.c | 64 +++++++++++++++++++++++++----------------
1 file changed, 40 insertions(+), 24 deletions(-)

--- 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(
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)
{