[LogFS] Prevent mempool_destroy NULL pointer dereference

It would probably be better to just accept NULL pointers in
mempool_destroy().  But for the current -rc series let's keep things
simple.

This patch was lost in the cracks for a while.
Kevin Cernekee <cernekee@gmail.com> had to rediscover the problem and
send a similar patch because of it. :(

Signed-off-by: Joern Engel <joern@logfs.org>

4 files changed, 11 insertions, 7 deletions

diff --git a/fs/logfs/logfs.h b/fs/logfs/logfs.h
index c9929eed80b1..0a3df1a0c936 100644
--- a/fs/logfs/logfs.h
+++ b/fs/logfs/logfs.h
@@ -727,4 +727,10 @@ static inline struct logfs_area *get_area(struct super_block *sb,
         return logfs_super(sb)->s_area[(__force u8)gc_level];
 }
 
+static inline void logfs_mempool_destroy(mempool_t *pool)
+{
+        if (pool)
+                mempool_destroy(pool);
+}
+
 #endif
diff --git a/fs/logfs/readwrite.c b/fs/logfs/readwrite.c
index 7e0c39c49719..aca6c56a107a 100644
--- a/fs/logfs/readwrite.c
+++ b/fs/logfs/readwrite.c
@@ -2243,8 +2243,6 @@ void logfs_cleanup_rw(struct super_block *sb)
         struct logfs_super *super = logfs_super(sb);
 
         destroy_meta_inode(super->s_segfile_inode);
-        if (super->s_block_pool)
-                mempool_destroy(super->s_block_pool);
-        if (super->s_shadow_pool)
-                mempool_destroy(super->s_shadow_pool);
+        logfs_mempool_destroy(super->s_block_pool);
+        logfs_mempool_destroy(super->s_shadow_pool);
 }
diff --git a/fs/logfs/segment.c b/fs/logfs/segment.c
index 02db22ebbf13..8c82fe05d3e1 100644
--- a/fs/logfs/segment.c
+++ b/fs/logfs/segment.c
@@ -912,7 +912,7 @@ err:
         for (i--; i >= 0; i--)
                 free_area(super->s_area[i]);
         free_area(super->s_journal_area);
-        mempool_destroy(super->s_alias_pool);
+        logfs_mempool_destroy(super->s_alias_pool);
         return -ENOMEM;
 }
 
diff --git a/fs/logfs/super.c b/fs/logfs/super.c
index d6e1f4fc3115..d4531eb46d0a 100644
--- a/fs/logfs/super.c
+++ b/fs/logfs/super.c
@@ -517,8 +517,8 @@ static void logfs_kill_sb(struct super_block *sb)
         if (super->s_erase_page)
                 __free_page(super->s_erase_page);
         super->s_devops->put_device(sb);
-        mempool_destroy(super->s_btree_pool);
-        mempool_destroy(super->s_alias_pool);
+        logfs_mempool_destroy(super->s_btree_pool);
+        logfs_mempool_destroy(super->s_alias_pool);
         kfree(super);
         log_super("LogFS: Finished unmounting\n");
 }