ext4: dynamically allocate the jbd2_inode in ext4_inode_info as necessary

Replace the jbd2_inode structure (which is 48 bytes) with a pointer
and only allocate the jbd2_inode when it is needed --- that is, when
the file system has a journal present and the inode has been opened
for writing.  This allows us to further slim down the ext4_inode_info
structure.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 18 insertions, 2 deletions

diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 2ae86aa21fce..27e79c27ba08 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -94,7 +94,7 @@ extern void jbd2_free(void *ptr, size_t size);
  *
  * This is an opaque datatype.
  **/
-typedef struct handle_s         handle_t;       /* Atomic operation type */
+typedef struct jbd2_journal_handle handle_t;    /* Atomic operation type */
 
 
 /**
@@ -416,7 +416,7 @@ struct jbd2_revoke_table_s;
  * in so it can be fixed later.
  */
 
-struct handle_s
+struct jbd2_journal_handle
 {
         /* Which compound transaction is this update a part of? */
         transaction_t           *h_transaction;
@@ -1158,6 +1158,22 @@ static inline void jbd2_free_handle(handle_t *handle)
         kmem_cache_free(jbd2_handle_cache, handle);
 }
 
+/*
+ * jbd2_inode management (optional, for those file systems that want to use
+ * dynamically allocated jbd2_inode structures)
+ */
+extern struct kmem_cache *jbd2_inode_cache;
+
+static inline struct jbd2_inode *jbd2_alloc_inode(gfp_t gfp_flags)
+{
+        return kmem_cache_alloc(jbd2_inode_cache, gfp_flags);
+}
+
+static inline void jbd2_free_inode(struct jbd2_inode *jinode)
+{
+        kmem_cache_free(jbd2_inode_cache, jinode);
+}
+
 /* Primary revoke support */
 #define JOURNAL_REVOKE_DEFAULT_HASH 256
 extern int         jbd2_journal_init_revoke(journal_t *, int);