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, 13 insertions, 7 deletions

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 2447bd86f801..9e4686900f18 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -94,6 +94,7 @@ EXPORT_SYMBOL(jbd2_journal_file_inode);
 EXPORT_SYMBOL(jbd2_journal_init_jbd_inode);
 EXPORT_SYMBOL(jbd2_journal_release_jbd_inode);
 EXPORT_SYMBOL(jbd2_journal_begin_ordered_truncate);
+EXPORT_SYMBOL(jbd2_inode_cache);
 
 static int journal_convert_superblock_v1(journal_t *, journal_superblock_t *);
 static void __journal_abort_soft (journal_t *journal, int errno);
@@ -2286,17 +2287,19 @@ static void __exit jbd2_remove_jbd_stats_proc_entry(void)
 
 #endif
 
-struct kmem_cache *jbd2_handle_cache;
+struct kmem_cache *jbd2_handle_cache, *jbd2_inode_cache;
 
 static int __init journal_init_handle_cache(void)
 {
-        jbd2_handle_cache = kmem_cache_create("jbd2_journal_handle",
-                                sizeof(handle_t),
-                                0,              /* offset */
-                                SLAB_TEMPORARY, /* flags */
-                                NULL);          /* ctor */
+        jbd2_handle_cache = KMEM_CACHE(jbd2_journal_handle, SLAB_TEMPORARY);
         if (jbd2_handle_cache == NULL) {
-                printk(KERN_EMERG "JBD: failed to create handle cache\n");
+                printk(KERN_EMERG "JBD2: failed to create handle cache\n");
+                return -ENOMEM;
+        }
+        jbd2_inode_cache = KMEM_CACHE(jbd2_inode, 0);
+        if (jbd2_inode_cache == NULL) {
+                printk(KERN_EMERG "JBD2: failed to create inode cache\n");
+                kmem_cache_destroy(jbd2_handle_cache);
                 return -ENOMEM;
         }
         return 0;
@@ -2306,6 +2309,9 @@ static void jbd2_journal_destroy_handle_cache(void)
 {
         if (jbd2_handle_cache)
                 kmem_cache_destroy(jbd2_handle_cache);
+        if (jbd2_inode_cache)
+                kmem_cache_destroy(jbd2_inode_cache);
+
 }
 
 /*