jbd2: allocate transaction from separate slab cache

There is normally only a handful of these active at any one time, but
putting them in a separate slab cache makes debugging memory
corruption problems easier.  Manish Katiyar also wanted this make it
easier to test memory failure scenarios in the jbd2 layer.

Cc: Manish Katiyar <mkatiyar@gmail.com>
Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

4 files changed, 38 insertions, 5 deletions

diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c
index 453c9068b7d7..253e91890e71 100644
--- a/fs/jbd2/checkpoint.c
+++ b/fs/jbd2/checkpoint.c
@@ -722,7 +722,7 @@ int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
                                     transaction->t_tid, stats);
 
         __jbd2_journal_drop_transaction(journal, transaction);
-        kfree(transaction);
+        jbd2_journal_free_transaction(transaction);
 
         /* Just in case anybody was waiting for more transactions to be
            checkpointed... */
diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index 5069b8475150..8adc5d460f56 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -1048,7 +1048,7 @@ restart_loop:
         jbd_debug(1, "JBD2: commit %d complete, head %d\n",
                   journal->j_commit_sequence, journal->j_tail_sequence);
         if (to_free)
-                kfree(commit_transaction);
+                jbd2_journal_free_transaction(commit_transaction);
 
         wake_up(&journal->j_wait_done_commit);
 }
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 93a595c69616..aa8f5986f8da 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -2361,6 +2361,8 @@ static int __init journal_init_caches(void)
                 ret = journal_init_jbd2_journal_head_cache();
         if (ret == 0)
                 ret = journal_init_handle_cache();
+        if (ret == 0)
+                ret = jbd2_journal_init_transaction_cache();
         return ret;
 }
 
@@ -2369,6 +2371,7 @@ static void jbd2_journal_destroy_caches(void)
         jbd2_journal_destroy_revoke_caches();
         jbd2_journal_destroy_jbd2_journal_head_cache();
         jbd2_journal_destroy_handle_cache();
+        jbd2_journal_destroy_transaction_cache();
         jbd2_journal_destroy_slabs();
 }
 
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 526533062548..d0a8b017b281 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -33,6 +33,35 @@
 static void __jbd2_journal_temp_unlink_buffer(struct journal_head *jh);
 static void __jbd2_journal_unfile_buffer(struct journal_head *jh);
 
+static struct kmem_cache *transaction_cache;
+int __init jbd2_journal_init_transaction_cache(void)
+{
+        J_ASSERT(!transaction_cache);
+        transaction_cache = kmem_cache_create("jbd2_transaction_s",
+                                        sizeof(transaction_t),
+                                        0,
+                                        SLAB_HWCACHE_ALIGN|SLAB_TEMPORARY,
+                                        NULL);
+        if (transaction_cache)
+                return 0;
+        return -ENOMEM;
+}
+
+void jbd2_journal_destroy_transaction_cache(void)
+{
+        if (transaction_cache) {
+                kmem_cache_destroy(transaction_cache);
+                transaction_cache = NULL;
+        }
+}
+
+void jbd2_journal_free_transaction(transaction_t *transaction)
+{
+        if (unlikely(ZERO_OR_NULL_PTR(transaction)))
+                return;
+        kmem_cache_free(transaction_cache, transaction);
+}
+
 /*
  * jbd2_get_transaction: obtain a new transaction_t object.
  *
@@ -133,7 +162,8 @@ static int start_this_handle(journal_t *journal, handle_t *handle,
 
 alloc_transaction:
         if (!journal->j_running_transaction) {
-                new_transaction = kzalloc(sizeof(*new_transaction), gfp_mask);
+                new_transaction = kmem_cache_alloc(transaction_cache,
+                                                   gfp_mask | __GFP_ZERO);
                 if (!new_transaction) {
                         /*
                          * If __GFP_FS is not present, then we may be
@@ -162,7 +192,7 @@ repeat:
         if (is_journal_aborted(journal) ||
             (journal->j_errno != 0 && !(journal->j_flags & JBD2_ACK_ERR))) {
                 read_unlock(&journal->j_state_lock);
-                kfree(new_transaction);
+                jbd2_journal_free_transaction(new_transaction);
                 return -EROFS;
         }
 
@@ -284,7 +314,7 @@ repeat:
         read_unlock(&journal->j_state_lock);
 
         lock_map_acquire(&handle->h_lockdep_map);
-        kfree(new_transaction);
+        jbd2_journal_free_transaction(new_transaction);
         return 0;
 }