jbd2: Remove a large array of bh's from the stack of the checkpoint routine

jbd2_log_do_checkpoint()n is one of the kernel's largest stack users.
Move the array of buffer head's from the stack of jbd2_log_do_checkpoint()
to the in-core journal structure.

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

1 files changed, 10 insertions, 0 deletions

diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index a3cd647ea1bc..004c9a8d63ed 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -687,6 +687,8 @@ jbd2_time_diff(unsigned long start, unsigned long end)
         return end + (MAX_JIFFY_OFFSET - start);
 }
 
+#define JBD2_NR_BATCH   64
+
 /**
  * struct journal_s - The journal_s type is the concrete type associated with
  *     journal_t.
@@ -831,6 +833,14 @@ struct journal_s
         struct mutex            j_checkpoint_mutex;
 
         /*
+         * List of buffer heads used by the checkpoint routine.  This
+         * was moved from jbd2_log_do_checkpoint() to reduce stack
+         * usage.  Access to this array is controlled by the
+         * j_checkpoint_mutex.  [j_checkpoint_mutex]
+         */
+        struct buffer_head      *j_chkpt_bhs[JBD2_NR_BATCH];
+        
+        /*
          * Journal head: identifies the first unused block in the journal.
          * [j_state_lock]
          */