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>

3 files changed, 21 insertions, 13 deletions

diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c
index 9497718fe920..adc08ec875ed 100644
--- a/fs/jbd2/checkpoint.c
+++ b/fs/jbd2/checkpoint.c
@@ -249,16 +249,14 @@ restart:
         return ret;
 }
 
-#define NR_BATCH        64
-
 static void
-__flush_batch(journal_t *journal, struct buffer_head **bhs, int *batch_count)
+__flush_batch(journal_t *journal, int *batch_count)
 {
         int i;
 
-        ll_rw_block(SWRITE, *batch_count, bhs);
+        ll_rw_block(SWRITE, *batch_count, journal->j_chkpt_bhs);
         for (i = 0; i < *batch_count; i++) {
-                struct buffer_head *bh = bhs[i];
+                struct buffer_head *bh = journal->j_chkpt_bhs[i];
                 clear_buffer_jwrite(bh);
                 BUFFER_TRACE(bh, "brelse");
                 __brelse(bh);
@@ -277,8 +275,7 @@ __flush_batch(journal_t *journal, struct buffer_head **bhs, int *batch_count)
  * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
  */
 static int __process_buffer(journal_t *journal, struct journal_head *jh,
-                        struct buffer_head **bhs, int *batch_count,
-                        transaction_t *transaction)
+                            int *batch_count, transaction_t *transaction)
 {
         struct buffer_head *bh = jh2bh(jh);
         int ret = 0;
@@ -325,14 +322,14 @@ static int __process_buffer(journal_t *journal, struct journal_head *jh,
                 get_bh(bh);
                 J_ASSERT_BH(bh, !buffer_jwrite(bh));
                 set_buffer_jwrite(bh);
-                bhs[*batch_count] = bh;
+                journal->j_chkpt_bhs[*batch_count] = bh;
                 __buffer_relink_io(jh);
                 jbd_unlock_bh_state(bh);
                 transaction->t_chp_stats.cs_written++;
                 (*batch_count)++;
-                if (*batch_count == NR_BATCH) {
+                if (*batch_count == JBD2_NR_BATCH) {
                         spin_unlock(&journal->j_list_lock);
-                        __flush_batch(journal, bhs, batch_count);
+                        __flush_batch(journal, batch_count);
                         ret = 1;
                 }
         }
@@ -388,7 +385,6 @@ restart:
         if (journal->j_checkpoint_transactions == transaction &&
                         transaction->t_tid == this_tid) {
                 int batch_count = 0;
-                struct buffer_head *bhs[NR_BATCH];
                 struct journal_head *jh;
                 int retry = 0, err;
 
@@ -402,7 +398,7 @@ restart:
                                 retry = 1;
                                 break;
                         }
-                        retry = __process_buffer(journal, jh, bhs, &batch_count,
+                        retry = __process_buffer(journal, jh, &batch_count,
                                                  transaction);
                         if (retry < 0 && !result)
                                 result = retry;
@@ -419,7 +415,7 @@ restart:
                                 spin_unlock(&journal->j_list_lock);
                                 retry = 1;
                         }
-                        __flush_batch(journal, bhs, &batch_count);
+                        __flush_batch(journal, &batch_count);
                 }
 
                 if (retry) {
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index fd1d7557a098..34ef98057202 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -1477,7 +1477,9 @@ int jbd2_journal_destroy(journal_t *journal)
         spin_lock(&journal->j_list_lock);
         while (journal->j_checkpoint_transactions != NULL) {
                 spin_unlock(&journal->j_list_lock);
+                mutex_lock(&journal->j_checkpoint_mutex);
                 jbd2_log_do_checkpoint(journal);
+                mutex_unlock(&journal->j_checkpoint_mutex);
                 spin_lock(&journal->j_list_lock);
         }
 
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]
          */