jbd2: Remove a large array of bh's from the stack of the checkpoint routine
Theodore Ts'o [Wed, 5 Nov 2008 05:09:22 +0000 (00:09 -0500)]
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>

fs/jbd2/checkpoint.c
fs/jbd2/journal.c
include/linux/jbd2.h

index 9497718..adc08ec 100644 (file)
@@ -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) {
index fd1d755..34ef980 100644 (file)
@@ -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);
        }
 
index a3cd647..004c9a8 100644 (file)
@@ -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]
         */