jbd2: don't call get_bh() before calling __jbd2_journal_remove_checkpoint()

The __jbd2_journal_remove_checkpoint() doesn't require an elevated
b_count; indeed, until the jh structure gets released by the call to
jbd2_journal_put_journal_head(), the bh's b_count is elevated by
virtue of the existence of the jh structure.

Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c
index 18c7a8d3da1390ec28bfbff4588d0f8f7058d7f3..90d6091d7e187e2b77c6776764f8df9e2ef7560b 100644 (file)
--- a/fs/jbd2/checkpoint.c
+++ b/fs/jbd2/checkpoint.c
@@ -96,15 +96,8 @@ static int __try_to_free_cp_buf(struct journal_head *jh)
 
        if (jh->b_transaction == NULL && !buffer_locked(bh) &&
            !buffer_dirty(bh) && !buffer_write_io_error(bh)) {
-               /*
-                * Get our reference so that bh cannot be freed before
-                * we unlock it
-                */
-               get_bh(bh);
                JBUFFER_TRACE(jh, "remove from checkpoint list");
                ret = __jbd2_journal_remove_checkpoint(jh) + 1;
-               BUFFER_TRACE(bh, "release");
-               __brelse(bh);
        }
        return ret;
 }
@@ -216,7 +209,7 @@ int jbd2_log_do_checkpoint(journal_t *journal)
        struct buffer_head      *bh;
        transaction_t           *transaction;
        tid_t                   this_tid;
-       int                     result, batch_count = 0, done = 0;
+       int                     result, batch_count = 0;
 
        jbd_debug(1, "Start checkpoint\n");
 
@@ -291,11 +284,9 @@ restart:
                if (!buffer_dirty(bh)) {
                        if (unlikely(buffer_write_io_error(bh)) && !result)
                                result = -EIO;
-                       get_bh(bh);
                        BUFFER_TRACE(bh, "remove from checkpoint");
                        __jbd2_journal_remove_checkpoint(jh);
                        spin_unlock(&journal->j_list_lock);
-                       __brelse(bh);
                        goto retry;
                }
                /*
@@ -338,12 +329,12 @@ restart2:
            transaction->t_tid != this_tid)
                goto out;
 
-       while (!done && transaction->t_checkpoint_io_list) {
+       while (transaction->t_checkpoint_io_list) {
                jh = transaction->t_checkpoint_io_list;
                bh = jh2bh(jh);
-               get_bh(bh);
                if (buffer_locked(bh)) {
                        spin_unlock(&journal->j_list_lock);
+                       get_bh(bh);
                        wait_on_buffer(bh);
                        /* the journal_head may have gone by now */
                        BUFFER_TRACE(bh, "brelse");
@@ -359,8 +350,8 @@ restart2:
                 * know that it has been written out and so we can
                 * drop it from the list
                 */
-               done = __jbd2_journal_remove_checkpoint(jh);
-               __brelse(bh);
+               if (__jbd2_journal_remove_checkpoint(jh))
+                       break;
        }
 out:
        spin_unlock(&journal->j_list_lock);