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>

1 files changed, 5 insertions, 14 deletions

diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c
index 18c7a8d3da13..90d6091d7e18 100644
--- 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);