From mboxrd@z Thu Jan 1 00:00:00 1970 From: Theodore Ts'o Subject: [PATCH -v2] jbd2: don't call get_bh() before calling __jbd2_journal_remove_checkpoint() Date: Wed, 3 Sep 2014 14:38:34 -0400 Message-ID: <1409769514-17501-1-git-send-email-tytso@mit.edu> References: <20140903160837.GC17066@quack.suse.cz> Cc: Theodore Ts'o To: Ext4 Developers List Return-path: Received: from imap.thunk.org ([74.207.234.97]:35643 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752453AbaICSil (ORCPT ); Wed, 3 Sep 2014 14:38:41 -0400 In-Reply-To: <20140903160837.GC17066@quack.suse.cz> Sender: linux-ext4-owner@vger.kernel.org List-ID: 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 Reviewed-by: Jan Kara Signed-off-by: Theodore Ts'o --- fs/jbd2/checkpoint.c | 19 +++++-------------- 1 file changed, 5 insertions(+), 14 deletions(-) diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c index 18c7a8d..90d6091 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); -- 2.1.0