From 4407c2b6b297339e296facf62e020cf66e55053d Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Tue, 6 Sep 2005 15:19:17 -0700 Subject: [PATCH] [PATCH] Fix race in do_get_write_access() attached patch should fix the following race: Proc 1 Proc 2 __flush_batch() ll_rw_block() do_get_write_access() lock_buffer jh is only waiting for checkpoint -> b_transaction == NULL -> do nothing unlock_buffer test_set_buffer_locked() test_clear_buffer_dirty() __journal_file_buffer() change the data submit_bh() and we have sent wrong data to disk... We now clean the dirty buffer flag under buffer lock in all cases and hence we know that whenever a buffer is starting to be journaled we either finish the pending write-out before attaching a buffer to a transaction or we won't write the buffer until the transaction is going to be committed. The test in jbd_unexpected_dirty_buffer() is redundant - remove it. Furthermore we have to clear the buffer dirty bit under the buffer lock to prevent races with buffer write-out (and hence prevent returning a buffer with IO happening). Signed-off-by: Jan Kara Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/jbd/transaction.c | 39 +++++++++++++++++++++------------------ 1 file changed, 21 insertions(+), 18 deletions(-) diff --git a/fs/jbd/transaction.c b/fs/jbd/transaction.c index 77b7662b840b..c6ec66fd8766 100644 --- a/fs/jbd/transaction.c +++ b/fs/jbd/transaction.c @@ -490,23 +490,21 @@ void journal_unlock_updates (journal_t *journal) */ static void jbd_unexpected_dirty_buffer(struct journal_head *jh) { - struct buffer_head *bh = jh2bh(jh); int jlist; - if (buffer_dirty(bh)) { - /* If this buffer is one which might reasonably be dirty - * --- ie. data, or not part of this journal --- then - * we're OK to leave it alone, but otherwise we need to - * move the dirty bit to the journal's own internal - * JBDDirty bit. */ - jlist = jh->b_jlist; - - if (jlist == BJ_Metadata || jlist == BJ_Reserved || - jlist == BJ_Shadow || jlist == BJ_Forget) { - if (test_clear_buffer_dirty(jh2bh(jh))) { - set_bit(BH_JBDDirty, &jh2bh(jh)->b_state); - } - } + /* If this buffer is one which might reasonably be dirty + * --- ie. data, or not part of this journal --- then + * we're OK to leave it alone, but otherwise we need to + * move the dirty bit to the journal's own internal + * JBDDirty bit. */ + jlist = jh->b_jlist; + + if (jlist == BJ_Metadata || jlist == BJ_Reserved || + jlist == BJ_Shadow || jlist == BJ_Forget) { + struct buffer_head *bh = jh2bh(jh); + + if (test_clear_buffer_dirty(bh)) + set_buffer_jbddirty(bh); } } @@ -574,9 +572,14 @@ repeat: if (jh->b_next_transaction) J_ASSERT_JH(jh, jh->b_next_transaction == transaction); - JBUFFER_TRACE(jh, "Unexpected dirty buffer"); - jbd_unexpected_dirty_buffer(jh); - } + } + /* + * In any case we need to clean the dirty flag and we must + * do it under the buffer lock to be sure we don't race + * with running write-out. + */ + JBUFFER_TRACE(jh, "Unexpected dirty buffer"); + jbd_unexpected_dirty_buffer(jh); } unlock_buffer(bh); -- 2.30.2