jbd: Delay discarding buffers in journal_unmap_buffer

Delay discarding buffers in journal_unmap_buffer until
we know that "add to orphan" operation has definitely been
committed, otherwise the log space of committing transation
may be freed and reused before truncate get committed, updates
may get lost if crash happens.

This patch is a backport of JBD2 fix by dingdinghua <dingdinghua@nrchpc.ac.cn>.

Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 5 insertions, 5 deletions

diff --git a/fs/jbd/commit.c b/fs/jbd/commit.c
index 4bd8825..2c90e3e 100644
--- a/fs/jbd/commit.c
+++ b/fs/jbd/commit.c
@@ -862,12 +862,12 @@ restart_loop:
 		/* A buffer which has been freed while still being
 		 * journaled by a previous transaction may end up still
 		 * being dirty here, but we want to avoid writing back
-		 * that buffer in the future now that the last use has
-		 * been committed.  That's not only a performance gain,
-		 * it also stops aliasing problems if the buffer is left
-		 * behind for writeback and gets reallocated for another
+		 * that buffer in the future after the "add to orphan"
+		 * operation been committed,  That's not only a performance
+		 * gain, it also stops aliasing problems if the buffer is
+		 * left behind for writeback and gets reallocated for another
 		 * use in a different page. */
-		if (buffer_freed(bh)) {
+		if (buffer_freed(bh) && !jh->b_next_transaction) {
 			clear_buffer_freed(bh);
 			clear_buffer_jbddirty(bh);
 		}