Merge tag 'v4.20-rc5' into irq/core, to pick up fixes

Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 24 insertions, 0 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index a3c22e16509b..58e93bce3036 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -2089,6 +2089,30 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
 	atomic_inc(&root->log_batch);
 
 	/*
+	 * Before we acquired the inode's lock, someone may have dirtied more
+	 * pages in the target range. We need to make sure that writeback for
+	 * any such pages does not start while we are logging the inode, because
+	 * if it does, any of the following might happen when we are not doing a
+	 * full inode sync:
+	 *
+	 * 1) We log an extent after its writeback finishes but before its
+	 *    checksums are added to the csum tree, leading to -EIO errors
+	 *    when attempting to read the extent after a log replay.
+	 *
+	 * 2) We can end up logging an extent before its writeback finishes.
+	 *    Therefore after the log replay we will have a file extent item
+	 *    pointing to an unwritten extent (and no data checksums as well).
+	 *
+	 * So trigger writeback for any eventual new dirty pages and then we
+	 * wait for all ordered extents to complete below.
+	 */
+	ret = start_ordered_ops(inode, start, end);
+	if (ret) {
+		inode_unlock(inode);
+		goto out;
+	}
+
+	/*
 	 * We have to do this here to avoid the priority inversion of waiting on
 	 * IO of a lower priority task while holding a transaciton open.
 	 */