linux-kernel - [PATCH 3.16 083/366] Btrfs: fix copy_items() return value when logging an inode

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Message-ID: <lsq.1539530741.195468558@decadent.org.uk>
Date:   Sun, 14 Oct 2018 16:25:41 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "David Sterba" <dsterba@...e.com>,
        "Filipe Manana" <fdmanana@...e.com>
Subject: [PATCH 3.16 083/366] Btrfs: fix copy_items() return value when
 logging an inode

3.16.60-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Filipe Manana <fdmanana@...e.com>

commit 8434ec46c6e3232cebc25a910363b29f5c617820 upstream.

When logging an inode, at tree-log.c:copy_items(), if we call
btrfs_next_leaf() at the loop which checks for the need to log holes, we
need to make sure copy_items() returns the value 1 to its caller and
not 0 (on success). This is because the path the caller passed was
released and is now different from what is was before, and the caller
expects a return value of 0 to mean both success and that the path
has not changed, while a return value of 1 means both success and
signals the caller that it can not reuse the path, it has to perform
another tree search.

Even though this is a case that should not be triggered on normal
circumstances or very rare at least, its consequences can be very
unpredictable (especially when replaying a log tree).

Fixes: 16e7549f045d ("Btrfs: incompatible format change to remove hole extents")
Signed-off-by: Filipe Manana <fdmanana@...e.com>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/btrfs/tree-log.c | 1 +
 1 file changed, 1 insertion(+)

--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -3524,6 +3524,7 @@ fill_holes:
 			ASSERT(ret == 0);
 			src = src_path->nodes[0];
 			i = 0;
+			need_find_last_extent = true;
 		}

 		btrfs_item_key_to_cpu(src, &key, i);