This is a note to let you know that I've just added the patch titled
Btrfs: catch invalid free space trees
to the 4.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
btrfs-catch-invalid-free-space-trees.patch
and it can be found in the queue-4.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 6675df311db87aa2107a04ef97e19420953cbace Mon Sep 17 00:00:00 2001
From: Omar Sandoval <osandov@xxxxxx>
Date: Thu, 22 Sep 2016 17:24:22 -0700
Subject: Btrfs: catch invalid free space trees
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From: Omar Sandoval <osandov@xxxxxx>
commit 6675df311db87aa2107a04ef97e19420953cbace upstream.
There are two separate issues that can lead to corrupted free space
trees.
1. The free space tree bitmaps had an endianness issue on big-endian
systems which is fixed by an earlier patch in this series.
2. btrfs-progs before v4.7.3 modified filesystems without updating the
free space tree.
To catch both of these issues at once, we need to force the free space
tree to be rebuilt. To do so, add a FREE_SPACE_TREE_VALID compat_ro bit.
If the bit isn't set, we know that it was either produced by a broken
big-endian kernel or may have been corrupted by btrfs-progs.
This also provides us with a way to add rudimentary read-write support
for the free space tree to btrfs-progs: it can just clear this bit and
have the kernel rebuild the free space tree.
Tested-by: Holger Hoffstätte <holger@xxxxxxxxxxxxxxxxxxxxxx>
Tested-by: Chandan Rajendra <chandan@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Omar Sandoval <osandov@xxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/btrfs/ctree.h | 3 ++-
fs/btrfs/disk-io.c | 9 +++++++++
fs/btrfs/free-space-tree.c | 2 ++
include/uapi/linux/btrfs.h | 12 +++++++++++-
4 files changed, 24 insertions(+), 2 deletions(-)
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -251,7 +251,8 @@ struct btrfs_super_block {
#define BTRFS_FEATURE_COMPAT_SAFE_CLEAR 0ULL
#define BTRFS_FEATURE_COMPAT_RO_SUPP \
- (BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE)
+ (BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE | \
+ BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE_VALID)
#define BTRFS_FEATURE_COMPAT_RO_SAFE_SET 0ULL
#define BTRFS_FEATURE_COMPAT_RO_SAFE_CLEAR 0ULL
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2566,6 +2566,7 @@ int open_ctree(struct super_block *sb,
int num_backups_tried = 0;
int backup_index = 0;
int max_active;
+ int clear_free_space_tree = 0;
tree_root = fs_info->tree_root = btrfs_alloc_root(fs_info, GFP_KERNEL);
chunk_root = fs_info->chunk_root = btrfs_alloc_root(fs_info, GFP_KERNEL);
@@ -3131,6 +3132,14 @@ retry_root_backup:
if (btrfs_test_opt(fs_info, CLEAR_CACHE) &&
btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE)) {
+ clear_free_space_tree = 1;
+ } else if (btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE) &&
+ !btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE_VALID)) {
+ btrfs_warn(fs_info, "free space tree is invalid");
+ clear_free_space_tree = 1;
+ }
+
+ if (clear_free_space_tree) {
btrfs_info(fs_info, "clearing free space tree");
ret = btrfs_clear_free_space_tree(fs_info);
if (ret) {
--- a/fs/btrfs/free-space-tree.c
+++ b/fs/btrfs/free-space-tree.c
@@ -1182,6 +1182,7 @@ int btrfs_create_free_space_tree(struct
}
btrfs_set_fs_compat_ro(fs_info, FREE_SPACE_TREE);
+ btrfs_set_fs_compat_ro(fs_info, FREE_SPACE_TREE_VALID);
fs_info->creating_free_space_tree = 0;
ret = btrfs_commit_transaction(trans, tree_root);
@@ -1250,6 +1251,7 @@ int btrfs_clear_free_space_tree(struct b
return PTR_ERR(trans);
btrfs_clear_fs_compat_ro(fs_info, FREE_SPACE_TREE);
+ btrfs_clear_fs_compat_ro(fs_info, FREE_SPACE_TREE_VALID);
fs_info->free_space_root = NULL;
ret = clear_free_space_tree(trans, free_space_root);
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -239,7 +239,17 @@ struct btrfs_ioctl_fs_info_args {
* Used by:
* struct btrfs_ioctl_feature_flags
*/
-#define BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE (1ULL << 0)
+#define BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE (1ULL << 0)
+/*
+ * Older kernels (< 4.9) on big-endian systems produced broken free space tree
+ * bitmaps, and btrfs-progs also used to corrupt the free space tree (versions
+ * < 4.7.3). If this bit is clear, then the free space tree cannot be trusted.
+ * btrfs-progs can also intentionally clear this bit to ask the kernel to
+ * rebuild the free space tree, however this might not work on older kernels
+ * that do not know about this bit. If not sure, clear the cache manually on
+ * first mount when booting older kernel versions.
+ */
+#define BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE_VALID (1ULL << 1)
#define BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF (1ULL << 0)
#define BTRFS_FEATURE_INCOMPAT_DEFAULT_SUBVOL (1ULL << 1)
Patches currently in stable-queue which might be from osandov@xxxxxx are
queue-4.8/btrfs-fix-free-space-tree-bitmaps-on-big-endian-systems.patch
queue-4.8/btrfs-catch-invalid-free-space-trees.patch
queue-4.8/btrfs-fix-mount-o-clear_cache-space_cache-v2.patch
--
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