From: Filipe Manana fdmanana@suse.com
commit 6d3d970b2735b967650d319be27268fedc5598d1 upstream.
When logging a directory, at log_dir_items(), if we get an error when attempting to search the subvolume tree for a dir index item, we end up returning 0 (success) from log_dir_items() because 'err' is left with a value of 0.
This can lead to a few problems, specially in the case the variable 'last_offset' has a value of (u64)-1 (and it's initialized to that when it was declared):
1) By returning from log_dir_items() with success (0) and a value of (u64)-1 for '*last_offset_ret', we end up not logging any other dir index keys that follow the missing, just deleted, index key. The (u64)-1 value makes log_directory_changes() not call log_dir_items() again;
2) Before returning with success (0), log_dir_items(), will log a dir index range item covering a range from the last old dentry index (stored in the variable 'last_old_dentry_offset') to the value of 'last_offset'. If 'last_offset' has a value of (u64)-1, then it means if the log is persisted and replayed after a power failure, it will cause deletion of all the directory entries that have an index number between last_old_dentry_offset + 1 and (u64)-1;
3) We can end up returning from log_dir_items() with ctx->last_dir_item_offset having a lower value than inode->last_dir_index_offset, because the former is set to the current key we are processing at process_dir_items_leaf(), and at the end of log_directory_changes() we set inode->last_dir_index_offset to the current value of ctx->last_dir_item_offset. So if for example a deletion of a lower dir index key happened, we set ctx->last_dir_item_offset to that index value, then if we return from log_dir_items() because btrfs_search_slot() returned an error, we end up returning without any error from log_dir_items() and then log_directory_changes() sets inode->last_dir_index_offset to a lower value than it had before. This can result in unpredictable and unexpected behaviour when we need to log again the directory in the same transaction, and can result in ending up with a log tree leaf that has duplicated keys, as we do batch insertions of dir index keys into a log tree.
Fix this by setting 'err' to the value of 'ret' in case btrfs_search_slot() or btrfs_previous_item() returned an error. That will result in falling back to a full transaction commit.
Reported-by: David Arendt admin@prnet.org Link: https://lore.kernel.org/linux-btrfs/ae169fc6-f504-28f0-a098-6fa6a4dfb612@lee... Fixes: e02119d5a7b4 ("Btrfs: Add a write ahead tree log to optimize synchronous operations") CC: stable@vger.kernel.org # 4.14+ Reviewed-by: Josef Bacik josef@toxicpanda.com Signed-off-by: Filipe Manana fdmanana@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/tree-log.c | 9 +++++++++ 1 file changed, 9 insertions(+)
--- a/fs/btrfs/tree-log.c +++ b/fs/btrfs/tree-log.c @@ -3857,7 +3857,10 @@ static noinline int log_dir_items(struct path->slots[0]); if (tmp.type == BTRFS_DIR_INDEX_KEY) last_old_dentry_offset = tmp.offset; + } else if (ret < 0) { + err = ret; } + goto done; }
@@ -3877,7 +3880,11 @@ static noinline int log_dir_items(struct */ if (tmp.type == BTRFS_DIR_INDEX_KEY) last_old_dentry_offset = tmp.offset; + } else if (ret < 0) { + err = ret; + goto done; } + btrfs_release_path(path);
/* @@ -3890,6 +3897,8 @@ static noinline int log_dir_items(struct */ search: ret = btrfs_search_slot(NULL, root, &min_key, path, 0, 0); + if (ret < 0) + err = ret; if (ret != 0) goto done;