From a96295965b600f2dc6ad661c4803c86e87db3d7b Mon Sep 17 00:00:00 2001 From: Filipe Manana Date: Mon, 18 May 2015 19:11:40 +0100 Subject: [PATCH] Btrfs: fix racy system chunk allocation when setting block group ro If while setting a block group read-only we end up allocating a system chunk, through check_system_chunk(), we were not doing it while holding the chunk mutex which is a problem if a concurrent chunk allocation is happening, through do_chunk_alloc(), as it means both block groups can end up using the same logical addresses and physical regions in the device(s). So make sure we hold the chunk mutex. Cc: stable@vger.kernel.org # 4.0+ Fixes: 2f0810880f08 ("btrfs: delete chunk allocation attemp when setting block group ro") Signed-off-by: Filipe Manana Signed-off-by: Chris Mason --- fs/btrfs/extent-tree.c | 2 ++ fs/btrfs/volumes.c | 1 + 2 files changed, 3 insertions(+) diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 7effed6f2fa6..45e3f086790b 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -8842,7 +8842,9 @@ again: out: if (cache->flags & BTRFS_BLOCK_GROUP_SYSTEM) { alloc_flags = update_block_group_flags(root, cache->flags); + lock_chunks(root->fs_info->chunk_root); check_system_chunk(trans, root, alloc_flags); + unlock_chunks(root->fs_info->chunk_root); } mutex_unlock(&root->fs_info->ro_block_group_mutex); diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 96aebf3bcd5b..174f5e1e00ab 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -4625,6 +4625,7 @@ int btrfs_alloc_chunk(struct btrfs_trans_handle *trans, { u64 chunk_offset; + ASSERT(mutex_is_locked(&extent_root->fs_info->chunk_mutex)); chunk_offset = find_next_chunk(extent_root->fs_info); return __btrfs_alloc_chunk(trans, extent_root, chunk_offset, type); } -- 2.20.1