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authorFilipe Manana <fdmanana@suse.com>2014-12-02 18:07:49 +0000
committerChris Mason <clm@fb.com>2014-12-02 18:35:10 -0800
commit8dbcd10f6978ca3ccee2f43288d16b7b9da2fb2b (patch)
tree88a5485643a8487ca6e3358d65a0a6fb21fa88dc
parent495e64f4fe0363bc79fa0dfb41c271787e01b5c3 (diff)
downloadop-kernel-dev-8dbcd10f6978ca3ccee2f43288d16b7b9da2fb2b.zip
op-kernel-dev-8dbcd10f6978ca3ccee2f43288d16b7b9da2fb2b.tar.gz
Btrfs: fix unprotected deletion from pending_chunks list
On block group remove if the corresponding extent map was on the transaction->pending_chunks list, we were deleting the extent map from that list, through remove_extent_mapping(), without any synchronization with chunk allocation (which iterates that list and adds new elements to it). Fix this by ensure that this is done while the chunk mutex is held, since that's the mutex that protects the list in the chunk allocation code path. This applies on top (depends on) of my previous patch titled: "Btrfs: fix race between fs trimming and block group remove/allocation" But the issue in fact was already present before that change, it only became easier to hit after Josef's 3.18 patch that added automatic removal of empty block groups. Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: Chris Mason <clm@fb.com>
-rw-r--r--fs/btrfs/extent-tree.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index ba7042e..17b052a 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -9514,19 +9514,25 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
list_move_tail(&em->list, &root->fs_info->pinned_chunks);
}
spin_unlock(&block_group->lock);
- unlock_chunks(root);
if (remove_em) {
struct extent_map_tree *em_tree;
em_tree = &root->fs_info->mapping_tree.map_tree;
write_lock(&em_tree->lock);
+ /*
+ * The em might be in the pending_chunks list, so make sure the
+ * chunk mutex is locked, since remove_extent_mapping() will
+ * delete us from that list.
+ */
remove_extent_mapping(em_tree, em);
write_unlock(&em_tree->lock);
/* once for the tree */
free_extent_map(em);
}
+ unlock_chunks(root);
+
btrfs_put_block_group(block_group);
btrfs_put_block_group(block_group);
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