Btrfs: fix deadlock during allocating chunks
This deadlock comes from xfstests 251.
We'll hold the chunk_mutex throughout the whole of a chunk allocation.
But if we find that we've used up system chunk space, we need to allocate a
new system chunk, but this will lead to a recursion of chunk allocation and end
up with a deadlock on chunk_mutex.
So instead we need to allocate the system chunk first if we find we're in ENOSPC.
Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 7c23340..a844204 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3445,6 +3445,50 @@
return 1;
}
+static u64 get_system_chunk_thresh(struct btrfs_root *root, u64 type)
+{
+ u64 num_dev;
+
+ if (type & BTRFS_BLOCK_GROUP_RAID10 ||
+ type & BTRFS_BLOCK_GROUP_RAID0)
+ num_dev = root->fs_info->fs_devices->rw_devices;
+ else if (type & BTRFS_BLOCK_GROUP_RAID1)
+ num_dev = 2;
+ else
+ num_dev = 1; /* DUP or single */
+
+ /* metadata for updaing devices and chunk tree */
+ return btrfs_calc_trans_metadata_size(root, num_dev + 1);
+}
+
+static void check_system_chunk(struct btrfs_trans_handle *trans,
+ struct btrfs_root *root, u64 type)
+{
+ struct btrfs_space_info *info;
+ u64 left;
+ u64 thresh;
+
+ info = __find_space_info(root->fs_info, BTRFS_BLOCK_GROUP_SYSTEM);
+ spin_lock(&info->lock);
+ left = info->total_bytes - info->bytes_used - info->bytes_pinned -
+ info->bytes_reserved - info->bytes_readonly;
+ spin_unlock(&info->lock);
+
+ thresh = get_system_chunk_thresh(root, type);
+ if (left < thresh && btrfs_test_opt(root, ENOSPC_DEBUG)) {
+ printk(KERN_INFO "left=%llu, need=%llu, flags=%llu\n",
+ left, thresh, type);
+ dump_space_info(info, 0, 0);
+ }
+
+ if (left < thresh) {
+ u64 flags;
+
+ flags = btrfs_get_alloc_profile(root->fs_info->chunk_root, 0);
+ btrfs_alloc_chunk(trans, root, flags);
+ }
+}
+
static int do_chunk_alloc(struct btrfs_trans_handle *trans,
struct btrfs_root *extent_root, u64 alloc_bytes,
u64 flags, int force)
@@ -3515,6 +3559,12 @@
force_metadata_allocation(fs_info);
}
+ /*
+ * Check if we have enough space in SYSTEM chunk because we may need
+ * to update devices.
+ */
+ check_system_chunk(trans, extent_root, flags);
+
ret = btrfs_alloc_chunk(trans, extent_root, flags);
if (ret < 0 && ret != -ENOSPC)
goto out;
