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>
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@ -3445,6 +3445,50 @@ static int should_alloc_chunk(struct btrfs_root *root,
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return 1;
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}
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static u64 get_system_chunk_thresh(struct btrfs_root *root, u64 type)
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{
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u64 num_dev;
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if (type & BTRFS_BLOCK_GROUP_RAID10 ||
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type & BTRFS_BLOCK_GROUP_RAID0)
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num_dev = root->fs_info->fs_devices->rw_devices;
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else if (type & BTRFS_BLOCK_GROUP_RAID1)
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num_dev = 2;
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else
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num_dev = 1; /* DUP or single */
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/* metadata for updaing devices and chunk tree */
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return btrfs_calc_trans_metadata_size(root, num_dev + 1);
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}
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static void check_system_chunk(struct btrfs_trans_handle *trans,
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struct btrfs_root *root, u64 type)
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{
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struct btrfs_space_info *info;
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u64 left;
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u64 thresh;
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info = __find_space_info(root->fs_info, BTRFS_BLOCK_GROUP_SYSTEM);
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spin_lock(&info->lock);
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left = info->total_bytes - info->bytes_used - info->bytes_pinned -
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info->bytes_reserved - info->bytes_readonly;
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spin_unlock(&info->lock);
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thresh = get_system_chunk_thresh(root, type);
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if (left < thresh && btrfs_test_opt(root, ENOSPC_DEBUG)) {
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printk(KERN_INFO "left=%llu, need=%llu, flags=%llu\n",
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left, thresh, type);
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dump_space_info(info, 0, 0);
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}
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if (left < thresh) {
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u64 flags;
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flags = btrfs_get_alloc_profile(root->fs_info->chunk_root, 0);
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btrfs_alloc_chunk(trans, root, flags);
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}
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}
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static int do_chunk_alloc(struct btrfs_trans_handle *trans,
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struct btrfs_root *extent_root, u64 alloc_bytes,
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u64 flags, int force)
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@ -3515,6 +3559,12 @@ again:
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force_metadata_allocation(fs_info);
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}
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/*
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* Check if we have enough space in SYSTEM chunk because we may need
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* to update devices.
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*/
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check_system_chunk(trans, extent_root, flags);
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ret = btrfs_alloc_chunk(trans, extent_root, flags);
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if (ret < 0 && ret != -ENOSPC)
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goto out;
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