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btrfs: don't go readonly on existing qgroup items
btrfs_drop_snapshot() leaves subvolume qgroup items on disk after completion. This can cause problems with snapshot creation. If a new snapshot tries to claim the deleted subvolumes id, btrfs will get -EEXIST from add_qgroup_item() and go read-only. The following commands will reproduce this problem (assume btrfs is on /dev/sda and is mounted at /btrfs) mkfs.btrfs -f /dev/sda mount -t btrfs /dev/sda /btrfs/ btrfs quota enable /btrfs/ btrfs su sna /btrfs/ /btrfs/snap btrfs su de /btrfs/snap sleep 45 umount /btrfs/ mount -t btrfs /dev/sda /btrfs/ We can fix this by catching -EEXIST in add_qgroup_item() and initializing the existing items. We have the problem of orphaned relation items being on disk from an old snapshot but that is outside the scope of this patch. Signed-off-by: Mark Fasheh <mfasheh@suse.de> Signed-off-by: Chris Mason <clm@fb.com>
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@ -551,9 +551,15 @@ static int add_qgroup_item(struct btrfs_trans_handle *trans,
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key.type = BTRFS_QGROUP_INFO_KEY;
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key.offset = qgroupid;
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/*
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* Avoid a transaction abort by catching -EEXIST here. In that
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* case, we proceed by re-initializing the existing structure
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* on disk.
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*/
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ret = btrfs_insert_empty_item(trans, quota_root, path, &key,
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sizeof(*qgroup_info));
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if (ret)
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if (ret && ret != -EEXIST)
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goto out;
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leaf = path->nodes[0];
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@ -572,7 +578,7 @@ static int add_qgroup_item(struct btrfs_trans_handle *trans,
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key.type = BTRFS_QGROUP_LIMIT_KEY;
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ret = btrfs_insert_empty_item(trans, quota_root, path, &key,
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sizeof(*qgroup_limit));
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if (ret)
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if (ret && ret != -EEXIST)
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goto out;
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leaf = path->nodes[0];
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