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Qu Wenruo
04188a67ae
Btrfs qgroup reserve codes lacks check for rewrite dirty page, causing every write, even rewriting a uncommitted dirty page, to reserve space. But only written data will free the reserved space, causing reserved space leaking. The bug exists almost from the beginning of btrfs qgroup codes, but nobody found it. For example: 1)Write [0, 12K) into file A reserve 12K space File A: 0 4K 8K 12K |<--------dirty-------->| reserved: 12K 2)Write [0,4K) into file A 0 4K 8K 12K |<--------dirty-------->| reserved: 16K <<< Should be 12K 3) Commit transaction Dirty pages [0,12) written to disk. Free 12K reserved space. reserved: 4K <<< Should be 0 This testcase will test such problem. Kernel fix will need some huge change, so won't be soon. Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com> Reviewed-by: Filipe Manana <fdmanana@suse.com>