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Date:   Mon, 6 Dec 2021 18:48:46 +0100
From:   David Sterba <dsterba@suse.cz>
To:     Johannes Thumshirn <johannes.thumshirn@wdc.com>
Cc:     David Sterba <dsterba@suse.com>, linux-btrfs@vger.kernel.org,
        Filipe Manana <fdmanana@suse.com>
Subject: Re: [PATCH] btrfs: free exchange changeset on failures
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On Fri, Dec 03, 2021 at 02:55:33AM -0800, Johannes Thumshirn wrote:
> Fstests runs on my VMs have show several kmemleak reports like the following.
> 
>   unreferenced object 0xffff88811ae59080 (size 64):
>     comm "xfs_io", pid 12124, jiffies 4294987392 (age 6.368s)
>     hex dump (first 32 bytes):
>       00 c0 1c 00 00 00 00 00 ff cf 1c 00 00 00 00 00  ................
>       90 97 e5 1a 81 88 ff ff 90 97 e5 1a 81 88 ff ff  ................
>     backtrace:
>       [<00000000ac0176d2>] ulist_add_merge+0x60/0x150 [btrfs]
>       [<0000000076e9f312>] set_state_bits+0x86/0xc0 [btrfs]
>       [<0000000014fe73d6>] set_extent_bit+0x270/0x690 [btrfs]
>       [<000000004f675208>] set_record_extent_bits+0x19/0x20 [btrfs]
>       [<00000000b96137b1>] qgroup_reserve_data+0x274/0x310 [btrfs]
>       [<0000000057e9dcbb>] btrfs_check_data_free_space+0x5c/0xa0 [btrfs]
>       [<0000000019c4511d>] btrfs_delalloc_reserve_space+0x1b/0xa0 [btrfs]
>       [<000000006d37e007>] btrfs_dio_iomap_begin+0x415/0x970 [btrfs]
>       [<00000000fb8a74b8>] iomap_iter+0x161/0x1e0
>       [<0000000071dff6ff>] __iomap_dio_rw+0x1df/0x700
>       [<000000002567ba53>] iomap_dio_rw+0x5/0x20
>       [<0000000072e555f8>] btrfs_file_write_iter+0x290/0x530 [btrfs]
>       [<000000005eb3d845>] new_sync_write+0x106/0x180
>       [<000000003fb505bf>] vfs_write+0x24d/0x2f0
>       [<000000009bb57d37>] __x64_sys_pwrite64+0x69/0xa0
>       [<000000003eba3fdf>] do_syscall_64+0x43/0x90
> 
> In case brtfs_qgroup_reserve_data() or btrfs_delalloc_reserve_metadata()
> fail the allocated extent_changeset will not be freed.
> 
> So in btrfs_check_data_free_space() and btrfs_delalloc_reserve_space()
> free the allocated extent_changeset to get rid of the allocated memory.
> 
> Cc: Filipe Manana <fdmanana@suse.com>
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>

Added to devel with Filipe's comment, thanks.