Re: [PATCH] btrfs: zoned: free zone_cache when freeing zone_info

[David Sterba <dsterba@suse.cz>]

On Fri, Dec 03, 2021 at 03:12:27AM -0800, Johannes Thumshirn wrote:
> Kmemleak was reporting the following memory leak on fstests btrfs/224 on my
> zoned test setup:
> 
>  unreferenced object 0xffffc900001a9000 (size 4096):
>    comm "mount", pid 1781, jiffies 4295339102 (age 5.740s)
>    hex dump (first 32 bytes):
>      00 00 00 00 00 00 00 00 00 00 08 00 00 00 00 00  ................
>      00 00 08 00 00 00 00 00 01 00 00 00 00 00 00 00  ................
>    backtrace:
>      [<00000000b0ef6261>] __vmalloc_node_range+0x240/0x3d0
>      [<00000000aa06ac88>] vzalloc+0x3c/0x50
>      [<000000001824c35c>] btrfs_get_dev_zone_info+0x426/0x7e0 [btrfs]
>      [<0000000004ba8d9d>] btrfs_get_dev_zone_info_all_devices+0x52/0x80 [btrfs]
>      [<0000000054bc27eb>] open_ctree+0x1022/0x1709 [btrfs]
>      [<0000000074fe7dc0>] btrfs_mount_root.cold+0x13/0xe5 [btrfs]
>      [<00000000a54ca18b>] legacy_get_tree+0x22/0x40
>      [<00000000ce480896>] vfs_get_tree+0x1b/0x80
>      [<000000006423c6bd>] vfs_kern_mount.part.0+0x6c/0xa0
>      [<000000003cf6fc28>] btrfs_mount+0x10d/0x380 [btrfs]
>      [<00000000a54ca18b>] legacy_get_tree+0x22/0x40
>      [<00000000ce480896>] vfs_get_tree+0x1b/0x80
>      [<00000000995da674>] path_mount+0x6b6/0xa10
>      [<00000000a5b4b6ec>] __x64_sys_mount+0xde/0x110
>      [<00000000fe985c23>] do_syscall_64+0x43/0x90
>      [<00000000c6071ff4>] entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> The allocated object in question is the zone_cache.
> 
> Free it when freeing a btrfs_device's zone_info.
> 
> Cc: Naohiro Aota <naohiro.aota@wdc.com>
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
> ---
>  fs/btrfs/zoned.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
> index c917867a4261..fc9c6ae7bc00 100644
> --- a/fs/btrfs/zoned.c
> +++ b/fs/btrfs/zoned.c
> @@ -612,6 +612,7 @@ void btrfs_destroy_dev_zone_info(struct btrfs_device *device)
>  	bitmap_free(zone_info->active_zones);
>  	bitmap_free(zone_info->seq_zones);
>  	bitmap_free(zone_info->empty_zones);
> +	vfree(zone_info->zone_cache);
>  	kfree(zone_info);
>  	device->zone_info = NULL;

This is the exact sequence that's at the end of btrfs_get_dev_zone_info
(that had the vfree call), please clean it up so there's only the helper
called from btrfs_get_dev_zone_info.

The zone_cache is also pending for some stable backport so please add
the Fixes: tag. Thanks.