On 28.01.19 г. 18:45 ч., David Sterba wrote:
> The fstests generic/475 stresses transaction aborts and can reveal
> space accounting or use-after-free bugs regarding block goups.
>
> In this case the pending block groups that remain linked to the
> structures after transaction commit aborts in the middle.
>
> The corrupted slabs lead to failures in following tests, eg. generic/476
>
> [ 8172.752887] BUG: unable to handle kernel NULL pointer dereference at 0000000000000058
> [ 8172.755799] #PF error: [normal kernel read fault]
> [ 8172.757571] PGD 661ae067 P4D 661ae067 PUD 3db8e067 PMD 0
> [ 8172.759000] Oops: 0000 [#1] PREEMPT SMP
> [ 8172.760209] CPU: 0 PID: 39 Comm: kswapd0 Tainted: G W 5.0.0-rc2-default #408
> [ 8172.762495] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.11.2-0-gf9626cc-prebuilt.qemu-project.org 04/01/2014
> [ 8172.765772] RIP: 0010:shrink_page_list+0x2f9/0xe90
> [ 8172.770453] RSP: 0018:ffff967f00663b18 EFLAGS: 00010287
> [ 8172.771184] RAX: 0000000000000000 RBX: ffff967f00663c20 RCX: 0000000000000000
> [ 8172.772850] RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff8c0620ab20e0
> [ 8172.774629] RBP: ffff967f00663dd8 R08: 0000000000000000 R09: 0000000000000000
> [ 8172.776094] R10: ffff8c0620ab22f8 R11: ffff8c063f772688 R12: ffff967f00663b78
> [ 8172.777533] R13: ffff8c063f625600 R14: ffff8c063f625608 R15: dead000000000200
> [ 8172.778886] FS: 0000000000000000(0000) GS:ffff8c063d400000(0000) knlGS:0000000000000000
> [ 8172.780545] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 8172.781787] CR2: 0000000000000058 CR3: 000000004e962000 CR4: 00000000000006f0
> [ 8172.783547] Call Trace:
> [ 8172.784112] shrink_inactive_list+0x194/0x410
> [ 8172.784747] shrink_node_memcg.constprop.85+0x3a5/0x6a0
> [ 8172.785472] shrink_node+0x62/0x1e0
> [ 8172.786011] balance_pgdat+0x216/0x460
> [ 8172.786577] kswapd+0xe3/0x4a0
> [ 8172.787085] ? finish_wait+0x80/0x80
> [ 8172.787795] ? balance_pgdat+0x460/0x460
> [ 8172.788799] kthread+0x116/0x130
> [ 8172.789640] ? kthread_create_on_node+0x60/0x60
> [ 8172.790323] ret_from_fork+0x24/0x30
> [ 8172.794253] CR2: 0000000000000058
>
> or accounting errors at umount time:
>
> [ 8159.537251] WARNING: CPU: 2 PID: 19031 at fs/btrfs/extent-tree.c:5987 btrfs_free_block_groups+0x3d5/0x410 [btrfs]
> [ 8159.543325] CPU: 2 PID: 19031 Comm: umount Tainted: G W 5.0.0-rc2-default #408
> [ 8159.545472] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.11.2-0-gf9626cc-prebuilt.qemu-project.org 04/01/2014
> [ 8159.548155] RIP: 0010:btrfs_free_block_groups+0x3d5/0x410 [btrfs]
> [ 8159.554030] RSP: 0018:ffff967f079cbde8 EFLAGS: 00010206
> [ 8159.555144] RAX: 0000000001000000 RBX: ffff8c06366cf800 RCX: 0000000000000000
> [ 8159.556730] RDX: 0000000000000002 RSI: 0000000000000001 RDI: ffff8c06255ad800
> [ 8159.558279] RBP: ffff8c0637ac0000 R08: 0000000000000001 R09: 0000000000000000
> [ 8159.559797] R10: 0000000000000000 R11: 0000000000000001 R12: ffff8c0637ac0108
> [ 8159.561296] R13: ffff8c0637ac0158 R14: 0000000000000000 R15: dead000000000100
> [ 8159.562852] FS: 00007f7f693b9fc0(0000) GS:ffff8c063d800000(0000) knlGS:0000000000000000
> [ 8159.564839] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 8159.566160] CR2: 00007f7f68fab7b0 CR3: 000000000aec7000 CR4: 00000000000006e0
> [ 8159.567898] Call Trace:
> [ 8159.568597] close_ctree+0x17f/0x350 [btrfs]
> [ 8159.569628] generic_shutdown_super+0x64/0x100
> [ 8159.570808] kill_anon_super+0x14/0x30
> [ 8159.571857] btrfs_kill_super+0x12/0xa0 [btrfs]
> [ 8159.573063] deactivate_locked_super+0x29/0x60
> [ 8159.574234] cleanup_mnt+0x3b/0x70
> [ 8159.575176] task_work_run+0x98/0xc0
> [ 8159.576177] exit_to_usermode_loop+0x83/0x90
> [ 8159.577315] do_syscall_64+0x15b/0x180
> [ 8159.578339] entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> This fix is based on 2 Josef's patches that used sideefects of
> btrfs_create_pending_block_groups, this fix introduces the helper that
> does what we need.
>
> CC: stable@xxxxxxxxxxxxxxx # 4.4+
> CC: Josef Bacik <josef@xxxxxxxxxxxxxx>
> Signed-off-by: David Sterba <dsterba@xxxxxxxx>
> ---
> fs/btrfs/transaction.c | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
> index 127fa1535f58..1c23f227525c 100644
> --- a/fs/btrfs/transaction.c
> +++ b/fs/btrfs/transaction.c
> @@ -1895,6 +1895,20 @@ static inline int btrfs_start_delalloc_flush(struct btrfs_fs_info *fs_info)
> return 0;
> }
>
> +static void btrfs_cleanup_pending_block_groups(struct btrfs_trans_handle *trans)
> +{
> + struct btrfs_fs_info *fs_info = trans->fs_info;
> + struct btrfs_block_group_cache *block_group;
> +
> + while (!list_empty(&trans->new_bgs)) {
> + block_group = list_first_entry(&trans->new_bgs,
> + struct btrfs_block_group_cache,
> + bg_list);
> + btrfs_delayed_refs_rsv_release(fs_info, 1);
> + list_del_init(&block_group->bg_list);
> + }
> +}
This is much cleaner and understandable, thanks.
nit:Can't we use list_for_each_entry_safe though and save the explicit
list_first_entry. IMO this is fine here since the transaction is aborted
hence no new pending bgs can be added to the ->new_bgs list. In any case:
Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx>
> +
> static inline void btrfs_wait_delalloc_flush(struct btrfs_fs_info *fs_info)
> {
> if (btrfs_test_opt(fs_info, FLUSHONCOMMIT))
> @@ -2270,6 +2284,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
> btrfs_scrub_continue(fs_info);
> cleanup_transaction:
> btrfs_trans_release_metadata(trans);
> + btrfs_cleanup_pending_block_groups(trans);
> btrfs_trans_release_chunk_metadata(trans);
> trans->block_rsv = NULL;
> btrfs_warn(fs_info, "Skipping commit of aborted transaction.");
>
