The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 938fcbfb0cbcf532a1869efab58e6009446b1ced Mon Sep 17 00:00:00 2001

From: Josef Bacik josef@toxicpanda.com Date: Thu, 14 Jan 2021 14:02:43 -0500 Subject: [PATCH] btrfs: splice remaining dirty_bg's onto the transaction dirty bg list

While doing error injection testing with my relocation patches I hit the following assert:

assertion failed: list_empty(&block_group->dirty_list), in fs/btrfs/block-group.c:3356 ------------[ cut here ]------------ kernel BUG at fs/btrfs/ctree.h:3357! invalid opcode: 0000 [#1] SMP NOPTI CPU: 0 PID: 24351 Comm: umount Tainted: G W 5.10.0-rc3+ #193 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 04/01/2014 RIP: 0010:assertfail.constprop.0+0x18/0x1a RSP: 0018:ffffa09b019c7e00 EFLAGS: 00010282 RAX: 0000000000000056 RBX: ffff8f6492c18000 RCX: 0000000000000000 RDX: ffff8f64fbc27c60 RSI: ffff8f64fbc19050 RDI: ffff8f64fbc19050 RBP: ffff8f6483bbdc00 R08: 0000000000000000 R09: 0000000000000000 R10: ffffa09b019c7c38 R11: ffffffff85d70928 R12: ffff8f6492c18100 R13: ffff8f6492c18148 R14: ffff8f6483bbdd70 R15: dead000000000100 FS: 00007fbfda4cdc40(0000) GS:ffff8f64fbc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fbfda666fd0 CR3: 000000013cf66002 CR4: 0000000000370ef0 Call Trace: btrfs_free_block_groups.cold+0x55/0x55 close_ctree+0x2c5/0x306 ? fsnotify_destroy_marks+0x14/0x100 generic_shutdown_super+0x6c/0x100 kill_anon_super+0x14/0x30 btrfs_kill_super+0x12/0x20 deactivate_locked_super+0x36/0xa0 cleanup_mnt+0x12d/0x190 task_work_run+0x5c/0xa0 exit_to_user_mode_prepare+0x1b1/0x1d0 syscall_exit_to_user_mode+0x54/0x280 entry_SYSCALL_64_after_hwframe+0x44/0xa9

This happened because I injected an error in btrfs_cow_block() while running the dirty block groups. When we run the dirty block groups, we splice the list onto a local list to process. However if an error occurs, we only cleanup the transactions dirty block group list, not any pending block groups we have on our locally spliced list.

In fact if we fail to allocate a path in this function we'll also fail to clean up the splice list.

Fix this by splicing the list back onto the transaction dirty block group list so that the block groups are cleaned up. Then add a 'out' label and have the error conditions jump to out so that the errors are handled properly. This also has the side-effect of fixing a problem where we would clear 'ret' on error because we unconditionally ran btrfs_run_delayed_refs().

CC: stable@vger.kernel.org # 4.4+ Signed-off-by: Josef Bacik josef@toxicpanda.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com

diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c index 763a3671b7af..dda495b2a862 100644 --- a/fs/btrfs/block-group.c +++ b/fs/btrfs/block-group.c @@ -2564,8 +2564,10 @@ int btrfs_start_dirty_block_groups(struct btrfs_trans_handle *trans)

if (!path) { path = btrfs_alloc_path(); - if (!path) - return -ENOMEM; + if (!path) { + ret = -ENOMEM; + goto out; + } }

/* @@ -2659,16 +2661,14 @@ int btrfs_start_dirty_block_groups(struct btrfs_trans_handle *trans) btrfs_put_block_group(cache); if (drop_reserve) btrfs_delayed_refs_rsv_release(fs_info, 1); - - if (ret) - break; - /* * Avoid blocking other tasks for too long. It might even save * us from writing caches for block groups that are going to be * removed. */ mutex_unlock(&trans->transaction->cache_write_mutex); + if (ret) + goto out; mutex_lock(&trans->transaction->cache_write_mutex); } mutex_unlock(&trans->transaction->cache_write_mutex); @@ -2692,7 +2692,12 @@ int btrfs_start_dirty_block_groups(struct btrfs_trans_handle *trans) goto again; } spin_unlock(&cur_trans->dirty_bgs_lock); - } else if (ret < 0) { + } +out: + if (ret < 0) { + spin_lock(&cur_trans->dirty_bgs_lock); + list_splice_init(&dirty, &cur_trans->dirty_bgs); + spin_unlock(&cur_trans->dirty_bgs_lock); btrfs_cleanup_dirty_bgs(cur_trans, fs_info); }