Re: 'ls /mnt/scratch/' freeze(deadlock?) when run xfstest(btrfs/232)

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

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On 2021/4/22 上午7:19, Qu Wenruo wrote:
>
>
> On 2021/4/22 上午12:03, Filipe Manana wrote:
>> On Wed, Apr 21, 2021 at 4:57 PM Wang Yugui <wangyugui@e16-tech.com>
>> wrote:
>>>
>>> Hi,
>>>
>>>> That's the problem, qgroup flushing triggers writeback for an inode
>>>> for which we have a page dirtied and locked.
>>>> This should fix it:  https://pastebin.com/raw/U9GUZiEf
>>>>
>>>> Try it out and I'll write a changelog later.
>>>> Thanks.
>>>
>>> we run xfstest on two server with this patch.
>>> one passed the tests.
>>> but one got a btrfs/232 error.
>>>
>>> btrfs/232 32s ... _check_btrfs_filesystem: filesystem on
>>> /dev/nvme0n1p1is inconsistent
>>> (see /usr/hpc-bio/xfstests/results//btrfs/232.full for details)
>>> ...
>>> [4/7] checking fs roots
>>> root 5 inode 337 errors 400, nbytes wrong
>>> ERROR: errors found in fs roots
>>
>> Ok, that's a different problem caused by something else.
>> It's possible to be due to the recent refactorings for preparation to
>> subpage block size.
>
> This error looks exactly what I have seen during subpage development.
> The subpage bug is caused by incorrect btrfs_invalidatepage() though,
> and not yet merged into misc-next anyway.
>
> I guess it's some error path not clearing extent states correctly, thus
> leaving the inode nbytes accounting wrong.
>
> BTW, the new @in_reclaim_context parameter for start_delalloc_inodes()
> is already in misc-next:
> commit 3d45f221ce627d13e2e6ef3274f06750c84a6542
> Author: Filipe Manana <fdmanana@suse.com>
> Date:   Wed Dec 2 11:55:58 2020 +0000
>
>     btrfs: fix deadlock when cloning inline extent and low on free
> metadata space
>
> We only need to make btrfs_start_delalloc_snapshot() to accept the new
> parameter and pass in_reclaim_context = true for qgroup.

Strangely, on my subpage branch, with new @in_reclaim_context parameter
added to btrfs_start_delalloc_snapshot(), I can't reproduce the nbytes
mismatch error in 32 runs loop.
I guess one of the refactor around ordered extents and invalidatepage
may fix the problem by accident.

Mind to test my subpage branch
(https://github.com/adam900710/linux/tree/subpage) with the attached diff?

Thanks,
Qu
>
> Thanks,
> Qu
>>
>> Will try to look into that later.
>>
>> Thanks.
>>
>>> ...
>>>
>>> Best Regards
>>> Wang Yugui (wangyugui@e16-tech.com)
>>> 2021/04/21
>>>
>>
>>

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diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 0a66b57f40f1..7fa747f81d5a 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3115,7 +3115,8 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
 			       struct btrfs_inode *inode, u64 new_size,
 			       u32 min_type);
 
-int btrfs_start_delalloc_snapshot(struct btrfs_root *root);
+int btrfs_start_delalloc_snapshot(struct btrfs_root *root,
+				  bool in_reclaim_context);
 int btrfs_start_delalloc_roots(struct btrfs_fs_info *fs_info, long nr,
 			       bool in_reclaim_context);
 int btrfs_set_extent_delalloc(struct btrfs_inode *inode, u64 start, u64 end,
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 401820c7e381..91c1162893fb 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -9730,7 +9730,8 @@ static int start_delalloc_inodes(struct btrfs_root *root,
 	return ret;
 }
 
-int btrfs_start_delalloc_snapshot(struct btrfs_root *root)
+int btrfs_start_delalloc_snapshot(struct btrfs_root *root,
+				  bool in_reclaim_context)
 {
 	struct writeback_control wbc = {
 		.nr_to_write = LONG_MAX,
@@ -9743,7 +9744,7 @@ int btrfs_start_delalloc_snapshot(struct btrfs_root *root)
 	if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state))
 		return -EROFS;
 
-	return start_delalloc_inodes(root, &wbc, true, false);
+	return start_delalloc_inodes(root, &wbc, true, in_reclaim_context);
 }
 
 int btrfs_start_delalloc_roots(struct btrfs_fs_info *fs_info, long nr,
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index be174dc9bcd0..9b2b268eb088 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1039,7 +1039,7 @@ static noinline int btrfs_mksnapshot(const struct path *parent,
 	 */
 	btrfs_drew_read_lock(&root->snapshot_lock);
 
-	ret = btrfs_start_delalloc_snapshot(root);
+	ret = btrfs_start_delalloc_snapshot(root, false);
 	if (ret)
 		goto out;
 
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 2319c923c9e6..366a6a289796 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -3562,7 +3562,7 @@ static int try_flush_qgroup(struct btrfs_root *root)
 		return 0;
 	}
 
-	ret = btrfs_start_delalloc_snapshot(root);
+	ret = btrfs_start_delalloc_snapshot(root, true);
 	if (ret < 0)
 		goto out;
 	btrfs_wait_ordered_extents(root, U64_MAX, 0, (u64)-1);
diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 55741adf9071..bd69db72acc5 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -7170,7 +7170,7 @@ static int flush_delalloc_roots(struct send_ctx *sctx)
 	int i;
 
 	if (root) {
-		ret = btrfs_start_delalloc_snapshot(root);
+		ret = btrfs_start_delalloc_snapshot(root, false);
 		if (ret)
 			return ret;
 		btrfs_wait_ordered_extents(root, U64_MAX, 0, U64_MAX);
@@ -7178,7 +7178,7 @@ static int flush_delalloc_roots(struct send_ctx *sctx)
 
 	for (i = 0; i < sctx->clone_roots_cnt; i++) {
 		root = sctx->clone_roots[i].root;
-		ret = btrfs_start_delalloc_snapshot(root);
+		ret = btrfs_start_delalloc_snapshot(root, false);
 		if (ret)
 			return ret;
 		btrfs_wait_ordered_extents(root, U64_MAX, 0, U64_MAX);