[PATCH] btrfs: bail out of uuid tree scanning if we're closing

[PATCH] btrfs: bail out of uuid tree scanning if we're closing

[Josef Bacik]

In doing my fsstress+EIO stress testing I started running into issues
where umount would get stuck forever because the uuid checker was
chewing through the thousands of subvolumes I had created.  We shouldn't
block umount on this, simply bail if we're unmounting the fs.  We need
to make sure we don't mark the UUID tree as ok, so we only set that bit
if we made it through the whole rescan operation, but otherwise this is
completely safe.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/uuid-tree.c |  4 ++++
 fs/btrfs/volumes.c   | 11 +++++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/uuid-tree.c b/fs/btrfs/uuid-tree.c
index 76b84f2397b1..30078b74220e 100644
--- a/fs/btrfs/uuid-tree.c
+++ b/fs/btrfs/uuid-tree.c
@@ -278,6 +278,10 @@ int btrfs_uuid_tree_iterate(struct btrfs_fs_info *fs_info,
 	}
 
 	while (1) {
+		if (btrfs_fs_closing(fs_info)) {
+			ret = -EINTR;
+			goto out;
+		}
 		cond_resched();
 		leaf = path->nodes[0];
 		slot = path->slots[0];
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 387f80656476..e40adf38ae5c 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4286,6 +4286,7 @@ static int btrfs_uuid_scan_kthread(void *data)
 	struct btrfs_root_item root_item;
 	u32 item_size;
 	struct btrfs_trans_handle *trans = NULL;
+	bool closing = false;
 
 	path = btrfs_alloc_path();
 	if (!path) {
@@ -4298,6 +4299,10 @@ static int btrfs_uuid_scan_kthread(void *data)
 	key.offset = 0;
 
 	while (1) {
+		if (btrfs_fs_closing(fs_info)) {
+			closing = true;
+			break;
+		}
 		ret = btrfs_search_forward(root, &key, path,
 				BTRFS_OLDEST_GENERATION);
 		if (ret) {
@@ -4397,7 +4402,7 @@ static int btrfs_uuid_scan_kthread(void *data)
 		btrfs_end_transaction(trans);
 	if (ret)
 		btrfs_warn(fs_info, "btrfs_uuid_scan_kthread failed %d", ret);
-	else
+	else if (!closing)
 		set_bit(BTRFS_FS_UPDATE_UUID_TREE_GEN, &fs_info->flags);
 	up(&fs_info->uuid_tree_rescan_sem);
 	return 0;
@@ -4460,7 +4465,9 @@ static int btrfs_uuid_rescan_kthread(void *data)
 	 */
 	ret = btrfs_uuid_tree_iterate(fs_info, btrfs_check_uuid_tree_entry);
 	if (ret < 0) {
-		btrfs_warn(fs_info, "iterating uuid_tree failed %d", ret);
+		if (ret != -EINTR)
+			btrfs_warn(fs_info, "iterating uuid_tree failed %d",
+				   ret);
 		up(&fs_info->uuid_tree_rescan_sem);
 		return ret;
 	}
-- 
2.24.1

Re: [PATCH] btrfs: bail out of uuid tree scanning if we're closing

[Johannes Thumshirn]

Looks good,
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>

Re: [PATCH] btrfs: bail out of uuid tree scanning if we're closing

[David Sterba]

On Fri, Feb 14, 2020 at 03:05:01PM -0500, Josef Bacik wrote:
> In doing my fsstress+EIO stress testing I started running into issues
> where umount would get stuck forever because the uuid checker was
> chewing through the thousands of subvolumes I had created.  We shouldn't
> block umount on this, simply bail if we're unmounting the fs.  We need
> to make sure we don't mark the UUID tree as ok, so we only set that bit
> if we made it through the whole rescan operation, but otherwise this is
> completely safe.
> 
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>

Added to misc-next, thanks.