linux-kernel - [PATCH 5.4 07/86] btrfs: dont get an EINTR during drop

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Date:   Mon, 25 Jan 2021 19:38:49 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>
Subject: [PATCH 5.4 07/86] btrfs: dont get an EINTR during drop_snapshot for reloc

From: Josef Bacik <josef@...icpanda.com>

commit 18d3bff411c8d46d40537483bdc0b61b33ce0371 upstream.

This was partially fixed by f3e3d9cc3525 ("btrfs: avoid possible signal
interruption of btrfs_drop_snapshot() on relocation tree"), however it
missed a spot when we restart a trans handle because we need to end the
transaction.  The fix is the same, simply use btrfs_join_transaction()
instead of btrfs_start_transaction() when deleting reloc roots.

Fixes: f3e3d9cc3525 ("btrfs: avoid possible signal interruption of btrfs_drop_snapshot() on relocation tree")
CC: stable@...r.kernel.org # 5.4+
Signed-off-by: Josef Bacik <josef@...icpanda.com>
Reviewed-by: David Sterba <dsterba@...e.com>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/btrfs/extent-tree.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -5390,7 +5390,15 @@ int btrfs_drop_snapshot(struct btrfs_roo
 				goto out_free;
 			}
 
-			trans = btrfs_start_transaction(tree_root, 0);
+		       /*
+			* Use join to avoid potential EINTR from transaction
+			* start. See wait_reserve_ticket and the whole
+			* reservation callchain.
+			*/
+			if (for_reloc)
+				trans = btrfs_join_transaction(tree_root);
+			else
+				trans = btrfs_start_transaction(tree_root, 0);
 			if (IS_ERR(trans)) {
 				err = PTR_ERR(trans);
 				goto out_free;