btrfs: avoid monopolizing a core when activating a swap file

commit 2c8507c63f5498d4ee4af404a8e44ceae4345056 upstream.

During swap activation we iterate over the extents of a file and we can
have many thousands of them, so we can end up in a busy loop monopolizing
a core. Avoid this by doing a voluntary reschedule after processing each
extent.

CC: stable@vger.kernel.org # 5.4+
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index eb5f03c3336cf74258bb5bf2328be90f2e52cffb..16789490078ff2c5b84f6a0de7767450eaa8e4fa 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7387,6 +7387,8 @@ noinline int can_nocow_extent(struct inode *inode, u64 offset, u64 *len,
                        ret = -EAGAIN;
                        goto out;
                }
+
+               cond_resched();
        }
 
        if (orig_start)