From 010a47bde94201d9abdab7ff04bedc17b6e8c357 Mon Sep 17 00:00:00 2001 From: David Sterba Date: Tue, 20 Mar 2018 19:51:04 +0100 Subject: [PATCH] btrfs: add proper safety check before resuming dev-replace The device replace is paused by unmount or read only remount, and resumed on next mount or write remount. The exclusive status should be checked properly as it's a global invariant and we must not allow 2 operations run. In this case, the balance can be also paused and resumed under same conditions. It's always checked first so dev-replace could see the EXCL_OP already taken, BUT, the ioctl would never let start both at the same time. Replace the WARN_ON with message and return 0, indicating no error as this is purely theoretical and the user will be informed. Resolving that manually should be possible by waiting for the other operation to finish or cancel the paused state. Reviewed-by: Anand Jain Reviewed-by: Nikolay Borisov Signed-off-by: David Sterba --- fs/btrfs/dev-replace.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c index 8531b5dae777..9fe7be7fdbef 100644 --- a/fs/btrfs/dev-replace.c +++ b/fs/btrfs/dev-replace.c @@ -896,7 +896,17 @@ int btrfs_resume_dev_replace_async(struct btrfs_fs_info *fs_info) } btrfs_dev_replace_write_unlock(dev_replace); - WARN_ON(test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags)); + /* + * This could collide with a paused balance, but the exclusive op logic + * should never allow both to start and pause. We don't want to allow + * dev-replace to start anyway. + */ + if (test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags)) { + btrfs_info(fs_info, + "cannot resume dev-replace, other exclusive operation running"); + return 0; + } + task = kthread_run(btrfs_dev_replace_kthread, fs_info, "btrfs-devrepl"); return PTR_ERR_OR_ZERO(task); } -- GitLab