Ceph

when testing the case which doing the truncate-then-write loop to a file,
I found the file-truncating will not be allowed when the previous truncating is in process.

the "is_truncating" function returns true when the object-truncating has not finished,
which causes the caller to add a waiter to re-dispatch the request after the previous truncating finished.

so there will be a delay between truncating and writing, especially when the OSDs are busy.

I wonder if there will be a new feature to allow multi-truncating on the same file ? or any ideas can help me to walk around? thanks