On Wed, Dec 06, 2023 at 05:05:37PM +1100, Dave Chinner wrote: > + /* > + * There are some callers that come through here without synchronisation > + * and potentially with multiple references to the inode. Hence we have > + * to handle the case that we might race with a remove and insert to a > + * different list. Coda, in particular, seems to have a userspace API > + * that can directly trigger "unhash/rehash to different list" behaviour > + * without any serialisation at all. > + * > + * Hence we have to handle the situation where the inode->i_hash_head > + * might point to a different list than what we expect, indicating that > + * we raced with another unhash and potentially a new insertion. This > + * means we have to retest the head once we have everything locked up > + * and loop again if it doesn't match. > + */
coda_replace_fid() is an old headache, but it's thankfully unique - nobody else does that kind of shit (just rechecked). Note that coda_replace_fid() is not going to have the sucker racing with removal from another source, and I'm 100% sure that they really want some serialization for handling those requests. remove_inode_hash() is misused there - "in the middle of hash key change" is not the same state as "unhashed". Any races between insert and unhash are bugs, not something to support.
