Andreas Dilger [off-list ref] wrote:

As described elsewhere in the thread, allowing concurrent create and unlink
in a directory (rename probably not needed) would be invaluable for scaling
multi-threaded workloads.  Neil Brown posted a prototype patch to add this
to the VFS for NFS:

Actually, one thing I'm looking at is using vfs_tmpfile() to create a new file
(or a replacement file when invalidation is required) and then using
vfs_link() to attach directory entries in the background (possibly using
vfs_link() with AT_LINK_REPLACE[1] instead of unlink+link).

Any thoughts on how that might scale?  vfs_tmpfile() doesn't appear to require
the directory inode lock.  I presume the directory is required for security
purposes in addition to being a way to specify the target filesystem.

David

[1] https://lore.kernel.org/linux-fsdevel/cover.1580251857.git.osandov@fb.com/ (local)