On Tue, Jan 14, 2020 at 04:34:25PM +0000, David Howells wrote: > > when a file gets invalidated by the server - and, under some circumstances, > modified locally - I have the cache create a temporary file with vfs_tmpfile() > that I'd like to just link into place over the old one - but I can't because > vfs_link() doesn't allow you to do that. Instead I have to either unlink the > old one and then link the new one in or create it elsewhere and rename across. > > Would it be possible to make linkat() take a flag, say AT_LINK_REPLACE, that > causes the target to be replaced and not give EEXIST? Or make it so that > rename() can take a tmpfile as the source and replace the target with that. I > presume that, either way, this would require journal changes on ext4, xfs and > btrfs. This sounds like a very useful primitive, and from the low-level XFS point of view should be very easy to implement and will not require any on-disk changes. I can't really think of any good userspace interface but a new syscall, though.
