On Thu, May 03, 2018 at 02:24:47PM -0700, Darrick J. Wong wrote: > On Thu, May 03, 2018 at 01:58:03PM -0700, Omar Sandoval wrote: > > On Thu, May 03, 2018 at 10:46:59AM -0700, Darrick J. Wong wrote: > > > From: Darrick J. Wong <darrick.wong@xxxxxxxxxx> > > > > > > Add a new iomap_swapfile_activate function so that filesystems can > > > activate swap files without having to use the obsolete and slow bmap > > > function. This enables XFS to support fallocate'd swap files and > > > swap files on realtime devices. > > > > > > > Shouldn't we also prevent the extents of an active swapfile from > > becoming shared? If I swapon(a) and reflink(a, b), swapout to a now has > > to break the reflink or corrupt b! In my old Btrfs swapfile series [1] I > > just forbid all reflink operations on active swapfiles. > > xfs already does this in its reflink handler: it takes the inode lock & > bails out if IS_SWAPFILE(). swapon calls claim_swapfile to take the > inode lock and sets S_SWAPFILE (if successful) so the two are > effectively locked out from each other... > > > One thing to note is that then this will need a matching > > ->swap_deactivate(), which currently isn't called if ->swap_activate() > > returned > 0. > > ...so there shouldn't be any state to undo if the > iomap_swapfile_activate fails. Makes sense, thanks.
