On Tue, Apr 26, 2022 at 05:52:14PM -0700, Darrick J. Wong wrote: > From: Darrick J. Wong <djwong@xxxxxxxxxx> > > Every time someone changes the transaction reservation sizes, they > introduce potential compatibility problems if the changes affect the > minimum log size that we validate at mount time. If the minimum log > size gets larger (which should be avoided because doing so presents a > serious risk of log livelock), filesystems created with old mkfs will > not mount on a newer kernel; if the minimum size shrinks, filesystems > created with newer mkfs will not mount on older kernels. > > Therefore, enable the creation of a shadow log reservation structure > where we can "undo" the effects of tweaks when computing minimum log > sizes. These shadow reservations should never be used in practice, but > they insulate us from perturbations in minimum log size. Looks good: Reviewed-by: Christoph Hellwig <hch@xxxxxx>
