On Wed, Apr 23, 2025 at 10:32:09AM +0200, Christoph Hellwig wrote: > On Tue, Apr 22, 2025 at 12:27:39PM +0000, John Garry wrote: > > From: "Darrick J. Wong" <djwong@xxxxxxxxxx> > > > > Introduce a mount option to allow sysadmins to specify the maximum size > > of an atomic write. If the filesystem can work with the supplied value, > > that becomes the new guaranteed maximum. > > > > The value mustn't be too big for the existing filesystem geometry (max > > write size, max AG/rtgroup size). We dynamically recompute the > > tr_atomic_write transaction reservation based on the given block size, > > check that the current log size isn't less than the new minimum log size > > constraints, and set a new maximum. > > > > The actual software atomic write max is still computed based off of > > tr_atomic_ioend the same way it has for the past few commits. > > The cap is a good idea, but a mount option for something that has > strong effects for persistent application formats is a little suboptimal. > But adding a sb field and an incompat bit wouldn't be great either. > > Maybe this another use case for a trusted xattr on the root inode like > the autofsck flag? That would be even better, since you could set it at mkfs time and it would persist until the next xfs_property set call. --D
