On Mon, Mar 03, 2025 at 05:06:16PM +0100, Heinz Mauelshagen wrote: > On Mon, Mar 3, 2025 at 4:24 PM Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: > > > On Mon, Mar 03, 2025 at 03:57:23PM +0100, Heinz Mauelshagen wrote: > > > dm-loop avoids the file system abstraction, thus gains the resulting > > > performance advantage versus the loop driver. > > > > How? > > > > It uses a predefined map and thus avoids VFS -> FS write path overhead > completelly. But you simply can't use a "pre-defined map". It's fundamentally unsafe. > The inode fiemap() operation would avoid issues relative to outdated bmap(). No, using that for I/O is even worse.
