On Mon, 3 Mar 2025, Bryn M. Reeves wrote: > On Mon, Mar 03, 2025 at 11:24:27AM +0100, Mikulas Patocka wrote: > > This is the dm-loop target - a replacement for the regular loop driver > > with better performance. The dm-loop target builds a map of the file in > > the constructor and it just remaps bios according to this map. > > > > Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> > > This looks like it is based on my dm-loop patch from almost 20 years > ago. Yes, it is. I copied some of the code from it. > Afaik the locking problems that hch pointed out back then are still > valid now - stashing the bmap lookup in memory lead to weird and hard to > debug problems back then and I don't think this has changed. The dm-loop driver does the same thing as swapfile activation - so I presume that if swapfile activation is correct, then dm-loop is also correct. The S_SWAPFILE flag prevents the kernel from truncating, extending or deleting the file - it just returns "Text file busy". Mikulas
