I'm writing a device-mapper which has to edit incoming writes, for example: Incoming bio request contains a biovec with a page full of 0 bytes, and I want to change it to all 0xFF bytes. I tried using bvec_kmap_local() to get the page address, to then read the data and if needed adjust it using memcpy or similar. Initial tests seemed to work, but if I execute things like mkfs on the created dm, I get a lot of segmentation faults. I narrowed down the problem that this only happens if I actually write something to the mapped page. However, I see no reason why it should cause this fault as I (after checking probably 100 times) don't access invalid memory. I'm wondering whether my method of editing the write is actually correct, or if I am doing something else very stupid. Any help is appreciated Thanks! Cheers, Jasper
