On Mon, 7 Jul 2025, Dongsheng Yang wrote: > Hi Mikulas, > This is V2 for dm-pcache, please take a look. > > Code: > https://github.com/DataTravelGuide/linux tags/pcache_v2 > > Changelogs > > V2 from V1: > - introduce req_alloc() and req_init() in backing_dev.c, then we > can do req_alloc() before holding spinlock and do req_init() > in subtree_walk(). > - introduce pre_alloc_key and pre_alloc_req in walk_ctx, that > means we can pre-allocate cache_key or backing_dev_request > before subtree walking. > - use mempool_alloc() with NOIO for the allocation of cache_key > and backing_dev_req. > - some coding style changes from comments of Jonathan. Hi mempool_alloc with GFP_NOIO never fails - so you don't have to check the returned value for NULL and propagate the error upwards. "backing_req->kmem.bvecs = kmalloc_array(n_vecs, sizeof(struct bio_vec), GFP_NOIO)" - this call may fail and you should handle the error gracefully (i.e. don't end the bio with an error). Would it be possible to trim the request to BACKING_DEV_REQ_INLINE_BVECS vectors and retry it? Alternativelly, you can create a mempool for the largest possible n_vecs and allocate from this mempool if kmalloc_array fails. I'm sending two patches for dm-pcache - the first patch adds the include file linux/bitfield.h - it is needed in my config. The second patch makes slab caches per-module rather than per-device, if you have them per-device, there are warnings about duplicate cache names. BTW. What kind of persistent memory do you use? (afaik Intel killed the Optane products and I don't know of any replacement) Some times ago I created a filesystem for persistent memory - see git://leontynka.twibright.com/nvfs.git - I'd be interested if you can test it on your persistent memory implementation. Mikulas
