在 7/1/2025 9:56 PM, Jonathan Cameron 写道:
On Tue, 24 Jun 2025 07:33:49 +0000 Dongsheng Yang <dongsheng.y...@linux.dev> wrote:This patch introduces *backing_dev.{c,h}*, a self-contained layer that handles all interaction with the *backing block device* where cache write-back and cache-miss reads are serviced. Isolating this logic keeps the core dm-pcache code free of low-level bio plumbing. * Device setup / teardown - Opens the target with `dm_get_device()`, stores `bdev`, file and size, and initialises a dedicated `bioset`. - Gracefully releases resources via `backing_dev_stop()`. * Request object (`struct pcache_backing_dev_req`) - Two request flavours: - REQ-type – cloned from an upper `struct bio` issued to dm-pcache; trimmed and re-targeted to the backing LBA. - KMEM-type – maps an arbitrary kernel memory buffer into a freshly built. - Private completion callback (`end_req`) propagates status to the upper layer and handles resource recycling. * Submission & completion path - Lock-protected submit queue + worker (`req_submit_work`) let pcache push many requests asynchronously, at the same time, allow caller to submit backing_dev_req in atomic context. - End-io handler moves finished requests to a completion list processed by `req_complete_work`, ensuring callbacks run in process context. - Direct-submit option for non-atomic context. * Flush - `backing_dev_flush()` issues a flush to persist backing-device data. Signed-off-by: Dongsheng Yang <dongsheng.y...@linux.dev> --- drivers/md/dm-pcache/backing_dev.c | 292 +++++++++++++++++++++++++++++ drivers/md/dm-pcache/backing_dev.h | 88 +++++++++ 2 files changed, 380 insertions(+) create mode 100644 drivers/md/dm-pcache/backing_dev.c create mode 100644 drivers/md/dm-pcache/backing_dev.h + +struct pcache_backing_dev_req *backing_dev_req_create(struct pcache_backing_dev *backing_dev, + struct pcache_backing_dev_req_opts *opts) +{ + if (opts->type == BACKING_DEV_REQ_TYPE_REQ) + return req_type_req_create(backing_dev, opts); + else if (opts->type == BACKING_DEV_REQ_TYPE_KMEM)returned in earlier branch so go with simpler if (opts->type..)
Hi Jonathan, This looks good, I am willing to do this change. Thanx Dongsheng
Or use a switch statement if you expect to get more entries in this over time.+ return kmem_type_req_create(backing_dev, opts); + + return NULL; +} + +void backing_dev_flush(struct pcache_backing_dev *backing_dev) +{ + blkdev_issue_flush(backing_dev->dm_dev->bdev); +}
