Niklas Cassel <Niklas.Cassel@xxxxxxx> writes: > On Mon, Feb 27, 2023 at 12:59:45PM +0100, Andreas Hindborg wrote: > > (snip) > >> >> +#else >> >> +void ublk_set_nr_zones(struct ublk_device *ub); >> >> +void ublk_dev_param_zoned_apply(struct ublk_device *ub); >> >> +int ublk_revalidate_disk_zones(struct gendisk *disk); >> > >> > These are declarations, shouldn't they be dummy definitions instead? >> >> I looked at how nvme host defines nvme_revalidate_zones() when I did >> this. The functions become undefined symbols but because the call sites >> are optimized out they go away. > > Looking at e.g. nvme_revalidate_zones > > $ git grep nvme_revalidate_zones > drivers/nvme/host/core.c: ret = nvme_revalidate_zones(ns); > drivers/nvme/host/nvme.h:int nvme_revalidate_zones(struct nvme_ns *ns); > drivers/nvme/host/zns.c:int nvme_revalidate_zones(struct nvme_ns *ns) > > The function is declared in nvme.h, but like you say, without any definition. > > zns.c provides a definition, but that file is only build if > CONFIG_BLK_DEV_ZONED is set. > > >> > https://github.com/torvalds/linux/blob/v6.2/fs/btrfs/Makefile#L39 >> > https://github.com/torvalds/linux/blob/v6.2/drivers/block/null_blk/Makefile#L11 >> > >> > They have put the zoned stuff in a separate C file that is only compiled >> > when CONFIG_BLK_DEV_ZONED is set. >> > >> > I'm not sure if a similar design is desired for ublk or not. >> > >> > However, if a similar design pattern was used, it could probably avoid >> > some of these unpleasant dummy definitions altogether. >> >> This is the same as I do here, except I put the declarations in the c >> file instead of a header. I did this for two reasons 1) there is no ublk >> header besides the uapi header (I would add a header just for this), 2) >> the declarations need only exist inside ublk_drv.c. For btrfs, null_blk, >> nvme, the declarations go in a header file and the functions in question >> do not have static linkage. >> >> I could move the function declarations out of the #else block, but then >> they would need to be declared static and that gives a compiler warning >> when the implementation is not present. > > I would love to hear someone else's opinion about this as well, but I do > think that having #ifdef and #else with both a declaration and a definition > in the C file is quite ugly. > > If having an internal only header (in the same directory as the C file), > makes the C code easier to read, I'm all for it. > > It seems to work for nvme to only have a declaration in an internal header > file, and only provide a definition if CONFIG_BLK_DEV_ZONED is set, > presumably without giving a warning. Perhaps ublk can do the same? Sure, I can do that if that is preferred. As I said the result will be he same with he exception that the function symbols will not have static linkage when defined in a separate file with declarations in a header. I will let this version sit for a while to see if anyone has an opinion, and then I will ship a new version next week. BR Andreas
