Messages in this thread | | | Date | Tue, 04 Nov 2014 10:25:29 +0100 | From | Daniel Borkmann <> | Subject | Re: [PATCH net-next 1/7] bpf: add 'flags' attribute to BPF_MAP_UPDATE_ELEM command |
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On 11/04/2014 03:54 AM, Alexei Starovoitov wrote: > the current meaning of BPF_MAP_UPDATE_ELEM syscall command is: > either update existing map element or create a new one. > Initially the plan was to add a new command to handle the case of > 'create new element if it didn't exist', but 'flags' style looks > cleaner and overall diff is much smaller (more code reused), so add 'flags' > attribute to BPF_MAP_UPDATE_ELEM command with the following meaning: > enum { > BPF_MAP_UPDATE_OR_CREATE = 0, /* add new element or update existing */ > BPF_MAP_CREATE_ONLY, /* add new element if it didn't exist */ > BPF_MAP_UPDATE_ONLY /* update existing element */ > };
From you commit message/code I currently don't see an explanation why it cannot be done in typical ``flags style'' as various syscalls do, i.e. BPF_MAP_UPDATE_OR_CREATE rather represented as ...
BPF_MAP_CREATE | BPF_MAP_UPDATE
Do you expect more than 64 different flags to be passed from user space for BPF_MAP?
> BPF_MAP_CREATE_ONLY can fail with EEXIST if element already exists. > BPF_MAP_UPDATE_ONLY can fail with ENOENT if element doesn't exist. > > Userspace will call it as: > int bpf_update_elem(int fd, void *key, void *value, __u64 flags) > { > union bpf_attr attr = { > .map_fd = fd, > .key = ptr_to_u64(key), > .value = ptr_to_u64(value), > .flags = flags; > }; > > return bpf(BPF_MAP_UPDATE_ELEM, &attr, sizeof(attr)); > } > > Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
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