Message ID | 20190411082700.26888-1-bpoirier@suse.com |
---|---|
State | Changes Requested |
Delegated to: | BPF Maintainers |
Headers | show |
Series | [bpf-next] bpftool: Exit early when it's not possible to dump a REUSEPORT_SOCKARRAY map | expand |
2019-04-11 17:27 UTC+0900 ~ Benjamin Poirier <bpoirier@suse.com> > avoids outputting a series of > value: > No space left on device > > The value itself is not wrong but bpf_fd_reuseport_array_lookup_elem() can > only return it if the map was created with value_size = 8. There's nothing > bpftool can do about it. Instead of repeating this error for every key in > the map, print the error once, print an explanatory message and exit. > > Signed-off-by: Benjamin Poirier <bpoirier@suse.com> > --- > > Note that this will lead to a merge conflict if the patch "bpftool: Fix > errno variable usage" is merged in the bpf branch: > > <<<<<<< HEAD > if (lookup_errno == ENOENT) > ======= > if (errno == ENOENT) { >>>>>>>> bpf-next > > The resolution should be trivial: > if (lookup_errno == ENOENT) { > > tools/bpf/bpftool/map.c | 21 +++++++++++++++------ > 1 file changed, 15 insertions(+), 6 deletions(-) > > diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c > index e96903078991..bb648e42923c 100644 > --- a/tools/bpf/bpftool/map.c > +++ b/tools/bpf/bpftool/map.c > @@ -684,7 +684,6 @@ static int dump_map_elem(int fd, void *key, void *value, > struct bpf_map_info *map_info, struct btf *btf, > json_writer_t *btf_wtr) > { > - int num_elems = 0; > int lookup_errno; > > if (!bpf_map_lookup_elem(fd, key, value)) { > @@ -702,9 +701,8 @@ static int dump_map_elem(int fd, void *key, void *value, > } else { > print_entry_plain(map_info, key, value); > } > - num_elems++; > } > - return num_elems; > + return 1; > } > > /* lookup error handling */ > @@ -722,11 +720,13 @@ static int dump_map_elem(int fd, void *key, void *value, > jsonw_string_field(json_wtr, "error", strerror(lookup_errno)); > jsonw_end_object(json_wtr); > } else { > - if (errno == ENOENT) > + if (errno == ENOENT) { > print_entry_plain(map_info, key, NULL); > - else > + } else { > print_entry_error(map_info, key, > strerror(lookup_errno)); > + return -lookup_errno; Hi, thanks! One comment: if we return -lookup_errno here... > + } > } > > return 0; > @@ -787,7 +787,16 @@ static int do_dump(int argc, char **argv) > err = 0; > break; > } > - num_elems += dump_map_elem(fd, key, value, &info, btf, btf_wtr); > + err = dump_map_elem(fd, key, value, &info, btf, btf_wtr); > + /* bpf_fd_reuseport_array_lookup_elem() can only return a > + * value if the map's value_size == 8 > + */ > + if (info.type == BPF_MAP_TYPE_REUSEPORT_SOCKARRAY && > + info.value_size != 8 && err == -ENOSPC) { > + p_err("cannot dump REUSEPORT_SOCKARRAY map with value_size != 8"); > + goto exit_free; > + } > + num_elems += err; ... I think we can have a negative err value here (if we're not in the case of reuseport_sockarray with wrong map size)? In that case, the function could print something like "Found -1 elements"? So maybe update num_elems only if err is positive? Although I'd like even better if we could somehow find a way to move this error handling along with the rest of it in dump_map_elem(), and avoid making that function return either a number of elements or an error depending on the result from the lookup. Best regards, Quentin
On Thu, 11 Apr 2019 17:27:00 +0900, Benjamin Poirier wrote: > avoids outputting a series of > value: > No space left on device > > The value itself is not wrong but bpf_fd_reuseport_array_lookup_elem() can > only return it if the map was created with value_size = 8. There's nothing > bpftool can do about it. Instead of repeating this error for every key in > the map, print the error once, print an explanatory message and exit. > > Signed-off-by: Benjamin Poirier <bpoirier@suse.com> > @@ -787,7 +787,16 @@ static int do_dump(int argc, char **argv) > err = 0; > break; > } > - num_elems += dump_map_elem(fd, key, value, &info, btf, btf_wtr); > + err = dump_map_elem(fd, key, value, &info, btf, btf_wtr); > + /* bpf_fd_reuseport_array_lookup_elem() can only return a > + * value if the map's value_size == 8 > + */ > + if (info.type == BPF_MAP_TYPE_REUSEPORT_SOCKARRAY && > + info.value_size != 8 && err == -ENOSPC) { > + p_err("cannot dump REUSEPORT_SOCKARRAY map with value_size != 8"); > + goto exit_free; Hmm... could it still be useful to walk the map to see the keys, even if the kernel can't return meaningful values? > + } > + num_elems += err; > prev_key = key; > } >
======= if (errno == ENOENT) { >>>>>>> bpf-next The resolution should be trivial: if (lookup_errno == ENOENT) { tools/bpf/bpftool/map.c | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-) diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c index e96903078991..bb648e42923c 100644 --- a/tools/bpf/bpftool/map.c +++ b/tools/bpf/bpftool/map.c @@ -684,7 +684,6 @@ static int dump_map_elem(int fd, void *key, void *value, struct bpf_map_info *map_info, struct btf *btf, json_writer_t *btf_wtr) { - int num_elems = 0; int lookup_errno; if (!bpf_map_lookup_elem(fd, key, value)) { @@ -702,9 +701,8 @@ static int dump_map_elem(int fd, void *key, void *value, } else { print_entry_plain(map_info, key, value); } - num_elems++; } - return num_elems; + return 1; } /* lookup error handling */ @@ -722,11 +720,13 @@ static int dump_map_elem(int fd, void *key, void *value, jsonw_string_field(json_wtr, "error", strerror(lookup_errno)); jsonw_end_object(json_wtr); } else { - if (errno == ENOENT) + if (errno == ENOENT) { print_entry_plain(map_info, key, NULL); - else + } else { print_entry_error(map_info, key, strerror(lookup_errno)); + return -lookup_errno; + } } return 0; @@ -787,7 +787,16 @@ static int do_dump(int argc, char **argv) err = 0; break; } - num_elems += dump_map_elem(fd, key, value, &info, btf, btf_wtr); + err = dump_map_elem(fd, key, value, &info, btf, btf_wtr); + /* bpf_fd_reuseport_array_lookup_elem() can only return a + * value if the map's value_size == 8 + */ + if (info.type == BPF_MAP_TYPE_REUSEPORT_SOCKARRAY && + info.value_size != 8 && err == -ENOSPC) { + p_err("cannot dump REUSEPORT_SOCKARRAY map with value_size != 8"); + goto exit_free; + } + num_elems += err; prev_key = key; }
avoids outputting a series of value: No space left on device The value itself is not wrong but bpf_fd_reuseport_array_lookup_elem() can only return it if the map was created with value_size = 8. There's nothing bpftool can do about it. Instead of repeating this error for every key in the map, print the error once, print an explanatory message and exit. Signed-off-by: Benjamin Poirier <bpoirier@suse.com> --- Note that this will lead to a merge conflict if the patch "bpftool: Fix errno variable usage" is merged in the bpf branch: <<<<<<< HEAD if (lookup_errno == ENOENT)