[thin_dump (rust)] First pass at thin_dump.

Doesn't include --repair.

This includes <def> and <ref> sections for shared regions.
This commit is contained in:
Joe Thornber 2020-09-28 15:42:07 +01:00
parent a88ae3ca18
commit e9fbcc31de
9 changed files with 571 additions and 4 deletions

105
src/bin/thin_dump.rs Normal file
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@ -0,0 +1,105 @@
extern crate clap;
extern crate thinp;
use atty::Stream;
use clap::{App, Arg};
use std::path::Path;
use std::process;
use std::process::exit;
use std::sync::Arc;
use thinp::file_utils;
use thinp::report::*;
use thinp::thin::dump::{dump, ThinDumpOptions};
fn main() {
let parser = App::new("thin_check")
.version(thinp::version::TOOLS_VERSION)
.about("Validates thin provisioning metadata on a device or file.")
.arg(
Arg::with_name("QUIET")
.help("Suppress output messages, return only exit code.")
.short("q")
.long("quiet"),
)
.arg(
Arg::with_name("SB_ONLY")
.help("Only check the superblock.")
.long("super-block-only")
.value_name("SB_ONLY"),
)
.arg(
Arg::with_name("SKIP_MAPPINGS")
.help("Don't check the mapping tree")
.long("skip-mappings")
.value_name("SKIP_MAPPINGS"),
)
.arg(
Arg::with_name("AUTO_REPAIR")
.help("Auto repair trivial issues.")
.long("auto-repair"),
)
.arg(
Arg::with_name("IGNORE_NON_FATAL")
.help("Only return a non-zero exit code if a fatal error is found.")
.long("ignore-non-fatal-errors"),
)
.arg(
Arg::with_name("CLEAR_NEEDS_CHECK")
.help("Clears the 'needs_check' flag in the superblock")
.long("clear-needs-check"),
)
.arg(
Arg::with_name("OVERRIDE_MAPPING_ROOT")
.help("Specify a mapping root to use")
.long("override-mapping-root")
.value_name("OVERRIDE_MAPPING_ROOT")
.takes_value(true),
)
.arg(
Arg::with_name("METADATA_SNAPSHOT")
.help("Check the metadata snapshot on a live pool")
.short("m")
.long("metadata-snapshot")
.value_name("METADATA_SNAPSHOT"),
)
.arg(
Arg::with_name("INPUT")
.help("Specify the input device to check")
.required(true)
.index(1),
)
.arg(
Arg::with_name("SYNC_IO")
.help("Force use of synchronous io")
.long("sync-io"),
);
let matches = parser.get_matches();
let input_file = Path::new(matches.value_of("INPUT").unwrap());
if !file_utils::file_exists(input_file) {
eprintln!("Couldn't find input file '{:?}'.", &input_file);
exit(1);
}
let report;
if matches.is_present("QUIET") {
report = std::sync::Arc::new(mk_quiet_report());
} else if atty::is(Stream::Stdout) {
report = std::sync::Arc::new(mk_progress_bar_report());
} else {
report = Arc::new(mk_simple_report());
}
let opts = ThinDumpOptions {
dev: &input_file,
async_io: !matches.is_present("SYNC_IO"),
report,
};
if let Err(reason) = dump(opts) {
println!("{}", reason);
process::exit(1);
}
}

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@ -550,6 +550,11 @@ pub trait NodeVisitor<V: Unpack> {
values: &[V], values: &[V],
) -> Result<()>; ) -> Result<()>;
// Nodes may be shared and thus visited multiple times. The walker avoids
// doing repeated IO, but it does call this method to keep the visitor up to
// date.
fn visit_again(&self, path: &Vec<u64>, b: u64) -> Result<()>;
fn end_walk(&self) -> Result<()>; fn end_walk(&self) -> Result<()>;
} }
@ -654,7 +659,11 @@ impl BTreeWalker {
// This node has already been checked ... // This node has already been checked ...
match self.failed(bs[i]) { match self.failed(bs[i]) {
None => { None => {
// ... it was clean so we can ignore. // ... it was clean.
if let Err(e) = visitor.visit_again(path, bs[i]) {
// ... but the visitor isn't happy
errs.push(e.clone());
}
} }
Some(e) => { Some(e) => {
// ... there was an error // ... there was an error
@ -773,7 +782,7 @@ impl BTreeWalker {
if let Some(e) = self.failed(root) { if let Some(e) = self.failed(root) {
Err(e.clone()) Err(e.clone())
} else { } else {
Ok(()) visitor.visit_again(path, root)
} }
} else { } else {
let root = self.engine.read(root).map_err(|_| io_err(path))?; let root = self.engine.read(root).map_err(|_| io_err(path))?;
@ -878,7 +887,11 @@ where
// This node has already been checked ... // This node has already been checked ...
match w.failed(bs[i]) { match w.failed(bs[i]) {
None => { None => {
// ... it was clean so we can ignore. // ... it was clean.
if let Err(e) = visitor.visit_again(path, bs[i]) {
// ... but the visitor isn't happy
errs.push(e.clone());
}
} }
Some(e) => { Some(e) => {
// ... there was an error // ... there was an error
@ -953,7 +966,7 @@ where
if let Some(e) = w.failed(root) { if let Some(e) = w.failed(root) {
Err(e.clone()) Err(e.clone())
} else { } else {
Ok(()) visitor.visit_again(path, root)
} }
} else { } else {
let root = w.engine.read(root).map_err(|_| io_err(path))?; let root = w.engine.read(root).map_err(|_| io_err(path))?;
@ -997,6 +1010,10 @@ impl<V: Unpack + Copy> NodeVisitor<V> for ValueCollector<V> {
Ok(()) Ok(())
} }
fn visit_again(&self, _path: &Vec<u64>, _b: u64) -> Result<()> {
Ok(())
}
fn end_walk(&self) -> Result<()> { fn end_walk(&self) -> Result<()> {
Ok(()) Ok(())
} }
@ -1060,6 +1077,10 @@ impl<V: Unpack + Clone> NodeVisitor<V> for ValuePathCollector<V> {
Ok(()) Ok(())
} }
fn visit_again(&self, _path: &Vec<u64>, _b: u64) -> Result<()> {
Ok(())
}
fn end_walk(&self) -> Result<()> { fn end_walk(&self) -> Result<()> {
Ok(()) Ok(())
} }

View File

@ -225,6 +225,10 @@ pub trait SpaceMap {
fn get_nr_blocks(&self) -> Result<u64>; fn get_nr_blocks(&self) -> Result<u64>;
fn get_nr_allocated(&self) -> Result<u64>; fn get_nr_allocated(&self) -> Result<u64>;
fn get(&self, b: u64) -> Result<u32>; fn get(&self, b: u64) -> Result<u32>;
// Returns the old ref count
fn set(&mut self, b: u64, v: u32) -> Result<u32>;
fn inc(&mut self, begin: u64, len: u64) -> Result<()>; fn inc(&mut self, begin: u64, len: u64) -> Result<()>;
} }
@ -265,6 +269,20 @@ where
Ok(self.counts[b as usize].into()) Ok(self.counts[b as usize].into())
} }
fn set(&mut self, b: u64, v: u32) -> Result<u32> {
let old = self.counts[b as usize];
assert!(v < 0xff); // FIXME: we can't assume this
self.counts[b as usize] = V::from(v as u8);
if old == V::from(0u8) && v != 0 {
self.nr_allocated += 1;
} else if old != V::from(0u8) && v == 0 {
self.nr_allocated -= 1;
}
Ok(old.into())
}
fn inc(&mut self, begin: u64, len: u64) -> Result<()> { fn inc(&mut self, begin: u64, len: u64) -> Result<()> {
for b in begin..(begin + len) { for b in begin..(begin + len) {
if self.counts[b as usize] == V::from(0u8) { if self.counts[b as usize] == V::from(0u8) {
@ -325,6 +343,24 @@ impl SpaceMap for RestrictedSpaceMap {
} }
} }
fn set(&mut self, b: u64, v: u32) -> Result<u32> {
let old = self.counts.contains(b as usize);
if v > 0 {
if !old {
self.nr_allocated += 1;
}
self.counts.insert(b as usize);
} else {
if old {
self.nr_allocated -= 1;
}
self.counts.set(b as usize, false);
}
Ok(if old {1} else {0})
}
fn inc(&mut self, begin: u64, len: u64) -> Result<()> { fn inc(&mut self, begin: u64, len: u64) -> Result<()> {
for b in begin..(begin + len) { for b in begin..(begin + len) {
if !self.counts.contains(b as usize) { if !self.counts.contains(b as usize) {

View File

@ -45,6 +45,14 @@ impl xml::MetadataVisitor for Pass1 {
Ok(Visit::Continue) Ok(Visit::Continue)
} }
fn def_shared_b(&mut self, _name: &str) -> Result<Visit> {
todo!();
}
fn def_shared_e(&mut self) -> Result<Visit> {
todo!();
}
fn device_b(&mut self, _d: &xml::Device) -> Result<Visit> { fn device_b(&mut self, _d: &xml::Device) -> Result<Visit> {
Ok(Visit::Continue) Ok(Visit::Continue)
} }
@ -63,6 +71,10 @@ impl xml::MetadataVisitor for Pass1 {
Ok(Visit::Continue) Ok(Visit::Continue)
} }
fn ref_shared(&mut self, _name: &str) -> Result<Visit> {
todo!();
}
fn eof(&mut self) -> Result<Visit> { fn eof(&mut self) -> Result<Visit> {
Ok(Visit::Continue) Ok(Visit::Continue)
} }
@ -96,6 +108,14 @@ impl<W: Write> xml::MetadataVisitor for Pass2<W> {
self.writer.superblock_e() self.writer.superblock_e()
} }
fn def_shared_b(&mut self, _name: &str) -> Result<Visit> {
todo!();
}
fn def_shared_e(&mut self) -> Result<Visit> {
todo!();
}
fn device_b(&mut self, d: &xml::Device) -> Result<Visit> { fn device_b(&mut self, d: &xml::Device) -> Result<Visit> {
self.writer.device_b(d) self.writer.device_b(d)
} }
@ -127,6 +147,10 @@ impl<W: Write> xml::MetadataVisitor for Pass2<W> {
Ok(Visit::Continue) Ok(Visit::Continue)
} }
fn ref_shared(&mut self, _name: &str) -> Result<Visit> {
todo!();
}
fn eof(&mut self) -> Result<Visit> { fn eof(&mut self) -> Result<Visit> {
self.writer.eof() self.writer.eof()
} }

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@ -59,6 +59,10 @@ impl NodeVisitor<BlockTime> for BottomLevelVisitor {
Ok(()) Ok(())
} }
fn visit_again(&self, _path: &Vec<u64>, _b: u64) -> btree::Result<()> {
Ok(())
}
fn end_walk(&self) -> btree::Result<()> { fn end_walk(&self) -> btree::Result<()> {
Ok(()) Ok(())
} }
@ -98,6 +102,10 @@ impl<'a> NodeVisitor<u32> for OverflowChecker<'a> {
Ok(()) Ok(())
} }
fn visit_again(&self, _path: &Vec<u64>, _b: u64) -> btree::Result<()> {
Ok(())
}
fn end_walk(&self) -> btree::Result<()> { fn end_walk(&self) -> btree::Result<()> {
Ok(()) Ok(())
} }

323
src/thin/dump.rs Normal file
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@ -0,0 +1,323 @@
use anyhow::Result;
use std::collections::{BTreeMap, BTreeSet};
use std::path::Path;
use std::sync::{Arc, Mutex};
use crate::io_engine::{AsyncIoEngine, IoEngine, SyncIoEngine};
use crate::pdata::btree::{self, *};
use crate::pdata::space_map::*;
use crate::pdata::unpack::*;
use crate::report::*;
use crate::thin::block_time::*;
use crate::thin::device_detail::*;
use crate::thin::superblock::*;
use crate::thin::xml::{self, MetadataVisitor};
//------------------------------------------
struct RunBuilder {
run: Option<xml::Map>,
}
impl RunBuilder {
fn new() -> RunBuilder {
RunBuilder { run: None }
}
fn next(&mut self, thin_block: u64, data_block: u64, time: u32) -> Option<xml::Map> {
use xml::Map;
match self.run {
None => {
self.run = Some(xml::Map {
thin_begin: thin_block,
data_begin: data_block,
time: time,
len: 1,
});
None
}
Some(xml::Map {
thin_begin,
data_begin,
time: mtime,
len,
}) => {
if thin_block == (thin_begin + len)
&& data_block == (data_begin + len)
&& mtime == time
{
self.run.as_mut().unwrap().len += 1;
None
} else {
self.run.replace(Map {
thin_begin: thin_block,
data_begin: data_block,
time: time,
len: 1,
})
}
}
}
}
fn complete(&mut self) -> Option<xml::Map> {
self.run.take()
}
}
//------------------------------------------
struct MVInner<'a> {
md_out: &'a mut dyn xml::MetadataVisitor,
builder: RunBuilder,
}
struct MappingVisitor<'a> {
inner: Mutex<MVInner<'a>>,
}
//------------------------------------------
impl<'a> MappingVisitor<'a> {
fn new(md_out: &'a mut dyn xml::MetadataVisitor) -> MappingVisitor<'a> {
MappingVisitor {
inner: Mutex::new(MVInner {
md_out,
builder: RunBuilder::new(),
}),
}
}
}
impl<'a> NodeVisitor<BlockTime> for MappingVisitor<'a> {
fn visit(
&self,
_path: &Vec<u64>,
_kr: &KeyRange,
_h: &NodeHeader,
keys: &[u64],
values: &[BlockTime],
) -> btree::Result<()> {
let mut inner = self.inner.lock().unwrap();
for (k, v) in keys.iter().zip(values.iter()) {
if let Some(run) = inner.builder.next(*k, v.block, v.time) {
inner
.md_out
.map(&run)
.map_err(|e| btree::value_err(format!("{}", e)))?;
}
}
Ok(())
}
fn visit_again(&self, _path: &Vec<u64>, b: u64) -> btree::Result<()> {
let mut inner = self.inner.lock().unwrap();
inner
.md_out
.ref_shared(&format!("{}", b))
.map_err(|e| btree::value_err(format!("{}", e)))?;
Ok(())
}
fn end_walk(&self) -> btree::Result<()> {
let mut inner = self.inner.lock().unwrap();
if let Some(run) = inner.builder.complete() {
inner
.md_out
.map(&run)
.map_err(|e| btree::value_err(format!("{}", e)))?;
}
Ok(())
}
}
//------------------------------------------
const MAX_CONCURRENT_IO: u32 = 1024;
pub struct ThinDumpOptions<'a> {
pub dev: &'a Path,
pub async_io: bool,
pub report: Arc<Report>,
}
struct Context {
report: Arc<Report>,
engine: Arc<dyn IoEngine + Send + Sync>,
}
fn mk_context(opts: &ThinDumpOptions) -> Result<Context> {
let engine: Arc<dyn IoEngine + Send + Sync>;
if opts.async_io {
engine = Arc::new(AsyncIoEngine::new(opts.dev, MAX_CONCURRENT_IO, false)?);
} else {
let nr_threads = std::cmp::max(8, num_cpus::get() * 2);
engine = Arc::new(SyncIoEngine::new(opts.dev, nr_threads, false)?);
}
Ok(Context {
report: opts.report.clone(),
engine,
})
}
//------------------------------------------
struct NoopVisitor {}
impl<V: Unpack> btree::NodeVisitor<V> for NoopVisitor {
fn visit(
&self,
_path: &Vec<u64>,
_kr: &btree::KeyRange,
_h: &btree::NodeHeader,
_k: &[u64],
_values: &[V],
) -> btree::Result<()> {
Ok(())
}
fn visit_again(&self, _path: &Vec<u64>, _b: u64) -> btree::Result<()> {
Ok(())
}
fn end_walk(&self) -> btree::Result<()> {
Ok(())
}
}
fn find_shared_nodes(
ctx: &Context,
nr_metadata_blocks: u64,
roots: &BTreeMap<u64, u64>,
) -> Result<(BTreeSet<u64>, Arc<Mutex<dyn SpaceMap + Send + Sync>>)> {
// By default the walker uses a restricted space map that can only count to 1. So
// we explicitly create a full sm.
let sm = core_sm(nr_metadata_blocks, roots.len() as u32);
let w = BTreeWalker::new_with_sm(ctx.engine.clone(), sm.clone(), false)?;
let mut path = Vec::new();
path.push(0);
for (thin_id, root) in roots {
ctx.report.info(&format!("scanning {}", thin_id));
let v = NoopVisitor {};
w.walk::<NoopVisitor, BlockTime>(&mut path, &v, *root)?;
}
let mut shared = BTreeSet::new();
{
let sm = sm.lock().unwrap();
for i in 0..sm.get_nr_blocks().unwrap() {
if sm.get(i).expect("couldn't get count from space map.") > 1 {
shared.insert(i);
}
}
}
return Ok((shared, sm));
}
//------------------------------------------
fn dump_node(
ctx: &Context,
out: &mut dyn xml::MetadataVisitor,
root: u64,
sm: &Arc<Mutex<dyn SpaceMap + Send + Sync>>,
force: bool, // sets the ref count for the root to zero to force output.
) -> Result<()> {
let w = BTreeWalker::new_with_sm(ctx.engine.clone(), sm.clone(), false)?;
let mut path = Vec::new();
path.push(0);
let v = MappingVisitor::new(out);
// Temporarily set the ref count for the root to zero.
let mut old_count = 0;
if force {
let mut sm = sm.lock().unwrap();
old_count = sm.get(root).unwrap();
sm.set(root, 0)?;
}
w.walk::<MappingVisitor, BlockTime>(&mut path, &v, root)?;
// Reset the ref count for root.
if force {
let mut sm = sm.lock().unwrap();
sm.set(root, old_count)?;
}
Ok(())
}
//------------------------------------------
pub fn dump(opts: ThinDumpOptions) -> Result<()> {
let ctx = mk_context(&opts)?;
let report = &ctx.report;
let engine = &ctx.engine;
// superblock
report.set_title("Reading superblock");
let sb = read_superblock(engine.as_ref(), SUPERBLOCK_LOCATION)?;
let metadata_root = unpack::<SMRoot>(&sb.metadata_sm_root[0..])?;
let data_root = unpack::<SMRoot>(&sb.data_sm_root[0..])?;
let mut path = Vec::new();
path.push(0);
report.set_title("Reading device details");
let devs = btree_to_map::<DeviceDetail>(&mut path, engine.clone(), true, sb.details_root)?;
report.set_title("Reading mappings roots");
let roots = btree_to_map::<u64>(&mut path, engine.clone(), true, sb.mapping_root)?;
report.set_title("Finding shared mappings");
let (shared, sm) = find_shared_nodes(&ctx, metadata_root.nr_blocks, &roots)?;
report.info(&format!("{} shared nodes found", shared.len()));
let mut out = xml::XmlWriter::new(std::io::stdout());
let xml_sb = xml::Superblock {
uuid: "".to_string(),
time: sb.time as u64,
transaction: sb.transaction_id,
flags: None,
version: Some(2),
data_block_size: sb.data_block_size,
nr_data_blocks: data_root.nr_blocks,
metadata_snap: None,
};
out.superblock_b(&xml_sb)?;
report.set_title("Dumping shared regions");
for b in shared {
out.def_shared_b(&format!("{}", b))?;
dump_node(&ctx, &mut out, b, &sm, true)?;
out.def_shared_e()?;
}
report.set_title("Dumping mappings");
for (thin_id, detail) in devs {
let d = xml::Device {
dev_id: thin_id as u32,
mapped_blocks: detail.mapped_blocks,
transaction: detail.transaction_id,
creation_time: detail.creation_time as u64,
snap_time: detail.snapshotted_time as u64,
};
out.device_b(&d)?;
let root = roots.get(&thin_id).unwrap();
dump_node(&ctx, &mut out, *root, &sm, false)?;
out.device_e()?;
}
out.superblock_e()?;
Ok(())
}
//------------------------------------------

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@ -2,4 +2,5 @@ pub mod block_time;
pub mod device_detail; pub mod device_detail;
pub mod superblock; pub mod superblock;
pub mod check; pub mod check;
pub mod dump;
pub mod xml; pub mod xml;

View File

@ -46,10 +46,14 @@ pub trait MetadataVisitor {
fn superblock_b(&mut self, sb: &Superblock) -> Result<Visit>; fn superblock_b(&mut self, sb: &Superblock) -> Result<Visit>;
fn superblock_e(&mut self) -> Result<Visit>; fn superblock_e(&mut self) -> Result<Visit>;
fn def_shared_b(&mut self, name: &str) -> Result<Visit>;
fn def_shared_e(&mut self) -> Result<Visit>;
fn device_b(&mut self, d: &Device) -> Result<Visit>; fn device_b(&mut self, d: &Device) -> Result<Visit>;
fn device_e(&mut self) -> Result<Visit>; fn device_e(&mut self) -> Result<Visit>;
fn map(&mut self, m: &Map) -> Result<Visit>; fn map(&mut self, m: &Map) -> Result<Visit>;
fn ref_shared(&mut self, name: &str) -> Result<Visit>;
fn eof(&mut self) -> Result<Visit>; fn eof(&mut self) -> Result<Visit>;
} }
@ -110,6 +114,19 @@ impl<W: Write> MetadataVisitor for XmlWriter<W> {
Ok(Visit::Continue) Ok(Visit::Continue)
} }
fn def_shared_b(&mut self, name: &str) -> Result<Visit> {
let tag = b"def";
let mut elem = BytesStart::owned(tag.to_vec(), tag.len());
elem.push_attribute(mk_attr(b"name", name));
self.w.write_event(Event::Start(elem))?;
Ok(Visit::Continue)
}
fn def_shared_e(&mut self) -> Result<Visit> {
self.w.write_event(Event::End(BytesEnd::borrowed(b"def")))?;
Ok(Visit::Continue)
}
fn device_b(&mut self, d: &Device) -> Result<Visit> { fn device_b(&mut self, d: &Device) -> Result<Visit> {
let tag = b"device"; let tag = b"device";
let mut elem = BytesStart::owned(tag.to_vec(), tag.len()); let mut elem = BytesStart::owned(tag.to_vec(), tag.len());
@ -151,6 +168,14 @@ impl<W: Write> MetadataVisitor for XmlWriter<W> {
Ok(Visit::Continue) Ok(Visit::Continue)
} }
fn ref_shared(&mut self, name: &str) -> Result<Visit> {
let tag = b"ref";
let mut elem = BytesStart::owned(tag.to_vec(), tag.len());
elem.push_attribute(mk_attr(b"name", name));
self.w.write_event(Event::Empty(elem))?;
Ok(Visit::Continue)
}
fn eof(&mut self) -> Result<Visit> { fn eof(&mut self) -> Result<Visit> {
let w = self.w.inner(); let w = self.w.inner();
w.flush()?; w.flush()?;
@ -379,6 +404,14 @@ impl MetadataVisitor for SBVisitor {
Ok(Visit::Continue) Ok(Visit::Continue)
} }
fn def_shared_b(&mut self, _name: &str) -> Result<Visit> {
Ok(Visit::Continue)
}
fn def_shared_e(&mut self) -> Result<Visit> {
Ok(Visit::Continue)
}
fn device_b(&mut self, _d: &Device) -> Result<Visit> { fn device_b(&mut self, _d: &Device) -> Result<Visit> {
Ok(Visit::Continue) Ok(Visit::Continue)
} }
@ -390,6 +423,10 @@ impl MetadataVisitor for SBVisitor {
Ok(Visit::Continue) Ok(Visit::Continue)
} }
fn ref_shared(&mut self, _name: &str) -> Result<Visit> {
Ok(Visit::Continue)
}
fn eof(&mut self) -> Result<Visit> { fn eof(&mut self) -> Result<Visit> {
Ok(Visit::Stop) Ok(Visit::Stop)
} }

View File

@ -103,6 +103,14 @@ impl<'a, V: ThinVisitor> xml::MetadataVisitor for ThinXmlVisitor<'a, V> {
Ok(Visit::Continue) Ok(Visit::Continue)
} }
fn def_shared_b(&mut self, _name: &str) -> Result<Visit> {
todo!();
}
fn def_shared_e(&mut self) -> Result<Visit> {
todo!();
}
fn device_b(&mut self, d: &xml::Device) -> Result<Visit> { fn device_b(&mut self, d: &xml::Device) -> Result<Visit> {
self.thin_id = Some(d.dev_id); self.thin_id = Some(d.dev_id);
Ok(Visit::Continue) Ok(Visit::Continue)
@ -125,6 +133,10 @@ impl<'a, V: ThinVisitor> xml::MetadataVisitor for ThinXmlVisitor<'a, V> {
Ok(Visit::Continue) Ok(Visit::Continue)
} }
fn ref_shared(&mut self, _name: &str) -> Result<Visit> {
todo!();
}
fn eof(&mut self) -> Result<Visit> { fn eof(&mut self) -> Result<Visit> {
Ok(Visit::Stop) Ok(Visit::Stop)
} }