src/pxar/fuse.rs

   1 //! Asynchronous fuse implementation.
   2
   3 use std::collections::BTreeMap;
   4 use std::convert::TryFrom;
   5 use std::ffi::{OsStr, OsString};
   6 use std::future::Future;
   7 use std::io;
   8 use std::mem;
   9 use std::ops::Range;
  10 use std::os::unix::ffi::OsStrExt;
  11 use std::path::Path;
  12 use std::pin::Pin;
  13 use std::sync::atomic::{AtomicUsize, Ordering};
  14 use std::sync::{Arc, RwLock};
  15 use std::task::{Context, Poll};
  16
  17 use anyhow::{format_err, Error};
  18 use futures::channel::mpsc::UnboundedSender;
  19 use futures::select;
  20 use futures::sink::SinkExt;
  21 use futures::stream::{StreamExt, TryStreamExt};
  22
  23 use proxmox::tools::vec;
  24 use pxar::accessor::{self, EntryRangeInfo, ReadAt};
  25
  26 use proxmox_fuse::requests::{self, FuseRequest};
  27 use proxmox_fuse::{EntryParam, Fuse, ReplyBufState, Request, ROOT_ID};
  28
  29 use crate::tools::xattr;
  30
  31 /// We mark inodes for regular files this way so we know how to access them.
  32 const NON_DIRECTORY_INODE: u64 = 1u64 << 63;
  33
  34 #[inline]
  35 fn is_dir_inode(inode: u64) -> bool {
  36     0 == (inode & NON_DIRECTORY_INODE)
  37 }
  38
  39 /// Our reader type instance used for accessors.
  40 pub type Reader = Arc<dyn ReadAt + Send + Sync + 'static>;
  41
  42 /// Our Accessor type instance.
  43 pub type Accessor = accessor::aio::Accessor<Reader>;
  44
  45 /// Our Directory type instance.
  46 pub type Directory = accessor::aio::Directory<Reader>;
  47
  48 /// Our FileEntry type instance.
  49 pub type FileEntry = accessor::aio::FileEntry<Reader>;
  50
  51 /// Our FileContents type instance.
  52 pub type FileContents = accessor::aio::FileContents<Reader>;
  53
  54 pub struct Session {
  55     fut: Pin<Box<dyn Future<Output = Result<(), Error>> + Send + Sync + 'static>>,
  56 }
  57
  58 impl Session {
  59     /// Create a fuse session for an archive.
  60     pub async fn mount_path(
  61         archive_path: &Path,
  62         options: &OsStr,
  63         verbose: bool,
  64         mountpoint: &Path,
  65     ) -> Result<Self, Error> {
  66         // TODO: Add a buffered/caching ReadAt layer?
  67         let file = std::fs::File::open(archive_path)?;
  68         let file_size = file.metadata()?.len();
  69         let reader: Reader = Arc::new(accessor::sync::FileReader::new(file));
  70         let accessor = Accessor::new(reader, file_size).await?;
  71         Self::mount(accessor, options, verbose, mountpoint)
  72     }
  73
  74     /// Create a new fuse session for the given pxar `Accessor`.
  75     pub fn mount(
  76         accessor: Accessor,
  77         options: &OsStr,
  78         verbose: bool,
  79         path: &Path,
  80     ) -> Result<Self, Error> {
  81         let fuse = Fuse::builder("pxar-mount")?
  82             .debug()
  83             .options_os(options)?
  84             .enable_readdirplus()
  85             .enable_read()
  86             .enable_readlink()
  87             .enable_read_xattr()
  88             .build()?
  89             .mount(path)?;
  90
  91         let session = SessionImpl::new(accessor, verbose);
  92
  93         Ok(Self {
  94             fut: Box::pin(session.main(fuse)),
  95         })
  96     }
  97 }
  98
  99 impl Future for Session {
 100     type Output = Result<(), Error>;
 101
 102     fn poll(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
 103         Pin::new(&mut self.fut).poll(cx)
 104     }
 105 }
 106
 107 /// We use this to return an errno value back to the kernel.
 108 macro_rules! io_return {
 109     ($errno:expr) => {
 110         return Err(::std::io::Error::from_raw_os_error($errno).into());
 111     };
 112 }
 113
 114 /// Format an "other" error, see `io_bail` below for details.
 115 macro_rules! io_format_err {
 116     ($($fmt:tt)*) => {
 117         ::std::io::Error::new(::std::io::ErrorKind::Other, format!($($fmt)*))
 118     }
 119 }
 120
 121 /// We use this to bail out of a functionin an unexpected error case. This will cause the fuse
 122 /// request to be answered with a generic `EIO` error code. The error message contained in here
 123 /// will be printed to stdout if the verbose flag is used, otherwise silently dropped.
 124 macro_rules! io_bail {
 125     ($($fmt:tt)*) => { return Err(io_format_err!($($fmt)*).into()); }
 126 }
 127
 128 /// This is what we need to cache as a "lookup" entry. The kernel assumes that these are easily
 129 /// accessed.
 130 struct Lookup {
 131     refs: AtomicUsize,
 132
 133     inode: u64,
 134     parent: u64,
 135     entry_range_info: EntryRangeInfo,
 136     content_range: Option<Range<u64>>,
 137 }
 138
 139 impl Lookup {
 140     fn new(
 141         inode: u64,
 142         parent: u64,
 143         entry_range_info: EntryRangeInfo,
 144         content_range: Option<Range<u64>>,
 145     ) -> Box<Lookup> {
 146         Box::new(Self {
 147             refs: AtomicUsize::new(1),
 148             inode,
 149             parent,
 150             entry_range_info,
 151             content_range,
 152         })
 153     }
 154
 155     /// Decrease the reference count by `count`. Note that this must not include the reference held
 156     /// by `self` itself, so this must not decrease the count below 2.
 157     fn forget(&self, count: usize) -> Result<(), Error> {
 158         loop {
 159             let old = self.refs.load(Ordering::Acquire);
 160             if count >= old {
 161                 io_bail!("reference count underflow");
 162             }
 163             let new = old - count;
 164             match self
 165                 .refs
 166                 .compare_exchange(old, new, Ordering::SeqCst, Ordering::SeqCst)
 167             {
 168                 Ok(_) => break Ok(()),
 169                 Err(_) => continue,
 170             }
 171         }
 172     }
 173
 174     fn get_ref<'a>(&self, session: &'a SessionImpl) -> LookupRef<'a> {
 175         if self.refs.fetch_add(1, Ordering::AcqRel) == 0 {
 176             panic!("atomic refcount increased from 0 to 1");
 177         }
 178
 179         LookupRef {
 180             session,
 181             lookup: self as *const Lookup,
 182         }
 183     }
 184 }
 185
 186 struct LookupRef<'a> {
 187     session: &'a SessionImpl,
 188     lookup: *const Lookup,
 189 }
 190
 191 unsafe impl<'a> Send for LookupRef<'a> {}
 192 unsafe impl<'a> Sync for LookupRef<'a> {}
 193
 194 impl<'a> Clone for LookupRef<'a> {
 195     fn clone(&self) -> Self {
 196         self.get_ref(self.session)
 197     }
 198 }
 199
 200 impl<'a> std::ops::Deref for LookupRef<'a> {
 201     type Target = Lookup;
 202
 203     fn deref(&self) -> &Self::Target {
 204         unsafe { &*self.lookup }
 205     }
 206 }
 207
 208 impl<'a> Drop for LookupRef<'a> {
 209     fn drop(&mut self) {
 210         if self.lookup.is_null() {
 211             return;
 212         }
 213
 214         if self.refs.fetch_sub(1, Ordering::AcqRel) == 1 {
 215             let inode = self.inode;
 216             drop(self.session.lookups.write().unwrap().remove(&inode));
 217         }
 218     }
 219 }
 220
 221 impl<'a> LookupRef<'a> {
 222     fn leak(mut self) -> &'a Lookup {
 223         unsafe { &*mem::replace(&mut self.lookup, std::ptr::null()) }
 224     }
 225 }
 226
 227 struct SessionImpl {
 228     accessor: Accessor,
 229     verbose: bool,
 230     lookups: RwLock<BTreeMap<u64, Box<Lookup>>>,
 231 }
 232
 233 impl SessionImpl {
 234     fn new(accessor: Accessor, verbose: bool) -> Self {
 235         let root = Lookup::new(
 236             ROOT_ID,
 237             ROOT_ID,
 238             EntryRangeInfo::toplevel(0..accessor.size()),
 239             None,
 240         );
 241
 242         let mut tree = BTreeMap::new();
 243         tree.insert(ROOT_ID, root);
 244
 245         Self {
 246             accessor,
 247             verbose,
 248             lookups: RwLock::new(tree),
 249         }
 250     }
 251
 252     /// Here's how we deal with errors:
 253     ///
 254     /// Any error will be printed if the verbose flag was set, otherwise the message will be
 255     /// silently dropped.
 256     ///
 257     /// Opaque errors will cause the fuse main loop to bail out with that error.
 258     ///
 259     /// `io::Error`s will cause the fuse request to responded to with the given `io::Error`. An
 260     /// `io::ErrorKind::Other` translates to a generic `EIO`.
 261     async fn handle_err(
 262         &self,
 263         request: impl FuseRequest,
 264         err: Error,
 265         mut sender: UnboundedSender<Error>,
 266     ) {
 267         let final_result = match err.downcast::<io::Error>() {
 268             Ok(err) => {
 269                 if err.kind() == io::ErrorKind::Other && self.verbose {
 270                     eprintln!("an IO error occurred: {}", err);
 271                 }
 272
 273                 // fail the request
 274                 request.io_fail(err).map_err(Error::from)
 275             }
 276             Err(err) => {
 277                 // `bail` (non-`io::Error`) is used for fatal errors which should actually cancel:
 278                 if self.verbose {
 279                     eprintln!("internal error: {}, bailing out", err);
 280                 }
 281                 Err(err)
 282             }
 283         };
 284         if let Err(err) = final_result {
 285             // either we failed to send the error code to fuse, or the above was not an
 286             // `io::Error`, so in this case notify the main loop:
 287             sender
 288                 .send(err)
 289                 .await
 290                 .expect("failed to propagate error to main loop");
 291         }
 292     }
 293
 294     async fn main(self, fuse: Fuse) -> Result<(), Error> {
 295         Arc::new(self).main_do(fuse).await
 296     }
 297
 298     async fn main_do(self: Arc<Self>, fuse: Fuse) -> Result<(), Error> {
 299         let (err_send, mut err_recv) = futures::channel::mpsc::unbounded::<Error>();
 300         let mut fuse = fuse.fuse(); // make this a futures::stream::FusedStream!
 301         loop {
 302             select! {
 303                 request = fuse.try_next() => match request? {
 304                     Some(request) => {
 305                         tokio::spawn(Arc::clone(&self).handle_request(request, err_send.clone()));
 306                     }
 307                     None => break,
 308                 },
 309                 err = err_recv.next() => match err {
 310                     Some(err) => if self.verbose {
 311                         eprintln!("cancelling fuse main loop due to error: {}", err);
 312                         return Err(err);
 313                     },
 314                     None => panic!("error channel was closed unexpectedly"),
 315                 },
 316             }
 317         }
 318         Ok(())
 319     }
 320
 321     async fn handle_request(
 322         self: Arc<Self>,
 323         request: Request,
 324         mut err_sender: UnboundedSender<Error>,
 325     ) {
 326         let result: Result<(), Error> = match request {
 327             Request::Lookup(request) => {
 328                 match self.lookup(request.parent, &request.file_name).await {
 329                     Ok((entry, lookup)) => match request.reply(&entry) {
 330                         Ok(()) => {
 331                             lookup.leak();
 332                             Ok(())
 333                         }
 334                         Err(err) => Err(Error::from(err)),
 335                     },
 336                     Err(err) => return self.handle_err(request, err, err_sender).await,
 337                 }
 338             }
 339             Request::Forget(request) => match self.forget(request.inode, request.count as usize) {
 340                 Ok(()) => {
 341                     request.reply();
 342                     Ok(())
 343                 }
 344                 Err(err) => return self.handle_err(request, err, err_sender).await,
 345             },
 346             Request::Getattr(request) => match self.getattr(request.inode).await {
 347                 Ok(stat) => request.reply(&stat, std::f64::MAX).map_err(Error::from),
 348                 Err(err) => return self.handle_err(request, err, err_sender).await,
 349             },
 350             Request::ReaddirPlus(mut request) => match self.readdirplus(&mut request).await {
 351                 Ok(lookups) => match request.reply() {
 352                     Ok(()) => {
 353                         for i in lookups {
 354                             i.leak();
 355                         }
 356                         Ok(())
 357                     }
 358                     Err(err) => Err(Error::from(err)),
 359                 },
 360                 Err(err) => return self.handle_err(request, err, err_sender).await,
 361             },
 362             Request::Read(request) => {
 363                 match self.read(request.inode, request.size, request.offset).await {
 364                     Ok(data) => request.reply(&data).map_err(Error::from),
 365                     Err(err) => return self.handle_err(request, err, err_sender).await,
 366                 }
 367             }
 368             Request::Readlink(request) => match self.readlink(request.inode).await {
 369                 Ok(data) => request.reply(&data).map_err(Error::from),
 370                 Err(err) => return self.handle_err(request, err, err_sender).await,
 371             },
 372             Request::ListXAttrSize(request) => match self.listxattrs(request.inode).await {
 373                 Ok(data) => request
 374                     .reply(
 375                         data.into_iter()
 376                             .fold(0, |sum, i| sum + i.name().to_bytes_with_nul().len()),
 377                     )
 378                     .map_err(Error::from),
 379                 Err(err) => return self.handle_err(request, err, err_sender).await,
 380             },
 381             Request::ListXAttr(mut request) => match self.listxattrs_into(&mut request).await {
 382                 Ok(ReplyBufState::Ok) => request.reply().map_err(Error::from),
 383                 Ok(ReplyBufState::Full) => request.fail_full().map_err(Error::from),
 384                 Err(err) => return self.handle_err(request, err, err_sender).await,
 385             },
 386             Request::GetXAttrSize(request) => {
 387                 match self.getxattr(request.inode, &request.attr_name).await {
 388                     Ok(xattr) => request.reply(xattr.value().len()).map_err(Error::from),
 389                     Err(err) => return self.handle_err(request, err, err_sender).await,
 390                 }
 391             }
 392             Request::GetXAttr(request) => {
 393                 match self.getxattr(request.inode, &request.attr_name).await {
 394                     Ok(xattr) => request.reply(xattr.value()).map_err(Error::from),
 395                     Err(err) => return self.handle_err(request, err, err_sender).await,
 396                 }
 397             }
 398             other => {
 399                 if self.verbose {
 400                     eprintln!("Received unexpected fuse request");
 401                 }
 402                 other.fail(libc::ENOSYS).map_err(Error::from)
 403             }
 404         };
 405
 406         if let Err(err) = result {
 407             err_sender
 408                 .send(err)
 409                 .await
 410                 .expect("failed to propagate error to main loop");
 411         }
 412     }
 413
 414     fn get_lookup(&self, inode: u64) -> Result<LookupRef, Error> {
 415         let lookups = self.lookups.read().unwrap();
 416         if let Some(lookup) = lookups.get(&inode) {
 417             return Ok(lookup.get_ref(self));
 418         }
 419         io_return!(libc::ENOENT);
 420     }
 421
 422     async fn open_dir(&self, inode: u64) -> Result<Directory, Error> {
 423         if inode == ROOT_ID {
 424             Ok(self.accessor.open_root().await?)
 425         } else if !is_dir_inode(inode) {
 426             io_return!(libc::ENOTDIR);
 427         } else {
 428             Ok(unsafe { self.accessor.open_dir_at_end(inode).await? })
 429         }
 430     }
 431
 432     async fn open_entry(&self, lookup: &LookupRef<'_>) -> io::Result<FileEntry> {
 433         unsafe {
 434             self.accessor
 435                 .open_file_at_range(&lookup.entry_range_info)
 436                 .await
 437         }
 438     }
 439
 440     fn open_content(&self, lookup: &LookupRef) -> Result<FileContents, Error> {
 441         if is_dir_inode(lookup.inode) {
 442             io_return!(libc::EISDIR);
 443         }
 444
 445         match lookup.content_range.clone() {
 446             Some(range) => Ok(unsafe { self.accessor.open_contents_at_range(range) }),
 447             None => io_return!(libc::EBADF),
 448         }
 449     }
 450
 451     fn make_lookup(&self, parent: u64, inode: u64, entry: &FileEntry) -> Result<LookupRef, Error> {
 452         let lookups = self.lookups.read().unwrap();
 453         if let Some(lookup) = lookups.get(&inode) {
 454             return Ok(lookup.get_ref(self));
 455         }
 456         drop(lookups);
 457
 458         let entry = Lookup::new(
 459             inode,
 460             parent,
 461             entry.entry_range_info().clone(),
 462             entry.content_range()?,
 463         );
 464         let reference = entry.get_ref(self);
 465         entry.refs.store(1, Ordering::Release);
 466
 467         let mut lookups = self.lookups.write().unwrap();
 468         if let Some(lookup) = lookups.get(&inode) {
 469             return Ok(lookup.get_ref(self));
 470         }
 471
 472         lookups.insert(inode, entry);
 473         drop(lookups);
 474         Ok(reference)
 475     }
 476
 477     fn forget(&self, inode: u64, count: usize) -> Result<(), Error> {
 478         let node = self.get_lookup(inode)?;
 479         node.forget(count)?;
 480         Ok(())
 481     }
 482
 483     async fn lookup(
 484         &'_ self,
 485         parent: u64,
 486         file_name: &OsStr,
 487     ) -> Result<(EntryParam, LookupRef<'_>), Error> {
 488         let dir = self.open_dir(parent).await?;
 489
 490         let entry = match { dir }.lookup(file_name).await? {
 491             Some(entry) => entry,
 492             None => io_return!(libc::ENOENT),
 493         };
 494
 495         let entry = if let pxar::EntryKind::Hardlink(_) = entry.kind() {
 496             // we don't know the file's end-offset, so we'll just allow the decoder to decode the
 497             // entire rest of the archive until we figure out something better...
 498             let entry = self.accessor.follow_hardlink(&entry).await?;
 499
 500             if let pxar::EntryKind::Hardlink(_) = entry.kind() {
 501                 // hardlinks must not point to other hardlinks...
 502                 io_return!(libc::ELOOP);
 503             }
 504
 505             entry
 506         } else {
 507             entry
 508         };
 509
 510         let response = to_entry(&entry)?;
 511         let inode = response.inode;
 512         Ok((response, self.make_lookup(parent, inode, &entry)?))
 513     }
 514
 515     async fn getattr(&self, inode: u64) -> Result<libc::stat, Error> {
 516         let entry = unsafe {
 517             self.accessor.open_file_at_range(&self.get_lookup(inode)?.entry_range_info).await?
 518         };
 519         to_stat(inode, &entry)
 520     }
 521
 522     async fn readdirplus(
 523         &'_ self,
 524         request: &mut requests::ReaddirPlus,
 525     ) -> Result<Vec<LookupRef<'_>>, Error> {
 526         let mut lookups = Vec::new();
 527         let offset = usize::try_from(request.offset)
 528             .map_err(|_| io_format_err!("directory offset out of range"))?;
 529
 530         let dir = self.open_dir(request.inode).await?;
 531         let dir_lookup = self.get_lookup(request.inode)?;
 532
 533         let entry_count = dir.read_dir().count() as isize;
 534
 535         let mut next = offset as isize;
 536         let mut iter = dir.read_dir().skip(offset);
 537         while let Some(file) = iter.next().await {
 538             next += 1;
 539             let file = file?.decode_entry().await?;
 540             let stat = to_stat(to_inode(&file), &file)?;
 541             let name = file.file_name();
 542             match request.add_entry(name, &stat, next, 1, std::f64::MAX, std::f64::MAX)? {
 543                 ReplyBufState::Ok => (),
 544                 ReplyBufState::Full => return Ok(lookups),
 545             }
 546             lookups.push(self.make_lookup(request.inode, stat.st_ino, &file)?);
 547         }
 548
 549         if next == entry_count {
 550             next += 1;
 551             let file = dir.lookup_self().await?;
 552             let stat = to_stat(to_inode(&file), &file)?;
 553             let name = OsStr::new(".");
 554             match request.add_entry(name, &stat, next, 1, std::f64::MAX, std::f64::MAX)? {
 555                 ReplyBufState::Ok => (),
 556                 ReplyBufState::Full => return Ok(lookups),
 557             }
 558             lookups.push(LookupRef::clone(&dir_lookup));
 559         }
 560
 561         if next == entry_count + 1 {
 562             next += 1;
 563             let lookup = self.get_lookup(dir_lookup.parent)?;
 564             let parent_dir = self.open_dir(lookup.inode).await?;
 565             let file = parent_dir.lookup_self().await?;
 566             let stat = to_stat(to_inode(&file), &file)?;
 567             let name = OsStr::new("..");
 568             match request.add_entry(name, &stat, next, 1, std::f64::MAX, std::f64::MAX)? {
 569                 ReplyBufState::Ok => (),
 570                 ReplyBufState::Full => return Ok(lookups),
 571             }
 572             lookups.push(lookup);
 573         }
 574
 575         Ok(lookups)
 576     }
 577
 578     async fn read(&self, inode: u64, len: usize, offset: u64) -> Result<Vec<u8>, Error> {
 579         let file = self.get_lookup(inode)?;
 580         let content = self.open_content(&file)?;
 581         let mut buf = vec::undefined(len);
 582         let got = content.read_at(&mut buf, offset).await?;
 583         buf.truncate(got);
 584         Ok(buf)
 585     }
 586
 587     async fn readlink(&self, inode: u64) -> Result<OsString, Error> {
 588         let lookup = self.get_lookup(inode)?;
 589         let file = self.open_entry(&lookup).await?;
 590         match file.get_symlink() {
 591             None => io_return!(libc::EINVAL),
 592             Some(link) => Ok(link.to_owned()),
 593         }
 594     }
 595
 596     async fn listxattrs(&self, inode: u64) -> Result<Vec<pxar::format::XAttr>, Error> {
 597         let lookup = self.get_lookup(inode)?;
 598         let metadata = self
 599             .open_entry(&lookup)
 600             .await?
 601             .into_entry()
 602             .into_metadata();
 603
 604         let mut xattrs = metadata.xattrs;
 605
 606         use pxar::format::XAttr;
 607
 608         if let Some(fcaps) = metadata.fcaps {
 609             xattrs.push(XAttr::new(xattr::xattr_name_fcaps().to_bytes(), fcaps.data));
 610         }
 611
 612         // TODO: Special cases:
 613         //     b"system.posix_acl_access
 614         //     b"system.posix_acl_default
 615         //
 616         // For these we need to be able to create posix acl format entries, at that point we could
 617         // just ditch libacl as well...
 618
 619         Ok(xattrs)
 620     }
 621
 622     async fn listxattrs_into(
 623         &self,
 624         request: &mut requests::ListXAttr,
 625     ) -> Result<ReplyBufState, Error> {
 626         let xattrs = self.listxattrs(request.inode).await?;
 627
 628         for entry in xattrs {
 629             match request.add_c_string(entry.name()) {
 630                 ReplyBufState::Ok => (),
 631                 ReplyBufState::Full => return Ok(ReplyBufState::Full),
 632             }
 633         }
 634
 635         Ok(ReplyBufState::Ok)
 636     }
 637
 638     async fn getxattr(&self, inode: u64, xattr: &OsStr) -> Result<pxar::format::XAttr, Error> {
 639         // TODO: pxar::Accessor could probably get a more optimized method to fetch a specific
 640         // xattr for an entry...
 641         let xattrs = self.listxattrs(inode).await?;
 642         for entry in xattrs {
 643             if entry.name().to_bytes() == xattr.as_bytes() {
 644                 return Ok(entry);
 645             }
 646         }
 647         io_return!(libc::ENODATA);
 648     }
 649 }
 650
 651 #[inline]
 652 fn to_entry(entry: &FileEntry) -> Result<EntryParam, Error> {
 653     to_entry_param(to_inode(&entry), &entry)
 654 }
 655
 656 #[inline]
 657 fn to_inode(entry: &FileEntry) -> u64 {
 658     if entry.is_dir() {
 659         entry.entry_range_info().entry_range.end
 660     } else {
 661         entry.entry_range_info().entry_range.start | NON_DIRECTORY_INODE
 662     }
 663 }
 664
 665 fn to_entry_param(inode: u64, entry: &pxar::Entry) -> Result<EntryParam, Error> {
 666     Ok(EntryParam::simple(inode, to_stat(inode, entry)?))
 667 }
 668
 669 fn to_stat(inode: u64, entry: &pxar::Entry) -> Result<libc::stat, Error> {
 670     let nlink = if entry.is_dir() { 2 } else { 1 };
 671
 672     let metadata = entry.metadata();
 673
 674     let mut stat: libc::stat = unsafe { mem::zeroed() };
 675     stat.st_ino = inode;
 676     stat.st_nlink = nlink;
 677     stat.st_mode = u32::try_from(metadata.stat.mode)
 678         .map_err(|err| format_err!("mode does not fit into st_mode field: {}", err))?;
 679     stat.st_size = i64::try_from(entry.file_size().unwrap_or(0))
 680         .map_err(|err| format_err!("size does not fit into st_size field: {}", err))?;
 681     stat.st_uid = metadata.stat.uid;
 682     stat.st_gid = metadata.stat.gid;
 683     stat.st_atime = metadata.stat.mtime.secs;
 684     stat.st_atime_nsec = metadata.stat.mtime.nanos as _;
 685     stat.st_mtime = metadata.stat.mtime.secs;
 686     stat.st_mtime_nsec = metadata.stat.mtime.nanos as _;
 687     stat.st_ctime = metadata.stat.mtime.secs;
 688     stat.st_ctime_nsec = metadata.stat.mtime.nanos as _;
 689     Ok(stat)
 690 }