s/std::fs::read_dir/nix::dir::Dir/ in a few spots

This is nicer in a few ways:

   * I can use openat so there's no possibility of any kind of a race
     involving scanning a different directory than the one used in
     other ways (locking, metadata file, adding/removing sample files)
   * filename() doesn't need to allocate memory, so it's a bit more
     efficient
   * dogfooding - I wrote nix::dir.

db/check.rs

@@ -38,11 +38,11 @@ use crate::recording;
 use failure::Error;
 use fnv::FnvHashMap;
 use log::error;
+use nix::fcntl::AtFlags;
 use protobuf::prelude::MessageField;
 use rusqlite::types::ToSql;
 use crate::schema;
-use std::os::unix::ffi::OsStrExt;
-use std::fs;
+use std::os::unix::io::AsRawFd;
 
 pub struct Options {
     pub compare_lens: bool,
@@ -86,8 +86,8 @@ pub fn run(conn: &rusqlite::Connection, opts: &Options) -> Result<(), Error> {
             }
 
             // Open the directory (checking its metadata) and hold it open (for the lock).
-            let _dir = dir::SampleFileDir::open(&dir_path, &meta)?;
-            let mut streams = read_dir(&dir_path, opts)?;
+            let dir = dir::SampleFileDir::open(&dir_path, &meta)?;
+            let mut streams = read_dir(&dir, opts)?;
             let mut rows = garbage_stmt.query(&[&dir_id])?;
             while let Some(row) = rows.next()? {
                 let id = CompositeId(row.get(0)?);
@@ -186,24 +186,27 @@ fn summarize_index(video_index: &[u8]) -> Result<RecordingSummary, Error> {
 /// Reads through the given sample file directory.
 /// Logs unexpected files and creates a hash map of the files found there.
 /// If `opts.compare_lens` is set, the values are lengths; otherwise they're insignificant.
-fn read_dir(path: &str, opts: &Options) -> Result<Dir, Error> {
+fn read_dir(d: &dir::SampleFileDir, opts: &Options) -> Result<Dir, Error> {
     let mut dir = Dir::default();
-    for e in fs::read_dir(path)? {
+    let mut d = d.opendir()?;
+    let fd = d.as_raw_fd();
+    for e in d.iter() {
         let e = e?;
         let f = e.file_name();
-        let f = f.as_bytes();
-        match f {
-            b"meta" => continue,
+        match f.to_bytes() {
+            b"." | b".." | b"meta" => continue,
             _ => {},
         };
-        let id = match dir::parse_id(f) {
+        let id = match dir::parse_id(f.to_bytes()) {
             Ok(id) => id,
             Err(_) => {
                 error!("sample file directory contains file {:?} which isn't an id", f);
                 continue;
             }
         };
-        let len = if opts.compare_lens { e.metadata()?.len() } else { 0 };
+        let len = if opts.compare_lens {
+            nix::sys::stat::fstatat(fd, f, AtFlags::empty())?.st_size as u64
+        } else { 0 };
         let stream = dir.entry(id.stream()).or_insert_with(Stream::default);
         stream.entry(id.recording()).or_insert_with(Recording::default).file = Some(len);
     }

db/db.rs

@@ -1590,7 +1590,7 @@ impl LockedDatabase {
                 _ => arc,
             },
         };
-        if !dir::SampleFileDir::is_empty(&d.get().path)? {
+        if !dir.is_empty()? {
             bail!("Can't delete sample file directory {} which still has files", &d.get().path);
         }
         let mut meta = d.get().meta(&self.uuid);

db/dir.rs

@@ -44,8 +44,7 @@ use nix::sys::statvfs::Statvfs;
 use std::ffi::{CStr, CString};
 use std::fs;
 use std::io::{Read, Write};
-use std::os::unix::ffi::OsStrExt;
-use std::os::unix::io::FromRawFd;
+use std::os::unix::io::{AsRawFd, RawFd};
 use std::sync::Arc;
 
 /// The fixed length of a directory's `meta` file.
@@ -121,13 +120,6 @@ impl Fd {
         nix::unistd::fsync(self.0)
     }
 
-    /// Opens a sample file within this directory with the given flags and (if creating) mode.
-    pub(crate) fn openat<P: ?Sized + NixPath>(&self, p: &P, oflag: OFlag, mode: Mode)
-                                              -> Result<fs::File, nix::Error> {
-        let fd = nix::fcntl::openat(self.0, p, oflag, mode)?;
-        Ok(unsafe { fs::File::from_raw_fd(fd) })
-    }
-
     /// Locks the directory with the specified `flock` operation.
     pub fn lock(&self, arg: FlockArg) -> Result<(), nix::Error> {
         nix::fcntl::flock(self.0, arg)
@@ -141,7 +133,7 @@ impl Fd {
 /// Reads `dir`'s metadata. If none is found, returns an empty proto.
 pub(crate) fn read_meta(dir: &Fd) -> Result<schema::DirMeta, Error> {
     let mut meta = schema::DirMeta::default();
-    let mut f = match dir.openat(cstr!("meta"), OFlag::O_RDONLY, Mode::empty()) {
+    let mut f = match crate::fs::openat(dir.0, cstr!("meta"), OFlag::O_RDONLY, Mode::empty()) {
         Err(e) => {
             if e == nix::Error::Sys(nix::errno::Errno::ENOENT) {
                 return Ok(meta);
@@ -165,21 +157,21 @@ pub(crate) fn read_meta(dir: &Fd) -> Result<schema::DirMeta, Error> {
 }
 
 /// Write `dir`'s metadata, clobbering existing data.
-pub(crate) fn write_meta(dir: &Fd, meta: &schema::DirMeta) -> Result<(), Error> {
+pub(crate) fn write_meta(dirfd: RawFd, meta: &schema::DirMeta) -> Result<(), Error> {
     let mut data = meta.write_length_delimited_to_bytes().expect("proto3->vec is infallible");
     if data.len() > FIXED_DIR_META_LEN {
         bail!("Length-delimited DirMeta message requires {} bytes, over limit of {}",
               data.len(), FIXED_DIR_META_LEN);
     }
     data.resize(FIXED_DIR_META_LEN, 0);  // pad to required length.
-    let mut f = dir.openat(cstr!("meta"), OFlag::O_CREAT | OFlag::O_WRONLY,
+    let mut f = crate::fs::openat(dirfd, cstr!("meta"), OFlag::O_CREAT | OFlag::O_WRONLY,
                                   Mode::S_IRUSR | Mode::S_IWUSR)?;
     let stat = f.metadata()?;
     if stat.len() == 0 {
         // Need to sync not only the data but also the file metadata and dirent.
         f.write_all(&data)?;
         f.sync_all()?;
-        dir.sync()?;
+        nix::unistd::fsync(dirfd)?;
     } else if stat.len() == FIXED_DIR_META_LEN as u64 {
         // Just syncing the data will suffice; existing metadata and dirent are fine.
         f.write_all(&data)?;
@@ -247,18 +239,24 @@ impl SampleFileDir {
         if old_meta.last_complete_open.is_some() {
             bail!("Can't create dir at path {}: is already in use:\n{:?}", path, old_meta);
         }
-        if !SampleFileDir::is_empty(path)? {
+        if !s.is_empty()? {
             bail!("Can't create dir at path {} with existing files", path);
         }
         s.write_meta(db_meta)?;
         Ok(s)
     }
 
+    pub(crate) fn opendir(&self) -> Result<nix::dir::Dir, nix::Error> {
+        nix::dir::Dir::openat(self.fd.as_raw_fd(), ".", OFlag::O_DIRECTORY | OFlag::O_RDONLY,
+                              Mode::empty())
+    }
+
     /// Determines if the directory is empty, aside form metadata.
-    pub(crate) fn is_empty(path: &str) -> Result<bool, Error> {
-        for e in fs::read_dir(path)? {
+    pub(crate) fn is_empty(&self) -> Result<bool, Error> {
+        let mut dir = self.opendir()?;
+        for e in dir.iter() {
             let e = e?;
-            match e.file_name().as_bytes() {
+            match e.file_name().to_bytes() {
                 b"." | b".." => continue,
                 b"meta" => continue,  // existing metadata is fine.
                 _ => return Ok(false),
@@ -278,17 +276,17 @@ impl SampleFileDir {
     /// Opens the given sample file for reading.
     pub fn open_file(&self, composite_id: CompositeId) -> Result<fs::File, nix::Error> {
         let p = CompositeIdPath::from(composite_id);
-        self.fd.openat(&p, OFlag::O_RDONLY, Mode::empty())
+        crate::fs::openat(self.fd.0, &p, OFlag::O_RDONLY, Mode::empty())
     }
 
     pub fn create_file(&self, composite_id: CompositeId) -> Result<fs::File, nix::Error> {
         let p = CompositeIdPath::from(composite_id);
-        self.fd.openat(&p, OFlag::O_WRONLY | OFlag::O_EXCL | OFlag::O_CREAT,
+        crate::fs::openat(self.fd.0, &p, OFlag::O_WRONLY | OFlag::O_EXCL | OFlag::O_CREAT,
                           Mode::S_IRUSR | Mode::S_IWUSR)
     }
 
     pub(crate) fn write_meta(&self, meta: &schema::DirMeta) -> Result<(), Error> {
-        write_meta(&self.fd, meta)
+        write_meta(self.fd.0, meta)
     }
 
     pub fn statfs(&self) -> Result<Statvfs, nix::Error> { self.fd.statfs() }

db/fs.rs

@@ -0,0 +1,40 @@
+// This file is part of Moonfire NVR, a security camera network video recorder.
+// Copyright (C) 2019 Scott Lamb <slamb@slamb.org>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// In addition, as a special exception, the copyright holders give
+// permission to link the code of portions of this program with the
+// OpenSSL library under certain conditions as described in each
+// individual source file, and distribute linked combinations including
+// the two.
+//
+// You must obey the GNU General Public License in all respects for all
+// of the code used other than OpenSSL. If you modify file(s) with this
+// exception, you may extend this exception to your version of the
+// file(s), but you are not obligated to do so. If you do not wish to do
+// so, delete this exception statement from your version. If you delete
+// this exception statement from all source files in the program, then
+// also delete it here.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+use std::os::unix::io::{FromRawFd, RawFd};
+use nix::NixPath;
+use nix::fcntl::OFlag;
+use nix::sys::stat::Mode;
+
+pub fn openat<P: ?Sized + NixPath>(dirfd: RawFd, path: &P, oflag: OFlag, mode: Mode)
+                                   -> Result<std::fs::File, nix::Error> {
+    let fd = nix::fcntl::openat(dirfd, path, oflag, mode)?;
+    Ok(unsafe { std::fs::File::from_raw_fd(fd) })
+}

db/lib.rs

@@ -36,6 +36,7 @@ mod coding;
 mod compare;
 pub mod db;
 pub mod dir;
+mod fs;
 mod raw;
 pub mod recording;
 mod schema;

db/upgrade/v1_to_v2.rs

@@ -32,12 +32,12 @@
 
 use crate::dir;
 use failure::{Error, bail, format_err};
-use nix::fcntl::FlockArg;
+use nix::fcntl::{FlockArg, OFlag};
+use nix::sys::stat::Mode;
 use protobuf::prelude::MessageField;
 use rusqlite::types::ToSql;
 use crate::schema::DirMeta;
-use std::fs;
-use std::os::unix::ffi::OsStrExt;
+use std::os::unix::io::AsRawFd;
 use uuid::Uuid;
 
 pub fn run(args: &super::Args, tx: &rusqlite::Transaction) -> Result<(), Error> {
@@ -46,9 +46,10 @@ pub fn run(args: &super::Args, tx: &rusqlite::Transaction) -> Result<(), Error>
             .ok_or_else(|| format_err!("--sample-file-dir required when upgrading from \
                                         schema version 1 to 2."))?;
 
-    let d = dir::Fd::open(sample_file_path, false)?;
-    d.lock(FlockArg::LockExclusiveNonblock)?;
-    verify_dir_contents(sample_file_path, tx)?;
+    let mut d = nix::dir::Dir::open(sample_file_path, OFlag::O_DIRECTORY | OFlag::O_RDONLY,
+                                    Mode::empty())?;
+    nix::fcntl::flock(d.as_raw_fd(), FlockArg::LockExclusiveNonblock)?;
+    verify_dir_contents(sample_file_path, &mut d, tx)?;
 
     // These create statements match the schema.sql when version 2 was the latest.
     tx.execute_batch(r#"
@@ -119,7 +120,7 @@ pub fn run(args: &super::Args, tx: &rusqlite::Transaction) -> Result<(), Error>
         open.id = open_id;
         open.uuid.extend_from_slice(&open_uuid_bytes);
     }
-    dir::write_meta(&d, &meta)?;
+    dir::write_meta(d.as_raw_fd(), &meta)?;
 
     tx.execute(r#"
         insert into sample_file_dir (path,  uuid, last_complete_open_id)
@@ -292,7 +293,8 @@ pub fn run(args: &super::Args, tx: &rusqlite::Transaction) -> Result<(), Error>
 /// *   optional: reserved sample file uuids.
 /// *   optional: meta and meta-tmp from half-completed update attempts.
 /// *   forbidden: anything else.
-fn verify_dir_contents(sample_file_path: &str, tx: &rusqlite::Transaction) -> Result<(), Error> {
+fn verify_dir_contents(sample_file_path: &str, dir: &mut nix::dir::Dir,
+                       tx: &rusqlite::Transaction) -> Result<(), Error> {
     // Build a hash of the uuids found in the directory.
     let n: i64 = tx.query_row(r#"
         select
@@ -302,10 +304,10 @@ fn verify_dir_contents(sample_file_path: &str, tx: &rusqlite::Transaction) -> Re
           (select count(*) as c from reserved_sample_files) b;
     "#, &[] as &[&dyn ToSql], |r| r.get(0))?;
     let mut files = ::fnv::FnvHashSet::with_capacity_and_hasher(n as usize, Default::default());
-    for e in fs::read_dir(sample_file_path)? {
+    for e in dir.iter() {
         let e = e?;
         let f = e.file_name();
-        match f.as_bytes() {
+        match f.to_bytes() {
             b"." | b".." => continue,
             b"meta" | b"meta-tmp" => {
                 // Ignore metadata files. These might from a half-finished update attempt.
@@ -315,8 +317,8 @@ fn verify_dir_contents(sample_file_path: &str, tx: &rusqlite::Transaction) -> Re
             _ => {},
         };
         let s = match f.to_str() {
-            Some(s) => s,
-            None => bail!("unexpected file {:?} in {:?}", f, sample_file_path),
+            Ok(s) => s,
+            Err(_) => bail!("unexpected file {:?} in {:?}", f, sample_file_path),
         };
         let uuid = match Uuid::parse_str(s) {
             Ok(u) => u,

db/upgrade/v4_to_v5.rs

@@ -82,7 +82,7 @@ pub fn run(_args: &super::Args, tx: &rusqlite::Transaction) -> Result<(), Error>
         dir.lock(FlockArg::LockExclusiveNonblock)?;
         let tmp_path = cstr!("meta.tmp");
         let path = cstr!("meta");
-        let mut f = dir.openat(path, OFlag::O_RDONLY, Mode::empty())?;
+        let mut f = crate::fs::openat(dir.as_raw_fd(), path, OFlag::O_RDONLY, Mode::empty())?;
         let mut data = Vec::new();
         f.read_to_end(&mut data)?;
         if data.len() == FIXED_DIR_META_LEN {
@@ -95,7 +95,8 @@ pub fn run(_args: &super::Args, tx: &rusqlite::Transaction) -> Result<(), Error>
         if !dir::SampleFileDir::consistent(&db_meta, &dir_meta) {
             bail!("Inconsistent db_meta={:?} dir_meta={:?}", &db_meta, &dir_meta);
         }
-        let mut f = dir.openat(tmp_path, OFlag::O_CREAT | OFlag::O_TRUNC | OFlag::O_WRONLY,
+        let mut f = crate::fs::openat(dir.as_raw_fd(), tmp_path,
+                                      OFlag::O_CREAT | OFlag::O_TRUNC | OFlag::O_WRONLY,
                                       Mode::S_IRUSR | Mode::S_IWUSR)?;
         let mut data =
             dir_meta.write_length_delimited_to_bytes().expect("proto3->vec is infallible");

db/writer.rs

@@ -45,7 +45,6 @@ use std::cmp::Ordering;
 use std::cmp;
 use std::io;
 use std::mem;
-use std::os::unix::ffi::OsStrExt;
 use std::sync::Arc;
 use std::sync::mpsc;
 use std::thread;
@@ -263,12 +262,13 @@ impl<F: FileWriter> SyncerChannel<F> {
 
 /// Lists files which should be "abandoned" (deleted without ever recording in the database)
 /// on opening.
-fn list_files_to_abandon(path: &str, streams_to_next: FnvHashMap<i32, i32>)
+fn list_files_to_abandon(dir: &dir::SampleFileDir, streams_to_next: FnvHashMap<i32, i32>)
                          -> Result<Vec<CompositeId>, Error> {
     let mut v = Vec::new();
-    for e in ::std::fs::read_dir(path)? {
+    let mut d = dir.opendir()?;
+    for e in d.iter() {
         let e = e?;
-        let id = match dir::parse_id(e.file_name().as_bytes()) {
+        let id = match dir::parse_id(e.file_name().to_bytes()) {
             Ok(i) => i,
             Err(_) => continue,
         };
@@ -304,7 +304,7 @@ impl<C: Clocks + Clone> Syncer<C, Arc<dir::SampleFileDir>> {
                  }
              })
              .collect();
-        let to_abandon = list_files_to_abandon(&d.path, streams_to_next)?;
+        let to_abandon = list_files_to_abandon(&dir, streams_to_next)?;
         let mut undeletable = 0;
         for &id in &to_abandon {
             if let Err(e) = dir.unlink_file(id) {