Fix race condition in fs::create_dir_all

It is more robust to not fail if any directory in a path was created
concurrently. This change lifts rustc internal `create_dir_racy` that
was created to handle such conditions to be new `create_dir_all`
implementation.

Author: droundy

src/librustc/util/fs.rs

@@ -109,23 +109,3 @@ pub fn rename_or_copy_remove<P: AsRef<Path>, Q: AsRef<Path>>(p: P,
         }
     }
 }
-
-// Like std::fs::create_dir_all, except handles concurrent calls among multiple
-// threads or processes.
-pub fn create_dir_racy(path: &Path) -> io::Result<()> {
-    match fs::create_dir(path) {
-        Ok(()) => return Ok(()),
-        Err(ref e) if e.kind() == io::ErrorKind::AlreadyExists => return Ok(()),
-        Err(ref e) if e.kind() == io::ErrorKind::NotFound => (),
-        Err(e) => return Err(e),
-    }
-    match path.parent() {
-        Some(p) => try!(create_dir_racy(p)),
-        None => return Err(io::Error::new(io::ErrorKind::Other, "failed to create whole tree")),
-    }
-    match fs::create_dir(path) {
-        Ok(()) => Ok(()),
-        Err(ref e) if e.kind() == io::ErrorKind::AlreadyExists => Ok(()),
-        Err(e) => Err(e),
-    }
-}

src/librustc_incremental/persist/fs.rs

@@ -461,7 +461,7 @@ fn generate_session_dir_path(crate_dir: &Path) -> PathBuf {
 }
 
 fn create_dir(sess: &Session, path: &Path, dir_tag: &str) -> Result<(),()> {
-    match fs_util::create_dir_racy(path) {
+    match std_fs::create_dir_all(path) {
         Ok(()) => {
             debug!("{} directory created successfully", dir_tag);
             Ok(())

src/librustc_save_analysis/lib.rs

@@ -885,7 +885,7 @@ pub fn process_crate<'l, 'tcx>(tcx: TyCtxt<'l, 'tcx, 'tcx>,
         },
     };
 
-    if let Err(e) = rustc::util::fs::create_dir_racy(&root_path) {
+    if let Err(e) = std::fs::create_dir_all(&root_path) {
         tcx.sess.err(&format!("Could not create directory {}: {}",
                               root_path.display(),
                               e));

src/libstd/fs.rs

@@ -1534,6 +1534,12 @@ pub fn create_dir<P: AsRef<Path>>(path: P) -> io::Result<()> {
 /// error conditions for when a directory is being created (after it is
 /// determined to not exist) are outlined by `fs::create_dir`.
 ///
+/// Notable exception is made for situations where any of the directories
+/// specified in the `path` could not be created as it was created concurrently.
+/// Such cases are considered success. In other words: calling `create_dir_all`
+/// concurrently from multiple threads or processes is guaranteed to not fail
+/// due to race itself.
+///
 /// # Examples
 ///
 /// ```
@@ -1769,11 +1775,21 @@ impl DirBuilder {
     }
 
     fn create_dir_all(&self, path: &Path) -> io::Result<()> {
-        if path == Path::new("") || path.is_dir() { return Ok(()) }
-        if let Some(p) = path.parent() {
-            self.create_dir_all(p)?
+        match self.inner.mkdir(path) {
+            Ok(()) => return Ok(()),
+            Err(ref e) if e.kind() == io::ErrorKind::AlreadyExists => return Ok(()),
+            Err(ref e) if e.kind() == io::ErrorKind::NotFound => {}
+            Err(e) => return Err(e),
+        }
+        match path.parent() {
+            Some(p) => try!(create_dir_all(p)),
+            None => return Err(io::Error::new(io::ErrorKind::Other, "failed to create whole tree")),
+        }
+        match self.inner.mkdir(path) {
+            Ok(()) => Ok(()),
+            Err(ref e) if e.kind() == io::ErrorKind::AlreadyExists => Ok(()),
+            Err(e) => Err(e),
         }
-        self.inner.mkdir(path)
     }
 }
 

src/tools/compiletest/src/runtest.rs

@@ -25,7 +25,7 @@ use util::logv;
 use std::collections::HashSet;
 use std::env;
 use std::fmt;
-use std::fs::{self, File};
+use std::fs::{self, File, create_dir_all};
 use std::io::prelude::*;
 use std::io::{self, BufReader};
 use std::path::{Path, PathBuf};
@@ -395,7 +395,7 @@ actual:\n\
 
         let out_dir = self.output_base_name().with_extension("pretty-out");
         let _ = fs::remove_dir_all(&out_dir);
-        self.create_dir_racy(&out_dir);
+        create_dir_all(&out_dir).unwrap();
 
         // FIXME (#9639): This needs to handle non-utf8 paths
         let mut args = vec!["-".to_owned(),
@@ -1269,7 +1269,7 @@ actual:\n\
 
     fn compose_and_run_compiler(&self, args: ProcArgs, input: Option<String>) -> ProcRes {
         if !self.props.aux_builds.is_empty() {
-            self.create_dir_racy(&self.aux_output_dir_name());
+            create_dir_all(&self.aux_output_dir_name()).unwrap();
         }
 
         let aux_dir = self.aux_output_dir_name();
@@ -1340,22 +1340,6 @@ actual:\n\
                              input)
     }
 
-    // Like std::fs::create_dir_all, except handles concurrent calls among multiple
-    // threads or processes.
-    fn create_dir_racy(&self, path: &Path) {
-        match fs::create_dir(path) {
-            Ok(()) => return,
-            Err(ref e) if e.kind() == io::ErrorKind::AlreadyExists => return,
-            Err(ref e) if e.kind() == io::ErrorKind::NotFound => {}
-            Err(e) => panic!("failed to create dir {:?}: {}", path, e),
-        }
-        self.create_dir_racy(path.parent().unwrap());
-        match fs::create_dir(path) {
-            Ok(()) => {}
-            Err(ref e) if e.kind() == io::ErrorKind::AlreadyExists => {}
-            Err(e) => panic!("failed to create dir {:?}: {}", path, e),
-        }
-    }
 
     fn compose_and_run(&self,
                        ProcArgs{ args, prog }: ProcArgs,
@@ -1435,7 +1419,7 @@ actual:\n\
 
 
                 let mir_dump_dir = self.get_mir_dump_dir();
-                self.create_dir_racy(mir_dump_dir.as_path());
+                create_dir_all(mir_dump_dir.as_path()).unwrap();
                 let mut dir_opt = "dump-mir-dir=".to_string();
                 dir_opt.push_str(mir_dump_dir.to_str().unwrap());
                 debug!("dir_opt: {:?}", dir_opt);
@@ -1923,7 +1907,7 @@ actual:\n\
 
         let out_dir = self.output_base_name();
         let _ = fs::remove_dir_all(&out_dir);
-        self.create_dir_racy(&out_dir);
+        create_dir_all(&out_dir).unwrap();
 
         let proc_res = self.document(&out_dir);
         if !proc_res.status.success() {
@@ -2299,7 +2283,7 @@ actual:\n\
         if tmpdir.exists() {
             self.aggressive_rm_rf(&tmpdir).unwrap();
         }
-        self.create_dir_racy(&tmpdir);
+        create_dir_all(&tmpdir).unwrap();
 
         let host = &self.config.host;
         let make = if host.contains("bitrig") || host.contains("dragonfly") ||