fix: fs::remove_dir_all: treat ENOENT as success

fixes #127576

Author: lolbinarycat

library/std/src/sys/pal/unix/fs.rs

@@ -2113,6 +2113,16 @@ mod remove_dir_impl {
         }
     }
 
+	fn is_enoent(result: &io::Result<()>) -> bool {
+		if let Err(err) = result &&
+			matches!(err.raw_os_error(), Some(libc::ENOENT))
+		{
+			true
+		} else {
+			false
+		}
+	}
+
     fn remove_dir_all_recursive(parent_fd: Option<RawFd>, path: &CStr) -> io::Result<()> {
         // try opening as directory
         let fd = match openat_nofollow_dironly(parent_fd, &path) {
@@ -2128,36 +2138,58 @@ mod remove_dir_impl {
                     None => Err(err),
                 };
             }
+			Err(err) if matches!(err.raw_os_error(), Some(libc::ENOENT)) => {
+				// the file has already been removed by something else,
+				// do nothing.
+				return Ok(());
+			}
             result => result?,
         };
 
-        // open the directory passing ownership of the fd
-        let (dir, fd) = fdreaddir(fd)?;
-        for child in dir {
-            let child = child?;
-            let child_name = child.name_cstr();
-            match is_dir(&child) {
-                Some(true) => {
-                    remove_dir_all_recursive(Some(fd), child_name)?;
-                }
-                Some(false) => {
-                    cvt(unsafe { unlinkat(fd, child_name.as_ptr(), 0) })?;
-                }
-                None => {
-                    // POSIX specifies that calling unlink()/unlinkat(..., 0) on a directory can succeed
-                    // if the process has the appropriate privileges. This however can causing orphaned
-                    // directories requiring an fsck e.g. on Solaris and Illumos. So we try recursing
-                    // into it first instead of trying to unlink() it.
-                    remove_dir_all_recursive(Some(fd), child_name)?;
-                }
-            }
-        }
-
-        // unlink the directory after removing its contents
-        cvt(unsafe {
-            unlinkat(parent_fd.unwrap_or(libc::AT_FDCWD), path.as_ptr(), libc::AT_REMOVEDIR)
-        })?;
-        Ok(())
+		let result: io::Result<()> = try {
+			// open the directory passing ownership of the fd
+			let (dir, fd) = fdreaddir(fd)?;
+			for child in dir {
+				let child = child?;
+				let child_name = child.name_cstr();
+				// we need an inner try block, because if one of these
+				// directories has already been deleted, then we need to
+				// continue the loop, not return ok.
+				let result: io::Result<()> = try {
+					match is_dir(&child) {
+						Some(true) => {
+							remove_dir_all_recursive(Some(fd), child_name)?;
+						}
+						Some(false) => {
+							cvt(unsafe { unlinkat(fd, child_name.as_ptr(), 0) })?;
+						}
+						None => {
+							// POSIX specifies that calling unlink()/unlinkat(..., 0) on a directory can succeed
+							// if the process has the appropriate privileges. This however can causing orphaned
+							// directories requiring an fsck e.g. on Solaris and Illumos. So we try recursing
+							// into it first instead of trying to unlink() it.
+							remove_dir_all_recursive(Some(fd), child_name)?;
+						}
+					}
+				};
+				if result.is_err() && !is_enoent(&result) {
+					return result;
+				}
+			}
+
+			// unlink the directory after removing its contents
+			cvt(unsafe {
+				unlinkat(parent_fd.unwrap_or(libc::AT_FDCWD), path.as_ptr(), libc::AT_REMOVEDIR)
+			})?;
+		};
+		if is_enoent(&result)
+		{
+			// the file has already been removed by something else,
+			// do nothing.
+		    Ok(())
+		} else {
+			result
+		}
     }
 
     fn remove_dir_all_modern(p: &Path) -> io::Result<()> {

tests/run-make/remove-dir-all-race/rmake.rs

@@ -0,0 +1,25 @@
+use run_make_support::{run_in_tmpdir, fs_wrapper::{create_dir, write, remove_dir_all}};
+use std::thread;
+use std::time::Duration;
+
+fn main() {
+	run_in_tmpdir(|| {
+		for i in 0..10 {
+			create_dir("outer");
+			create_dir("outer/inner");
+			write("outer/inner.txt", b"sometext");
+
+			let t1 = thread::spawn(move || {
+				thread::sleep(Duration::from_millis(i * 10));
+				remove_dir_all("outer")
+			});
+
+			let t2 = thread::spawn(move || {
+				remove_dir_all("outer")
+			});
+
+			t1.join().unwrap();
+			t2.join().unwrap();
+		}
+	})
+}