fs: make sure to write entire buffer

fs.write(v) is not guaranteed to write everything in a single
call. Make sure we don't assume so.

PR-URL: #49211
Co-authored-by: Chemi Atlow <chemi@atlow.co.il>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Robert Nagy <ronagy@icloud.com>

lib/internal/fs/streams.js

@@ -13,8 +13,10 @@ const {
 
 const {
   ERR_INVALID_ARG_TYPE,
-  ERR_OUT_OF_RANGE,
   ERR_METHOD_NOT_IMPLEMENTED,
+  ERR_OUT_OF_RANGE,
+  ERR_STREAM_DESTROYED,
+  ERR_SYSTEM_ERROR,
 } = require('internal/errors').codes;
 const {
   deprecate,
@@ -392,22 +394,75 @@ WriteStream.prototype.open = openWriteFs;
 
 WriteStream.prototype._construct = _construct;
 
+function writeAll(data, size, pos, cb, retries = 0) {
+  this[kFs].write(this.fd, data, 0, size, pos, (er, bytesWritten, buffer) => {
+    // No data currently available and operation should be retried later.
+    if (er?.code === 'EAGAIN') {
+      er = null;
+      bytesWritten = 0;
+    }
+
+    if (this.destroyed || er) {
+      return cb(er || new ERR_STREAM_DESTROYED('write'));
+    }
+
+    this.bytesWritten += bytesWritten;
+
+    retries = bytesWritten ? 0 : retries + 1;
+    size -= bytesWritten;
+    pos += bytesWritten;
+
+    // Try writing non-zero number of bytes up to 5 times.
+    if (retries > 5) {
+      cb(new ERR_SYSTEM_ERROR('write failed'));
+    } else if (size) {
+      writeAll.call(this, buffer.slice(bytesWritten), size, pos, cb, retries);
+    } else {
+      cb();
+    }
+  });
+}
+
+function writevAll(chunks, size, pos, cb, retries = 0) {
+  this[kFs].writev(this.fd, chunks, this.pos, (er, bytesWritten, buffers) => {
+    // No data currently available and operation should be retried later.
+    if (er?.code === 'EAGAIN') {
+      er = null;
+      bytesWritten = 0;
+    }
+
+    if (this.destroyed || er) {
+      return cb(er || new ERR_STREAM_DESTROYED('writev'));
+    }
+
+    this.bytesWritten += bytesWritten;
+
+    retries = bytesWritten ? 0 : retries + 1;
+    size -= bytesWritten;
+    pos += bytesWritten;
+
+    // Try writing non-zero number of bytes up to 5 times.
+    if (retries > 5) {
+      cb(new ERR_SYSTEM_ERROR('writev failed'));
+    } else if (size) {
+      writevAll.call(this, [Buffer.concat(buffers).slice(bytesWritten)], size, pos, cb, retries);
+    } else {
+      cb();
+    }
+  });
+}
+
 WriteStream.prototype._write = function(data, encoding, cb) {
   this[kIsPerformingIO] = true;
-  this[kFs].write(this.fd, data, 0, data.length, this.pos, (er, bytes) => {
+  writeAll.call(this, data, data.length, this.pos, (er) => {
     this[kIsPerformingIO] = false;
     if (this.destroyed) {
       // Tell ._destroy() that it's safe to close the fd now.
       cb(er);
       return this.emit(kIoDone, er);
     }
 
-    if (er) {
-      return cb(er);
-    }
-
-    this.bytesWritten += bytes;
-    cb();
+    cb(er);
   });
 
   if (this.pos !== undefined)
@@ -427,20 +482,15 @@ WriteStream.prototype._writev = function(data, cb) {
   }
 
   this[kIsPerformingIO] = true;
-  this[kFs].writev(this.fd, chunks, this.pos, (er, bytes) => {
+  writevAll.call(this, chunks, size, this.pos, (er) => {
     this[kIsPerformingIO] = false;
     if (this.destroyed) {
       // Tell ._destroy() that it's safe to close the fd now.
       cb(er);
       return this.emit(kIoDone, er);
     }
 
-    if (er) {
-      return cb(er);
-    }
-
-    this.bytesWritten += bytes;
-    cb();
+    cb(er);
   });
 
   if (this.pos !== undefined)

test/parallel/test-fs-write-stream-eagain.mjs

@@ -0,0 +1,39 @@
+import * as common from '../common/index.mjs';
+import tmpdir from '../common/tmpdir.js';
+import assert from 'node:assert';
+import fs from 'node:fs';
+import { describe, it, mock } from 'node:test';
+import { finished } from 'node:stream/promises';
+
+tmpdir.refresh();
+const file = tmpdir.resolve('writeStreamEAGAIN.txt');
+const errorWithEAGAIN = (fd, buffer, offset, length, position, callback) => {
+  callback(Object.assign(new Error(), { code: 'EAGAIN' }), 0, buffer);
+};
+
+describe('WriteStream EAGAIN', { concurrency: true }, () => {
+  it('_write', async () => {
+    const mockWrite = mock.fn(fs.write);
+    mockWrite.mock.mockImplementationOnce(errorWithEAGAIN);
+    const stream = fs.createWriteStream(file, {
+      fs: {
+        open: common.mustCall(fs.open),
+        write: mockWrite,
+        close: common.mustCall(fs.close),
+      }
+    });
+    stream.end('foo');
+    stream.on('close', common.mustCall());
+    stream.on('error', common.mustNotCall());
+    await finished(stream);
+    assert.strictEqual(mockWrite.mock.callCount(), 2);
+    assert.strictEqual(fs.readFileSync(file, 'utf8'), 'foo');
+  });
+
+  it('_write', async () => {
+    const stream = fs.createWriteStream(file);
+    mock.getter(stream, 'destroyed', () => true);
+    stream.end('foo');
+    await finished(stream).catch(common.mustCall());
+  });
+});