feat(fs/mount): keep open file on mount to avoid external umount (#3998)

@xen-orchestra/fs/package.json

@@ -24,6 +24,7 @@
     "@marsaud/smb2": "^0.13.0",
     "@sindresorhus/df": "^2.1.0",
     "@xen-orchestra/async-map": "^0.0.0",
+    "decorator-synchronized": "^0.3.0",
     "execa": "^1.0.0",
     "fs-extra": "^7.0.0",
     "get-stream": "^4.0.0",

@xen-orchestra/fs/src/_mount.js

@@ -1,5 +1,6 @@
 import execa from 'execa'
 import fs from 'fs-extra'
+import { ignoreErrors } from 'promise-toolbox'
 import { join } from 'path'
 import { tmpdir } from 'os'
 
@@ -21,11 +22,12 @@ export default class MountHandler extends LocalHandler {
     super(remote, opts)
 
     this._execa = useSudo ? sudoExeca : execa
+    this._keeper = undefined
     this._params = {
       ...params,
-      options: [params.options, remote.options].filter(
-        _ => _ !== undefined
-      ).join(','),
+      options: [params.options, remote.options]
+        .filter(_ => _ !== undefined)
+        .join(','),
     }
     this._realPath = join(
       mountsDir,
@@ -37,19 +39,20 @@ export default class MountHandler extends LocalHandler {
   }
 
   async _forget() {
-    await this._execa('umount', ['--force', this._getRealPath()], {
+    const keeper = this._keeper
+    if (keeper === undefined) {
+      return
+    }
+    this._keeper = undefined
+    await fs.close(keeper)
+
+    await ignoreErrors.call(
+      this._execa('umount', [this._getRealPath()], {
         env: {
           LANG: 'C',
         },
-    }).catch(error => {
-      if (
-        error == null ||
-        typeof error.stderr !== 'string' ||
-        !error.stderr.includes('not mounted')
-      ) {
-        throw error
-      }
       })
+    )
   }
 
   _getRealPath() {
@@ -57,18 +60,32 @@ export default class MountHandler extends LocalHandler {
   }
 
   async _sync() {
-    await fs.ensureDir(this._getRealPath())
+    // in case of multiple `sync`s, ensure we properly close previous keeper
+    {
+      const keeper = this._keeper
+      if (keeper !== undefined) {
+        this._keeper = undefined
+        ignoreErrors.call(fs.close(keeper))
+      }
+    }
+
+    const realPath = this._getRealPath()
+
+    await fs.ensureDir(realPath)
+
+    try {
       const { type, device, options, env } = this._params
-    return this._execa(
+      await this._execa(
         'mount',
-      ['-t', type, device, this._getRealPath(), '-o', options],
+        ['-t', type, device, realPath, '-o', options],
         {
           env: {
             LANG: 'C',
             ...env,
           },
         }
-    ).catch(error => {
+      )
+    } catch (error) {
       let stderr
       if (
         error == null ||
@@ -77,6 +94,14 @@ export default class MountHandler extends LocalHandler {
       ) {
         throw error
       }
-    })
+    }
+
+    // keep an open file on the mount to prevent it from being unmounted if used
+    // by another handler/process
+    const keeperPath = `${realPath}/.keeper_${Math.random()
+      .toString(36)
+      .slice(2)}`
+    this._keeper = await fs.open(keeperPath, 'w')
+    ignoreErrors.call(fs.unlink(keeperPath))
   }
 }

@xen-orchestra/fs/src/abstract.js

@@ -5,6 +5,7 @@ import getStream from 'get-stream'
 
 import asyncMap from '@xen-orchestra/async-map'
 import path from 'path'
+import synchronized from 'decorator-synchronized'
 import { fromCallback, fromEvent, ignoreErrors, timeout } from 'promise-toolbox'
 import { parse } from 'xo-remote-parser'
 import { randomBytes } from 'crypto'
@@ -216,6 +217,7 @@ export default class RemoteHandlerAbstract {
   // FIXME: Some handlers are implemented based on system-wide mecanisms (such
   // as mount), forgetting them might breaking other processes using the same
   // remote.
+  @synchronized()
   async forget(): Promise<void> {
     await this._forget()
   }
@@ -354,6 +356,7 @@ export default class RemoteHandlerAbstract {
   // metadata
   //
   // This method MUST ALWAYS be called before using the handler.
+  @synchronized()
   async sync(): Promise<void> {
     await this._sync()
   }

CHANGELOG.unreleased.md

@@ -19,6 +19,7 @@
 
 ### Released packages
 
+- @xen-orchestra/fs v0.7.0
 - xen-api v0.24.3
 - xoa-updater v0.15.2
 - xo-server v5.36.0