Implement vfs-busy() and vfs-unbusy()

Which is used to guard against mount/unmount requests. Signed-off-by: Jorgen Lundman <lundman@lundman.net>
openzfsonwindows · Oct 12, 2023 · fee66c7 · fee66c7
1 parent 11cb959
commit fee66c7
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Showing 5 changed files with 65 additions and 10 deletions.
diff --git a/include/os/windows/spl/sys/mount.h b/include/os/windows/spl/sys/mount.h
@@ -119,6 +119,9 @@ typedef struct mount mount_t;
 typedef struct mount vfsp_t;
 #define	LK_NOWAIT 1
 
+int spl_vfs_init(void);
+void spl_vfs_fini(void);
+
 int   vfs_busy(mount_t *mp, int flags);
 void  vfs_unbusy(mount_t *mp);
 int   vfs_isrdonly(mount_t *mp);

diff --git a/module/os/windows/spl/spl-mount.c b/module/os/windows/spl/spl-mount.c
@@ -29,15 +29,45 @@
 #include <sys/types.h>
 #include <sys/mount.h>
 
+/*
+ * In Unix, this lock is to protect the list of
+ * mounted file-systems, to add and remove mounts.
+ * XNU uses mount_lock() to hold all, then calls
+ * lck_rw_lock_shared(mount_t) to hold this specific
+ * mount - in future we can make this enhancement.
+ */
+static kmutex_t vfs_main_lock;
+
+
+int
+spl_vfs_init(void)
+{
+	mutex_init(&vfs_main_lock, NULL, MUTEX_DEFAULT, NULL);
+	return (0);
+}
+
+void
+spl_vfs_fini(void)
+{
+	mutex_destroy(&vfs_main_lock);
+}
+
 int
 vfs_busy(mount_t *mp, int flags)
 {
+	mutex_enter(&vfs_main_lock);
+	if (mp == NULL) {
+		mutex_exit(&vfs_main_lock);
+		return (EINVAL);
+	}
+
 	return (0);
 }
 
 void
 vfs_unbusy(mount_t *mp)
 {
+	mutex_exit(&vfs_main_lock);
 }
 
 int

diff --git a/module/os/windows/spl/spl-windows.c b/module/os/windows/spl/spl-windows.c
@@ -545,6 +545,7 @@ spl_start(PUNICODE_STRING RegistryPath)
 	spl_mutex_subsystem_init();
 	spl_kmem_init(total_memory);
 
+	spl_vfs_init();
 	spl_vnode_init();
 	spl_kmem_thread_init();
 	spl_kmem_mp_init();
@@ -565,6 +566,7 @@ spl_stop(void)
 {
 	spl_kmem_thread_fini();
 	spl_vnode_fini();
+	spl_vfs_fini();
 	spl_taskq_fini();
 	spl_rwlock_fini();
 	spl_tsd_fini();

diff --git a/module/os/windows/zfs/zfs_vnops_windows.c b/module/os/windows/zfs/zfs_vnops_windows.c
@@ -133,11 +133,17 @@ zfs_AcquireForLazyWrite(void *Context, BOOLEAN Wait)
 	dprintf("%s:fo %p\n", __func__, fo);
 
 	/* Confirm we are mounted, and stop unmounting */
-	if ((zfsvfs->z_vfs == NULL) ||
-	    zfsvfs->z_unmounted ||
-	    zfs_enter(zfsvfs, FTAG) != 0)
+	if (vfs_busy(zfsvfs->z_vfs, 0) != 0)
 		return (FALSE);
 
+	if (zfsvfs->z_unmounted ||
+	    zfs_enter(zfsvfs, FTAG) != 0) {
+		vfs_unbusy(zfsvfs);
+		return (FALSE);
+	}
+
+	vfs_unbusy(zfsvfs);
+
 	if (vp == NULL ||
 	    VTOZ(vp) == NULL ||
 	    VN_HOLD(vp) != 0) {
@@ -204,10 +210,16 @@ zfs_AcquireForReadAhead(void *Context, BOOLEAN Wait)
 
 	dprintf("%s:\n", __func__);
 
-	if ((zfsvfs->z_vfs == NULL) ||
-	    zfsvfs->z_unmounted ||
-	    zfs_enter(zfsvfs, FTAG) != 0)
+	if (vfs_busy(zfsvfs->z_vfs, 0) != 0)
+		return (FALSE);
+
+	if (zfsvfs->z_unmounted ||
+	    zfs_enter(zfsvfs, FTAG) != 0) {
+		vfs_unbusy(zfsvfs);
 		return (FALSE);
+	}
+
+	vfs_unbusy(zfsvfs);
 
 	if (vp == NULL ||
 	    VTOZ(vp) == NULL ||
@@ -7938,10 +7950,16 @@ fastio_acquire_for_mod_write(PFILE_OBJECT FileObject,
 	NTSTATUS Status = STATUS_INVALID_PARAMETER;
 	dprintf("%s: \n", __func__);
 
-	if ((zfsvfs->z_vfs == NULL) ||
-	    zfsvfs->z_unmounted ||
-	    zfs_enter(zfsvfs, FTAG) != 0)
+	if (vfs_busy(zfsvfs->z_vfs, 0) != 0)
+		return (STATUS_INVALID_PARAMETER);
+
+	if (zfsvfs->z_unmounted ||
+	    zfs_enter(zfsvfs, FTAG) != 0) {
+		vfs_unbusy(zfsvfs);
 		return (STATUS_INVALID_PARAMETER);
+	}
+
+	vfs_unbusy(zfsvfs);
 
 	vp = FileObject->FsContext;
 

diff --git a/module/os/windows/zfs/zfs_vnops_windows_mount.c b/module/os/windows/zfs/zfs_vnops_windows_mount.c
@@ -1612,7 +1612,9 @@ zfs_windows_unmount(zfs_cmd_t *zc)
 
 out_unlock:
 		// counter to getzfvfs
-		vfs_unbusy(zfsvfs->z_vfs);
+		zfsvfs->z_vfs = NULL;
+		vfs_unbusy(zmo);
+
 	}
 	return (error);
 }