From 1efb51b1de174cdecf507d8731e462e9269da4c5 Mon Sep 17 00:00:00 2001
From: Thomas Veerman <thomas@minix3.org>
Date: Wed, 22 Feb 2012 13:54:35 +0000
Subject: [PATCH] VFS: improve crashed FS resource cleanup

When VFS detects that an FS has crashed and tries to clean up
resources, it marks fairly late in the process that a vmnt is not
to be used again (to send requests to). This allows a thread to
become blocked on a vmnt after all blocked threads were stopped, but
before it finds out it shouldn't try to send to that vmnt.
---
 servers/vfs/mount.c |  9 +++------
 servers/vfs/proto.h |  1 +
 servers/vfs/vmnt.c  | 23 +++++++++++++++++++----
 3 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/servers/vfs/mount.c b/servers/vfs/mount.c
index 4e4666d5a..a89c1c214 100644
--- a/servers/vfs/mount.c
+++ b/servers/vfs/mount.c
@@ -273,8 +273,7 @@ char mount_label[LABEL_MAX] )
   new_vmp->m_flags &= ~VMNT_MOUNTING;
 
   if (r != OK) {
-	new_vmp->m_fs_e = NONE;
-	new_vmp->m_dev = NO_DEV;
+	mark_vmnt_free(new_vmp);
 	unlock_vnode(root_node);
 	if (vp != NULL) {
 		unlock_vnode(vp);
@@ -349,11 +348,10 @@ char mount_label[LABEL_MAX] )
   if (r != OK) {
 	unlock_vnode(vp);
 	unlock_vnode(root_node);
+	mark_vmnt_free(new_vmp);
 	unlock_vmnt(new_vmp);
 	put_vnode(vp);
 	put_vnode(root_node);
-	new_vmp->m_dev = NO_DEV;
-	new_vmp->m_flags = 0;
 	unlock_bsf();
 	return(r);
   }
@@ -505,8 +503,7 @@ PUBLIC int unmount(
 	vmp->m_root_node->v_sdev = NO_DEV;
 	vmp->m_root_node = NULL;
   }
-  vmp->m_dev = NO_DEV;
-  vmp->m_fs_e = NONE;
+  mark_vmnt_free(vmp);
 
   unlock_vmnt(vmp);
 
diff --git a/servers/vfs/proto.h b/servers/vfs/proto.h
index 432ef3a52..ddb4859c9 100644
--- a/servers/vfs/proto.h
+++ b/servers/vfs/proto.h
@@ -331,6 +331,7 @@ _PROTOTYPE( int in_group, (struct fproc *rfp, gid_t grp)		);
 /* vmnt.c */
 _PROTOTYPE( void check_vmnt_locks, (void)				);
 _PROTOTYPE( void check_vmnt_locks_by_me, (struct fproc *rfp)		);
+_PROTOTYPE( void mark_vmnt_free, (struct vmnt *vmp)			);
 _PROTOTYPE( struct vmnt *get_free_vmnt, (void)				);
 _PROTOTYPE( struct vmnt *find_vmnt, (endpoint_t fs_e)			);
 _PROTOTYPE( struct vmnt *get_locked_vmnt, (struct fproc *rfp)		);
diff --git a/servers/vfs/vmnt.c b/servers/vfs/vmnt.c
index bb3dc0746..6e4c9ed0d 100644
--- a/servers/vfs/vmnt.c
+++ b/servers/vfs/vmnt.c
@@ -59,6 +59,17 @@ PUBLIC void check_vmnt_locks()
 #endif
 }
 
+/*===========================================================================*
+ *                             mark_vmnt_free				     *
+ *===========================================================================*/
+PUBLIC void mark_vmnt_free(struct vmnt *vmp)
+{
+  ASSERTVMP(vmp);
+
+  vmp->m_fs_e = NONE;
+  vmp->m_dev = NO_DEV;
+}
+
 /*===========================================================================*
  *                             clear_vmnt				     *
  *===========================================================================*/
@@ -83,10 +94,14 @@ PRIVATE void clear_vmnt(struct vmnt *vmp)
  *===========================================================================*/
 PUBLIC struct vmnt *get_free_vmnt(void)
 {
-  struct vmnt *vp;
+  struct vmnt *vmp;
 
-  for (vp = &vmnt[0]; vp < &vmnt[NR_MNTS]; ++vp)
-      if (vp->m_dev == NO_DEV) return(vp);
+  for (vmp = &vmnt[0]; vmp < &vmnt[NR_MNTS]; ++vmp) {
+	if (vmp->m_dev == NO_DEV) {
+		clear_vmnt(vmp);
+		return(vmp);
+	}
+  }
 
   return(NULL);
 }
@@ -167,6 +182,7 @@ PUBLIC void vmnt_unmap_by_endpt(endpoint_t proc_e)
   struct vmnt *vmp;
 
   if ((vmp = find_vmnt(proc_e)) != NULL) {
+	mark_vmnt_free(vmp);
 	fs_cancel(vmp);
 	invalidate_filp_by_endpt(proc_e);
 	if (vmp->m_mounted_on) {
@@ -174,7 +190,6 @@ PUBLIC void vmnt_unmap_by_endpt(endpoint_t proc_e)
 		 * point. That is, the mount was succesful. */
 		put_vnode(vmp->m_mounted_on);
 	}
-	clear_vmnt(vmp);
   }
 }