From 58b8ff5ffa09376b222598382583aff3e81bf112 Mon Sep 17 00:00:00 2001
From: Ben Gras <ben@minix3.org>
Date: Fri, 28 Feb 2014 16:26:13 +0100
Subject: [PATCH] VFS: add F_FLUSH_FS_CACHE fcntl

This fcntl requests all cached blocks associated with the minor device
number associated with the regular file are invalidated. If the file
is a block special, invalidate the blocks associated with that minor
device instead.

This is to be used for a test that tests unmapped file-mapped memory
ranges whose blocks are not in the cache and therefore must be fetched
from a FS.

Change-Id: Ide914b2e88413aa90bd731ae587ca06fa5f13ebc
---
 servers/mfs/misc.c |  2 +-
 servers/vfs/misc.c | 18 ++++++++++++++++++
 sys/sys/fcntl.h    |  1 +
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/servers/mfs/misc.c b/servers/mfs/misc.c
index 6b0a79d6d..b4af8d98e 100644
--- a/servers/mfs/misc.c
+++ b/servers/mfs/misc.c
@@ -39,7 +39,7 @@ int fs_flush()
  * to disk.
  */
   dev_t dev = fs_m_in.REQ_DEV;
-  if(dev == fs_dev) return(EBUSY);
+  if(dev == fs_dev && lmfs_bufs_in_use() > 0) return(EBUSY);
  
   lmfs_flushall();
   lmfs_invalidate(dev);
diff --git a/servers/vfs/misc.c b/servers/vfs/misc.c
index d9548cbda..7ab76b072 100644
--- a/servers/vfs/misc.c
+++ b/servers/vfs/misc.c
@@ -223,6 +223,24 @@ int do_fcntl(void)
 	fl = (O_NOSIGPIPE);
 	f->filp_flags = (f->filp_flags & ~fl) | (fcntl_argx & fl);
 	break;
+    case F_FLUSH_FS_CACHE:
+    {
+	struct vnode *vn = f->filp_vno;
+	mode_t mode = f->filp_vno->v_mode;
+	if (!super_user) {
+		r = EPERM;
+	} else if (S_ISBLK(mode)) {
+		/* Block device; flush corresponding device blocks. */
+		r = req_flush(vn->v_bfs_e, vn->v_sdev);
+	} else if (S_ISREG(mode) || S_ISDIR(mode)) {
+		/* Directory or regular file; flush hosting FS blocks. */
+		r = req_flush(vn->v_fs_e, vn->v_dev);
+	} else {
+		/* Remaining cases.. Meaning unclear. */
+		r = ENODEV;
+	}
+	break;
+    }
     default:
 	r = EINVAL;
   }
diff --git a/sys/sys/fcntl.h b/sys/sys/fcntl.h
index 3c96ad224..6caaf290e 100644
--- a/sys/sys/fcntl.h
+++ b/sys/sys/fcntl.h
@@ -326,6 +326,7 @@ __END_DECLS
 
 #if defined(__minix)
 #define F_FREESP       100
+#define F_FLUSH_FS_CACHE	101	/* invalidate cache on associated FS */
 #endif /* defined(__minix) */
 
 #endif /* !_SYS_FCNTL_H_ */