[PATCH -mm 6/9] unshare system call: allow unsharing of filesystem

[JANAK DESAI <janak@us.ibm.com>]

[PATCH -mm 6/9] unshare system call: allow unsharing of filesystem

If filesystem structure is being shared, allocate a new one and
copy information from the current, shared, structure.

Changes since the first submission of this patch on 12/12/05:
	- Removed an unnecessary local variable (12/13/05)
 
Signed-off-by: Janak Desai <janak@us.ibm.com>
 
---
 
 fork.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)
 
diff -Naurp 2.6.15-rc5-mm2+patch/kernel/fork.c 2.6.15-rc5-mm2+patch6/kernel/fork.c
--- 2.6.15-rc5-mm2+patch/kernel/fork.c	2005-12-13 18:38:26.000000000 +0000
+++ 2.6.15-rc5-mm2+patch6/kernel/fork.c	2005-12-13 19:38:03.000000000 +0000
@@ -1378,15 +1378,18 @@ static int unshare_thread(unsigned long 
 }
 
 /*
- * Unsharing of fs info for tasks created with CLONE_FS is not supported yet
+ * Unshare the filesystem structure if it is being shared
  */
 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
 {
 	struct fs_struct *fs = current->fs;
 
 	if ((unshare_flags & CLONE_FS) &&
-	    (fs && atomic_read(&fs->count) > 1))
-		return -EINVAL;
+	    (fs && atomic_read(&fs->count) > 1)) {
+		*new_fsp = __copy_fs_struct(current->fs);
+		if (!*new_fsp)
+			return -ENOMEM;
+	}
 
 	return 0;
 }


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