Re: [uml-devel] filemap feature 2.4.22-5um

["Steve Schmidtke" <steve_schmidtke@hotmail.com>]

[-- Attachment #1: Type: text/plain, Size: 1744 bytes --]

Jeff Dike wrote:
>Why so pessimistic?  I like filemap - IIRC, i suggested it.

Yeah, but finding the right interface to express it is tough.  I don't even 
want to go in the whole *in* OS_ layer/*above* os_* layer argument again. :) 
  I am also thinking that the filemap database should be generalized so that 
any translation can be supported - like an "xlate" table that can map Unix 
filenames to DOS filenames...

>I'd also like people to use this to see what's missing, if anything, and to
>get any improvements on the command line syntax.

Just so SKAS users don't feel left out, I've attached a small patch that 
adds a "mm" table to filemap for chrooted SKAS mode operation.  Just apply 
it after the first patch.

The following example shows how to use this patch to set up a chrooted SKAS 
UML with 20 available process slots:

  chroot /home/uml /linux mem=32M filemap=mm,30-49 \
  30>/proc/mm 31>/proc/mm 32>/proc/mm 33>/proc/mm 34>/proc/mm \
  35>/proc/mm 36>/proc/mm 37>/proc/mm 38>/proc/mm 39>/proc/mm \
  40>/proc/mm 41>/proc/mm 42>/proc/mm 43>/proc/mm 44>/proc/mm \
  45>/proc/mm 46>/proc/mm 47>/proc/mm 48>/proc/mm 49>/proc/mm \
  filemap=file,25,/proc/mm 25>/proc/mm \
  filemap=vm,20 20<>/dev/shm/vm-$$.0 con=null con0=fd:0,fd:1

Note the dummy "file" table entry for /proc/mm.  This is needed so the boot 
test for /proc/mm succeeds.

ISSUE:  The UML will panic if it runs out of /proc/mm fds.
ISSUE:  What side effects does re-using an address space have?
TODO:  Make the filemap lookup routine re-entrant safe.

Comments? Concerns?

Steve Schmidtke

_________________________________________________________________
STOP MORE SPAM with the new MSN 8 and get 2 months FREE*   
http://join.msn.com/?page=features/junkmail

[-- Attachment #2: filemap5-02.diff --]
[-- Type: application/octet-stream, Size: 2149 bytes --]

--- linux-2.4.22-5um.fm/arch/um/kernel/filemap.c	Tue Oct 14 10:44:50 2003
+++ linux-2.4.22-5um.new/arch/um/kernel/filemap.c	Tue Oct 14 13:56:37 2003
@@ -502,6 +502,11 @@
 		.entries = NULL,
 		.ops     = &fm_ops_pool,
 	},
+	{
+		.name    = "mm",
+		.entries = NULL,
+		.ops     = &fm_ops_pool,
+	},
 };
 
 static struct filemap_table* filemap_get_table(const char* table_name)
--- linux-2.4.22-5um.fm/arch/um/kernel/skas/process.c	Tue Oct 14 10:44:31 2003
+++ linux-2.4.22-5um.new/arch/um/kernel/skas/process.c	Tue Oct 14 14:28:39 2003
@@ -27,6 +27,8 @@
 #include "skas_ptrace.h"
 #include "chan_user.h"
 
+#include "filemap.h"
+
 int is_skas_winch(int pid, int fd, void *data)
 {
 	if(pid != getpid())
@@ -340,12 +342,27 @@
 int new_mm(int from)
 {
 	struct proc_mm_op copy;
-	int n, fd = os_open_file("/proc/mm", 
+	int n, fd;
+
+	/* use the raw access since /proc/mm opens a new file every time */ 
+        fd = filemap_access("mm", "/proc/mm");
+        if(fd >= 0) {
+                printk("filemap aquire: fd=%d, file=%s\n", fd, "/proc/mm");
+                goto handle_fd;
+        }
+
+	/* if /proc/mm exists, the same fd would be returned over and over */
+        if(filemap_access("file", "/proc/mm") >= 0) {
+		return(-1);	
+	}
+
+	fd = os_open_file("/proc/mm", 
 				 of_cloexec(of_write(OPENFLAGS())), 0);
 
 	if(fd < 0)
 		return(fd);
 
+handle_fd:
 	if(from != -1){
 		copy = ((struct proc_mm_op) { .op 	= MM_COPY_SEGMENTS,
 					      .u 	= 
--- linux-2.4.22-5um.fm/arch/um/kernel/skas/mmu.c	Tue Oct 14 10:44:31 2003
+++ linux-2.4.22-5um.new/arch/um/kernel/skas/mmu.c	Tue Oct 14 16:48:36 2003
@@ -21,14 +21,23 @@
 
 	mm->context.skas.mm_fd = new_mm(from);
 	if(mm->context.skas.mm_fd < 0)
+#if 1
 		panic("init_new_context_skas - new_mm failed, errno = %d\n",
 		      mm->context.skas.mm_fd);
+#else /* DON'T PANIC */
+		return(mm->context.skas.mm_fd);
+#endif
 
 	return(0);
 }
 
 void destroy_context_skas(struct mm_struct *mm)
 {
+	/* filemapped files will return something other than -ENOENT */
+	if(filemap_release("mm", mm->context.skas.mm_fd) != -ENOENT) {
+		return;
+	}
+
 	os_close_file(mm->context.skas.mm_fd);
 }