Re: PATCH: allow JFFS2 to write to really small disks

["Øyvind Harboe" <oyvind.harboe@zylin.com>]

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How about this patch?

It adds a mount option to allow Write Once Read Many if the disk is too
small to support read/write many times.

W.r.t. eCos, I expect the WORM capability to be enabled via a CDL
option.


-- 
Øyvind Harboe
http://www.zylin.com

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Index: fs/jffs2/build.c
===================================================================
RCS file: /home/cvs/mtd/fs/jffs2/build.c,v
retrieving revision 1.77
diff -u -r1.77 build.c
--- fs/jffs2/build.c	31 Aug 2005 13:51:00 -0000	1.77
+++ fs/jffs2/build.c	2 Sep 2005 12:42:49 -0000
@@ -279,6 +279,18 @@
 
 	c->resv_blocks_write = c->resv_blocks_deletion + (size / c->sector_size);
 
+	/* It is possible to mount a JFFS2 in a mode where it allows
+	   Write Once Read Many operation if the flash disk is too small
+	   to support read/write many times.
+	   
+	   If the flash disk is smaller than resv_blocks_write, then we 
+	   allow writing to the disk anyway. The flash disk is then most likely
+       being used as write once - read many medimum, e.g. in-system configuration of 
+	   static parameters(e.g. MAC address of device in stored in "ROM"). */
+	if ((c->flags & JFFS2_SB_FLAG_ALLOW_WORM)!=0)&& (c->resv_blocks_write * c->sector_size > c->flash_size)) {
+		c->resv_blocks_write = 0; 
+	}
+
 	/* When do we let the GC thread run in the background */
 
 	c->resv_blocks_gctrigger = c->resv_blocks_write + 1;
Index: include/linux/jffs2_fs_sb.h
===================================================================
RCS file: /home/cvs/mtd/include/linux/jffs2_fs_sb.h,v
retrieving revision 1.52
diff -u -r1.52 jffs2_fs_sb.h
--- include/linux/jffs2_fs_sb.h	19 May 2005 16:12:17 -0000	1.52
+++ include/linux/jffs2_fs_sb.h	2 Sep 2005 12:42:49 -0000
@@ -16,6 +16,9 @@
 #define JFFS2_SB_FLAG_RO 1
 #define JFFS2_SB_FLAG_SCANNING 2 /* Flash scanning is in progress */
 #define JFFS2_SB_FLAG_BUILDING 4 /* File system building is in progress */
+#define JFFS2_SB_FLAG_ALLOW_WORM 8 /* allow write once read many if the
+                                      disk is too small to support read/write
+                                      many times*/
 
 struct jffs2_inodirty;