Re: Some news for this: [PATCH] [MTD] BLOCK_RO: Readonly Block Device Layer Over MTD ?

Gregory CLEMENT
2007-11-23T14:35:28Z

2007/11/21, Vitaly Wool <vitalywool@gmail.com>:
> On Nov 21, 2007 8:45 PM, Jörn Engel <joern@logfs.org> wrote:
> > > Because we were explicitly directed by David to do so.
> >
> > And David has gone fishing. Did he tell you why?
>
> He didn't want to add confusion, that's what he said. He directed us
> to make it a separate translation layer an have a separate device
> major (which we did get BTW :) ).
>
> If there's no objections, I can rediff/repost against the current MTD
> git. I'll also add some comments about the limitations of this
> approach (still it's viable enough within a real environment if
> there's an application which just reads the whole partition say once
> in a week and rewrites it as soon as it detects bit error corrections;
> that's what we did for emo BTW).

As it seems that there is no objections on it, can you push the patch in mtd ?
I have to made some change to apply the patch on 2.6.23 kernel, if ti
can help you, I join the new patch.
I test it on my board it seems working pretty well.

But I have a question, why mtdblock and romblock were mutually
exclusive? I guess it is to avoid the same mtd partition mounted both
time. Can't we deal with this case?

Index: drivers/mtd/Kconfig
===================================================================
--- drivers/mtd/Kconfig
+++ drivers/mtd/Kconfig
@@ -200,6 +200,13 @@
You do not need this option for use with the DiskOnChip devices. For
those, enable NFTL support (CONFIG_NFTL) instead.

+config MTD_BLOCK_ROMBLOCK
+ tristate "Readonly Block Device Layer Over MTD"
+ depends on MTD
+ help
+ Same as readonly block driver, but this allow you to mount
read-only file
+ systems from an MTD device, containing bad blocks.
+
config FTL
tristate "FTL (Flash Translation Layer) support"
depends on BLOCK
Index: drivers/mtd/romblock.c
===================================================================
--- drivers/mtd/romblock.c
+++ drivers/mtd/romblock.c
@@ -0,0 +1,164 @@
+/*
+ * Readonly Block Device Layer Over MTD
+ *
+ * (C) 2006 Baydarov Konstantin <kbaidarov@dev.rtsoft.ru>
+ * Pantelis Antoniou <panto@intracom.gr>
+ * David Woodhouse <dwmw2@infradead.org>
+ *
+ * It allows to use any filesystem on this device in
+ * RO mode and thus gain faster mount times and better
+ * throughput rates.
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/blktrans.h>
+
+struct romblock_map {
+ struct mtd_blktrans_dev dev;
+ /* block map for RO */
+ int32_t *block_map;
+ int32_t block_top;
+ int32_t block_scantop;
+};
+
+static loff_t map_over_bad_blocks(struct mtd_blktrans_dev* dev, loff_t from)
+{
+ int i, block;
+ struct mtd_info *mtd = dev->mtd;
+ struct romblock_map* dev_cont = container_of(dev, struct
romblock_map, dev);
+ int32_t *block_map = dev_cont->block_map;
+ int32_t block_top = dev_cont->block_top;
+ int32_t block_scantop = dev_cont->block_scantop;
+
+ /* if no bad block checking is possible bail out */
+ if (mtd->block_isbad == NULL)
+ return from;
+
+ /* first time in */
+ if (block_map == NULL) {
+ block_top = mtd->size / mtd->erasesize;
+
+ block_map = kmalloc(sizeof(*block_map) * block_top, GFP_KERNEL);
+ if (block_map == NULL) {
+ printk (KERN_ERR "map_over_bad_blocks():
unable to allocate block map\n");
+ return -ENOMEM;
+ }
+ for (i = 0; i < block_top; i++)
+ block_map[i] = -1;
+
+ for (i = 0; i < block_top; i++)
+ if ((*mtd->block_isbad)(mtd, i * mtd->erasesize) == 0)
+ break;
+
+ if (i >= block_top) {
+ printk (KERN_WARNING "map_over_bad_blocks():
all blocks bad!\n");
+ return -EIO;
+ }
+ block_scantop = 0;
+ block_map[0] = i;
+
+ DEBUG(MTD_DEBUG_LEVEL0, "mtd: map %d -> %d\n",
block_scantop, block_map[block_scantop]);
+ }
+
+ block = ((int)from / mtd->erasesize);
+ if (block >= block_top)
+ return (loff_t)-1;
+
+ /* scan for bad block up to where we want */
+ while (block >= block_scantop) {
+ /* find a non bad block */
+ for (i = block_map[block_scantop] + 1; i < block_top; i++)
+ if ((*mtd->block_isbad)(mtd, i * mtd->erasesize) == 0)
+ break;
+
+ /* exhausted ? */
+ if (i >= block_top) {
+ printk (KERN_WARNING "map_over_bad_blocks():
no more good blocks!\n");
+ return (loff_t)-1;
+ }
+
+ block_map[++block_scantop] = i;
+ DEBUG(MTD_DEBUG_LEVEL0, "mtd: map %d -> %d\n",
block_scantop, block_map[block_scantop]);
+ }
+
+ block = block_map[(int)from / mtd->erasesize];
+ from = (block * mtd->erasesize) | ((int)from & (mtd->erasesize - 1));
+ return from;
+}
+
+static int romblock_readsect(struct mtd_blktrans_dev *dev,
+ unsigned long block, char *buf)
+{
+ size_t retlen;
+ unsigned long from;
+
+ from = map_over_bad_blocks(dev, block<<9);
+
+ if (dev->mtd->read(dev->mtd, from, 512, &retlen, buf))
+ return 1;
+ return 0;
+}
+
+static int romblock_writesect(struct mtd_blktrans_dev *dev,
+ unsigned long block, char *buf)
+{
+ size_t retlen;
+
+ if (dev->mtd->write(dev->mtd, (block * 512), 512, &retlen, buf))
+ return 1;
+ return 0;
+}
+
+static void romblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
+{
+ struct romblock_map *dev_cont = kzalloc(sizeof(*dev_cont), GFP_KERNEL);
+
+ if (!dev_cont)
+ return;
+
+ dev_cont->dev.mtd = mtd;
+ dev_cont->dev.devnum = mtd->index;
+ dev_cont->dev.size = mtd->size >> 9;
+ dev_cont->dev.tr = tr;
+ dev_cont->dev.readonly = 1;
+
+ add_mtd_blktrans_dev(&(dev_cont->dev));
+}
+
+static void romblock_remove_dev(struct mtd_blktrans_dev *dev)
+{
+ del_mtd_blktrans_dev(dev);
+ kfree(dev);
+}
+
+static struct mtd_blktrans_ops romblock_tr = {
+ .name = "romblock",
+ .major = 258,
+ .part_bits = 0,
+ .blksize = 512,
+ .readsect = romblock_readsect,
+ .writesect = romblock_writesect,
+ .add_mtd = romblock_add_mtd,
+ .remove_dev = romblock_remove_dev,
+ .owner = THIS_MODULE,
+};
+
+static int __init romblock_init(void)
+{
+ return register_mtd_blktrans(&romblock_tr);
+}
+
+static void __exit romblock_exit(void)
+{
+ deregister_mtd_blktrans(&romblock_tr);
+}
+
+module_init(romblock_init);
+module_exit(romblock_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Baydarov Konstantin <kbaidarov@dev.rtsoft.ru>");
+MODULE_DESCRIPTION("Readonly Block Device Layer Over MTD");
Index: drivers/mtd/Makefile
===================================================================
--- drivers/mtd/Makefile
+++ drivers/mtd/Makefile
@@ -17,6 +17,7 @@
obj-$(CONFIG_MTD_BLKDEVS) += mtd_blkdevs.o
obj-$(CONFIG_MTD_BLOCK) += mtdblock.o
obj-$(CONFIG_MTD_BLOCK_RO) += mtdblock_ro.o
+obj-$(CONFIG_MTD_BLOCK_ROMBLOCK) += romblock.o mtd_blkdevs.o
obj-$(CONFIG_FTL) += ftl.o
obj-$(CONFIG_NFTL) += nftl.o
obj-$(CONFIG_INFTL) += inftl.o

--
Gregory CLEMENT
Adeneo
Adetel Group
2, chemin du Ruisseau
69134 ECULLY - FRANCE
Tél. : +33 (0)4 72 18 08 40 - Fax : +33 (0)4 72 18 08 41