[PATCH] [MTD] BLOCK_RO: Readonly Block Device Layer Over MTD
kbaidarov
kbaidarov at dev.rtsoft.ru
Fri Nov 17 10:40:55 EST 2006
Description:
The following patch adds readonly block device layer over mtd
that allows to use any filesystem on this device in RO mode and
thus gain faster mount times and better throughput rates.
How it works:
Blocks translation routine was added to read sector function. Assuming
that bad block won't appear during MTD reading and BBT is correct, bad
block is skipped and requested block is lazily mapped to good one.
Block driver based on the mtd readonly device driver mtdblock_ro.c and
translation routine was taken from the patch of Pantelis Antoniou
(which can be found at
http://lists.infradead.org/pipermail/linux-mtd/2004-May/009672.html).
Large major 258 has already been assigned by LANANA.
Signed-off-by: Konstantin Baydarov <kbaidarov at dev.rtsoft.ru>
drivers/mtd/Kconfig | 7 +
drivers/mtd/Makefile | 1
drivers/mtd/mtdblock_ro_bbfree.c | 165 +++++++++++++++++++++++++++++++++++++++
3 files changed, 173 insertions(+)
Index: mips-kernel-2.6/drivers/mtd/mtdblock_ro_bbfree.c
===================================================================
--- /dev/null
+++ mips-kernel-2.6/drivers/mtd/mtdblock_ro_bbfree.c
@@ -0,0 +1,165 @@
+/*
+ * Readonly Block Device Layer Over MTD
+ *
+ * (C) 2006 Baydarov Konstantin <kbaidarov at dev.rtsoft.ru>
+ * Pantelis Antoniou <panto at intracom.gr>
+ * David Woodhouse <dwmw2 at 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 mtd_block_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 mtd_block_map* dev_cont = container_of(dev, struct mtd_block_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_WARNING "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(0, "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;
+
+ /* exchausted ? */
+ 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(0, "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 mtdblock_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 mtdblock_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 mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
+{
+ struct mtd_block_map *dev_cont = kmalloc(sizeof(*dev_cont), GFP_KERNEL);
+
+ if (!dev_cont)
+ return;
+
+ memset(dev_cont, 0, sizeof(*dev_cont));
+
+ dev_cont->dev.mtd = mtd;
+ dev_cont->dev.devnum = mtd->index;
+ dev_cont->dev.blksize = 512;
+ 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 mtdblock_remove_dev(struct mtd_blktrans_dev *dev)
+{
+ del_mtd_blktrans_dev(dev);
+ kfree(dev);
+}
+
+static struct mtd_blktrans_ops mtdblock_tr = {
+ .name = "mtdblock",
+ .major = 258,
+ .part_bits = 0,
+ .readsect = mtdblock_readsect,
+ .writesect = mtdblock_writesect,
+ .add_mtd = mtdblock_add_mtd,
+ .remove_dev = mtdblock_remove_dev,
+ .owner = THIS_MODULE,
+};
+
+static int __init mtdblock_init(void)
+{
+ return register_mtd_blktrans(&mtdblock_tr);
+}
+
+static void __exit mtdblock_exit(void)
+{
+ deregister_mtd_blktrans(&mtdblock_tr);
+}
+
+module_init(mtdblock_init);
+module_exit(mtdblock_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Baydarov Konstantin <kbaidarov at dev.rtsoft.ru>");
+MODULE_DESCRIPTION("Readonly Block Device Layer Over MTD");
Index: mips-kernel-2.6/drivers/mtd/Makefile
===================================================================
--- mips-kernel-2.6.orig/drivers/mtd/Makefile
+++ mips-kernel-2.6/drivers/mtd/Makefile
@@ -17,6 +17,7 @@ obj-$(CONFIG_MTD_AFS_PARTS) += afs.o
obj-$(CONFIG_MTD_CHAR) += mtdchar.o
obj-$(CONFIG_MTD_BLOCK) += mtdblock.o mtd_blkdevs.o
obj-$(CONFIG_MTD_BLOCK_RO) += mtdblock_ro.o mtd_blkdevs.o
+obj-$(CONFIG_MTD_BLOCK_RO_BBFREE) += mtdblock_ro_bbfree.o mtd_blkdevs.o
obj-$(CONFIG_FTL) += ftl.o mtd_blkdevs.o
obj-$(CONFIG_NFTL) += nftl.o mtd_blkdevs.o
obj-$(CONFIG_INFTL) += inftl.o mtd_blkdevs.o
Index: mips-kernel-2.6/drivers/mtd/Kconfig
===================================================================
--- mips-kernel-2.6.orig/drivers/mtd/Kconfig
+++ mips-kernel-2.6/drivers/mtd/Kconfig
@@ -197,6 +197,13 @@ config MTD_BLOCK_RO
You do not need this option for use with the DiskOnChip devices. For
those, enable NFTL support (CONFIG_NFTL) instead.
+config MTD_BLOCK_RO_BBFREE
+ tristate "Readonly bad block free block device access to MTD devices"
+ depends on MTD_BLOCK!=y && MTD && MTD_BLOCK_RO!=y
+ 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 MTD && BLOCK
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