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Subject[PATCH 3/3] squashfs: add MTD backend
Date
---
fs/squashfs/Kconfig | 1 +
fs/squashfs/Makefile | 1 +
fs/squashfs/backend.c | 15 ++++
fs/squashfs/mtd.c | 179 ++++++++++++++++++++++++++++++++++++++++++++++++
fs/squashfs/squashfs.h | 4 +
5 files changed, 200 insertions(+), 0 deletions(-)
create mode 100644 fs/squashfs/mtd.c
diff --git a/fs/squashfs/Kconfig b/fs/squashfs/Kconfig
index 40a3f15..6849e70 100644
--- a/fs/squashfs/Kconfig
+++ b/fs/squashfs/Kconfig
@@ -1,5 +1,6 @@
config SQUASHFS
tristate "SquashFS 4.0 - Squashed file system support"
+ depends on BLOCK || MTD
select ZLIB_INFLATE
help
Saying Y here includes support for SquashFS 4.0 (a Compressed
diff --git a/fs/squashfs/Makefile b/fs/squashfs/Makefile
index 80f1cbe..8d5c0b8 100644
--- a/fs/squashfs/Makefile
+++ b/fs/squashfs/Makefile
@@ -7,3 +7,4 @@ squashfs-y += cache.o dir.o export.o file.o fragment.o id.o inode.o
squashfs-y += namei.o super.o symlink.o zlib_wrapper.o decompressor.o backend.o
squashfs-$(CONFIG_SQUASHFS_LZMA) += lzma_wrapper.o
squashfs-$(CONFIG_BLOCK) += block.o
+squashfs-$(CONFIG_MTD) += mtd.o
diff --git a/fs/squashfs/backend.c b/fs/squashfs/backend.c
index b83a5e2..a6136ca 100644
--- a/fs/squashfs/backend.c
+++ b/fs/squashfs/backend.c
@@ -1,6 +1,7 @@
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/buffer_head.h>
+#include <linux/mtd/super.h>

#include "squashfs_fs_i.h"
#include "squashfs.h"
@@ -13,6 +14,10 @@ int squashfs_find_backend(struct file_system_type *fs_type, int flags,
if (!get_sb_bdev(fs_type, flags, dev_name, data, fill_bdev_super, mnt))
return 0;
#endif
+#ifdef CONFIG_MTD
+ if (!get_sb_mtd(fs_type, flags, dev_name, data, fill_mtd_super, mnt))
+ return 0;
+#endif
WARNING("no suitable backend found\n");
return -EINVAL;
}
@@ -25,6 +30,12 @@ void squashfs_kill_super(struct super_block *sb)
return;
}
#endif
+#ifdef CONFIG_MTD
+ if (sb->s_mtd) {
+ kill_mtd_super(sb);
+ return;
+ }
+#endif
ERROR("squashfs_kill_super: no device behind the super block\n");
}

@@ -43,6 +54,10 @@ int squashfs_read_data(struct super_block *sb, void **buffer, u64 index,
if (sb->s_bdev)
return bdev_read_data(sb, buffer, index, length, next_index, srclength, pages);
#endif
+#ifdef CONFIG_MTD
+ if (sb->s_mtd)
+ return mtd_read_data(sb, buffer, index, length, next_index, srclength, pages);
+#endif
ERROR("squashfs_read_data: no device behind the super block\n");
return -EIO;
}
diff --git a/fs/squashfs/mtd.c b/fs/squashfs/mtd.c
new file mode 100644
index 0000000..b067616
--- /dev/null
+++ b/fs/squashfs/mtd.c
@@ -0,0 +1,179 @@
+/*
+ * mtd.c
+ */
+
+/*
+ * This file implements the low-level routines to read and decompress
+ * datablocks and metadata blocks from an MTD.
+ */
+
+#include <linux/fs.h>
+#include <linux/vfs.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/buffer_head.h>
+#include <linux/mtd/mtd.h>
+
+#include "squashfs_fs.h"
+#include "squashfs_fs_sb.h"
+#include "squashfs_fs_i.h"
+#include "squashfs.h"
+#include "decompressor.h"
+
+static int checked_mtd_read(struct mtd_info *mi, u64 index, int length,
+ void *buf)
+{
+ int ret, retlen;
+
+ TRACE("Entering checked_mtd_read: index=0x%llx, length=%d\n",
+ index, length);
+ ret = mi->read(mi, index, length, &retlen, buf);
+ if (ret) {
+ if (ret == -EUCLEAN || ret == -EBADMSG)
+ WARNING("checked_mtd_read(index=0x%llx, length=%d): "
+ "recoverable error %d\n", index, length, ret);
+ else {
+ ERROR("checked_mtd_read(index=0x%llx, length=%d): %d\n",
+ index, length, ret);
+ return ret;
+ }
+ }
+ if (retlen != length) {
+ ERROR("checked_mtd_read(index=0x%llx, length=%d) short read: %d\n",
+ index, length, retlen);
+ return -EIO;
+ }
+ return 0;
+}
+
+static int update_buffer(struct buffer_head *bh)
+{
+ struct mtd_info *mi = (struct mtd_info *)bh->b_bdev;
+ int ret = checked_mtd_read(mi, bh->b_blocknr, bh->b_size, bh->b_data);
+ if (ret)
+ return 0;
+ return 1;
+}
+
+static void put_buffer(struct buffer_head *bh)
+{
+}
+
+/*
+ * Big buffer_heads require more memory, but if a single one is enough,
+ * that can be special-cased in unlzma to avoid the extra memcpy.
+ * A better unlzma interface would be preferable, though.
+ */
+int mtd_read_data(struct super_block *sb, void **buffer, u64 index,
+ int length, u64 *next_index, int srclength, int pages)
+{
+ struct squashfs_sb_info *msblk = sb->s_fs_info;
+ struct mtd_info *mi = sb->s_mtd;
+ u64 i = index;
+ int bytes_left, compressed;
+
+ if (length) { /* Data block */
+ compressed = SQUASHFS_COMPRESSED_BLOCK(length);
+ length = SQUASHFS_COMPRESSED_SIZE_BLOCK(length);
+
+ TRACE("Block @ 0x%llx, %scompressed size %d, src size %d\n",
+ index, compressed ? "" : "un", length, srclength);
+ } else { /* Metadata block */
+ u16 metalen;
+ if ((index + 2) > msblk->bytes_used)
+ goto read_failure;
+ if (checked_mtd_read(mi, index, 2, &metalen))
+ goto read_failure;
+ i += 2;
+ length = le16_to_cpu(metalen);
+ compressed = SQUASHFS_COMPRESSED(length);
+ length = SQUASHFS_COMPRESSED_SIZE(length);
+
+ TRACE("Block @ 0x%llx, %scompressed size %d\n", index,
+ compressed ? "" : "un", length);
+ }
+ if (next_index)
+ *next_index = i + length;
+
+ if (length < 0 || length > srclength || i + length > msblk->bytes_used)
+ goto read_failure;
+
+ if (compressed) {
+ struct buffer_head **bh, *bhs;
+ int bh_num = (max_t(int, msblk->block_size, SQUASHFS_METADATA_SIZE) >>
+ msblk->devblksize_log2) + 1;
+ u_char *data;
+ int b;
+
+ bh = kmalloc(bh_num * sizeof(*bh), GFP_KERNEL);
+ if (bh == NULL)
+ return -ENOMEM;
+ bhs = kmalloc(bh_num * sizeof(*bhs), GFP_KERNEL);
+ if (bhs == NULL) {
+ kfree(bh);
+ return -ENOMEM;
+ }
+ data = kmalloc(msblk->devblksize, GFP_KERNEL);
+ if (data == NULL) {
+ kfree(bhs);
+ kfree(bh);
+ return -ENOMEM;
+ }
+
+ bytes_left = length;
+ for (b = 0; bytes_left > 0; b++) {
+ bh[b] = &bhs[b];
+ bhs[b].b_blocknr = i;
+ bhs[b].b_size = min(msblk->devblksize, bytes_left);
+ /* We know that the decompressors will use each buffer_head
+ * only once, so update_buffer may change the data under them. */
+ bhs[b].b_data = data;
+ bhs[b].b_bdev = (void *)mi;
+ i += msblk->devblksize;
+ bytes_left -= msblk->devblksize;
+ }
+
+ length = squashfs_decompress(msblk, buffer, bh, b, 0,
+ length, srclength, pages, update_buffer, put_buffer);
+ if (length < 0) {
+ kfree(data);
+ kfree(bhs);
+ kfree(bh);
+ goto read_failure;
+ }
+ } else { /* Not compressed */
+ int page = 0;
+ bytes_left = length;
+ while (bytes_left > 0) {
+ int blk = min_t(int, bytes_left, PAGE_CACHE_SIZE);
+ if (checked_mtd_read(mi, i, blk, buffer[page++]))
+ goto read_failure;
+ bytes_left -= blk;
+ i += blk;
+ }
+ }
+ return length;
+
+read_failure:
+ ERROR("mtd_read_data failed to read block 0x%llx\n",
+ (unsigned long long) index);
+ return -EIO;
+}
+
+int fill_mtd_super(struct super_block *sb, void *data, int silent)
+{
+ struct squashfs_sb_info *msblk;
+ char b[BDEVNAME_SIZE];
+
+ TRACE("Entering fill_mtd_super\n");
+
+ msblk = kzalloc(sizeof(*msblk), GFP_KERNEL);
+ if (!msblk)
+ return -ENOMEM;
+
+ sb->s_fs_info = msblk;
+ msblk->devblksize = PAGE_CACHE_SIZE;
+ msblk->devblksize_log2 = PAGE_CACHE_SHIFT;
+ snprintf(b, sizeof b, "mtd%d", sb->s_mtd->index);
+ return squashfs_fill_super(sb, data, silent, b, sb->s_mtd->size);
+}
diff --git a/fs/squashfs/squashfs.h b/fs/squashfs/squashfs.h
index 7c5cd72..05a85e2 100644
--- a/fs/squashfs/squashfs.h
+++ b/fs/squashfs/squashfs.h
@@ -105,6 +105,10 @@ extern const struct squashfs_decompressor squashfs_lzma_comp_ops;
extern int fill_bdev_super(struct super_block *, void *, int);
extern int bdev_read_data(struct super_block *, void **, u64, int, u64 *, int, int);

+/* mtd.c */
+extern int fill_mtd_super(struct super_block *, void *, int);
+extern int mtd_read_data(struct super_block *, void **, u64, int, u64 *, int, int);
+
#ifndef CONFIG_BLOCK
struct buffer_head {
sector_t b_blocknr;
--
1.6.5


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