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SubjectRe: [PATCH 2.6.21] cramfs: add cramfs Linear XIP
On Thu, Jun 07, 2007 at 08:37:07PM +0100, Christoph Hellwig wrote:
> The code is at http://verein.lst.de/~hch/cramfs-xip.tar.gz.

And for thus just wanting to take a quick glance, this is the
diff vs an out of tree cramfs where uncompress.c and cramfs_fs_sb.h
are merged into inode.c:

--- ./inode.c 2007/06/07 11:52:32 1.1
+++ ./inode.c 2007/06/07 14:06:04
@@ -36,6 +36,7 @@
unsigned long blocks;
unsigned long files;
unsigned long flags;
+ void __iomem *linear_virt_addr;
};

static inline struct cramfs_sb_info *CRAMFS_SB(struct super_block *sb)
@@ -43,12 +44,20 @@
return sb->s_fs_info;
}

+#define CRAMFS_INODE_IS_XIP(x) \
+ ((x)->i_mode & S_ISVTX)
+
+static const struct file_operations cramfs_xip_fops;
static const struct super_operations cramfs_ops;
static const struct inode_operations cramfs_dir_inode_operations;
static const struct file_operations cramfs_directory_operations;
static const struct address_space_operations cramfs_aops;
+static const struct address_space_operations cramfs_xip_aops;
+
+static struct backing_dev_info cramfs_backing_dev_info = {
+ .ra_pages = 0, /* No readahead */
+};

-static DEFINE_MUTEX(read_mutex);
static z_stream stream;


@@ -94,19 +103,31 @@
/* Struct copy intentional */
inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
inode->i_ino = CRAMINO(cramfs_inode);
+
+ if (CRAMFS_INODE_IS_XIP(inode))
+ inode->i_mapping->backing_dev_info = &cramfs_backing_dev_info;
+
/* inode->i_nlink is left 1 - arguably wrong for directories,
but it's the best we can do without reading the directory
contents. 1 yields the right result in GNU find, even
without -noleaf option. */
if (S_ISREG(inode->i_mode)) {
- inode->i_fop = &generic_ro_fops;
- inode->i_data.a_ops = &cramfs_aops;
+ if (CRAMFS_INODE_IS_XIP(inode)) {
+ inode->i_fop = &cramfs_xip_fops;
+ inode->i_data.a_ops = &cramfs_xip_aops;
+ } else {
+ inode->i_fop = &generic_ro_fops;
+ inode->i_data.a_ops = &cramfs_aops;
+ }
} else if (S_ISDIR(inode->i_mode)) {
inode->i_op = &cramfs_dir_inode_operations;
inode->i_fop = &cramfs_directory_operations;
} else if (S_ISLNK(inode->i_mode)) {
inode->i_op = &page_symlink_inode_operations;
- inode->i_data.a_ops = &cramfs_aops;
+ if (CRAMFS_INODE_IS_XIP(inode))
+ inode->i_data.a_ops = &cramfs_xip_aops;
+ else
+ inode->i_data.a_ops = &cramfs_aops;
} else {
inode->i_size = 0;
inode->i_blocks = 0;
@@ -122,42 +143,11 @@
struct inode *inode = iget5_locked(sb, CRAMINO(cramfs_inode),
cramfs_iget5_test, cramfs_iget5_set,
cramfs_inode);
- if (inode && (inode->i_state & I_NEW)) {
+ if (inode && (inode->i_state & I_NEW))
unlock_new_inode(inode);
- }
return inode;
}

-/*
- * We have our own block cache: don't fill up the buffer cache
- * with the rom-image, because the way the filesystem is set
- * up the accesses should be fairly regular and cached in the
- * page cache and dentry tree anyway..
- *
- * This also acts as a way to guarantee contiguous areas of up to
- * BLKS_PER_BUF*PAGE_CACHE_SIZE, so that the caller doesn't need to
- * worry about end-of-buffer issues even when decompressing a full
- * page cache.
- */
-#define READ_BUFFERS (2)
-/* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */
-#define NEXT_BUFFER(_ix) ((_ix) ^ 1)
-
-/*
- * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed"
- * data that takes up more space than the original and with unlucky
- * alignment.
- */
-#define BLKS_PER_BUF_SHIFT (2)
-#define BLKS_PER_BUF (1 << BLKS_PER_BUF_SHIFT)
-#define BUFFER_SIZE (BLKS_PER_BUF*PAGE_CACHE_SIZE)
-
-static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
-static unsigned buffer_blocknr[READ_BUFFERS];
-static struct super_block * buffer_dev[READ_BUFFERS];
-static int next_buffer;
-
-
/* Returns length of decompressed data. */
static int cramfs_uncompress_block(void *dst, int dstlen, void *src,
int srclen)
@@ -194,78 +184,11 @@
*/
static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len)
{
- struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
- struct page *pages[BLKS_PER_BUF];
- unsigned i, blocknr, buffer, unread;
- unsigned long devsize;
- char *data;
+ struct cramfs_sb_info *sbi = CRAMFS_SB(sb);

if (!len)
return NULL;
- blocknr = offset >> PAGE_CACHE_SHIFT;
- offset &= PAGE_CACHE_SIZE - 1;
-
- /* Check if an existing buffer already has the data.. */
- for (i = 0; i < READ_BUFFERS; i++) {
- unsigned int blk_offset;
-
- if (buffer_dev[i] != sb)
- continue;
- if (blocknr < buffer_blocknr[i])
- continue;
- blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_CACHE_SHIFT;
- blk_offset += offset;
- if (blk_offset + len > BUFFER_SIZE)
- continue;
- return read_buffers[i] + blk_offset;
- }
-
- devsize = mapping->host->i_size >> PAGE_CACHE_SHIFT;
-
- /* Ok, read in BLKS_PER_BUF pages completely first. */
- unread = 0;
- for (i = 0; i < BLKS_PER_BUF; i++) {
- struct page *page = NULL;
-
- if (blocknr + i < devsize) {
- page = read_mapping_page_async(mapping, blocknr + i,
- NULL);
- /* synchronous error? */
- if (IS_ERR(page))
- page = NULL;
- }
- pages[i] = page;
- }
-
- for (i = 0; i < BLKS_PER_BUF; i++) {
- struct page *page = pages[i];
- if (page) {
- wait_on_page_locked(page);
- if (!PageUptodate(page)) {
- /* asynchronous error */
- page_cache_release(page);
- pages[i] = NULL;
- }
- }
- }
-
- buffer = next_buffer;
- next_buffer = NEXT_BUFFER(buffer);
- buffer_blocknr[buffer] = blocknr;
- buffer_dev[buffer] = sb;
-
- data = read_buffers[buffer];
- for (i = 0; i < BLKS_PER_BUF; i++) {
- struct page *page = pages[i];
- if (page) {
- memcpy(data, kmap(page), PAGE_CACHE_SIZE);
- kunmap(page);
- page_cache_release(page);
- } else
- memset(data, 0, PAGE_CACHE_SIZE);
- data += PAGE_CACHE_SIZE;
- }
- return read_buffers[buffer] + offset;
+ return sbi->linear_virt_addr + offset;
}

static void cramfs_put_super(struct super_block *sb)
@@ -282,11 +205,12 @@

static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
{
- int i;
struct cramfs_super super;
unsigned long root_offset;
struct cramfs_sb_info *sbi;
struct inode *root;
+ unsigned long phys_addr;
+ char *p;

sb->s_flags |= MS_RDONLY;

@@ -295,38 +219,59 @@
return -ENOMEM;
sb->s_fs_info = sbi;

- /* Invalidate the read buffers on mount: think disk change.. */
- mutex_lock(&read_mutex);
- for (i = 0; i < READ_BUFFERS; i++)
- buffer_blocknr[i] = -1;
+ p = strstr(data, "physaddr=");
+ if (!p)
+ goto out_kfree;
+
+ phys_addr = simple_strtoul(p + 9, NULL, 0);
+ if (phys_addr & (PAGE_SIZE-1)) {
+ printk(KERN_ERR "cramfs: physical address 0x%lx for linear"
+ "cramfs isn't aligned to a page boundary\n",
+ phys_addr);
+ goto out_kfree;
+ }
+
+ if (phys_addr == 0) {
+ printk(KERN_ERR "cramfs: physical address for linear cramfs"
+ "image can't be 0\n");
+ goto out_kfree;
+ }
+
+ printk(KERN_INFO "cramfs: checking physical address 0x%lx for linear"
+ "cramfs image\n", phys_addr);
+
+ /* Map only one page for now. Will remap it when fs size is known. */
+ sbi->linear_virt_addr = ioremap(phys_addr, PAGE_SIZE);
+ if (!sbi->linear_virt_addr) {
+ printk(KERN_ERR "cramfs: ioremap of the linear cramfs image"
+ "failed\n");
+ goto out_kfree;
+ }

/* Read the first block and get the superblock from it */
memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
- mutex_unlock(&read_mutex);

/* Do sanity checks on the superblock */
if (super.magic != CRAMFS_MAGIC) {
/* check at 512 byte offset */
- mutex_lock(&read_mutex);
memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
- mutex_unlock(&read_mutex);
if (super.magic != CRAMFS_MAGIC) {
if (!silent)
printk(KERN_ERR "cramfs: wrong magic\n");
- goto out;
+ goto out_iounmap;
}
}

/* get feature flags first */
if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
printk(KERN_ERR "cramfs: unsupported filesystem features\n");
- goto out;
+ goto out_iounmap;
}

/* Check that the root inode is in a sane state */
if (!S_ISDIR(super.root.mode)) {
printk(KERN_ERR "cramfs: root is not a directory\n");
- goto out;
+ goto out_iounmap;
}
root_offset = super.root.offset << 2;
if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
@@ -347,21 +292,34 @@
(root_offset != 512 + sizeof(struct cramfs_super))))
{
printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset);
- goto out;
+ goto out_iounmap;
}

/* Set it all up.. */
sb->s_op = &cramfs_ops;
root = get_cramfs_inode(sb, &super.root);
if (!root)
- goto out;
+ goto out_iounmap;
sb->s_root = d_alloc_root(root);
if (!sb->s_root) {
iput(root);
- goto out;
+ goto out_iounmap;
}
+
+ /* Remap the whole filesystem now */
+ iounmap(sbi->linear_virt_addr);
+ sbi->linear_virt_addr = ioremap(phys_addr, sbi->size);
+ if (!sbi->linear_virt_addr) {
+ printk(KERN_ERR "cramfs: ioremap of the linear cramfs image"
+ " failed\n");
+ goto out_iounmap;
+ }
+
return 0;
-out:
+
+ out_iounmap:
+ iounmap(sbi->linear_virt_addr);
+ out_kfree:
kfree(sbi);
sb->s_fs_info = NULL;
return -EINVAL;
@@ -382,6 +340,13 @@
return 0;
}

+static int cramfs_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
+ return -EINVAL;
+ return xip_file_mmap(file, vma);
+}
+
/*
* Read a cramfs directory entry.
*/
@@ -414,7 +379,6 @@
mode_t mode;
int namelen, error;

- mutex_lock(&read_mutex);
de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+256);
name = (char *)(de+1);

@@ -427,7 +391,6 @@
memcpy(buf, name, namelen);
ino = CRAMINO(de);
mode = de->mode;
- mutex_unlock(&read_mutex);
nextoffset = offset + sizeof(*de) + namelen;
for (;;) {
if (!namelen) {
@@ -458,7 +421,6 @@
unsigned int offset = 0;
int sorted;

- mutex_lock(&read_mutex);
sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
while (offset < dir->i_size) {
struct cramfs_inode *de;
@@ -481,7 +443,6 @@

for (;;) {
if (!namelen) {
- mutex_unlock(&read_mutex);
return ERR_PTR(-EIO);
}
if (name[namelen-1])
@@ -495,7 +456,6 @@
continue;
if (!retval) {
struct cramfs_inode entry = *de;
- mutex_unlock(&read_mutex);
d_add(dentry, get_cramfs_inode(dir->i_sb, &entry));
return NULL;
}
@@ -503,7 +463,6 @@
if (sorted)
break;
}
- mutex_unlock(&read_mutex);
d_add(dentry, NULL);
return NULL;
}
@@ -522,23 +481,19 @@
u32 start_offset, compr_len;

start_offset = OFFSET(inode) + maxblock*4;
- mutex_lock(&read_mutex);
if (page->index)
start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, 4);
compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - start_offset);
- mutex_unlock(&read_mutex);
pgdata = kmap(page);
if (compr_len == 0)
; /* hole */
else if (compr_len > (PAGE_CACHE_SIZE << 1))
printk(KERN_ERR "cramfs: bad compressed blocksize %u\n", compr_len);
else {
- mutex_lock(&read_mutex);
bytes_filled = cramfs_uncompress_block(pgdata,
PAGE_CACHE_SIZE,
cramfs_read(sb, start_offset, compr_len),
compr_len);
- mutex_unlock(&read_mutex);
}
} else
pgdata = kmap(page);
@@ -550,13 +505,34 @@
return 0;
}

+static struct page *cramfs_get_xip_page(struct address_space *mapping,
+ sector_t offset, int create)
+{
+ struct inode *inode = mapping->host;
+ struct cramfs_sb_info *sbi = CRAMFS_SB(inode->i_sb);
+ unsigned long address;
+
+ address = PAGE_ALIGN((unsigned long)
+ (sbi->linear_virt_addr + OFFSET(inode)));
+
+ /* FIXME -- This shouldn't be hard coded */
+ address += (offset * 512);
+
+ return virt_to_page(address);
+}
+
static const struct address_space_operations cramfs_aops = {
- .readpage = cramfs_readpage
+ .readpage = cramfs_readpage,
};

-/*
- * Our operations:
- */
+static const struct address_space_operations cramfs_xip_aops = {
+ .get_xip_page = cramfs_get_xip_page,
+};
+
+static const struct file_operations cramfs_xip_fops = {
+ .read = xip_file_read,
+ .mmap = cramfs_mmap,
+};

/*
* A directory can only readdir
@@ -580,16 +556,14 @@
static int cramfs_get_sb(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
- return get_sb_bdev(fs_type, flags, dev_name, data, cramfs_fill_super,
- mnt);
+ return get_sb_nodev(fs_type, flags, data, cramfs_fill_super, mnt);
}

static struct file_system_type cramfs_fs_type = {
.owner = THIS_MODULE,
.name = "cramfs",
.get_sb = cramfs_get_sb,
- .kill_sb = kill_block_super,
- .fs_flags = FS_REQUIRES_DEV,
+ .kill_sb = kill_anon_super,
};

static int __init init_cramfs_fs(void)
-
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