AZFS file system proposal

[Maxim Shchetynin]

Hello,

there are some users which have interest on such kind of file system like azfs. Please, have a look at this version of a diff file which introduces a first version of azfs to 2.6.26. This file system may be useful for example on IBM CellBlades where user can mount DDR2 memory of Axon controller as a disk and to be able to access it directly without any caching mechanism in between.

Subject: azfs: initial submit of azfs, a non-buffered filesystem

From: Maxim Shchetynin <maxim@xxxxxxxxxx>

Non-buffered filesystem for block devices with a gendisk and
with direct_access() method in gendisk->fops.
AZFS does not buffer outgoing traffic and is doing no read ahead.
It supports mount options (given with -o) bs=x,uid=x,gid=x.
If block-size (bs) is not specified AZFS uses block-size used
by block device. Though mmap() method is available only if
block-size equals to or is greater than the system page size.

Signed-off-by: Maxim Shchetynin <maxim@xxxxxxxxxx>

diff -Nuar linux-2.6.26-rc5/arch/powerpc/configs/cell_defconfig linux-2.6.26-rc5-azfs/arch/powerpc/configs/cell_defconfig
--- linux-2.6.26-rc5/arch/powerpc/configs/cell_defconfig	2008-06-05 05:10:44.000000000 +0200
+++ linux-2.6.26-rc5-azfs/arch/powerpc/configs/cell_defconfig	2008-06-06 11:53:34.000000000 +0200
@@ -240,6 +240,7 @@
 # CPU Frequency drivers
 #
 CONFIG_AXON_RAM=m
+CONFIG_AZ_FS=m
 # CONFIG_FSL_ULI1575 is not set
 
 #
diff -Nuar linux-2.6.26-rc5/fs/Kconfig linux-2.6.26-rc5-azfs/fs/Kconfig
--- linux-2.6.26-rc5/fs/Kconfig	2008-06-05 05:10:44.000000000 +0200
+++ linux-2.6.26-rc5-azfs/fs/Kconfig	2008-06-06 16:55:11.616419992 +0200
@@ -360,6 +360,17 @@
 	  If you are not using a security module that requires using
 	  extended attributes for file security labels, say N.
 
+config AZ_FS
+	tristate "AZFS filesystem support"
+	help
+	  Non-buffered filesystem for block devices with a gendisk and
+	  with direct_access() method in gendisk->fops.
+	  AZFS does not buffer outgoing traffic and is doing no read ahead.
+	  It supports mount options (given with -o) bs=x,uid=x,gid=x.
+	  If block-size (bs) is not specified AZFS uses block-size used
+	  by block device. Though mmap() method is available only if
+	  block-size equals to or is greater than system page size.
+
 config JFS_FS
 	tristate "JFS filesystem support"
 	select NLS
diff -Nuar linux-2.6.26-rc5/fs/Makefile linux-2.6.26-rc5-azfs/fs/Makefile
--- linux-2.6.26-rc5/fs/Makefile	2008-06-05 05:10:44.000000000 +0200
+++ linux-2.6.26-rc5-azfs/fs/Makefile	2008-06-06 11:53:34.000000000 +0200
@@ -119,3 +119,4 @@
 obj-$(CONFIG_DEBUG_FS)		+= debugfs/
 obj-$(CONFIG_OCFS2_FS)		+= ocfs2/
 obj-$(CONFIG_GFS2_FS)           += gfs2/
+obj-$(CONFIG_AZ_FS)		+= azfs.o
diff -Nuar linux-2.6.26-rc5/fs/azfs.c linux-2.6.26-rc5-azfs/fs/azfs.c
--- linux-2.6.26-rc5/fs/azfs.c	1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.26-rc5-azfs/fs/azfs.c	2008-06-06 17:46:23.587653053 +0200
@@ -0,0 +1,1179 @@
+/*
+ * (C) Copyright IBM Deutschland Entwicklung GmbH 2007
+ *
+ * Author: Maxim Shchetynin <maxim@xxxxxxxxxx>
+ *
+ * Non-buffered filesystem driver.
+ * It registers a filesystem which may be used for all kind of block devices
+ * which have a direct_access() method in block_device_operations.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/backing-dev.h>
+#include <linux/blkdev.h>
+#include <linux/cache.h>
+#include <linux/dcache.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/fs.h>
+#include <linux/genhd.h>
+#include <linux/kernel.h>
+#include <linux/limits.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/mount.h>
+#include <linux/mm.h>
+#include <linux/mm_types.h>
+#include <linux/mutex.h>
+#include <linux/namei.h>
+#include <linux/pagemap.h>
+#include <linux/parser.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/stat.h>
+#include <linux/statfs.h>
+#include <linux/string.h>
+#include <linux/time.h>
+#include <linux/types.h>
+#include <linux/aio.h>
+#include <linux/uio.h>
+#include <asm/bug.h>
+#include <asm/page.h>
+#include <asm/pgtable.h>
+#include <asm/string.h>
+
+#define AZFS_FILESYSTEM_NAME		"azfs"
+#define AZFS_FILESYSTEM_FLAGS		FS_REQUIRES_DEV
+
+#define AZFS_SUPERBLOCK_MAGIC		0xABBA1972
+#define AZFS_SUPERBLOCK_FLAGS		MS_NOEXEC | \
+					MS_SYNCHRONOUS | \
+					MS_DIRSYNC | \
+					MS_ACTIVE
+
+#define AZFS_BDI_CAPABILITIES		BDI_CAP_NO_ACCT_DIRTY | \
+					BDI_CAP_NO_WRITEBACK | \
+					BDI_CAP_MAP_COPY | \
+					BDI_CAP_MAP_DIRECT | \
+					BDI_CAP_VMFLAGS
+
+#define AZFS_CACHE_FLAGS		SLAB_HWCACHE_ALIGN | \
+					SLAB_RECLAIM_ACCOUNT | \
+					SLAB_MEM_SPREAD
+
+enum azfs_direction {
+	AZFS_MMAP,
+	AZFS_READ,
+	AZFS_WRITE
+};
+
+struct azfs_super {
+	struct list_head		list;
+	unsigned long			media_size;
+	unsigned long			block_size;
+	unsigned short			block_shift;
+	unsigned long			sector_size;
+	unsigned short			sector_shift;
+	uid_t				uid;
+	gid_t				gid;
+	unsigned long			ph_addr;
+	unsigned long			io_addr;
+	struct block_device		*blkdev;
+	struct dentry			*root;
+	struct list_head		block_list;
+	rwlock_t			lock;
+};
+
+struct azfs_super_list {
+	struct list_head		head;
+	spinlock_t			lock;
+};
+
+struct azfs_block {
+	struct list_head		list;
+	unsigned long			id;
+	unsigned long			count;
+};
+
+struct azfs_znode {
+	struct list_head		block_list;
+	rwlock_t			lock;
+	loff_t				size;
+	struct inode			vfs_inode;
+};
+
+static struct azfs_super_list		super_list;
+static struct kmem_cache		*azfs_znode_cache __read_mostly = NULL;
+static struct kmem_cache		*azfs_block_cache __read_mostly = NULL;
+
+#define I2Z(inode) \
+	container_of(inode, struct azfs_znode, vfs_inode)
+
+#define for_each_block(block, block_list) \
+	list_for_each_entry(block, block_list, list)
+#define for_each_block_reverse(block, block_list) \
+	list_for_each_entry_reverse(block, block_list, list)
+#define for_each_block_safe(block, ding, block_list) \
+	list_for_each_entry_safe(block, ding, block_list, list)
+#define for_each_block_safe_reverse(block, ding, block_list) \
+	list_for_each_entry_safe_reverse(block, ding, block_list, list)
+
+/**
+ * azfs_block_init - create and initialise a new block in a list
+ * @block_list: destination list
+ * @id: block id
+ * @count: size of a block
+ */
+static inline struct azfs_block*
+azfs_block_init(struct list_head *block_list,
+		unsigned long id, unsigned long count)
+{
+	struct azfs_block *block;
+
+	block = kmem_cache_alloc(azfs_block_cache, GFP_KERNEL);
+	if (!block)
+		return NULL;
+
+	block->id = id;
+	block->count = count;
+
+	INIT_LIST_HEAD(&block->list);
+	list_add_tail(&block->list, block_list);
+
+	return block;
+}
+
+/**
+ * azfs_block_free - remove block from a list and free it back in cache
+ * @block: block to be removed
+ */
+static inline void
+azfs_block_free(struct azfs_block *block)
+{
+	list_del(&block->list);
+	kmem_cache_free(azfs_block_cache, block);
+}
+
+/**
+ * azfs_block_move - move block to another list
+ * @block: block to be moved
+ * @block_list: destination list
+ */
+static inline void
+azfs_block_move(struct azfs_block *block, struct list_head *block_list)
+{
+	list_move_tail(&block->list, block_list);
+}
+
+/**
+ * azfs_recherche - get real address of a part of a file
+ * @inode: inode
+ * @direction: data direction
+ * @from: offset for read/write operation
+ * @size: pointer to a value of the amount of data to be read/written
+ */
+static unsigned long
+azfs_recherche(struct inode *inode, enum azfs_direction direction,
+	       unsigned long from, unsigned long *size)
+{
+	struct azfs_super *super;
+	struct azfs_znode *znode;
+	struct azfs_block *block;
+	unsigned long block_id, west, east;
+
+	super = inode->i_sb->s_fs_info;
+	znode = I2Z(inode);
+
+	if (from + *size > znode->size) {
+		i_size_write(inode, from + *size);
+		inode->i_op->truncate(inode);
+	}
+
+	read_lock(&znode->lock);
+
+	if (list_empty(&znode->block_list)) {
+		read_unlock(&znode->lock);
+		return 0;
+	}
+
+	block_id = from >> super->block_shift;
+
+	for_each_block(block, &znode->block_list) {
+		if (block->count > block_id)
+			break;
+		block_id -= block->count;
+	}
+
+	west = from % super->block_size;
+	east = ((block->count - block_id) << super->block_shift) - west;
+
+	if (*size > east)
+		*size = east;
+
+	block_id = ((block->id + block_id) << super->block_shift) + west;
+
+	read_unlock(&znode->lock);
+
+	block_id += direction == AZFS_MMAP ? super->ph_addr : super->io_addr;
+
+	return block_id;
+}
+
+static struct inode*
+azfs_new_inode(struct super_block *, struct inode *, int, dev_t);
+
+/**
+ * azfs_mknod - mknod() method for inode_operations
+ * @dir, @dentry, @mode, @dev: see inode_operations methods
+ */
+static int
+azfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
+{
+	struct inode *inode;
+
+	inode = azfs_new_inode(dir->i_sb, dir, mode, dev);
+	if (!inode)
+		return -ENOSPC;
+
+	if (S_ISREG(mode))
+		I2Z(inode)->size = 0;
+
+	dget(dentry);
+	d_instantiate(dentry, inode);
+
+	return 0;
+}
+
+/**
+ * azfs_create - create() method for inode_operations
+ * @dir, @dentry, @mode, @nd: see inode_operations methods
+ */
+static int
+azfs_create(struct inode *dir, struct dentry *dentry, int mode,
+	    struct nameidata *nd)
+{
+	return azfs_mknod(dir, dentry, mode | S_IFREG, 0);
+}
+
+/**
+ * azfs_mkdir - mkdir() method for inode_operations
+ * @dir, @dentry, @mode: see inode_operations methods
+ */
+static int
+azfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
+{
+	int rc;
+
+	rc = azfs_mknod(dir, dentry, mode | S_IFDIR, 0);
+	if (rc == 0)
+		inc_nlink(dir);
+
+	return rc;
+}
+
+/**
+ * azfs_symlink - symlink() method for inode_operations
+ * @dir, @dentry, @name: see inode_operations methods
+ */
+static int
+azfs_symlink(struct inode *dir, struct dentry *dentry, const char *name)
+{
+	struct inode *inode;
+	int rc;
+
+	inode = azfs_new_inode(dir->i_sb, dir, S_IFLNK | S_IRWXUGO, 0);
+	if (!inode)
+		return -ENOSPC;
+
+	rc = page_symlink(inode, name, strlen(name) + 1);
+	if (rc) {
+		iput(inode);
+		return rc;
+	}
+
+	dget(dentry);
+	d_instantiate(dentry, inode);
+
+	return 0;
+}
+
+/**
+ * azfs_aio_read - aio_read() method for file_operations
+ * @iocb, @iov, @nr_segs, @pos: see file_operations methods
+ */
+static ssize_t
+azfs_aio_read(struct kiocb *iocb, const struct iovec *iov,
+	      unsigned long nr_segs, loff_t pos)
+{
+	struct inode *inode;
+	void *ziel;
+	unsigned long pin;
+	unsigned long size, todo, step;
+	ssize_t rc;
+
+	inode = iocb->ki_filp->f_mapping->host;
+
+	mutex_lock(&inode->i_mutex);
+
+	if (pos >= i_size_read(inode)) {
+		rc = 0;
+		goto out;
+	}
+
+	ziel = iov->iov_base;
+	todo = min((loff_t) iov->iov_len, i_size_read(inode) - pos);
+
+	for (step = todo; step; step -= size) {
+		size = step;
+		pin = azfs_recherche(inode, AZFS_READ, pos, &size);
+		if (!pin) {
+			rc = -ENOSPC;
+			goto out;
+		}
+		if (copy_to_user(ziel, (void*) pin, size)) {
+			rc = -EFAULT;
+			goto out;
+		}
+
+		iocb->ki_pos += size;
+		pos += size;
+		ziel += size;
+	}
+
+	rc = todo;
+
+out:
+	mutex_unlock(&inode->i_mutex);
+
+	return rc;
+}
+
+/**
+ * azfs_aio_write - aio_write() method for file_operations
+ * @iocb, @iov, @nr_segs, @pos: see file_operations methods
+ */
+static ssize_t
+azfs_aio_write(struct kiocb *iocb, const struct iovec *iov,
+	       unsigned long nr_segs, loff_t pos)
+{
+	struct inode *inode;
+	void *quell;
+	unsigned long pin;
+	unsigned long size, todo, step;
+	ssize_t rc;
+
+	inode = iocb->ki_filp->f_mapping->host;
+
+	quell = iov->iov_base;
+	todo = iov->iov_len;
+
+	mutex_lock(&inode->i_mutex);
+
+	for (step = todo; step; step -= size) {
+		size = step;
+		pin = azfs_recherche(inode, AZFS_WRITE, pos, &size);
+		if (!pin) {
+			rc = -ENOSPC;
+			goto out;
+		}
+		if (copy_from_user((void*) pin, quell, size)) {
+			rc = -EFAULT;
+			goto out;
+		}
+
+		iocb->ki_pos += size;
+		pos += size;
+		quell += size;
+	}
+
+	rc = todo;
+
+out:
+	mutex_unlock(&inode->i_mutex);
+
+	return rc;
+}
+
+/**
+ * azfs_open - open() method for file_operations
+ * @inode, @file: see file_operations methods
+ */
+static int
+azfs_open(struct inode *inode, struct file *file)
+{
+	file->private_data = inode;
+
+	if (file->f_flags & O_TRUNC) {
+		i_size_write(inode, 0);
+		inode->i_op->truncate(inode);
+	}
+	if (file->f_flags & O_APPEND)
+		inode->i_fop->llseek(file, 0, SEEK_END);
+
+	return 0;
+}
+
+/**
+ * azfs_mmap - mmap() method for file_operations
+ * @file, @vm: see file_operations methods
+ */
+static int
+azfs_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	struct azfs_super *super;
+	struct azfs_znode *znode;
+	struct inode *inode;
+	unsigned long cursor, pin;
+	unsigned long todo, size, vm_start;
+	pgprot_t page_prot;
+
+	inode = file->private_data;
+	znode = I2Z(inode);
+	super = inode->i_sb->s_fs_info;
+
+	if (super->block_size < PAGE_SIZE)
+		return -EINVAL;
+
+	cursor = vma->vm_pgoff << super->block_shift;
+	todo = vma->vm_end - vma->vm_start;
+
+	if (cursor + todo > i_size_read(inode))
+		return -EINVAL;
+
+	page_prot = pgprot_val(vma->vm_page_prot);
+	page_prot |= (_PAGE_NO_CACHE | _PAGE_RW);
+	page_prot &= ~_PAGE_GUARDED;
+	vma->vm_page_prot = __pgprot(page_prot);
+
+	vm_start = vma->vm_start;
+	for (size = todo; todo; todo -= size, size = todo) {
+		pin = azfs_recherche(inode, AZFS_MMAP, cursor, &size);
+		if (!pin)
+			return -EAGAIN;
+		pin >>= PAGE_SHIFT;
+		if (remap_pfn_range(vma, vm_start, pin, size, vma->vm_page_prot))
+			return -EAGAIN;
+
+		vm_start += size;
+		cursor += size;
+	}
+
+	return 0;
+}
+
+/**
+ * azfs_truncate - truncate() method for inode_operations
+ * @inode: see inode_operations methods
+ */
+static void
+azfs_truncate(struct inode *inode)
+{
+	struct azfs_super *super;
+	struct azfs_znode *znode;
+	struct azfs_block *block, *ding, *knoten, *west, *east;
+	unsigned long id, count;
+	signed long delta;
+
+	super = inode->i_sb->s_fs_info;
+	znode = I2Z(inode);
+
+	delta = i_size_read(inode) + (super->block_size - 1);
+	delta >>= super->block_shift;
+	delta -= inode->i_blocks;
+
+	if (delta == 0) {
+		znode->size = i_size_read(inode);
+		return;
+	}
+
+	write_lock(&znode->lock);
+
+	while (delta > 0) {
+		west = east = NULL;
+
+		write_lock(&super->lock);
+
+		if (list_empty(&super->block_list)) {
+			write_unlock(&super->lock);
+			break;
+		}
+
+		for (count = delta; count; count--) {
+			for_each_block(block, &super->block_list)
+				if (block->count >= count) {
+					east = block;
+					break;
+				}
+			if (east)
+				break;
+		}
+
+		for_each_block_reverse(block, &znode->block_list) {
+			if (block->id + block->count == east->id)
+				west = block;
+			break;
+		}
+
+		if (east->count == count) {
+			if (west) {
+				west->count += east->count;
+				azfs_block_free(east);
+			} else {
+				azfs_block_move(east, &znode->block_list);
+			}
+		} else {
+			if (west) {
+				west->count += count;
+			} else {
+				if (!azfs_block_init(&znode->block_list,
+						east->id, count)) {
+					write_unlock(&super->lock);
+					break;
+				}
+			}
+
+			east->id += count;
+			east->count -= count;
+		}
+
+		write_unlock(&super->lock);
+
+		inode->i_blocks += count;
+
+		delta -= count;
+	}
+
+	while (delta < 0) {
+		for_each_block_safe_reverse(block, knoten, &znode->block_list) {
+			id = block->id;
+			count = block->count;
+			if ((signed long) count + delta > 0) {
+				block->count += delta;
+				id += block->count;
+				count -= block->count;
+				block = NULL;
+			}
+
+			west = east = NULL;
+
+			write_lock(&super->lock);
+
+			for_each_block(ding, &super->block_list) {
+				if (!west && (ding->id + ding->count == id))
+					west = ding;
+				else if (!east && (id + count == ding->id))
+					east = ding;
+				if (west && east)
+					break;
+			}
+
+			if (west && east) {
+				west->count += count + east->count;
+				azfs_block_free(east);
+				if (block)
+					azfs_block_free(block);
+			} else if (west) {
+				west->count += count;
+				if (block)
+					azfs_block_free(block);
+			} else if (east) {
+				east->id -= count;
+				east->count += count;
+				if (block)
+					azfs_block_free(block);
+			} else {
+				if (!block) {
+					if (!azfs_block_init(&super->block_list,
+							id, count)) {
+						write_unlock(&super->lock);
+						break;
+					}
+				} else {
+					azfs_block_move(block, &super->block_list);
+				}
+			}
+
+			write_unlock(&super->lock);
+
+			inode->i_blocks -= count;
+
+			delta += count;
+
+			break;
+		}
+	}
+
+	write_unlock(&znode->lock);
+
+	znode->size = min(i_size_read(inode),
+			(loff_t) inode->i_blocks << super->block_shift);
+}
+
+/**
+ * azfs_getattr - getattr() method for inode_operations
+ * @mnt, @dentry, @stat: see inode_operations methods
+ */
+static int
+azfs_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
+{
+	struct azfs_super *super;
+	struct inode *inode;
+	unsigned short shift;
+
+	inode = dentry->d_inode;
+	super = inode->i_sb->s_fs_info;
+
+	generic_fillattr(inode, stat);
+	stat->blocks = inode->i_blocks;
+	shift = super->block_shift - super->sector_shift;
+	if (shift)
+		stat->blocks <<= shift;
+
+	return 0;
+}
+
+static const struct address_space_operations azfs_aops = {
+	.write_begin	= simple_write_begin,
+	.write_end	= simple_write_end
+};
+
+static struct backing_dev_info azfs_bdi = {
+	.ra_pages	= 0,
+	.capabilities	= AZFS_BDI_CAPABILITIES
+};
+
+static struct inode_operations azfs_dir_iops = {
+	.create		= azfs_create,
+	.lookup		= simple_lookup,
+	.link		= simple_link,
+	.unlink		= simple_unlink,
+	.symlink	= azfs_symlink,
+	.mkdir		= azfs_mkdir,
+	.rmdir		= simple_rmdir,
+	.mknod		= azfs_mknod,
+	.rename		= simple_rename
+};
+
+static const struct file_operations azfs_reg_fops = {
+	.llseek		= generic_file_llseek,
+	.aio_read	= azfs_aio_read,
+	.aio_write	= azfs_aio_write,
+	.open		= azfs_open,
+	.mmap		= azfs_mmap,
+	.fsync		= simple_sync_file,
+};
+
+static struct inode_operations azfs_reg_iops = {
+	.truncate	= azfs_truncate,
+	.getattr	= azfs_getattr
+};
+
+/**
+ * azfs_new_inode - cook a new inode
+ * @sb: super-block
+ * @dir: parent directory
+ * @mode: file mode
+ * @dev: to be forwarded to init_special_inode()
+ */
+static struct inode*
+azfs_new_inode(struct super_block *sb, struct inode *dir, int mode, dev_t dev)
+{
+	struct azfs_super *super;
+	struct inode *inode;
+
+	inode = new_inode(sb);
+	if (!inode)
+		return NULL;
+
+	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+
+	inode->i_mode = mode;
+	if (dir) {
+		dir->i_mtime = dir->i_ctime = inode->i_mtime;
+		inode->i_uid = current->fsuid;
+		if (dir->i_mode & S_ISGID) {
+			if (S_ISDIR(mode))
+				inode->i_mode |= S_ISGID;
+			inode->i_gid = dir->i_gid;
+		} else {
+			inode->i_gid = current->fsgid;
+		}
+	} else {
+		super = sb->s_fs_info;
+		inode->i_uid = super->uid;
+		inode->i_gid = super->gid;
+	}
+
+	inode->i_blocks = 0;
+	inode->i_mapping->a_ops = &azfs_aops;
+	inode->i_mapping->backing_dev_info = &azfs_bdi;
+
+	switch (mode & S_IFMT) {
+	case S_IFDIR:
+		inode->i_op = &azfs_dir_iops;
+		inode->i_fop = &simple_dir_operations;
+		inc_nlink(inode);
+		break;
+
+	case S_IFREG:
+		inode->i_op = &azfs_reg_iops;
+		inode->i_fop = &azfs_reg_fops;
+		break;
+
+	case S_IFLNK:
+		inode->i_op = &page_symlink_inode_operations;
+		break;
+
+	default:
+		init_special_inode(inode, mode, dev);
+		break;
+	}
+
+	return inode;
+}
+
+/**
+ * azfs_alloc_inode - alloc_inode() method for super_operations
+ * @sb: see super_operations methods
+ */
+static struct inode*
+azfs_alloc_inode(struct super_block *sb)
+{
+	struct azfs_znode *znode;
+
+	znode = kmem_cache_alloc(azfs_znode_cache, GFP_KERNEL);
+
+	INIT_LIST_HEAD(&znode->block_list);
+	rwlock_init(&znode->lock);
+
+	inode_init_once(&znode->vfs_inode);
+
+	return znode ? &znode->vfs_inode : NULL;
+}
+
+/**
+ * azfs_destroy_inode - destroy_inode() method for super_operations
+ * @inode: see super_operations methods
+ */
+static void
+azfs_destroy_inode(struct inode *inode)
+{
+	kmem_cache_free(azfs_znode_cache, I2Z(inode));
+}
+
+/**
+ * azfs_delete_inode - delete_inode() method for super_operations
+ * @inode: see super_operations methods
+ */
+static void
+azfs_delete_inode(struct inode *inode)
+{
+	if (S_ISREG(inode->i_mode)) {
+		i_size_write(inode, 0);
+		azfs_truncate(inode);
+	}
+	truncate_inode_pages(&inode->i_data, 0);
+	clear_inode(inode);
+}
+
+/**
+ * azfs_statfs - statfs() method for super_operations
+ * @dentry, @stat: see super_operations methods
+ */
+static int
+azfs_statfs(struct dentry *dentry, struct kstatfs *stat)
+{
+	struct super_block *sb;
+	struct azfs_super *super;
+	struct inode *inode;
+	unsigned long inodes, blocks;
+
+	sb = dentry->d_sb;
+	super = sb->s_fs_info;
+
+	inodes = blocks = 0;
+	mutex_lock(&sb->s_lock);
+	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+		inodes++;
+		blocks += inode->i_blocks;
+	}
+	mutex_unlock(&sb->s_lock);
+
+	stat->f_type = AZFS_SUPERBLOCK_MAGIC;
+	stat->f_bsize = super->block_size;
+	stat->f_blocks = super->media_size >> super->block_shift;
+	stat->f_bfree = stat->f_blocks - blocks;
+	stat->f_bavail = stat->f_blocks - blocks;
+	stat->f_files = inodes + blocks;
+	stat->f_ffree = blocks + 1;
+	stat->f_namelen = NAME_MAX;
+
+	return 0;
+}
+
+static struct super_operations azfs_ops = {
+	.alloc_inode	= azfs_alloc_inode,
+	.destroy_inode	= azfs_destroy_inode,
+	.drop_inode	= generic_delete_inode,
+	.delete_inode	= azfs_delete_inode,
+	.statfs		= azfs_statfs
+};
+
+enum {
+	Opt_blocksize_short,
+	Opt_blocksize_long,
+	Opt_uid,
+	Opt_gid,
+	Opt_err
+};
+
+static match_table_t tokens = {
+	{Opt_blocksize_short, "bs=%u"},
+	{Opt_blocksize_long, "blocksize=%u"},
+	{Opt_uid, "uid=%u"},
+	{Opt_gid, "gid=%u"},
+	{Opt_err, NULL}
+};
+
+/**
+ * azfs_parse_mount_parameters - parse options given to mount with -o
+ * @sb: super block
+ * @options: comma separated options
+ */
+static int
+azfs_parse_mount_parameters(struct super_block *sb, char *options)
+{
+	struct azfs_super *super;
+	char *option;
+	int token, value;
+	substring_t args[MAX_OPT_ARGS];
+
+	super = sb->s_fs_info;
+
+	while ((option = strsep(&options, ",")) != NULL) {
+		if (!*option)
+			continue;
+
+		token = match_token(option, tokens, args);
+		switch (token) {
+		case Opt_blocksize_short:
+		case Opt_blocksize_long:
+			if (match_int(&args[0], &value))
+				goto syntax_error;
+			super->block_size = value;
+			break;
+
+		case Opt_uid:
+			if (match_int(&args[0], &value))
+				goto syntax_error;
+			super->uid = value;
+			break;
+
+		case Opt_gid:
+			if (match_int(&args[0], &value))
+				goto syntax_error;
+			super->gid = value;
+			break;
+
+		default:
+			goto syntax_error;
+		}
+	}
+
+	return 1;
+
+syntax_error:
+	printk(KERN_ERR "%s: invalid mount option\n",
+			AZFS_FILESYSTEM_NAME);
+
+	return 0;
+}
+
+/**
+ * azfs_fill_super - fill_super routine for get_sb
+ * @sb, @data, @silent: see file_system_type methods
+ */
+static int
+azfs_fill_super(struct super_block *sb, void *data, int silent)
+{
+	struct gendisk *disk;
+	struct azfs_super *super = NULL, *knoten;
+	struct azfs_block *block = NULL;
+	struct inode *inode = NULL;
+	void *kaddr;
+	unsigned long pfn;
+	int rc;
+
+	BUG_ON(!sb->s_bdev);
+
+	disk = sb->s_bdev->bd_disk;
+
+	if (!disk || !disk->queue) {
+		printk(KERN_ERR "%s needs a block device which has a gendisk "
+				"with a queue\n",
+				AZFS_FILESYSTEM_NAME);
+		return -ENOSYS;
+	}
+
+	if (!disk->fops->direct_access) {
+		printk(KERN_ERR "%s needs a block device with a "
+				"direct_access() method\n",
+				AZFS_FILESYSTEM_NAME);
+		return -ENOSYS;
+	}
+
+	if (!get_device(disk->driverfs_dev)) {
+		printk(KERN_ERR "%s cannot get reference to device driver\n",
+				AZFS_FILESYSTEM_NAME);
+		return -EFAULT;
+	}
+
+	sb->s_magic = AZFS_SUPERBLOCK_MAGIC;
+	sb->s_flags = AZFS_SUPERBLOCK_FLAGS;
+	sb->s_op = &azfs_ops;
+	sb->s_maxbytes = get_capacity(disk) * disk->queue->hardsect_size;
+	sb->s_time_gran = 1;
+
+	spin_lock(&super_list.lock);
+	list_for_each_entry(knoten, &super_list.head, list)
+		if (knoten->blkdev == sb->s_bdev) {
+			super = knoten;
+			break;
+		}
+	spin_unlock(&super_list.lock);
+
+	if (super) {
+		if (strlen((char*) data))
+			printk(KERN_WARNING "/dev/%s was already mounted with "
+					"%s before, it will be mounted with "
+					"mount options used last time, "
+					"options just given would be ignored\n",
+					disk->disk_name, AZFS_FILESYSTEM_NAME);
+		sb->s_fs_info = super;
+	} else {
+		super = kzalloc(sizeof(struct azfs_super), GFP_KERNEL);
+		if (!super) {
+			rc = -ENOMEM;
+			goto failed;
+		}
+		sb->s_fs_info = super;
+
+		if (!azfs_parse_mount_parameters(sb, (char*) data)) {
+			rc = -EINVAL;
+			goto failed;
+		}
+
+		inode = azfs_new_inode(sb, NULL, S_IFDIR | S_IRWXUGO, 0);
+		if (!inode) {
+			rc = -ENOMEM;
+			goto failed;
+		}
+
+		super->root = d_alloc_root(inode);
+		if (!super->root) {
+			rc = -ENOMEM;
+			goto failed;
+		}
+		dget(super->root);
+
+		INIT_LIST_HEAD(&super->list);
+		INIT_LIST_HEAD(&super->block_list);
+		rwlock_init(&super->lock);
+
+		super->media_size = sb->s_maxbytes;
+
+		if (!super->block_size)
+			super->block_size = sb->s_blocksize;
+		super->block_shift = blksize_bits(super->block_size);
+
+		super->sector_size = disk->queue->hardsect_size;
+		super->sector_shift = blksize_bits(super->sector_size);
+
+		super->blkdev = sb->s_bdev;
+
+		block = azfs_block_init(&super->block_list,
+				0, super->media_size >> super->block_shift);
+		if (!block) {
+			rc = -ENOMEM;
+			goto failed;
+		}
+
+		rc = disk->fops->direct_access(super->blkdev, 0, &kaddr, &pfn);
+		if (rc < 0) {
+			rc = -EFAULT;
+			goto failed;
+		}
+		super->ph_addr = (unsigned long) kaddr;
+
+		super->io_addr = (unsigned long) ioremap_flags(
+				super->ph_addr, super->media_size, _PAGE_NO_CACHE);
+		if (!super->io_addr) {
+			rc = -EFAULT;
+			goto failed;
+		}
+
+		spin_lock(&super_list.lock);
+		list_add(&super->list, &super_list.head);
+		spin_unlock(&super_list.lock);
+	}
+
+	sb->s_root = super->root;
+	disk->driverfs_dev->driver_data = super;
+	disk->driverfs_dev->platform_data = sb;
+
+	if (super->block_size < PAGE_SIZE)
+		printk(KERN_INFO "Block size on %s is smaller then system "
+				"page size: mmap() would not be supported\n",
+				disk->disk_name);
+
+	return 0;
+
+failed:
+	if (super) {
+		sb->s_root = NULL;
+		sb->s_fs_info = NULL;
+		if (block)
+			azfs_block_free(block);
+		if (super->root)
+			dput(super->root);
+		if (inode)
+			iput(inode);
+		disk->driverfs_dev->driver_data = NULL;
+		kfree(super);
+		disk->driverfs_dev->platform_data = NULL;
+		put_device(disk->driverfs_dev);
+	}
+
+	return rc;
+}
+
+/**
+ * azfs_get_sb - get_sb() method for file_system_type
+ * @fs_type, @flags, @dev_name, @data, @mount: see file_system_type methods
+ */
+static int
+azfs_get_sb(struct file_system_type *fs_type, int flags,
+	    const char *dev_name, void *data, struct vfsmount *mount)
+{
+	return get_sb_bdev(fs_type, flags,
+			dev_name, data, azfs_fill_super, mount);
+}
+
+/**
+ * azfs_kill_sb - kill_sb() method for file_system_type
+ * @sb: see file_system_type methods
+ */
+static void
+azfs_kill_sb(struct super_block *sb)
+{
+	sb->s_root = NULL;
+	kill_block_super(sb);
+}
+
+static struct file_system_type azfs_fs = {
+	.owner		= THIS_MODULE,
+	.name		= AZFS_FILESYSTEM_NAME,
+	.get_sb		= azfs_get_sb,
+	.kill_sb	= azfs_kill_sb,
+	.fs_flags	= AZFS_FILESYSTEM_FLAGS
+};
+
+/**
+ * azfs_init
+ */
+static int __init
+azfs_init(void)
+{
+	int rc;
+
+	INIT_LIST_HEAD(&super_list.head);
+	spin_lock_init(&super_list.lock);
+
+	azfs_znode_cache = kmem_cache_create("azfs_znode_cache",
+			sizeof(struct azfs_znode), 0, AZFS_CACHE_FLAGS, NULL);
+	if (!azfs_znode_cache) {
+		printk(KERN_ERR "Could not allocate inode cache for %s\n",
+				AZFS_FILESYSTEM_NAME);
+		rc = -ENOMEM;
+		goto failed;
+	}
+
+	azfs_block_cache = kmem_cache_create("azfs_block_cache",
+			sizeof(struct azfs_block), 0, AZFS_CACHE_FLAGS, NULL);
+	if (!azfs_block_cache) {
+		printk(KERN_ERR "Could not allocate block cache for %s\n",
+				AZFS_FILESYSTEM_NAME);
+		rc = -ENOMEM;
+		goto failed;
+	}
+
+	rc = register_filesystem(&azfs_fs);
+	if (rc != 0) {
+		printk(KERN_ERR "Could not register %s\n",
+				AZFS_FILESYSTEM_NAME);
+		goto failed;
+	}
+
+	return 0;
+
+failed:
+	if (azfs_block_cache)
+		kmem_cache_destroy(azfs_block_cache);
+
+	if (azfs_znode_cache)
+		kmem_cache_destroy(azfs_znode_cache);
+
+	return rc;
+}
+
+/**
+ * azfs_exit
+ */
+static void __exit
+azfs_exit(void)
+{
+	struct azfs_super *super, *SUPER;
+	struct azfs_block *block, *knoten;
+	struct gendisk *disk;
+
+	spin_lock(&super_list.lock);
+	list_for_each_entry_safe(super, SUPER, &super_list.head, list) {
+		disk = super->blkdev->bd_disk;
+		list_del(&super->list);
+		iounmap((void*) super->io_addr);
+		write_lock(&super->lock);
+		for_each_block_safe(block, knoten, &super->block_list)
+			azfs_block_free(block);
+		write_unlock(&super->lock);
+		disk->driverfs_dev->driver_data = NULL;
+		disk->driverfs_dev->platform_data = NULL;
+		kfree(super);
+		put_device(disk->driverfs_dev);
+	}
+	spin_unlock(&super_list.lock);
+
+	unregister_filesystem(&azfs_fs);
+
+	kmem_cache_destroy(azfs_block_cache);
+	kmem_cache_destroy(azfs_znode_cache);
+}
+
+module_init(azfs_init);
+module_exit(azfs_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Maxim Shchetynin <maxim@xxxxxxxxxx>");
+MODULE_DESCRIPTION("Non-buffered file system for IO devices");


Mit freundlichen GrÃÃen / met vriendelijke groeten / avec regards

    Maxim V. Shchetynin
    Linux Kernel Entwicklung
    IBM Deutschland Entwicklung GmbH
    Linux fÃr Cell, Abteilung 3250
    SchÃnaicher StraÃe 220
    71032 BÃblingen

Vorsitzender des Aufsichtsrats: Johann Weihen
GeschÃftsfÃhrung: Herbert Kircher
Sitz der Gesellschaft: BÃblingen
Registriergericht: Amtsgericht Stuttgart, HRB 243294

Fahr nur so schnell wie dein Schutzengel fliegen kann!
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