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Date: Tue, 17 Jun 2008 18:02:41 +0300
From: Dmitri Vorobiev <dmitri.vorobiev@...ial.fi>
To: Maxim Shchetynin <maxim@...ux.vnet.ibm.com>
CC: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: AZFS file system proposal
Maxim Shchetynin wrote:
> 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@...ibm.com>
>
> 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@...ibm.com>
>
> 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@...ibm.com>
> + *
> + * 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,
At the risk of being damned by the entire francophone world, I'd still
suggest using an English keyword for the function name here.
> + 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);
Would it not be better to place this function prototype along with the
bunch of macro definitions you have above into a private header?
> +
> +/**
> + * 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)
Maybe "if (!rc)" ?
> + 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;
void *target?
> + 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;
void *source?
> + 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;
The risk of me getting damned increases with that, but maybe it would be
better to use an English keyword for "knoten"?
> + 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;
I think that yelling in deep desperation like that is not quite in
agreement with the kernel coding style.
> + 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@...ibm.com>");
> +MODULE_DESCRIPTION("Non-buffered file system for IO devices");
>
An unprecedented lack of comments in this driver can hardly boost the
reader's attention. Besides, I personally think that a kind of a design
document could be extremely useful - basically, explain the purpose of
the filesystem, the basic idead behind it, etc.
Thanks,
Dmitri
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