Message-ID: <4CDEA53E.2050602@gmail.com>
Date:	Sat, 13 Nov 2010 15:48:30 +0100
From:	Marco Stornelli <marco.stornelli@...il.com>
To:	Linux Kernel <linux-kernel@...r.kernel.org>
CC:	Linux Embedded <linux-embedded@...r.kernel.org>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	Tim Bird <tim.bird@...sony.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 02/16 v3] pramfs: super operations

From: Marco Stornelli <marco.stornelli@...il.com>

Super block operations.

Signed-off-by: Marco Stornelli <marco.stornelli@...il.com>
---
diff -Nurp linux-2.6.36-orig/fs/pramfs/super.c linux-2.6.36/fs/pramfs/super.c
--- linux-2.6.36-orig/fs/pramfs/super.c	1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.36/fs/pramfs/super.c	2010-09-25 14:09:47.000000000 +0200
@@ -0,0 +1,745 @@
+/*
+ * FILE NAME fs/pramfs/super.c
+ *
+ * BRIEF DESCRIPTION
+ *
+ * Super block operations.
+ *
+ * Copyright 2009-2010 Marco Stornelli <marco.stornelli@...il.com>
+ * Copyright 2003 Sony Corporation
+ * Copyright 2003 Matsushita Electric Industrial Co., Ltd.
+ * 2003-2004 (c) MontaVista Software, Inc. , Steve Longerbeam
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/blkdev.h>
+#include <linux/parser.h>
+#include <linux/vfs.h>
+#include <linux/uaccess.h>
+#include <linux/io.h>
+#include <linux/seq_file.h>
+#include <linux/mount.h>
+#include <linux/mm.h>
+#include <linux/ctype.h>
+#include <linux/bitops.h>
+#include <linux/magic.h>
+#include <linux/exportfs.h>
+#include <linux/random.h>
+#include "xattr.h"
+#include "pram.h"
+
+static struct super_operations pram_sops;
+static const struct export_operations pram_export_ops;
+static struct kmem_cache *pram_inode_cachep;
+
+#ifdef CONFIG_PRAMFS_TEST
+static void *first_pram_super;
+
+struct pram_super_block *get_pram_super(void)
+{
+	return (struct pram_super_block *)first_pram_super;
+}
+EXPORT_SYMBOL(get_pram_super);
+#endif
+
+static void pram_set_blocksize(struct super_block *sb, unsigned long size)
+{
+	int bits;
+
+	/*
+	 * We've already validated the user input and the value here must be
+	 * between PRAM_MAX_BLOCK_SIZE and PRAM_MIN_BLOCK_SIZE
+	 * and it must be a power of 2.
+	 */
+	bits = fls(size) - 1;
+	sb->s_blocksize_bits = bits;
+	sb->s_blocksize = (1<<bits);
+}
+
+static inline void *pram_ioremap(phys_addr_t phys_addr, ssize_t size)
+{
+	void *retval;
+
+	/*
+	 * NOTE: Userland may not map this resource, we will mark the region so
+	 * /dev/mem and the sysfs MMIO access will not be allowed. This
+	 * restriction depends on STRICT_DEVMEM option. If this option is
+	 * disabled or not available we mark the region only as busy.
+	 */
+	retval = request_mem_region_exclusive(phys_addr, size, "pramfs");
+	if (!retval)
+		goto fail;
+
+	retval = ioremap_nocache(phys_addr, size);
+
+	if (retval)
+		wrprotect(retval, size);
+fail:
+	return retval;
+}
+
+static loff_t pram_max_size(int bits)
+{
+	loff_t res;
+	res = (1ULL << (3*bits - 6)) - 1;
+
+	if (res > MAX_LFS_FILESIZE)
+		res = MAX_LFS_FILESIZE;
+
+	pram_info("Max file size %llu bytes", res);
+	return res;
+}
+
+enum {
+	Opt_addr, Opt_bpi, Opt_size,
+	Opt_num_inodes, Opt_mode, Opt_uid,
+	Opt_gid, Opt_blocksize, Opt_err
+};
+
+static const match_table_t tokens = {
+	{Opt_bpi,	"physaddr=%x"},
+	{Opt_bpi,	"bpi=%u"},
+	{Opt_size,	"init=%s"},
+	{Opt_num_inodes, "N=%u"},
+	{Opt_mode,	"mode=%o"},
+	{Opt_uid,	"uid=%u"},
+	{Opt_gid,	"gid=%u"},
+	{Opt_blocksize,	"bs=%s"},
+	{Opt_err,	NULL},
+};
+
+static phys_addr_t get_phys_addr(void **data)
+{
+	phys_addr_t phys_addr;
+	char *options = (char *) *data;
+
+	if (!options || strncmp(options, "physaddr=", 9) != 0)
+		return (phys_addr_t)ULLONG_MAX;
+	options += 9;
+	phys_addr = (phys_addr_t)simple_strtoull(options, &options, 0);
+	if (*options && *options != ',') {
+		pram_err("Invalid phys addr specification: %s\n",
+		       (char *) *data);
+		return (phys_addr_t)ULLONG_MAX;
+	}
+	if (phys_addr & (PAGE_SIZE - 1)) {
+		pram_err("physical address 0x%16llx for pramfs isn't "
+			  "aligned to a page boundary\n",
+			  (u64)phys_addr);
+		return (phys_addr_t)ULLONG_MAX;
+	}
+	if (*options == ',')
+		options++;
+	*data = (void *) options;
+	return phys_addr;
+}
+
+static int pram_parse_options(char *options, struct pram_sb_info *sbi)
+{
+	char *p, *rest;
+	substring_t args[MAX_OPT_ARGS];
+	int option;
+
+	if (!options)
+		return 0;
+
+	while ((p = strsep(&options, ",")) != NULL) {
+		int token;
+		if (!*p)
+			continue;
+
+		token = match_token(p, tokens, args);
+		switch (token) {
+			case Opt_addr: {
+				/* physaddr managed in get_phys_addr() */
+				break;
+			}
+			case Opt_bpi: {
+				if (match_int(&args[0], &option))
+					goto bad_val;
+				sbi->bpi = option;
+				break;
+			}
+			case Opt_uid: {
+				if (match_int(&args[0], &option))
+					goto bad_val;
+				sbi->uid = option;
+				break;
+			}
+			case Opt_gid: {
+				if (match_int(&args[0], &option))
+					goto bad_val;
+				sbi->gid = option;
+				break;
+			}
+			case Opt_mode: {
+				if (match_octal(&args[0], &option))
+					goto bad_val;
+				sbi->mode = option & 01777U;
+				break;
+			}
+			case Opt_size: {
+				/* memparse() will accept a K/M/G without a digit */
+				if (!isdigit(*args[0].from))
+					goto bad_val;
+				sbi->initsize = memparse(args[0].from, &rest);
+				break;
+			}
+			case Opt_num_inodes: {
+				if (match_int(&args[0], &option))
+					goto bad_val;
+				sbi->num_inodes = option;
+				break;
+			}
+			case Opt_blocksize: {
+				/* memparse() will accept a K/M/G without a digit */
+				if (!isdigit(*args[0].from))
+					goto bad_val;
+				sbi->blocksize = memparse(args[0].from, &rest);
+				if (sbi->blocksize < PRAM_MIN_BLOCK_SIZE ||
+					sbi->blocksize > PRAM_MAX_BLOCK_SIZE ||
+					!is_power_of_2(sbi->blocksize))
+					goto bad_val;
+				break;
+			}
+			default: {
+				pram_err("Bad mount option: \"%s\"\n", p);
+				return -EINVAL;
+				break;
+			}
+		}
+	}
+
+	return 0;
+
+bad_val:
+	pram_err("Bad value '%s' for mount option '%s'\n", args[0].from, p);
+	return -EINVAL;
+}
+
+static struct pram_inode *pram_init(struct super_block *sb, unsigned long size)
+{
+	unsigned long bpi, num_inodes, bitmap_size, blocksize, num_blocks;
+	u64 bitmap_start;
+	struct pram_inode *root_i;
+	struct pram_super_block *super;
+	struct pram_sb_info *sbi = (struct pram_sb_info *)sb->s_fs_info;
+
+	pram_info("creating an empty pramfs of size %lu\n", size);
+#ifdef CONFIG_PRAMFS_XIP
+	pram_info("pramfs with xip enabled\n");
+#endif
+	sbi->virt_addr = pram_ioremap(sbi->phys_addr, size);
+	if (!sbi->virt_addr) {
+		pram_err("ioremap of the pramfs image failed\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+#ifdef CONFIG_PRAMFS_TEST
+	if (!first_pram_super)
+		first_pram_super = sbi->virt_addr;
+#endif
+
+	if (!sbi->blocksize)
+		blocksize = PRAM_DEF_BLOCK_SIZE;
+	else
+		blocksize = sbi->blocksize;
+
+	pram_set_blocksize(sb, blocksize);
+	blocksize = sb->s_blocksize;
+
+	if (sbi->blocksize && sbi->blocksize != blocksize)
+		sbi->blocksize = blocksize;
+
+	if (size < blocksize) {
+		pram_err("size smaller then block size\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	if (!sbi->bpi)
+		/*
+		 * default is that 5% of the filesystem is
+		 * devoted to the inode table
+		 */
+		bpi = 20 * PRAM_INODE_SIZE;
+	else
+		bpi = sbi->bpi;
+
+	if (!sbi->num_inodes)
+		num_inodes = size / bpi;
+	else
+		num_inodes = sbi->num_inodes;
+
+	/*
+	 * up num_inodes such that the end of the inode table
+	 * (and start of bitmap) is on a block boundary
+	 */
+	bitmap_start = (PRAM_SB_SIZE*2) + (num_inodes<<PRAM_INODE_BITS);
+	if (bitmap_start & (blocksize - 1))
+		bitmap_start = (bitmap_start + blocksize) &
+			~(blocksize-1);
+	num_inodes = (bitmap_start - (PRAM_SB_SIZE*2)) >> PRAM_INODE_BITS;
+
+	if (sbi->num_inodes && num_inodes != sbi->num_inodes)
+		sbi->num_inodes = num_inodes;
+
+	num_blocks = (size - bitmap_start) >> sb->s_blocksize_bits;
+
+	if (!num_blocks) {
+		pram_err("num blocks equals to zero\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	/* calc the data blocks in-use bitmap size in bytes */
+	if (num_blocks & 7)
+		bitmap_size = ((num_blocks + 8) & ~7) >> 3;
+	else
+		bitmap_size = num_blocks >> 3;
+	/* round it up to the nearest blocksize boundary */
+	if (bitmap_size & (blocksize - 1))
+		bitmap_size = (bitmap_size + blocksize) & ~(blocksize-1);
+
+	pram_info("blocksize %lu, num inodes %lu, num blocks %lu\n",
+		  blocksize, num_inodes, num_blocks);
+	pram_dbg("bitmap start 0x%08x, bitmap size %lu\n",
+		 (unsigned int)bitmap_start, bitmap_size);
+	pram_dbg("max name length %d\n", (unsigned int)PRAM_NAME_LEN);
+
+	super = pram_get_super(sb);
+	pram_memunlock_range(super, bitmap_start + bitmap_size);
+
+	/* clear out super-block and inode table */
+	memset(super, 0, bitmap_start);
+	super->s_size = cpu_to_be64(size);
+	super->s_blocksize = cpu_to_be32(blocksize);
+	super->s_inodes_count = cpu_to_be32(num_inodes);
+	super->s_blocks_count = cpu_to_be32(num_blocks);
+	super->s_free_inodes_count = cpu_to_be32(num_inodes - 1);
+	super->s_bitmap_blocks = cpu_to_be32(bitmap_size >> sb->s_blocksize_bits);
+	super->s_free_blocks_count = cpu_to_be32(num_blocks - be32_to_cpu(super->s_bitmap_blocks));
+	super->s_free_inode_hint = cpu_to_be32(1);
+	super->s_bitmap_start = cpu_to_be64(bitmap_start);
+	super->s_magic = cpu_to_be16(PRAM_SUPER_MAGIC);
+	pram_sync_super(super);
+
+	root_i = pram_get_inode(sb, PRAM_ROOT_INO);
+
+	root_i->i_mode = cpu_to_be32(sbi->mode);
+	root_i->i_mode = cpu_to_be16(root_i->i_mode | S_IFDIR);
+	root_i->i_uid = cpu_to_be32(sbi->uid);
+	root_i->i_gid = cpu_to_be32(sbi->gid);
+	root_i->i_links_count = cpu_to_be16(2);
+	root_i->i_d.d_parent = cpu_to_be64(PRAM_ROOT_INO);
+	pram_sync_inode(root_i);
+
+	pram_init_bitmap(sb);
+
+	pram_memlock_range(super, bitmap_start + bitmap_size);
+
+	return root_i;
+}
+
+static int pram_fill_super(struct super_block *sb, void *data, int silent)
+{
+	struct pram_super_block *super, *super_redund;
+	struct pram_inode *root_i;
+	struct pram_sb_info *sbi = NULL;
+	u64 root_offset;
+	unsigned long blocksize, initsize = 0;
+	u32 random = 0;
+	int retval = -EINVAL;
+
+	sbi = kzalloc(sizeof(struct pram_sb_info), GFP_KERNEL);
+	if (!sbi)
+		return -ENOMEM;
+	sb->s_fs_info = sbi;
+
+#ifdef CONFIG_PRAMFS_XATTR
+	spin_lock_init(&sbi->desc_tree_lock);
+	sbi->desc_tree.rb_node = NULL;
+#endif
+
+	sbi->phys_addr = get_phys_addr(&data);
+	if (sbi->phys_addr == (phys_addr_t)ULLONG_MAX)
+		goto out;
+
+	get_random_bytes(&random, sizeof(u32));
+	atomic_set(&sbi->next_generation, random);
+
+	/* Init with default values */
+	sbi->mode = (S_IRWXUGO | S_ISVTX);
+	sbi->uid = current_fsuid();
+	sbi->gid = current_fsgid();
+
+	if (pram_parse_options(data, sbi))
+		goto out;
+
+	initsize = sbi->initsize;
+
+	/* Init a new pramfs instance */
+	if (initsize) {
+		root_i = pram_init(sb, initsize);
+
+		if (IS_ERR(root_i))
+			goto out;
+
+		super = pram_get_super(sb);
+
+		goto setup_sb;
+	}
+
+	pram_dbg("checking physical address 0x%016llx for pramfs image\n",
+		   (u64)sbi->phys_addr);
+
+	/* Map only one page for now. Will remap it when fs size is known. */
+	initsize = PAGE_SIZE;
+	sbi->virt_addr = pram_ioremap(sbi->phys_addr, initsize);
+	if (!sbi->virt_addr) {
+		pram_err("ioremap of the pramfs image failed\n");
+		goto out;
+	}
+
+	super = pram_get_super(sb);
+	super_redund = pram_get_redund_super(sb);
+
+	/* Do sanity checks on the superblock */
+	if (be16_to_cpu(super->s_magic) != PRAM_SUPER_MAGIC) {
+		if (be16_to_cpu(super_redund->s_magic) != PRAM_SUPER_MAGIC) {
+			if (!silent)
+				pram_err("Can't find a valid pramfs "
+								"partition\n");
+			goto out;
+		} else {
+			pram_warn("Error in super block: try to repair it with "
+							  "the redundant copy");
+			/* Try to auto-recover the super block */
+			memcpy(super, super_redund, PRAM_SB_SIZE);
+		}
+	}
+
+	/* Read the superblock */
+	if (pram_calc_checksum((u8 *)super, PRAM_SB_SIZE)) {
+		if (pram_calc_checksum((u8 *)super_redund, PRAM_SB_SIZE)) {
+			pram_err("checksum error in super block\n");
+			goto out;
+		} else {
+			pram_warn("Error in super block: try to repair it with "
+							  "the redundant copy");
+			/* Try to auto-recover the super block */
+			memcpy(super, super_redund, PRAM_SB_SIZE);
+		}
+	}
+
+	blocksize = be32_to_cpu(super->s_blocksize);
+	pram_set_blocksize(sb, blocksize);
+
+	initsize = be64_to_cpu(super->s_size);
+	pram_info("pramfs image appears to be %lu KB in size\n", initsize>>10);
+	pram_info("blocksize %lu\n", blocksize);
+
+	/* Read the root inode */
+	root_i = pram_get_inode(sb, PRAM_ROOT_INO);
+
+	/* Check that the root inode is in a sane state */
+	if (pram_calc_checksum((u8 *)root_i, PRAM_INODE_SIZE)) {
+		pram_err("checksum error in root inode!\n");
+		goto out;
+	}
+
+	if (be64_to_cpu(root_i->i_d.d_next)) {
+		pram_err("root->next not NULL??!!\n");
+		goto out;
+	}
+
+	if (!S_ISDIR(be16_to_cpu(root_i->i_mode))) {
+		pram_err("root is not a directory!\n");
+		goto out;
+	}
+
+	root_offset = be64_to_cpu(root_i->i_type.dir.head);
+	if (root_offset == 0)
+		pram_dbg("empty filesystem\n");
+
+	/* Remap the whole filesystem now */
+	iounmap(sbi->virt_addr);
+	release_mem_region(sbi->phys_addr, PAGE_SIZE);
+	sbi->virt_addr = pram_ioremap(sbi->phys_addr, initsize);
+	if (!sbi->virt_addr) {
+		pram_err("ioremap of the pramfs image failed\n");
+		goto out;
+	}
+	super = pram_get_super(sb);
+	root_i = pram_get_inode(sb, PRAM_ROOT_INO);
+
+#ifdef CONFIG_PRAMFS_TEST
+	if (!first_pram_super)
+		first_pram_super = sbi->virt_addr;
+#endif
+
+	/* Set it all up.. */
+ setup_sb:
+	sb->s_magic = be16_to_cpu(super->s_magic);
+	sb->s_op = &pram_sops;
+	sb->s_maxbytes = pram_max_size(sb->s_blocksize_bits);
+	sb->s_time_gran = 1;
+	sb->s_export_op = &pram_export_ops;
+	sb->s_xattr = pram_xattr_handlers;
+#ifdef	CONFIG_PRAMFS_POSIX_ACL
+	sb->s_flags |= MS_POSIXACL;
+#endif
+	sb->s_root = d_alloc_root(pram_iget(sb, PRAM_ROOT_INO));
+
+	retval = 0;
+ out:
+	if (retval && sbi->virt_addr) {
+		iounmap(sbi->virt_addr);
+		release_mem_region(sbi->phys_addr, initsize);
+		kfree(sbi);
+	}
+
+	return retval;
+}
+
+int pram_statfs(struct dentry *d, struct kstatfs *buf)
+{
+	struct super_block *sb = d->d_sb;
+	struct pram_super_block *ps = pram_get_super(sb);
+
+	buf->f_type = PRAM_SUPER_MAGIC;
+	buf->f_bsize = sb->s_blocksize;
+	buf->f_blocks = be32_to_cpu(ps->s_blocks_count);
+	buf->f_bfree = buf->f_bavail = pram_count_free_blocks(sb);
+	buf->f_files = be32_to_cpu(ps->s_inodes_count);
+	buf->f_ffree = be32_to_cpu(ps->s_free_inodes_count);
+	buf->f_namelen = PRAM_NAME_LEN;
+	return 0;
+}
+
+static int pram_show_options(struct seq_file *seq, struct vfsmount *vfs)
+{
+	struct pram_sb_info *sbi = (struct pram_sb_info *)vfs->mnt_sb->s_fs_info;
+
+	seq_printf(seq, ",physaddr=0x%016llx", (u64)sbi->phys_addr);
+	if (sbi->initsize)
+		seq_printf(seq, ",init=%luk", sbi->initsize >> 10);
+	if (sbi->blocksize)
+		seq_printf(seq, ",bs=%lu", sbi->blocksize);
+	if (sbi->bpi)
+		seq_printf(seq, ",bpi=%lu", sbi->bpi);
+	if (sbi->num_inodes)
+		seq_printf(seq, ",N=%lu", sbi->num_inodes);
+	if (sbi->mode != (S_IRWXUGO | S_ISVTX))
+		seq_printf(seq, ",mode=%03o", sbi->mode);
+	if (sbi->uid != 0)
+		seq_printf(seq, ",uid=%u", sbi->uid);
+	if (sbi->gid != 0)
+		seq_printf(seq, ",gid=%u", sbi->gid);
+
+	return 0;
+}
+
+int pram_remount(struct super_block *sb, int *mntflags, char *data)
+{
+	struct pram_super_block *ps;
+
+	if ((*mntflags & MS_RDONLY) != (sb->s_flags & MS_RDONLY)) {
+		ps = pram_get_super(sb);
+		pram_memunlock_super(ps);
+		ps->s_mtime = cpu_to_be32(get_seconds()); /* update mount time */
+		pram_memlock_super(ps);
+	}
+
+	return 0;
+}
+
+void pram_put_super(struct super_block *sb)
+{
+	struct pram_sb_info *sbi = (struct pram_sb_info *)sb->s_fs_info;
+	struct pram_super_block *ps = pram_get_super(sb);
+	u64 size = be64_to_cpu(ps->s_size);
+
+#ifdef CONFIG_PRAMFS_TEST
+	if (first_pram_super == sbi->virt_addr)
+		first_pram_super = NULL;
+#endif
+
+	pram_xattr_put_super(sb);
+	/* It's unmount time, so unmap the pramfs memory */
+	if (sbi->virt_addr) {
+		iounmap(sbi->virt_addr);
+		sbi->virt_addr = NULL;
+		release_mem_region(sbi->phys_addr, size);
+	}
+
+	sb->s_fs_info = NULL;
+	kfree(sbi);
+}
+
+static struct inode *pram_alloc_inode(struct super_block *sb)
+{
+	struct pram_inode_vfs *vi = (struct pram_inode_vfs *)
+				kmem_cache_alloc(pram_inode_cachep, GFP_KERNEL);
+	if (!vi)
+		return NULL;
+	vi->vfs_inode.i_version = 1;
+	return &vi->vfs_inode;
+}
+
+static void pram_destroy_inode(struct inode *inode)
+{
+	kmem_cache_free(pram_inode_cachep, PRAM_I(inode));
+}
+
+static void init_once(void *foo)
+{
+	struct pram_inode_vfs *vi = (struct pram_inode_vfs *) foo;
+
+#ifdef CONFIG_PRAMFS_XATTR
+	init_rwsem(&vi->xattr_sem);
+#endif
+	mutex_init(&vi->truncate_mutex);
+	inode_init_once(&vi->vfs_inode);
+}
+
+static int __init init_inodecache(void)
+{
+	pram_inode_cachep = kmem_cache_create("pram_inode_cache",
+					     sizeof(struct pram_inode_vfs),
+					     0, (SLAB_RECLAIM_ACCOUNT|
+						SLAB_MEM_SPREAD),
+					     init_once);
+	if (pram_inode_cachep == NULL)
+		return -ENOMEM;
+	return 0;
+}
+
+static void destroy_inodecache(void)
+{
+	kmem_cache_destroy(pram_inode_cachep);
+}
+
+/*
+ * the super block writes are all done "on the fly", so the
+ * super block is never in a "dirty" state, so there's no need
+ * for write_super.
+ */
+static struct super_operations pram_sops = {
+	.alloc_inode	= pram_alloc_inode,
+	.destroy_inode	= pram_destroy_inode,
+	.write_inode	= pram_write_inode,
+	.dirty_inode	= pram_dirty_inode,
+	.evict_inode	= pram_evict_inode,
+	.put_super	= pram_put_super,
+	.statfs		= pram_statfs,
+	.remount_fs	= pram_remount,
+	.show_options	= pram_show_options,
+};
+
+static int pram_get_sb(struct file_system_type *fs_type,
+	int flags, const char *dev_name, void *data, struct vfsmount *mnt)
+{
+	return get_sb_nodev(fs_type, flags, data, pram_fill_super, mnt);
+}
+
+static struct file_system_type pram_fs_type = {
+	.owner          = THIS_MODULE,
+	.name           = "pramfs",
+	.get_sb         = pram_get_sb,
+	.kill_sb        = kill_anon_super,
+};
+
+static struct inode *pram_nfs_get_inode(struct super_block *sb,
+		u64 ino, u32 generation)
+{
+	struct pram_super_block *ps = pram_get_super(sb);
+	struct inode *inode;
+
+	if (ino < PRAM_ROOT_INO)
+		return ERR_PTR(-ESTALE);
+	if (((ino - PRAM_ROOT_INO) >> PRAM_INODE_BITS) > be32_to_cpu(ps->s_inodes_count))
+		return ERR_PTR(-ESTALE);
+
+	inode = pram_iget(sb, ino);
+	if (!inode)
+		return ERR_PTR(-ESTALE);
+	if (generation && inode->i_generation != generation) {
+		/* we didn't find the right inode.. */
+		iput(inode);
+		return ERR_PTR(-ESTALE);
+	}
+	return inode;
+}
+
+static struct dentry *
+pram_fh_to_dentry(struct super_block *sb, struct fid *fid, int fh_len,
+		   int fh_type)
+{
+	return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
+				    pram_nfs_get_inode);
+}
+
+static struct dentry *
+pram_fh_to_parent(struct super_block *sb, struct fid *fid, int fh_len,
+		   int fh_type)
+{
+	return generic_fh_to_parent(sb, fid, fh_len, fh_type,
+				    pram_nfs_get_inode);
+}
+
+static const struct export_operations pram_export_ops = {
+	.fh_to_dentry = pram_fh_to_dentry,
+	.fh_to_parent = pram_fh_to_parent,
+	.get_parent = pram_get_parent,
+};
+
+static int __init init_pram_fs(void)
+{
+	int rc = 0;
+
+	rc = init_pram_xattr();
+	if (rc)
+		return rc;
+
+	rc = init_inodecache();
+	if (rc)
+		goto out1;
+
+	rc = bdi_init(&pram_backing_dev_info);
+	if (rc)
+		goto out2;
+
+	rc = register_filesystem(&pram_fs_type);
+	if (rc)
+		goto out3;
+
+	return 0;
+
+out3:
+	bdi_destroy(&pram_backing_dev_info);
+out2:
+	destroy_inodecache();
+out1:
+	exit_pram_xattr();
+	return rc;
+}
+
+static void __exit exit_pram_fs(void)
+{
+	unregister_filesystem(&pram_fs_type);
+	bdi_destroy(&pram_backing_dev_info);
+	destroy_inodecache();
+	exit_pram_xattr();
+}
+
+MODULE_AUTHOR("Marco Stornelli <marco.stornelli@...il.com>");
+MODULE_DESCRIPTION("Protected/Persistent RAM Filesystem");
+MODULE_LICENSE("GPL");
+
+module_init(init_pram_fs)
+module_exit(exit_pram_fs)
--
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