Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6

[deliverable/linux.git] / fs / ext2 / super.c

/*
 *  linux/fs/ext2/super.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card (card@masi.ibp.fr)
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  from
 *
 *  linux/fs/minix/inode.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller (davem@caip.rutgers.edu), 1995
 */

#include <linux/module.h>
#include <linux/string.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/blkdev.h>
#include <linux/parser.h>
#include <linux/random.h>
#include <linux/buffer_head.h>
#include <linux/exportfs.h>
#include <linux/vfs.h>
#include <linux/seq_file.h>
#include <linux/mount.h>
#include <linux/log2.h>
#include <linux/quotaops.h>
#include <asm/uaccess.h>
#include "ext2.h"
#include "xattr.h"
#include "acl.h"
#include "xip.h"

static void ext2_sync_super(struct super_block *sb,
                            struct ext2_super_block *es, int wait);
static int ext2_remount (struct super_block * sb, int * flags, char * data);
static int ext2_statfs (struct dentry * dentry, struct kstatfs * buf);
static int ext2_sync_fs(struct super_block *sb, int wait);

void ext2_error (struct super_block * sb, const char * function,
                 const char * fmt, ...)
{
        va_list args;
        struct ext2_sb_info *sbi = EXT2_SB(sb);
        struct ext2_super_block *es = sbi->s_es;

        if (!(sb->s_flags & MS_RDONLY)) {
                spin_lock(&sbi->s_lock);
                sbi->s_mount_state |= EXT2_ERROR_FS;
                es->s_state |= cpu_to_le16(EXT2_ERROR_FS);
                spin_unlock(&sbi->s_lock);
                ext2_sync_super(sb, es, 1);
        }

        va_start(args, fmt);
        printk(KERN_CRIT "EXT2-fs (%s): error: %s: ", sb->s_id, function);
        vprintk(fmt, args);
        printk("\n");
        va_end(args);

        if (test_opt(sb, ERRORS_PANIC))
                panic("EXT2-fs: panic from previous error\n");
        if (test_opt(sb, ERRORS_RO)) {
                ext2_msg(sb, KERN_CRIT,
                             "error: remounting filesystem read-only");
                sb->s_flags |= MS_RDONLY;
        }
}

void ext2_msg(struct super_block *sb, const char *prefix,
                const char *fmt, ...)
{
        va_list args;

        va_start(args, fmt);
        printk("%sEXT2-fs (%s): ", prefix, sb->s_id);
        vprintk(fmt, args);
        printk("\n");
        va_end(args);
}

/*
 * This must be called with sbi->s_lock held.
 */
void ext2_update_dynamic_rev(struct super_block *sb)
{
        struct ext2_super_block *es = EXT2_SB(sb)->s_es;

        if (le32_to_cpu(es->s_rev_level) > EXT2_GOOD_OLD_REV)
                return;

        ext2_msg(sb, KERN_WARNING,
                     "warning: updating to rev %d because of "
                     "new feature flag, running e2fsck is recommended",
                     EXT2_DYNAMIC_REV);

        es->s_first_ino = cpu_to_le32(EXT2_GOOD_OLD_FIRST_INO);
        es->s_inode_size = cpu_to_le16(EXT2_GOOD_OLD_INODE_SIZE);
        es->s_rev_level = cpu_to_le32(EXT2_DYNAMIC_REV);
        /* leave es->s_feature_*compat flags alone */
        /* es->s_uuid will be set by e2fsck if empty */

        /*
         * The rest of the superblock fields should be zero, and if not it
         * means they are likely already in use, so leave them alone.  We
         * can leave it up to e2fsck to clean up any inconsistencies there.
         */
}

static void ext2_put_super (struct super_block * sb)
{
        int db_count;
        int i;
        struct ext2_sb_info *sbi = EXT2_SB(sb);

        dquot_disable(sb, -1, DQUOT_USAGE_ENABLED | DQUOT_LIMITS_ENABLED);

        if (sb->s_dirt)
                ext2_write_super(sb);

        ext2_xattr_put_super(sb);
        if (!(sb->s_flags & MS_RDONLY)) {
                struct ext2_super_block *es = sbi->s_es;

                spin_lock(&sbi->s_lock);
                es->s_state = cpu_to_le16(sbi->s_mount_state);
                spin_unlock(&sbi->s_lock);
                ext2_sync_super(sb, es, 1);
        }
        db_count = sbi->s_gdb_count;
        for (i = 0; i < db_count; i++)
                if (sbi->s_group_desc[i])
                        brelse (sbi->s_group_desc[i]);
        kfree(sbi->s_group_desc);
        kfree(sbi->s_debts);
        percpu_counter_destroy(&sbi->s_freeblocks_counter);
        percpu_counter_destroy(&sbi->s_freeinodes_counter);
        percpu_counter_destroy(&sbi->s_dirs_counter);
        brelse (sbi->s_sbh);
        sb->s_fs_info = NULL;
        kfree(sbi->s_blockgroup_lock);
        kfree(sbi);
}

static struct kmem_cache * ext2_inode_cachep;

static struct inode *ext2_alloc_inode(struct super_block *sb)
{
        struct ext2_inode_info *ei;
        ei = (struct ext2_inode_info *)kmem_cache_alloc(ext2_inode_cachep, GFP_KERNEL);
        if (!ei)
                return NULL;
        ei->i_block_alloc_info = NULL;
        ei->vfs_inode.i_version = 1;
        return &ei->vfs_inode;
}

static void ext2_destroy_inode(struct inode *inode)
{
        kmem_cache_free(ext2_inode_cachep, EXT2_I(inode));
}

static void init_once(void *foo)
{
        struct ext2_inode_info *ei = (struct ext2_inode_info *) foo;

        rwlock_init(&ei->i_meta_lock);
#ifdef CONFIG_EXT2_FS_XATTR
        init_rwsem(&ei->xattr_sem);
#endif
        mutex_init(&ei->truncate_mutex);
        inode_init_once(&ei->vfs_inode);
}

static int init_inodecache(void)
{
        ext2_inode_cachep = kmem_cache_create("ext2_inode_cache",
                                             sizeof(struct ext2_inode_info),
                                             0, (SLAB_RECLAIM_ACCOUNT|
                                                SLAB_MEM_SPREAD),
                                             init_once);
        if (ext2_inode_cachep == NULL)
                return -ENOMEM;
        return 0;
}

static void destroy_inodecache(void)
{
        kmem_cache_destroy(ext2_inode_cachep);
}

static int ext2_show_options(struct seq_file *seq, struct vfsmount *vfs)
{
        struct super_block *sb = vfs->mnt_sb;
        struct ext2_sb_info *sbi = EXT2_SB(sb);
        struct ext2_super_block *es = sbi->s_es;
        unsigned long def_mount_opts;

        spin_lock(&sbi->s_lock);
        def_mount_opts = le32_to_cpu(es->s_default_mount_opts);

        if (sbi->s_sb_block != 1)
                seq_printf(seq, ",sb=%lu", sbi->s_sb_block);
        if (test_opt(sb, MINIX_DF))
                seq_puts(seq, ",minixdf");
        if (test_opt(sb, GRPID))
                seq_puts(seq, ",grpid");
        if (!test_opt(sb, GRPID) && (def_mount_opts & EXT2_DEFM_BSDGROUPS))
                seq_puts(seq, ",nogrpid");
        if (sbi->s_resuid != EXT2_DEF_RESUID ||
            le16_to_cpu(es->s_def_resuid) != EXT2_DEF_RESUID) {
                seq_printf(seq, ",resuid=%u", sbi->s_resuid);
        }
        if (sbi->s_resgid != EXT2_DEF_RESGID ||
            le16_to_cpu(es->s_def_resgid) != EXT2_DEF_RESGID) {
                seq_printf(seq, ",resgid=%u", sbi->s_resgid);
        }
        if (test_opt(sb, ERRORS_RO)) {
                int def_errors = le16_to_cpu(es->s_errors);

                if (def_errors == EXT2_ERRORS_PANIC ||
                    def_errors == EXT2_ERRORS_CONTINUE) {
                        seq_puts(seq, ",errors=remount-ro");
                }
        }
        if (test_opt(sb, ERRORS_CONT))
                seq_puts(seq, ",errors=continue");
        if (test_opt(sb, ERRORS_PANIC))
                seq_puts(seq, ",errors=panic");
        if (test_opt(sb, NO_UID32))
                seq_puts(seq, ",nouid32");
        if (test_opt(sb, DEBUG))
                seq_puts(seq, ",debug");
        if (test_opt(sb, OLDALLOC))
                seq_puts(seq, ",oldalloc");

#ifdef CONFIG_EXT2_FS_XATTR
        if (test_opt(sb, XATTR_USER))
                seq_puts(seq, ",user_xattr");
        if (!test_opt(sb, XATTR_USER) &&
            (def_mount_opts & EXT2_DEFM_XATTR_USER)) {
                seq_puts(seq, ",nouser_xattr");
        }
#endif

#ifdef CONFIG_EXT2_FS_POSIX_ACL
        if (test_opt(sb, POSIX_ACL))
                seq_puts(seq, ",acl");
        if (!test_opt(sb, POSIX_ACL) && (def_mount_opts & EXT2_DEFM_ACL))
                seq_puts(seq, ",noacl");
#endif

        if (test_opt(sb, NOBH))
                seq_puts(seq, ",nobh");

#if defined(CONFIG_QUOTA)
        if (sbi->s_mount_opt & EXT2_MOUNT_USRQUOTA)
                seq_puts(seq, ",usrquota");

        if (sbi->s_mount_opt & EXT2_MOUNT_GRPQUOTA)
                seq_puts(seq, ",grpquota");
#endif

#if defined(CONFIG_EXT2_FS_XIP)
        if (sbi->s_mount_opt & EXT2_MOUNT_XIP)
                seq_puts(seq, ",xip");
#endif

        if (!test_opt(sb, RESERVATION))
                seq_puts(seq, ",noreservation");

        spin_unlock(&sbi->s_lock);
        return 0;
}

#ifdef CONFIG_QUOTA
static ssize_t ext2_quota_read(struct super_block *sb, int type, char *data, size_t len, loff_t off);
static ssize_t ext2_quota_write(struct super_block *sb, int type, const char *data, size_t len, loff_t off);
#endif

static const struct super_operations ext2_sops = {
        .alloc_inode    = ext2_alloc_inode,
        .destroy_inode  = ext2_destroy_inode,
        .write_inode    = ext2_write_inode,
        .evict_inode    = ext2_evict_inode,
        .put_super      = ext2_put_super,
        .write_super    = ext2_write_super,
        .sync_fs        = ext2_sync_fs,
        .statfs         = ext2_statfs,
        .remount_fs     = ext2_remount,
        .show_options   = ext2_show_options,
#ifdef CONFIG_QUOTA
        .quota_read     = ext2_quota_read,
        .quota_write    = ext2_quota_write,
#endif
};

static struct inode *ext2_nfs_get_inode(struct super_block *sb,
                u64 ino, u32 generation)
{
        struct inode *inode;

        if (ino < EXT2_FIRST_INO(sb) && ino != EXT2_ROOT_INO)
                return ERR_PTR(-ESTALE);
        if (ino > le32_to_cpu(EXT2_SB(sb)->s_es->s_inodes_count))
                return ERR_PTR(-ESTALE);

        /* iget isn't really right if the inode is currently unallocated!!
         * ext2_read_inode currently does appropriate checks, but
         * it might be "neater" to call ext2_get_inode first and check
         * if the inode is valid.....
         */
        inode = ext2_iget(sb, ino);
        if (IS_ERR(inode))
                return ERR_CAST(inode);
        if (generation && inode->i_generation != generation) {
                /* we didn't find the right inode.. */
                iput(inode);
                return ERR_PTR(-ESTALE);
        }
        return inode;
}

static struct dentry *ext2_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,
                                    ext2_nfs_get_inode);
}

static struct dentry *ext2_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,
                                    ext2_nfs_get_inode);
}

/* Yes, most of these are left as NULL!!
 * A NULL value implies the default, which works with ext2-like file
 * systems, but can be improved upon.
 * Currently only get_parent is required.
 */
static const struct export_operations ext2_export_ops = {
        .fh_to_dentry = ext2_fh_to_dentry,
        .fh_to_parent = ext2_fh_to_parent,
        .get_parent = ext2_get_parent,
};

static unsigned long get_sb_block(void **data)
{
        unsigned long   sb_block;
        char            *options = (char *) *data;

        if (!options || strncmp(options, "sb=", 3) != 0)
                return 1;       /* Default location */
        options += 3;
        sb_block = simple_strtoul(options, &options, 0);
        if (*options && *options != ',') {
                printk("EXT2-fs: Invalid sb specification: %s\n",
                       (char *) *data);
                return 1;
        }
        if (*options == ',')
                options++;
        *data = (void *) options;
        return sb_block;
}

enum {
        Opt_bsd_df, Opt_minix_df, Opt_grpid, Opt_nogrpid,
        Opt_resgid, Opt_resuid, Opt_sb, Opt_err_cont, Opt_err_panic,
        Opt_err_ro, Opt_nouid32, Opt_nocheck, Opt_debug,
        Opt_oldalloc, Opt_orlov, Opt_nobh, Opt_user_xattr, Opt_nouser_xattr,
        Opt_acl, Opt_noacl, Opt_xip, Opt_ignore, Opt_err, Opt_quota,
        Opt_usrquota, Opt_grpquota, Opt_reservation, Opt_noreservation
};

static const match_table_t tokens = {
        {Opt_bsd_df, "bsddf"},
        {Opt_minix_df, "minixdf"},
        {Opt_grpid, "grpid"},
        {Opt_grpid, "bsdgroups"},
        {Opt_nogrpid, "nogrpid"},
        {Opt_nogrpid, "sysvgroups"},
        {Opt_resgid, "resgid=%u"},
        {Opt_resuid, "resuid=%u"},
        {Opt_sb, "sb=%u"},
        {Opt_err_cont, "errors=continue"},
        {Opt_err_panic, "errors=panic"},
        {Opt_err_ro, "errors=remount-ro"},
        {Opt_nouid32, "nouid32"},
        {Opt_nocheck, "check=none"},
        {Opt_nocheck, "nocheck"},
        {Opt_debug, "debug"},
        {Opt_oldalloc, "oldalloc"},
        {Opt_orlov, "orlov"},
        {Opt_nobh, "nobh"},
        {Opt_user_xattr, "user_xattr"},
        {Opt_nouser_xattr, "nouser_xattr"},
        {Opt_acl, "acl"},
        {Opt_noacl, "noacl"},
        {Opt_xip, "xip"},
        {Opt_grpquota, "grpquota"},
        {Opt_ignore, "noquota"},
        {Opt_quota, "quota"},
        {Opt_usrquota, "usrquota"},
        {Opt_reservation, "reservation"},
        {Opt_noreservation, "noreservation"},
        {Opt_err, NULL}
};

static int parse_options(char *options, struct super_block *sb)
{
        char *p;
        struct ext2_sb_info *sbi = EXT2_SB(sb);
        substring_t args[MAX_OPT_ARGS];
        int option;

        if (!options)
                return 1;

        while ((p = strsep (&options, ",")) != NULL) {
                int token;
                if (!*p)
                        continue;

                token = match_token(p, tokens, args);
                switch (token) {
                case Opt_bsd_df:
                        clear_opt (sbi->s_mount_opt, MINIX_DF);
                        break;
                case Opt_minix_df:
                        set_opt (sbi->s_mount_opt, MINIX_DF);
                        break;
                case Opt_grpid:
                        set_opt (sbi->s_mount_opt, GRPID);
                        break;
                case Opt_nogrpid:
                        clear_opt (sbi->s_mount_opt, GRPID);
                        break;
                case Opt_resuid:
                        if (match_int(&args[0], &option))
                                return 0;
                        sbi->s_resuid = option;
                        break;
                case Opt_resgid:
                        if (match_int(&args[0], &option))
                                return 0;
                        sbi->s_resgid = option;
                        break;
                case Opt_sb:
                        /* handled by get_sb_block() instead of here */
                        /* *sb_block = match_int(&args[0]); */
                        break;
                case Opt_err_panic:
                        clear_opt (sbi->s_mount_opt, ERRORS_CONT);
                        clear_opt (sbi->s_mount_opt, ERRORS_RO);
                        set_opt (sbi->s_mount_opt, ERRORS_PANIC);
                        break;
                case Opt_err_ro:
                        clear_opt (sbi->s_mount_opt, ERRORS_CONT);
                        clear_opt (sbi->s_mount_opt, ERRORS_PANIC);
                        set_opt (sbi->s_mount_opt, ERRORS_RO);
                        break;
                case Opt_err_cont:
                        clear_opt (sbi->s_mount_opt, ERRORS_RO);
                        clear_opt (sbi->s_mount_opt, ERRORS_PANIC);
                        set_opt (sbi->s_mount_opt, ERRORS_CONT);
                        break;
                case Opt_nouid32:
                        set_opt (sbi->s_mount_opt, NO_UID32);
                        break;
                case Opt_nocheck:
                        clear_opt (sbi->s_mount_opt, CHECK);
                        break;
                case Opt_debug:
                        set_opt (sbi->s_mount_opt, DEBUG);
                        break;
                case Opt_oldalloc:
                        set_opt (sbi->s_mount_opt, OLDALLOC);
                        break;
                case Opt_orlov:
                        clear_opt (sbi->s_mount_opt, OLDALLOC);
                        break;
                case Opt_nobh:
                        set_opt (sbi->s_mount_opt, NOBH);
                        break;
#ifdef CONFIG_EXT2_FS_XATTR
                case Opt_user_xattr:
                        set_opt (sbi->s_mount_opt, XATTR_USER);
                        break;
                case Opt_nouser_xattr:
                        clear_opt (sbi->s_mount_opt, XATTR_USER);
                        break;
#else
                case Opt_user_xattr:
                case Opt_nouser_xattr:
                        ext2_msg(sb, KERN_INFO, "(no)user_xattr options"
                                "not supported");
                        break;
#endif
#ifdef CONFIG_EXT2_FS_POSIX_ACL
                case Opt_acl:
                        set_opt(sbi->s_mount_opt, POSIX_ACL);
                        break;
                case Opt_noacl:
                        clear_opt(sbi->s_mount_opt, POSIX_ACL);
                        break;
#else
                case Opt_acl:
                case Opt_noacl:
                        ext2_msg(sb, KERN_INFO,
                                "(no)acl options not supported");
                        break;
#endif
                case Opt_xip:
#ifdef CONFIG_EXT2_FS_XIP
                        set_opt (sbi->s_mount_opt, XIP);
#else
                        ext2_msg(sb, KERN_INFO, "xip option not supported");
#endif
                        break;

#if defined(CONFIG_QUOTA)
                case Opt_quota:
                case Opt_usrquota:
                        set_opt(sbi->s_mount_opt, USRQUOTA);
                        break;

                case Opt_grpquota:
                        set_opt(sbi->s_mount_opt, GRPQUOTA);
                        break;
#else
                case Opt_quota:
                case Opt_usrquota:
                case Opt_grpquota:
                        ext2_msg(sb, KERN_INFO,
                                "quota operations not supported");
                        break;
#endif

                case Opt_reservation:
                        set_opt(sbi->s_mount_opt, RESERVATION);
                        ext2_msg(sb, KERN_INFO, "reservations ON");
                        break;
                case Opt_noreservation:
                        clear_opt(sbi->s_mount_opt, RESERVATION);
                        ext2_msg(sb, KERN_INFO, "reservations OFF");
                        break;
                case Opt_ignore:
                        break;
                default:
                        return 0;
                }
        }
        return 1;
}

static int ext2_setup_super (struct super_block * sb,
                              struct ext2_super_block * es,
                              int read_only)
{
        int res = 0;
        struct ext2_sb_info *sbi = EXT2_SB(sb);

        if (le32_to_cpu(es->s_rev_level) > EXT2_MAX_SUPP_REV) {
                ext2_msg(sb, KERN_ERR,
                        "error: revision level too high, "
                        "forcing read-only mode");
                res = MS_RDONLY;
        }
        if (read_only)
                return res;
        if (!(sbi->s_mount_state & EXT2_VALID_FS))
                ext2_msg(sb, KERN_WARNING,
                        "warning: mounting unchecked fs, "
                        "running e2fsck is recommended");
        else if ((sbi->s_mount_state & EXT2_ERROR_FS))
                ext2_msg(sb, KERN_WARNING,
                        "warning: mounting fs with errors, "
                        "running e2fsck is recommended");
        else if ((__s16) le16_to_cpu(es->s_max_mnt_count) >= 0 &&
                 le16_to_cpu(es->s_mnt_count) >=
                 (unsigned short) (__s16) le16_to_cpu(es->s_max_mnt_count))
                ext2_msg(sb, KERN_WARNING,
                        "warning: maximal mount count reached, "
                        "running e2fsck is recommended");
        else if (le32_to_cpu(es->s_checkinterval) &&
                (le32_to_cpu(es->s_lastcheck) +
                        le32_to_cpu(es->s_checkinterval) <= get_seconds()))
                ext2_msg(sb, KERN_WARNING,
                        "warning: checktime reached, "
                        "running e2fsck is recommended");
        if (!le16_to_cpu(es->s_max_mnt_count))
                es->s_max_mnt_count = cpu_to_le16(EXT2_DFL_MAX_MNT_COUNT);
        le16_add_cpu(&es->s_mnt_count, 1);
        if (test_opt (sb, DEBUG))
                ext2_msg(sb, KERN_INFO, "%s, %s, bs=%lu, fs=%lu, gc=%lu, "
                        "bpg=%lu, ipg=%lu, mo=%04lx]",
                        EXT2FS_VERSION, EXT2FS_DATE, sb->s_blocksize,
                        sbi->s_frag_size,
                        sbi->s_groups_count,
                        EXT2_BLOCKS_PER_GROUP(sb),
                        EXT2_INODES_PER_GROUP(sb),
                        sbi->s_mount_opt);
        return res;
}

static int ext2_check_descriptors(struct super_block *sb)
{
        int i;
        struct ext2_sb_info *sbi = EXT2_SB(sb);

        ext2_debug ("Checking group descriptors");

        for (i = 0; i < sbi->s_groups_count; i++) {
                struct ext2_group_desc *gdp = ext2_get_group_desc(sb, i, NULL);
                ext2_fsblk_t first_block = ext2_group_first_block_no(sb, i);
                ext2_fsblk_t last_block;

                if (i == sbi->s_groups_count - 1)
                        last_block = le32_to_cpu(sbi->s_es->s_blocks_count) - 1;
                else
                        last_block = first_block +
                                (EXT2_BLOCKS_PER_GROUP(sb) - 1);

                if (le32_to_cpu(gdp->bg_block_bitmap) < first_block ||
                    le32_to_cpu(gdp->bg_block_bitmap) > last_block)
                {
                        ext2_error (sb, "ext2_check_descriptors",
                                    "Block bitmap for group %d"
                                    " not in group (block %lu)!",
                                    i, (unsigned long) le32_to_cpu(gdp->bg_block_bitmap));
                        return 0;
                }
                if (le32_to_cpu(gdp->bg_inode_bitmap) < first_block ||
                    le32_to_cpu(gdp->bg_inode_bitmap) > last_block)
                {
                        ext2_error (sb, "ext2_check_descriptors",
                                    "Inode bitmap for group %d"
                                    " not in group (block %lu)!",
                                    i, (unsigned long) le32_to_cpu(gdp->bg_inode_bitmap));
                        return 0;
                }
                if (le32_to_cpu(gdp->bg_inode_table) < first_block ||
                    le32_to_cpu(gdp->bg_inode_table) + sbi->s_itb_per_group - 1 >
                    last_block)
                {
                        ext2_error (sb, "ext2_check_descriptors",
                                    "Inode table for group %d"
                                    " not in group (block %lu)!",
                                    i, (unsigned long) le32_to_cpu(gdp->bg_inode_table));
                        return 0;
                }
        }
        return 1;
}

/*
 * Maximal file size.  There is a direct, and {,double-,triple-}indirect
 * block limit, and also a limit of (2^32 - 1) 512-byte sectors in i_blocks.
 * We need to be 1 filesystem block less than the 2^32 sector limit.
 */
static loff_t ext2_max_size(int bits)
{
        loff_t res = EXT2_NDIR_BLOCKS;
        int meta_blocks;
        loff_t upper_limit;

        /* This is calculated to be the largest file size for a
         * dense, file such that the total number of
         * sectors in the file, including data and all indirect blocks,
         * does not exceed 2^32 -1
         * __u32 i_blocks representing the total number of
         * 512 bytes blocks of the file
         */
        upper_limit = (1LL << 32) - 1;

        /* total blocks in file system block size */
        upper_limit >>= (bits - 9);


        /* indirect blocks */
        meta_blocks = 1;
        /* double indirect blocks */
        meta_blocks += 1 + (1LL << (bits-2));
        /* tripple indirect blocks */
        meta_blocks += 1 + (1LL << (bits-2)) + (1LL << (2*(bits-2)));

        upper_limit -= meta_blocks;
        upper_limit <<= bits;

        res += 1LL << (bits-2);
        res += 1LL << (2*(bits-2));
        res += 1LL << (3*(bits-2));
        res <<= bits;
        if (res > upper_limit)
                res = upper_limit;

        if (res > MAX_LFS_FILESIZE)
                res = MAX_LFS_FILESIZE;

        return res;
}

static unsigned long descriptor_loc(struct super_block *sb,
                                    unsigned long logic_sb_block,
                                    int nr)
{
        struct ext2_sb_info *sbi = EXT2_SB(sb);
        unsigned long bg, first_meta_bg;
        int has_super = 0;
        
        first_meta_bg = le32_to_cpu(sbi->s_es->s_first_meta_bg);

        if (!EXT2_HAS_INCOMPAT_FEATURE(sb, EXT2_FEATURE_INCOMPAT_META_BG) ||
            nr < first_meta_bg)
                return (logic_sb_block + nr + 1);
        bg = sbi->s_desc_per_block * nr;
        if (ext2_bg_has_super(sb, bg))
                has_super = 1;

        return ext2_group_first_block_no(sb, bg) + has_super;
}

static int ext2_fill_super(struct super_block *sb, void *data, int silent)
{
        struct buffer_head * bh;
        struct ext2_sb_info * sbi;
        struct ext2_super_block * es;
        struct inode *root;
        unsigned long block;
        unsigned long sb_block = get_sb_block(&data);
        unsigned long logic_sb_block;
        unsigned long offset = 0;
        unsigned long def_mount_opts;
        long ret = -EINVAL;
        int blocksize = BLOCK_SIZE;
        int db_count;
        int i, j;
        __le32 features;
        int err;

        err = -ENOMEM;
        sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
        if (!sbi)
                goto failed_unlock;

        sbi->s_blockgroup_lock =
                kzalloc(sizeof(struct blockgroup_lock), GFP_KERNEL);
        if (!sbi->s_blockgroup_lock) {
                kfree(sbi);
                goto failed_unlock;
        }
        sb->s_fs_info = sbi;
        sbi->s_sb_block = sb_block;

        spin_lock_init(&sbi->s_lock);

        /*
         * See what the current blocksize for the device is, and
         * use that as the blocksize.  Otherwise (or if the blocksize
         * is smaller than the default) use the default.
         * This is important for devices that have a hardware
         * sectorsize that is larger than the default.
         */
        blocksize = sb_min_blocksize(sb, BLOCK_SIZE);
        if (!blocksize) {
                ext2_msg(sb, KERN_ERR, "error: unable to set blocksize");
                goto failed_sbi;
        }

        /*
         * If the superblock doesn't start on a hardware sector boundary,
         * calculate the offset.  
         */
        if (blocksize != BLOCK_SIZE) {
                logic_sb_block = (sb_block*BLOCK_SIZE) / blocksize;
                offset = (sb_block*BLOCK_SIZE) % blocksize;
        } else {
                logic_sb_block = sb_block;
        }

        if (!(bh = sb_bread(sb, logic_sb_block))) {
                ext2_msg(sb, KERN_ERR, "error: unable to read superblock");
                goto failed_sbi;
        }
        /*
         * Note: s_es must be initialized as soon as possible because
         *       some ext2 macro-instructions depend on its value
         */
        es = (struct ext2_super_block *) (((char *)bh->b_data) + offset);
        sbi->s_es = es;
        sb->s_magic = le16_to_cpu(es->s_magic);

        if (sb->s_magic != EXT2_SUPER_MAGIC)
                goto cantfind_ext2;

        /* Set defaults before we parse the mount options */
        def_mount_opts = le32_to_cpu(es->s_default_mount_opts);
        if (def_mount_opts & EXT2_DEFM_DEBUG)
                set_opt(sbi->s_mount_opt, DEBUG);
        if (def_mount_opts & EXT2_DEFM_BSDGROUPS)
                set_opt(sbi->s_mount_opt, GRPID);
        if (def_mount_opts & EXT2_DEFM_UID16)
                set_opt(sbi->s_mount_opt, NO_UID32);
#ifdef CONFIG_EXT2_FS_XATTR
        if (def_mount_opts & EXT2_DEFM_XATTR_USER)
                set_opt(sbi->s_mount_opt, XATTR_USER);
#endif
#ifdef CONFIG_EXT2_FS_POSIX_ACL
        if (def_mount_opts & EXT2_DEFM_ACL)
                set_opt(sbi->s_mount_opt, POSIX_ACL);
#endif
        
        if (le16_to_cpu(sbi->s_es->s_errors) == EXT2_ERRORS_PANIC)
                set_opt(sbi->s_mount_opt, ERRORS_PANIC);
        else if (le16_to_cpu(sbi->s_es->s_errors) == EXT2_ERRORS_CONTINUE)
                set_opt(sbi->s_mount_opt, ERRORS_CONT);
        else
                set_opt(sbi->s_mount_opt, ERRORS_RO);

        sbi->s_resuid = le16_to_cpu(es->s_def_resuid);
        sbi->s_resgid = le16_to_cpu(es->s_def_resgid);
        
        set_opt(sbi->s_mount_opt, RESERVATION);

        if (!parse_options((char *) data, sb))
                goto failed_mount;

        sb->s_flags = (sb->s_flags & ~MS_POSIXACL) |
                ((EXT2_SB(sb)->s_mount_opt & EXT2_MOUNT_POSIX_ACL) ?
                 MS_POSIXACL : 0);

        ext2_xip_verify_sb(sb); /* see if bdev supports xip, unset
                                    EXT2_MOUNT_XIP if not */

        if (le32_to_cpu(es->s_rev_level) == EXT2_GOOD_OLD_REV &&
            (EXT2_HAS_COMPAT_FEATURE(sb, ~0U) ||
             EXT2_HAS_RO_COMPAT_FEATURE(sb, ~0U) ||
             EXT2_HAS_INCOMPAT_FEATURE(sb, ~0U)))
                ext2_msg(sb, KERN_WARNING,
                        "warning: feature flags set on rev 0 fs, "
                        "running e2fsck is recommended");
        /*
         * Check feature flags regardless of the revision level, since we
         * previously didn't change the revision level when setting the flags,
         * so there is a chance incompat flags are set on a rev 0 filesystem.
         */
        features = EXT2_HAS_INCOMPAT_FEATURE(sb, ~EXT2_FEATURE_INCOMPAT_SUPP);
        if (features) {
                ext2_msg(sb, KERN_ERR,  "error: couldn't mount because of "
                       "unsupported optional features (%x)",
                        le32_to_cpu(features));
                goto failed_mount;
        }
        if (!(sb->s_flags & MS_RDONLY) &&
            (features = EXT2_HAS_RO_COMPAT_FEATURE(sb, ~EXT2_FEATURE_RO_COMPAT_SUPP))){
                ext2_msg(sb, KERN_ERR, "error: couldn't mount RDWR because of "
                       "unsupported optional features (%x)",
                       le32_to_cpu(features));
                goto failed_mount;
        }

        blocksize = BLOCK_SIZE << le32_to_cpu(sbi->s_es->s_log_block_size);

        if (ext2_use_xip(sb) && blocksize != PAGE_SIZE) {
                if (!silent)
                        ext2_msg(sb, KERN_ERR,
                                "error: unsupported blocksize for xip");
                goto failed_mount;
        }

        /* If the blocksize doesn't match, re-read the thing.. */
        if (sb->s_blocksize != blocksize) {
                brelse(bh);

                if (!sb_set_blocksize(sb, blocksize)) {
                        ext2_msg(sb, KERN_ERR, "error: blocksize is too small");
                        goto failed_sbi;
                }

                logic_sb_block = (sb_block*BLOCK_SIZE) / blocksize;
                offset = (sb_block*BLOCK_SIZE) % blocksize;
                bh = sb_bread(sb, logic_sb_block);
                if(!bh) {
                        ext2_msg(sb, KERN_ERR, "error: couldn't read"
                                "superblock on 2nd try");
                        goto failed_sbi;
                }
                es = (struct ext2_super_block *) (((char *)bh->b_data) + offset);
                sbi->s_es = es;
                if (es->s_magic != cpu_to_le16(EXT2_SUPER_MAGIC)) {
                        ext2_msg(sb, KERN_ERR, "error: magic mismatch");
                        goto failed_mount;
                }
        }

        sb->s_maxbytes = ext2_max_size(sb->s_blocksize_bits);

        if (le32_to_cpu(es->s_rev_level) == EXT2_GOOD_OLD_REV) {
                sbi->s_inode_size = EXT2_GOOD_OLD_INODE_SIZE;
                sbi->s_first_ino = EXT2_GOOD_OLD_FIRST_INO;
        } else {
                sbi->s_inode_size = le16_to_cpu(es->s_inode_size);
                sbi->s_first_ino = le32_to_cpu(es->s_first_ino);
                if ((sbi->s_inode_size < EXT2_GOOD_OLD_INODE_SIZE) ||
                    !is_power_of_2(sbi->s_inode_size) ||
                    (sbi->s_inode_size > blocksize)) {
                        ext2_msg(sb, KERN_ERR,
                                "error: unsupported inode size: %d",
                                sbi->s_inode_size);
                        goto failed_mount;
                }
        }

        sbi->s_frag_size = EXT2_MIN_FRAG_SIZE <<
                                   le32_to_cpu(es->s_log_frag_size);
        if (sbi->s_frag_size == 0)
                goto cantfind_ext2;
        sbi->s_frags_per_block = sb->s_blocksize / sbi->s_frag_size;

        sbi->s_blocks_per_group = le32_to_cpu(es->s_blocks_per_group);
        sbi->s_frags_per_group = le32_to_cpu(es->s_frags_per_group);
        sbi->s_inodes_per_group = le32_to_cpu(es->s_inodes_per_group);

        if (EXT2_INODE_SIZE(sb) == 0)
                goto cantfind_ext2;
        sbi->s_inodes_per_block = sb->s_blocksize / EXT2_INODE_SIZE(sb);
        if (sbi->s_inodes_per_block == 0 || sbi->s_inodes_per_group == 0)
                goto cantfind_ext2;
        sbi->s_itb_per_group = sbi->s_inodes_per_group /
                                        sbi->s_inodes_per_block;
        sbi->s_desc_per_block = sb->s_blocksize /
                                        sizeof (struct ext2_group_desc);
        sbi->s_sbh = bh;
        sbi->s_mount_state = le16_to_cpu(es->s_state);
        sbi->s_addr_per_block_bits =
                ilog2 (EXT2_ADDR_PER_BLOCK(sb));
        sbi->s_desc_per_block_bits =
                ilog2 (EXT2_DESC_PER_BLOCK(sb));

        if (sb->s_magic != EXT2_SUPER_MAGIC)
                goto cantfind_ext2;

        if (sb->s_blocksize != bh->b_size) {
                if (!silent)
                        ext2_msg(sb, KERN_ERR, "error: unsupported blocksize");
                goto failed_mount;
        }

        if (sb->s_blocksize != sbi->s_frag_size) {
                ext2_msg(sb, KERN_ERR,
                        "error: fragsize %lu != blocksize %lu"
                        "(not supported yet)",
                        sbi->s_frag_size, sb->s_blocksize);
                goto failed_mount;
        }

        if (sbi->s_blocks_per_group > sb->s_blocksize * 8) {
                ext2_msg(sb, KERN_ERR,
                        "error: #blocks per group too big: %lu",
                        sbi->s_blocks_per_group);
                goto failed_mount;
        }
        if (sbi->s_frags_per_group > sb->s_blocksize * 8) {
                ext2_msg(sb, KERN_ERR,
                        "error: #fragments per group too big: %lu",
                        sbi->s_frags_per_group);
                goto failed_mount;
        }
        if (sbi->s_inodes_per_group > sb->s_blocksize * 8) {
                ext2_msg(sb, KERN_ERR,
                        "error: #inodes per group too big: %lu",
                        sbi->s_inodes_per_group);
                goto failed_mount;
        }

        if (EXT2_BLOCKS_PER_GROUP(sb) == 0)
                goto cantfind_ext2;
        sbi->s_groups_count = ((le32_to_cpu(es->s_blocks_count) -
                                le32_to_cpu(es->s_first_data_block) - 1)
                                        / EXT2_BLOCKS_PER_GROUP(sb)) + 1;
        db_count = (sbi->s_groups_count + EXT2_DESC_PER_BLOCK(sb) - 1) /
                   EXT2_DESC_PER_BLOCK(sb);
        sbi->s_group_desc = kmalloc (db_count * sizeof (struct buffer_head *), GFP_KERNEL);
        if (sbi->s_group_desc == NULL) {
                ext2_msg(sb, KERN_ERR, "error: not enough memory");
                goto failed_mount;
        }
        bgl_lock_init(sbi->s_blockgroup_lock);
        sbi->s_debts = kcalloc(sbi->s_groups_count, sizeof(*sbi->s_debts), GFP_KERNEL);
        if (!sbi->s_debts) {
                ext2_msg(sb, KERN_ERR, "error: not enough memory");
                goto failed_mount_group_desc;
        }
        for (i = 0; i < db_count; i++) {
                block = descriptor_loc(sb, logic_sb_block, i);
                sbi->s_group_desc[i] = sb_bread(sb, block);
                if (!sbi->s_group_desc[i]) {
                        for (j = 0; j < i; j++)
                                brelse (sbi->s_group_desc[j]);
                        ext2_msg(sb, KERN_ERR,
                                "error: unable to read group descriptors");
                        goto failed_mount_group_desc;
                }
        }
        if (!ext2_check_descriptors (sb)) {
                ext2_msg(sb, KERN_ERR, "group descriptors corrupted");
                goto failed_mount2;
        }
        sbi->s_gdb_count = db_count;
        get_random_bytes(&sbi->s_next_generation, sizeof(u32));
        spin_lock_init(&sbi->s_next_gen_lock);

        /* per fileystem reservation list head & lock */
        spin_lock_init(&sbi->s_rsv_window_lock);
        sbi->s_rsv_window_root = RB_ROOT;
        /*
         * Add a single, static dummy reservation to the start of the
         * reservation window list --- it gives us a placeholder for
         * append-at-start-of-list which makes the allocation logic
         * _much_ simpler.
         */
        sbi->s_rsv_window_head.rsv_start = EXT2_RESERVE_WINDOW_NOT_ALLOCATED;
        sbi->s_rsv_window_head.rsv_end = EXT2_RESERVE_WINDOW_NOT_ALLOCATED;
        sbi->s_rsv_window_head.rsv_alloc_hit = 0;
        sbi->s_rsv_window_head.rsv_goal_size = 0;
        ext2_rsv_window_add(sb, &sbi->s_rsv_window_head);

        err = percpu_counter_init(&sbi->s_freeblocks_counter,
                                ext2_count_free_blocks(sb));
        if (!err) {
                err = percpu_counter_init(&sbi->s_freeinodes_counter,
                                ext2_count_free_inodes(sb));
        }
        if (!err) {
                err = percpu_counter_init(&sbi->s_dirs_counter,
                                ext2_count_dirs(sb));
        }
        if (err) {
                ext2_msg(sb, KERN_ERR, "error: insufficient memory");
                goto failed_mount3;
        }
        /*
         * set up enough so that it can read an inode
         */
        sb->s_op = &ext2_sops;
        sb->s_export_op = &ext2_export_ops;
        sb->s_xattr = ext2_xattr_handlers;

#ifdef CONFIG_QUOTA
        sb->dq_op = &dquot_operations;
        sb->s_qcop = &dquot_quotactl_ops;
#endif

        root = ext2_iget(sb, EXT2_ROOT_INO);
        if (IS_ERR(root)) {
                ret = PTR_ERR(root);
                goto failed_mount3;
        }
        if (!S_ISDIR(root->i_mode) || !root->i_blocks || !root->i_size) {
                iput(root);
                ext2_msg(sb, KERN_ERR, "error: corrupt root inode, run e2fsck");
                goto failed_mount3;
        }

        sb->s_root = d_alloc_root(root);
        if (!sb->s_root) {
                iput(root);
                ext2_msg(sb, KERN_ERR, "error: get root inode failed");
                ret = -ENOMEM;
                goto failed_mount3;
        }
        if (EXT2_HAS_COMPAT_FEATURE(sb, EXT3_FEATURE_COMPAT_HAS_JOURNAL))
                ext2_msg(sb, KERN_WARNING,
                        "warning: mounting ext3 filesystem as ext2");
        if (ext2_setup_super (sb, es, sb->s_flags & MS_RDONLY))
                sb->s_flags |= MS_RDONLY;
        ext2_write_super(sb);
        return 0;

cantfind_ext2:
        if (!silent)
                ext2_msg(sb, KERN_ERR,
                        "error: can't find an ext2 filesystem on dev %s.",
                        sb->s_id);
        goto failed_mount;
failed_mount3:
        percpu_counter_destroy(&sbi->s_freeblocks_counter);
        percpu_counter_destroy(&sbi->s_freeinodes_counter);
        percpu_counter_destroy(&sbi->s_dirs_counter);
failed_mount2:
        for (i = 0; i < db_count; i++)
                brelse(sbi->s_group_desc[i]);
failed_mount_group_desc:
        kfree(sbi->s_group_desc);
        kfree(sbi->s_debts);
failed_mount:
        brelse(bh);
failed_sbi:
        sb->s_fs_info = NULL;
        kfree(sbi->s_blockgroup_lock);
        kfree(sbi);
failed_unlock:
        return ret;
}

static void ext2_clear_super_error(struct super_block *sb)
{
        struct buffer_head *sbh = EXT2_SB(sb)->s_sbh;

        if (buffer_write_io_error(sbh)) {
                /*
                 * Oh, dear.  A previous attempt to write the
                 * superblock failed.  This could happen because the
                 * USB device was yanked out.  Or it could happen to
                 * be a transient write error and maybe the block will
                 * be remapped.  Nothing we can do but to retry the
                 * write and hope for the best.
                 */
                ext2_msg(sb, KERN_ERR,
                       "previous I/O error to superblock detected\n");
                clear_buffer_write_io_error(sbh);
                set_buffer_uptodate(sbh);
        }
}

static void ext2_sync_super(struct super_block *sb, struct ext2_super_block *es,
                            int wait)
{
        ext2_clear_super_error(sb);
        spin_lock(&EXT2_SB(sb)->s_lock);
        es->s_free_blocks_count = cpu_to_le32(ext2_count_free_blocks(sb));
        es->s_free_inodes_count = cpu_to_le32(ext2_count_free_inodes(sb));
        es->s_wtime = cpu_to_le32(get_seconds());
        /* unlock before we do IO */
        spin_unlock(&EXT2_SB(sb)->s_lock);
        mark_buffer_dirty(EXT2_SB(sb)->s_sbh);
        if (wait)
                sync_dirty_buffer(EXT2_SB(sb)->s_sbh);
        sb->s_dirt = 0;
}

/*
 * In the second extended file system, it is not necessary to
 * write the super block since we use a mapping of the
 * disk super block in a buffer.
 *
 * However, this function is still used to set the fs valid
 * flags to 0.  We need to set this flag to 0 since the fs
 * may have been checked while mounted and e2fsck may have
 * set s_state to EXT2_VALID_FS after some corrections.
 */
static int ext2_sync_fs(struct super_block *sb, int wait)
{
        struct ext2_sb_info *sbi = EXT2_SB(sb);
        struct ext2_super_block *es = EXT2_SB(sb)->s_es;

        spin_lock(&sbi->s_lock);
        if (es->s_state & cpu_to_le16(EXT2_VALID_FS)) {
                ext2_debug("setting valid to 0\n");
                es->s_state &= cpu_to_le16(~EXT2_VALID_FS);
        }
        spin_unlock(&sbi->s_lock);
        ext2_sync_super(sb, es, wait);
        return 0;
}


void ext2_write_super(struct super_block *sb)
{
        if (!(sb->s_flags & MS_RDONLY))
                ext2_sync_fs(sb, 1);
        else
                sb->s_dirt = 0;
}

static int ext2_remount (struct super_block * sb, int * flags, char * data)
{
        struct ext2_sb_info * sbi = EXT2_SB(sb);
        struct ext2_super_block * es;
        unsigned long old_mount_opt = sbi->s_mount_opt;
        struct ext2_mount_options old_opts;
        unsigned long old_sb_flags;
        int err;

        spin_lock(&sbi->s_lock);

        /* Store the old options */
        old_sb_flags = sb->s_flags;
        old_opts.s_mount_opt = sbi->s_mount_opt;
        old_opts.s_resuid = sbi->s_resuid;
        old_opts.s_resgid = sbi->s_resgid;

        /*
         * Allow the "check" option to be passed as a remount option.
         */
        if (!parse_options(data, sb)) {
                err = -EINVAL;
                goto restore_opts;
        }

        sb->s_flags = (sb->s_flags & ~MS_POSIXACL) |
                ((sbi->s_mount_opt & EXT2_MOUNT_POSIX_ACL) ? MS_POSIXACL : 0);

        ext2_xip_verify_sb(sb); /* see if bdev supports xip, unset
                                    EXT2_MOUNT_XIP if not */

        if ((ext2_use_xip(sb)) && (sb->s_blocksize != PAGE_SIZE)) {
                ext2_msg(sb, KERN_WARNING,
                        "warning: unsupported blocksize for xip");
                err = -EINVAL;
                goto restore_opts;
        }

        es = sbi->s_es;
        if ((sbi->s_mount_opt ^ old_mount_opt) & EXT2_MOUNT_XIP) {
                ext2_msg(sb, KERN_WARNING, "warning: refusing change of "
                         "xip flag with busy inodes while remounting");
                sbi->s_mount_opt &= ~EXT2_MOUNT_XIP;
                sbi->s_mount_opt |= old_mount_opt & EXT2_MOUNT_XIP;
        }
        if ((*flags & MS_RDONLY) == (sb->s_flags & MS_RDONLY)) {
                spin_unlock(&sbi->s_lock);
                return 0;
        }
        if (*flags & MS_RDONLY) {
                if (le16_to_cpu(es->s_state) & EXT2_VALID_FS ||
                    !(sbi->s_mount_state & EXT2_VALID_FS)) {
                        spin_unlock(&sbi->s_lock);
                        return 0;
                }

                /*
                 * OK, we are remounting a valid rw partition rdonly, so set
                 * the rdonly flag and then mark the partition as valid again.
                 */
                es->s_state = cpu_to_le16(sbi->s_mount_state);
                es->s_mtime = cpu_to_le32(get_seconds());
                spin_unlock(&sbi->s_lock);

                err = dquot_suspend(sb, -1);
                if (err < 0) {
                        spin_lock(&sbi->s_lock);
                        goto restore_opts;
                }

                ext2_sync_super(sb, es, 1);
        } else {
                __le32 ret = EXT2_HAS_RO_COMPAT_FEATURE(sb,
                                               ~EXT2_FEATURE_RO_COMPAT_SUPP);
                if (ret) {
                        ext2_msg(sb, KERN_WARNING,
                                "warning: couldn't remount RDWR because of "
                                "unsupported optional features (%x).",
                                le32_to_cpu(ret));
                        err = -EROFS;
                        goto restore_opts;
                }
                /*
                 * Mounting a RDONLY partition read-write, so reread and
                 * store the current valid flag.  (It may have been changed
                 * by e2fsck since we originally mounted the partition.)
                 */
                sbi->s_mount_state = le16_to_cpu(es->s_state);
                if (!ext2_setup_super (sb, es, 0))
                        sb->s_flags &= ~MS_RDONLY;
                spin_unlock(&sbi->s_lock);

                ext2_write_super(sb);

                dquot_resume(sb, -1);
        }

        return 0;
restore_opts:
        sbi->s_mount_opt = old_opts.s_mount_opt;
        sbi->s_resuid = old_opts.s_resuid;
        sbi->s_resgid = old_opts.s_resgid;
        sb->s_flags = old_sb_flags;
        spin_unlock(&sbi->s_lock);
        return err;
}

static int ext2_statfs (struct dentry * dentry, struct kstatfs * buf)
{
        struct super_block *sb = dentry->d_sb;
        struct ext2_sb_info *sbi = EXT2_SB(sb);
        struct ext2_super_block *es = sbi->s_es;
        u64 fsid;

        spin_lock(&sbi->s_lock);

        if (test_opt (sb, MINIX_DF))
                sbi->s_overhead_last = 0;
        else if (sbi->s_blocks_last != le32_to_cpu(es->s_blocks_count)) {
                unsigned long i, overhead = 0;
                smp_rmb();

                /*
                 * Compute the overhead (FS structures). This is constant
                 * for a given filesystem unless the number of block groups
                 * changes so we cache the previous value until it does.
                 */

                /*
                 * All of the blocks before first_data_block are
                 * overhead
                 */
                overhead = le32_to_cpu(es->s_first_data_block);

                /*
                 * Add the overhead attributed to the superblock and
                 * block group descriptors.  If the sparse superblocks
                 * feature is turned on, then not all groups have this.
                 */
                for (i = 0; i < sbi->s_groups_count; i++)
                        overhead += ext2_bg_has_super(sb, i) +
                                ext2_bg_num_gdb(sb, i);

                /*
                 * Every block group has an inode bitmap, a block
                 * bitmap, and an inode table.
                 */
                overhead += (sbi->s_groups_count *
                             (2 + sbi->s_itb_per_group));
                sbi->s_overhead_last = overhead;
                smp_wmb();
                sbi->s_blocks_last = le32_to_cpu(es->s_blocks_count);
        }

        buf->f_type = EXT2_SUPER_MAGIC;
        buf->f_bsize = sb->s_blocksize;
        buf->f_blocks = le32_to_cpu(es->s_blocks_count) - sbi->s_overhead_last;
        buf->f_bfree = ext2_count_free_blocks(sb);
        es->s_free_blocks_count = cpu_to_le32(buf->f_bfree);
        buf->f_bavail = buf->f_bfree - le32_to_cpu(es->s_r_blocks_count);
        if (buf->f_bfree < le32_to_cpu(es->s_r_blocks_count))
                buf->f_bavail = 0;
        buf->f_files = le32_to_cpu(es->s_inodes_count);
        buf->f_ffree = ext2_count_free_inodes(sb);
        es->s_free_inodes_count = cpu_to_le32(buf->f_ffree);
        buf->f_namelen = EXT2_NAME_LEN;
        fsid = le64_to_cpup((void *)es->s_uuid) ^
               le64_to_cpup((void *)es->s_uuid + sizeof(u64));
        buf->f_fsid.val[0] = fsid & 0xFFFFFFFFUL;
        buf->f_fsid.val[1] = (fsid >> 32) & 0xFFFFFFFFUL;
        spin_unlock(&sbi->s_lock);
        return 0;
}

static int ext2_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, ext2_fill_super, mnt);
}

#ifdef CONFIG_QUOTA

/* Read data from quotafile - avoid pagecache and such because we cannot afford
 * acquiring the locks... As quota files are never truncated and quota code
 * itself serializes the operations (and noone else should touch the files)
 * we don't have to be afraid of races */
static ssize_t ext2_quota_read(struct super_block *sb, int type, char *data,
                               size_t len, loff_t off)
{
        struct inode *inode = sb_dqopt(sb)->files[type];
        sector_t blk = off >> EXT2_BLOCK_SIZE_BITS(sb);
        int err = 0;
        int offset = off & (sb->s_blocksize - 1);
        int tocopy;
        size_t toread;
        struct buffer_head tmp_bh;
        struct buffer_head *bh;
        loff_t i_size = i_size_read(inode);

        if (off > i_size)
                return 0;
        if (off+len > i_size)
                len = i_size-off;
        toread = len;
        while (toread > 0) {
                tocopy = sb->s_blocksize - offset < toread ?
                                sb->s_blocksize - offset : toread;

                tmp_bh.b_state = 0;
                tmp_bh.b_size = sb->s_blocksize;
                err = ext2_get_block(inode, blk, &tmp_bh, 0);
                if (err < 0)
                        return err;
                if (!buffer_mapped(&tmp_bh))    /* A hole? */
                        memset(data, 0, tocopy);
                else {
                        bh = sb_bread(sb, tmp_bh.b_blocknr);
                        if (!bh)
                                return -EIO;
                        memcpy(data, bh->b_data+offset, tocopy);
                        brelse(bh);
                }
                offset = 0;
                toread -= tocopy;
                data += tocopy;
                blk++;
        }
        return len;
}

/* Write to quotafile */
static ssize_t ext2_quota_write(struct super_block *sb, int type,
                                const char *data, size_t len, loff_t off)
{
        struct inode *inode = sb_dqopt(sb)->files[type];
        sector_t blk = off >> EXT2_BLOCK_SIZE_BITS(sb);
        int err = 0;
        int offset = off & (sb->s_blocksize - 1);
        int tocopy;
        size_t towrite = len;
        struct buffer_head tmp_bh;
        struct buffer_head *bh;

        mutex_lock_nested(&inode->i_mutex, I_MUTEX_QUOTA);
        while (towrite > 0) {
                tocopy = sb->s_blocksize - offset < towrite ?
                                sb->s_blocksize - offset : towrite;

                tmp_bh.b_state = 0;
                err = ext2_get_block(inode, blk, &tmp_bh, 1);
                if (err < 0)
                        goto out;
                if (offset || tocopy != EXT2_BLOCK_SIZE(sb))
                        bh = sb_bread(sb, tmp_bh.b_blocknr);
                else
                        bh = sb_getblk(sb, tmp_bh.b_blocknr);
                if (!bh) {
                        err = -EIO;
                        goto out;
                }
                lock_buffer(bh);
                memcpy(bh->b_data+offset, data, tocopy);
                flush_dcache_page(bh->b_page);
                set_buffer_uptodate(bh);
                mark_buffer_dirty(bh);
                unlock_buffer(bh);
                brelse(bh);
                offset = 0;
                towrite -= tocopy;
                data += tocopy;
                blk++;
        }
out:
        if (len == towrite) {
                mutex_unlock(&inode->i_mutex);
                return err;
        }
        if (inode->i_size < off+len-towrite)
                i_size_write(inode, off+len-towrite);
        inode->i_version++;
        inode->i_mtime = inode->i_ctime = CURRENT_TIME;
        mark_inode_dirty(inode);
        mutex_unlock(&inode->i_mutex);
        return len - towrite;
}

#endif

static struct file_system_type ext2_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "ext2",
        .get_sb         = ext2_get_sb,
        .kill_sb        = kill_block_super,
        .fs_flags       = FS_REQUIRES_DEV,
};

static int __init init_ext2_fs(void)
{
        int err = init_ext2_xattr();
        if (err)
                return err;
        err = init_inodecache();
        if (err)
                goto out1;
        err = register_filesystem(&ext2_fs_type);
        if (err)
                goto out;
        return 0;
out:
        destroy_inodecache();
out1:
        exit_ext2_xattr();
        return err;
}

static void __exit exit_ext2_fs(void)
{
        unregister_filesystem(&ext2_fs_type);
        destroy_inodecache();
        exit_ext2_xattr();
}

module_init(init_ext2_fs)
module_exit(exit_ext2_fs)