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Message-ID: <0c9f9da087571c7c4b1e01a6da16822eb115bf9a.camel@dubeyko.com>
Subject: Re: [PATCH v6 02/13] exfat: add super block operations
From:   Vyacheslav Dubeyko <slava@dubeyko.com>
To:     Namjae Jeon <namjae.jeon@samsung.com>,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
Cc:     gregkh@linuxfoundation.org, valdis.kletnieks@vt.edu, hch@lst.de,
        sj1557.seo@samsung.com
Date:   Mon, 09 Dec 2019 12:24:11 +0300
In-Reply-To: <20191209065149.2230-3-namjae.jeon@samsung.com>
References: <20191209065149.2230-1-namjae.jeon@samsung.com>
         <CGME20191209065458epcas1p1104c7fa3f7a34164a0b51d902b78af0e@epcas1p1.samsung.com>
         <20191209065149.2230-3-namjae.jeon@samsung.com>
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On Mon, 2019-12-09 at 01:51 -0500, Namjae Jeon wrote:
> This adds the implementation of superblock operations for exfat.
> 
> Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
> Signed-off-by: Sungjong Seo <sj1557.seo@samsung.com>
> ---
>  fs/exfat/super.c | 738
> +++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 738 insertions(+)
>  create mode 100644 fs/exfat/super.c
> 
> diff --git a/fs/exfat/super.c b/fs/exfat/super.c
> new file mode 100644
> index 000000000000..f5d5144bd72a
> --- /dev/null
> +++ b/fs/exfat/super.c
> @@ -0,0 +1,738 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + *  Copyright (C) 2012-2013 Samsung Electronics Co., Ltd.
> + */
> +
> +#include <linux/fs_context.h>
> +#include <linux/fs_parser.h>
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/time.h>
> +#include <linux/mount.h>
> +#include <linux/cred.h>
> +#include <linux/statfs.h>
> +#include <linux/seq_file.h>
> +#include <linux/blkdev.h>
> +#include <linux/fs_struct.h>
> +#include <linux/iversion.h>
> +#include <linux/nls.h>
> +#include <linux/buffer_head.h>
> +
> +#include "exfat_raw.h"
> +#include "exfat_fs.h"
> +
> +static char exfat_default_iocharset[] =
> CONFIG_EXFAT_FS_DEFAULT_IOCHARSET;
> +static const char exfat_iocharset_with_utf8[] = "iso8859-1";
> +static struct kmem_cache *exfat_inode_cachep;
> +
> +static void exfat_free_iocharset(struct exfat_sb_info *sbi)
> +{
> +	if (sbi->options.iocharset != exfat_default_iocharset)
> +		kfree(sbi->options.iocharset);
> +}
> +
> +static void exfat_put_super(struct super_block *sb)
> +{
> +	struct exfat_sb_info *sbi = EXFAT_SB(sb);
> +
> +	mutex_lock(&sbi->s_lock);
> +	if (test_and_clear_bit(EXFAT_SB_DIRTY, &sbi->s_state))
> +		sync_blockdev(sb->s_bdev);
> +	exfat_set_vol_flags(sb, VOL_CLEAN);
> +	exfat_free_upcase_table(sb);
> +	exfat_free_bitmap(sb);
> +	mutex_unlock(&sbi->s_lock);
> +
> +	if (sbi->nls_io) {
> +		unload_nls(sbi->nls_io);
> +		sbi->nls_io = NULL;
> +	}
> +	exfat_free_iocharset(sbi);
> +	sb->s_fs_info = NULL;
> +	kfree(sbi);
> +}
> +
> +static int exfat_sync_fs(struct super_block *sb, int wait)
> +{
> +	struct exfat_sb_info *sbi = EXFAT_SB(sb);
> +	int err = 0;
> +
> +	/* If there are some dirty buffers in the bdev inode */
> +	mutex_lock(&sbi->s_lock);
> +	if (test_and_clear_bit(EXFAT_SB_DIRTY, &sbi->s_state)) {
> +		sync_blockdev(sb->s_bdev);
> +		if (exfat_set_vol_flags(sb, VOL_CLEAN))
> +			err = -EIO;
> +	}
> +	mutex_unlock(&sbi->s_lock);
> +	return err;
> +}
> +
> +static int exfat_statfs(struct dentry *dentry, struct kstatfs *buf)
> +{
> +	struct super_block *sb = dentry->d_sb;
> +	struct exfat_sb_info *sbi = EXFAT_SB(sb);
> +	unsigned long long id = huge_encode_dev(sb->s_bdev->bd_dev);
> +
> +	if (sbi->used_clusters == ~0u) {
> +		mutex_lock(&sbi->s_lock);
> +		if (exfat_count_used_clusters(sb, &sbi->used_clusters)) 
> {
> +			mutex_unlock(&sbi->s_lock);
> +			return -EIO;
> +		}
> +		mutex_unlock(&sbi->s_lock);
> +	}
> +
> +	buf->f_type = sb->s_magic;
> +	buf->f_bsize = sbi->cluster_size;
> +	buf->f_blocks = sbi->num_clusters - 2; /* clu 0 & 1 */


Why does it need to subtract 2? Maybe, it needs to add some comments
here? I believe it's good to introduce some constant instead of
hardcoded value.


> +	buf->f_bfree = buf->f_blocks - sbi->used_clusters;
> +	buf->f_bavail = buf->f_bfree;
> +	buf->f_fsid.val[0] = (unsigned int)id;
> +	buf->f_fsid.val[1] = (unsigned int)(id >> 32);
> +	buf->f_namelen = 260;


Why it was used 260? Maybe 256? If it needs to use some special
constant then it makes sense to explain why it's so. And it will be
good to introduce the special constant again.

> +	return 0;
> +}
> +
> +static int __exfat_set_vol_flags(struct super_block *sb,
> +		unsigned short new_flag, int always_sync)
> +{
> +	struct exfat_sb_info *sbi = EXFAT_SB(sb);
> +	struct pbr64 *bpb;
> +	int sync = 0;

Why sync is not bool type? I believe that bool type could be better
here.

> +
> +	/* flags are not changed */
> +	if (sbi->vol_flag == new_flag)
> +		return 0;
> +
> +	sbi->vol_flag = new_flag;
> +
> +	/* skip updating volume dirty flag,
> +	 * if this volume has been mounted with read-only
> +	 */
> +	if (sb_rdonly(sb))
> +		return 0;
> +
> +	if (!sbi->pbr_bh) {
> +		sbi->pbr_bh = sb_bread(sb, 0);
> +		if (!sbi->pbr_bh) {
> +			exfat_msg(sb, KERN_ERR, "failed to read boot
> sector");
> +			return -ENOMEM;
> +		}
> +	}
> +
> +	bpb = (struct pbr64 *)sbi->pbr_bh->b_data;
> +	bpb->bsx.vol_flags = cpu_to_le16(new_flag);
> +
> +	if (always_sync)
> +		sync = 1;
> +	else if ((new_flag == VOL_DIRTY) && (!buffer_dirty(sbi-
> >pbr_bh)))
> +		sync = 1;
> +	else
> +		sync = 0;
> +
> +	set_buffer_uptodate(sbi->pbr_bh);
> +	mark_buffer_dirty(sbi->pbr_bh);
> +
> +	if (sync)
> +		sync_dirty_buffer(sbi->pbr_bh);
> +	return 0;
> +}
> +
> +int exfat_set_vol_flags(struct super_block *sb, unsigned short
> new_flag)
> +{
> +	return __exfat_set_vol_flags(sb, new_flag, 0);
> +}
> +
> +static int exfat_show_options(struct seq_file *m, struct dentry
> *root)
> +{
> +	struct super_block *sb = root->d_sb;
> +	struct exfat_sb_info *sbi = EXFAT_SB(sb);
> +	struct exfat_mount_options *opts = &sbi->options;
> +
> +	/* Show partition info */
> +	if (!uid_eq(opts->fs_uid, GLOBAL_ROOT_UID))
> +		seq_printf(m, ",uid=%u",
> +				from_kuid_munged(&init_user_ns, opts-
> >fs_uid));
> +	if (!gid_eq(opts->fs_gid, GLOBAL_ROOT_GID))
> +		seq_printf(m, ",gid=%u",
> +				from_kgid_munged(&init_user_ns, opts-
> >fs_gid));
> +	seq_printf(m, ",fmask=%04o,dmask=%04o", opts->fs_fmask, opts-
> >fs_dmask);
> +	if (opts->allow_utime)
> +		seq_printf(m, ",allow_utime=%04o", opts->allow_utime);
> +	if (sbi->nls_io)
> +		seq_printf(m, ",iocharset=%s", sbi->nls_io->charset);
> +	if (opts->utf8)
> +		seq_puts(m, ",utf8");
> +	seq_printf(m, ",case_sensitive=%u", opts->case_sensitive);
> +	if (opts->tz_utc)
> +		seq_puts(m, ",tz=UTC");
> +	seq_printf(m, ",bps=%ld", sb->s_blocksize);
> +	if (opts->errors == EXFAT_ERRORS_CONT)
> +		seq_puts(m, ",errors=continue");
> +	else if (opts->errors == EXFAT_ERRORS_PANIC)
> +		seq_puts(m, ",errors=panic");
> +	else
> +		seq_puts(m, ",errors=remount-ro");
> +	if (opts->discard)
> +		seq_puts(m, ",discard");
> +	return 0;
> +}
> +
> +static struct inode *exfat_alloc_inode(struct super_block *sb)
> +{
> +	struct exfat_inode_info *ei;
> +
> +	ei = kmem_cache_alloc(exfat_inode_cachep, GFP_NOFS);
> +	if (!ei)
> +		return NULL;
> +
> +	init_rwsem(&ei->truncate_lock);
> +	return &ei->vfs_inode;
> +}
> +
> +static void exfat_destroy_inode(struct inode *inode)
> +{
> +	kmem_cache_free(exfat_inode_cachep, EXFAT_I(inode));
> +}
> +
> +static const struct super_operations exfat_sops = {
> +	.alloc_inode   = exfat_alloc_inode,
> +	.destroy_inode = exfat_destroy_inode,
> +	.write_inode   = exfat_write_inode,
> +	.evict_inode  = exfat_evict_inode,
> +	.put_super     = exfat_put_super,
> +	.sync_fs       = exfat_sync_fs,
> +	.statfs        = exfat_statfs,
> +	.show_options  = exfat_show_options,
> +};
> +
> +enum {
> +	Opt_uid,
> +	Opt_gid,
> +	Opt_umask,
> +	Opt_dmask,
> +	Opt_fmask,
> +	Opt_allow_utime,
> +	Opt_charset,
> +	Opt_utf8,
> +	Opt_case_sensitive,
> +	Opt_tz,
> +	Opt_errors,
> +	Opt_discard,
> +};
> +
> +static const struct fs_parameter_spec exfat_param_specs[] = {
> +	fsparam_u32("uid",			Opt_uid),
> +	fsparam_u32("gid",			Opt_gid),
> +	fsparam_u32oct("umask",			Opt_umask),
> +	fsparam_u32oct("dmask",			Opt_dmask),
> +	fsparam_u32oct("fmask",			Opt_fmask),
> +	fsparam_u32oct("allow_utime",		Opt_allow_utime),
> +	fsparam_string("iocharset",		Opt_charset),
> +	fsparam_flag("utf8",			Opt_utf8),
> +	fsparam_flag("case_sensitive",		Opt_case_sensitive),
> +	fsparam_string("tz",			Opt_tz),
> +	fsparam_enum("errors",			Opt_errors),
> +	fsparam_flag("discard",			Opt_discard),
> +	{}
> +};
> +
> +static const struct fs_parameter_enum exfat_param_enums[] = {
> +	{ Opt_errors,	"continue",		EXFAT_ERRORS_CONT },
> +	{ Opt_errors,	"panic",		EXFAT_ERRORS_PANIC },
> +	{ Opt_errors,	"remount-ro",		EXFAT_ERRORS_RO },
> +	{}
> +};
> +
> +static const struct fs_parameter_description exfat_parameters = {
> +	.name		= "exfat",
> +	.specs		= exfat_param_specs,
> +	.enums		= exfat_param_enums,
> +};
> +
> +static int exfat_parse_param(struct fs_context *fc, struct
> fs_parameter *param)
> +{
> +	struct exfat_sb_info *sbi = fc->s_fs_info;
> +	struct exfat_mount_options *opts = &sbi->options;
> +	struct fs_parse_result result;
> +	int opt;
> +
> +	opt = fs_parse(fc, &exfat_parameters, param, &result);
> +	if (opt < 0)
> +		return opt;
> +
> +	switch (opt) {
> +	case Opt_uid:
> +		opts->fs_uid = make_kuid(current_user_ns(),
> result.uint_32);
> +		break;
> +	case Opt_gid:
> +		opts->fs_gid = make_kgid(current_user_ns(),
> result.uint_32);
> +		break;
> +	case Opt_umask:
> +		opts->fs_fmask = result.uint_32;
> +		opts->fs_dmask = result.uint_32;
> +		break;
> +	case Opt_dmask:
> +		opts->fs_dmask = result.uint_32;
> +		break;
> +	case Opt_fmask:
> +		opts->fs_fmask = result.uint_32;
> +		break;
> +	case Opt_allow_utime:
> +		opts->allow_utime = result.uint_32 & 0022;


Maybe it makes sense not to use the hardcoded value here?


> +		break;
> +	case Opt_charset:
> +		exfat_free_iocharset(sbi);
> +		opts->iocharset = kstrdup(param->string, GFP_KERNEL);
> +		if (!opts->iocharset)
> +			return -ENOMEM;
> +		break;
> +	case Opt_case_sensitive:
> +		opts->case_sensitive = 1;
> +		break;
> +	case Opt_utf8:
> +		opts->utf8 = 1;
> +		break;
> +	case Opt_tz:
> +		if (!strcmp(param->string, "UTC"))
> +			opts->tz_utc = 1;
> +		break;
> +	case Opt_errors:
> +		opts->errors = result.uint_32;
> +		break;
> +	case Opt_discard:
> +		opts->discard = 1;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
> +static void exfat_hash_init(struct super_block *sb)
> +{
> +	struct exfat_sb_info *sbi = EXFAT_SB(sb);
> +	int i;
> +
> +	spin_lock_init(&sbi->inode_hash_lock);
> +	for (i = 0; i < EXFAT_HASH_SIZE; i++)
> +		INIT_HLIST_HEAD(&sbi->inode_hashtable[i]);
> +}
> +
> +static int exfat_read_root(struct inode *inode)
> +{
> +	struct super_block *sb = inode->i_sb;
> +	struct exfat_sb_info *sbi = EXFAT_SB(sb);
> +	struct exfat_inode_info *ei = EXFAT_I(inode);
> +	struct exfat_chain cdir;
> +	int num_subdirs, num_clu = 0;
> +
> +	exfat_chain_set(&ei->dir, sbi->root_dir, 0, ALLOC_FAT_CHAIN);
> +	ei->entry = -1;
> +	ei->start_clu = sbi->root_dir;
> +	ei->flags = ALLOC_FAT_CHAIN;
> +	ei->type = TYPE_DIR;
> +	ei->version = 0;
> +	ei->rwoffset = 0;
> +	ei->hint_bmap.off = EOF_CLUSTER;
> +	ei->hint_stat.eidx = 0;
> +	ei->hint_stat.clu = sbi->root_dir;
> +	ei->hint_femp.eidx = EXFAT_HINT_NONE;
> +
> +	exfat_chain_set(&cdir, sbi->root_dir, 0, ALLOC_FAT_CHAIN);
> +	if (exfat_count_num_clusters(sb, &cdir, &num_clu))
> +		return -EIO;
> +	i_size_write(inode, num_clu << sbi->cluster_size_bits);
> +
> +	num_subdirs = exfat_count_dir_entries(sb, &cdir);
> +	if (num_subdirs < 0)
> +		return -EIO;
> +	set_nlink(inode, num_subdirs + EXFAT_MIN_SUBDIR);
> +
> +	inode->i_uid = sbi->options.fs_uid;
> +	inode->i_gid = sbi->options.fs_gid;
> +	inode_inc_iversion(inode);
> +	inode->i_generation = 0;
> +	inode->i_mode = exfat_make_mode(sbi, ATTR_SUBDIR, 0777);


Ditto. Maybe it makes sense to use the constants here instead of
hardcoded value?


> +	inode->i_op = &exfat_dir_inode_operations;
> +	inode->i_fop = &exfat_dir_operations;
> +
> +	inode->i_blocks = ((i_size_read(inode) + (sbi->cluster_size -
> 1))
> +			& ~(sbi->cluster_size - 1)) >> inode-
> >i_blkbits;
> +	EXFAT_I(inode)->i_pos = ((loff_t)sbi->root_dir << 32) |
> 0xffffffff;
> +	EXFAT_I(inode)->i_size_aligned = i_size_read(inode);
> +	EXFAT_I(inode)->i_size_ondisk = i_size_read(inode);
> +
> +	exfat_save_attr(inode, ATTR_SUBDIR);
> +	inode->i_mtime = inode->i_atime = inode->i_ctime =
> current_time(inode);
> +	exfat_cache_init_inode(inode);
> +	return 0;
> +}
> +
> +static bool is_exfat(struct pbr *pbr)
> +{
> +	int i = 53;


Why 53? Maybe constant?

> +
> +	do {
> +		if (pbr->bpb.f64.res_zero[i - 1])
> +			break;
> +	} while (--i);
> +	return i ? false : true;
> +}
> +
> +static struct pbr *exfat_read_pbr_with_logical_sector(struct
> super_block *sb,
> +		struct buffer_head **prev_bh)
> +{
> +	struct pbr *p_pbr = (struct pbr *) (*prev_bh)->b_data;
> +	unsigned short logical_sect = 0;
> +
> +	logical_sect = 1 << p_pbr->bsx.f64.sect_size_bits;
> +
> +	if (!is_power_of_2(logical_sect) ||
> +	    logical_sect < 512 || logical_sect > 4096) {


What about constants here instead of hardcoded values?


> +		exfat_msg(sb, KERN_ERR, "bogus logical sector size %u",
> +				logical_sect);
> +		return NULL;
> +	}
> +
> +	if (logical_sect < sb->s_blocksize) {
> +		exfat_msg(sb, KERN_ERR,
> +			"logical sector size too small for device
> (logical sector size = %u)",
> +			logical_sect);
> +		return NULL;
> +	}
> +
> +	if (logical_sect > sb->s_blocksize) {
> +		struct buffer_head *bh = NULL;
> +
> +		__brelse(*prev_bh);
> +		*prev_bh = NULL;
> +
> +		if (!sb_set_blocksize(sb, logical_sect)) {
> +			exfat_msg(sb, KERN_ERR,
> +				"unable to set blocksize %u",
> logical_sect);
> +			return NULL;
> +		}
> +		bh = sb_bread(sb, 0);
> +		if (!bh) {
> +			exfat_msg(sb, KERN_ERR,
> +				"unable to read boot sector (logical
> sector size = %lu)",
> +				sb->s_blocksize);
> +			return NULL;
> +		}
> +
> +		*prev_bh = bh;
> +		p_pbr = (struct pbr *) bh->b_data;
> +	}
> +	return p_pbr;
> +}
> +
> +/* mount the file system volume */
> +static int __exfat_fill_super(struct super_block *sb)
> +{
> +	int ret;
> +	struct pbr *p_pbr;
> +	struct pbr64 *p_bpb;
> +	struct buffer_head *bh;
> +	struct exfat_sb_info *sbi = EXFAT_SB(sb);
> +
> +	/* set block size to read super block */
> +	sb_min_blocksize(sb, 512);

Ditto. What's about constant here?

> +
> +	/* read boot sector */
> +	bh = sb_bread(sb, 0);
> +	if (!bh) {
> +		exfat_msg(sb, KERN_ERR, "unable to read boot sector");
> +		return -EIO;
> +	}
> +
> +	/* PRB is read */
> +	p_pbr = (struct pbr *)bh->b_data;
> +
> +	/* check the validity of PBR */
> +	if (le16_to_cpu((p_pbr->signature)) != PBR_SIGNATURE) {
> +		exfat_msg(sb, KERN_ERR, "invalid boot record
> signature");
> +		ret = -EINVAL;
> +		goto free_bh;
> +	}
> +
> +
> +	/* check logical sector size */
> +	p_pbr = exfat_read_pbr_with_logical_sector(sb, &bh);
> +	if (!p_pbr) {
> +		ret = -EIO;
> +		goto free_bh;
> +	}
> +
> +	if (!is_exfat(p_pbr)) {
> +		ret = -EINVAL;
> +		goto free_bh;
> +	}
> +
> +	/* set maximum file size for exFAT */
> +	sb->s_maxbytes = 0x7fffffffffffffffLL;
> +
> +	p_bpb = (struct pbr64 *)p_pbr;
> +	if (!p_bpb->bsx.num_fats) {
> +		exfat_msg(sb, KERN_ERR, "bogus number of FAT
> structure");
> +		ret = -EINVAL;
> +		goto free_bh;
> +	}
> +
> +	sbi->sect_per_clus = 1 << p_bpb->bsx.sect_per_clus_bits;
> +	sbi->sect_per_clus_bits = p_bpb->bsx.sect_per_clus_bits;
> +	sbi->cluster_size_bits = sbi->sect_per_clus_bits + sb-
> >s_blocksize_bits;
> +	sbi->cluster_size = 1 << sbi->cluster_size_bits;
> +	sbi->num_FAT_sectors = le32_to_cpu(p_bpb->bsx.fat_length);
> +	sbi->FAT1_start_sector = le32_to_cpu(p_bpb->bsx.fat_offset);
> +	sbi->FAT2_start_sector = p_bpb->bsx.num_fats == 1 ?
> +		sbi->FAT1_start_sector :
> +			sbi->FAT1_start_sector + sbi->num_FAT_sectors;
> +	sbi->root_start_sector = le32_to_cpu(p_bpb->bsx.clu_offset);
> +	sbi->data_start_sector = sbi->root_start_sector;
> +	sbi->num_sectors = le64_to_cpu(p_bpb->bsx.vol_length);
> +	/* because the cluster index starts with 2 */
> +	sbi->num_clusters = le32_to_cpu(p_bpb->bsx.clu_count) + 2;
> +
> +	sbi->vol_id = le32_to_cpu(p_bpb->bsx.vol_serial);
> +	sbi->root_dir = le32_to_cpu(p_bpb->bsx.root_cluster);
> +	sbi->dentries_in_root = 0;
> +	sbi->dentries_per_clu = 1 <<
> +		(sbi->cluster_size_bits - DENTRY_SIZE_BITS);
> +
> +	sbi->vol_flag = le16_to_cpu(p_bpb->bsx.vol_flags);
> +	sbi->clu_srch_ptr = BASE_CLUSTER;
> +	sbi->used_clusters = ~0u;
> +
> +	if (le16_to_cpu(p_bpb->bsx.vol_flags) & VOL_DIRTY) {
> +		sbi->vol_flag |= VOL_DIRTY;
> +		exfat_msg(sb, KERN_WARNING,
> +			"Volume was not properly unmounted. Some data
> may be corrupt. Please run fsck.");
> +	}
> +
> +	ret = exfat_create_upcase_table(sb);
> +	if (ret) {
> +		exfat_msg(sb, KERN_ERR, "failed to load upcase table");
> +		goto free_bh;
> +	}
> +
> +	/* allocate-bitmap is only for exFAT */
> +	ret = exfat_load_bitmap(sb);
> +	if (ret) {
> +		exfat_msg(sb, KERN_ERR, "failed to load alloc-bitmap");
> +		goto free_upcase_table;
> +	}
> +
> +	ret = exfat_count_used_clusters(sb, &sbi->used_clusters);
> +	if (ret) {
> +		exfat_msg(sb, KERN_ERR, "failed to scan clusters");
> +		goto free_alloc_bitmap;
> +	}
> +
> +	return 0;
> +
> +free_alloc_bitmap:
> +	exfat_free_bitmap(sb);
> +free_upcase_table:
> +	exfat_free_upcase_table(sb);
> +free_bh:
> +	brelse(bh);
> +	return ret;
> +}
> +
> +static int exfat_fill_super(struct super_block *sb, struct
> fs_context *fc)
> +{
> +	struct exfat_sb_info *sbi = sb->s_fs_info;
> +	struct exfat_mount_options *opts = &sbi->options;
> +	struct inode *root_inode;
> +	int err;
> +
> +	if (opts->allow_utime == (unsigned short)-1)
> +		opts->allow_utime = ~opts->fs_dmask & 0022;
> +
> +	if (opts->utf8 && strcmp(opts->iocharset,
> exfat_iocharset_with_utf8)) {
> +		exfat_msg(sb, KERN_WARNING,
> +			"utf8 enabled, \"iocharset=%s\" is
> recommended",
> +			exfat_iocharset_with_utf8);
> +	}
> +
> +	if (opts->discard) {
> +		struct request_queue *q = bdev_get_queue(sb->s_bdev);
> +
> +		if (!blk_queue_discard(q))
> +			exfat_msg(sb, KERN_WARNING,
> +				"mounting with \"discard\" option, but
> the device does not support discard");
> +		opts->discard = 0;
> +	}
> +
> +	sb->s_flags |= SB_NODIRATIME;
> +	sb->s_magic = EXFAT_SUPER_MAGIC;
> +	sb->s_op = &exfat_sops;
> +
> +	sb->s_d_op = EXFAT_SB(sb)->options.case_sensitive ?
> +			&exfat_dentry_ops : &exfat_ci_dentry_ops;
> +
> +	err = __exfat_fill_super(sb);
> +	if (err) {
> +		exfat_msg(sb, KERN_ERR, "failed to recognize exfat
> type");
> +		goto check_nls_io;
> +	}
> +
> +	/* set up enough so that it can read an inode */
> +	exfat_hash_init(sb);
> +
> +	sbi->nls_io = load_nls(sbi->options.iocharset);
> +	if (!sbi->nls_io) {
> +		exfat_msg(sb, KERN_ERR, "IO charset %s not found",
> +				sbi->options.iocharset);
> +		err = -EINVAL;
> +		goto free_table;
> +	}
> +
> +	root_inode = new_inode(sb);
> +	if (!root_inode) {
> +		exfat_msg(sb, KERN_ERR, "failed to allocate root
> inode.");
> +		err = -ENOMEM;
> +		goto free_table;
> +	}
> +
> +	root_inode->i_ino = EXFAT_ROOT_INO;
> +	inode_set_iversion(root_inode, 1);
> +	err = exfat_read_root(root_inode);
> +	if (err) {
> +		exfat_msg(sb, KERN_ERR, "failed to initialize root
> inode.");
> +		goto put_inode;
> +	}
> +
> +	exfat_hash_inode(root_inode, EXFAT_I(root_inode)->i_pos);
> +	insert_inode_hash(root_inode);
> +
> +	sb->s_root = d_make_root(root_inode);
> +	if (!sb->s_root) {
> +		exfat_msg(sb, KERN_ERR, "failed to get the root
> dentry");
> +		err = -ENOMEM;
> +		goto put_inode;
> +	}
> +
> +	return 0;
> +
> +put_inode:
> +	iput(root_inode);
> +	sb->s_root = NULL;
> +
> +free_table:
> +	exfat_free_upcase_table(sb);
> +	exfat_free_bitmap(sb);
> +
> +check_nls_io:
> +	if (sbi->nls_io)
> +		unload_nls(sbi->nls_io);
> +	exfat_free_iocharset(sbi);
> +	sb->s_fs_info = NULL;
> +	kfree(sbi);
> +	return err;
> +}
> +
> +static int exfat_get_tree(struct fs_context *fc)
> +{
> +	return get_tree_bdev(fc, exfat_fill_super);
> +}
> +
> +static void exfat_free(struct fs_context *fc)
> +{
> +	kfree(fc->s_fs_info);
> +}
> +
> +static const struct fs_context_operations exfat_context_ops = {
> +	.parse_param	= exfat_parse_param,
> +	.get_tree	= exfat_get_tree,
> +	.free		= exfat_free,
> +};
> +
> +static int exfat_init_fs_context(struct fs_context *fc)
> +{
> +	struct exfat_sb_info *sbi;
> +
> +	sbi = kzalloc(sizeof(struct exfat_sb_info), GFP_KERNEL);
> +	if (!sbi)
> +		return -ENOMEM;
> +
> +	mutex_init(&sbi->s_lock);
> +	ratelimit_state_init(&sbi->ratelimit,
> DEFAULT_RATELIMIT_INTERVAL,
> +			DEFAULT_RATELIMIT_BURST);
> +
> +	sbi->options.fs_uid = current_uid();
> +	sbi->options.fs_gid = current_gid();
> +	sbi->options.fs_fmask = current->fs->umask;
> +	sbi->options.fs_dmask = current->fs->umask;
> +	sbi->options.allow_utime = -1;

Why -1? Any special purpose?

Thanks,
Viacheslav Dubeyko.