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Subject: Re: [PATCH v2] f2fs: introduce F2FS_IOC_RELEASE_COMPRESS_BLOCKS
To:     Jaegeuk Kim <jaegeuk@kernel.org>
CC:     <linux-f2fs-devel@lists.sourceforge.net>,
        <linux-kernel@vger.kernel.org>, <chao@kernel.org>
References: <20200227112621.126505-1-yuchao0@huawei.com>
 <20200227183052.GA55284@google.com>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <8cb4552e-e6a2-e57b-1baa-40171e53e120@huawei.com>
Date:   Fri, 28 Feb 2020 16:20:09 +0800
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On 2020/2/28 2:30, Jaegeuk Kim wrote:
> On 02/27, Chao Yu wrote:
>> There are still reserved blocks on compressed inode, this patch
>> introduce a new ioctl to help release reserved blocks back to
>> filesystem, so that userspace can reuse those freed space.
> 
> Hmm, once we release the blocks, what happens if we remove the immutable
> bit back?

Oh, if we allow to overwrite on compress file, i_blocks and real physical blocks
usage may be inconsistent?

So if we need to support above scenario, should we add another ioctl interface
to rollback all compress inode status:
- add reserved blocks in dnode blocks
- increase i_compr_blocks, i_blocks, total_valid_block_count
- remove immutable

Thanks,

> 
>>
>> Signed-off-by: Chao Yu <yuchao0@huawei.com>
>> ---
>> v2:
>> - set inode as immutable in ioctl.
>>  fs/f2fs/f2fs.h |   6 +++
>>  fs/f2fs/file.c | 136 ++++++++++++++++++++++++++++++++++++++++++++++++-
>>  2 files changed, 141 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>> index 23b93a116c73..4a02edc2454b 100644
>> --- a/fs/f2fs/f2fs.h
>> +++ b/fs/f2fs/f2fs.h
>> @@ -427,6 +427,8 @@ static inline bool __has_cursum_space(struct f2fs_journal *journal,
>>  #define F2FS_IOC_PRECACHE_EXTENTS	_IO(F2FS_IOCTL_MAGIC, 15)
>>  #define F2FS_IOC_RESIZE_FS		_IOW(F2FS_IOCTL_MAGIC, 16, __u64)
>>  #define F2FS_IOC_GET_COMPRESS_BLOCKS	_IOR(F2FS_IOCTL_MAGIC, 17, __u64)
>> +#define F2FS_IOC_RELEASE_COMPRESS_BLOCKS				\
>> +					_IOR(F2FS_IOCTL_MAGIC, 18, __u64)
>>  
>>  #define F2FS_IOC_GET_VOLUME_NAME	FS_IOC_GETFSLABEL
>>  #define F2FS_IOC_SET_VOLUME_NAME	FS_IOC_SETFSLABEL
>> @@ -3956,6 +3958,10 @@ static inline void f2fs_i_compr_blocks_update(struct inode *inode,
>>  {
>>  	int diff = F2FS_I(inode)->i_cluster_size - blocks;
>>  
>> +	/* don't update i_compr_blocks if saved blocks were released */
>> +	if (!add && !F2FS_I(inode)->i_compr_blocks)
>> +		return;
>> +
>>  	if (add) {
>>  		F2FS_I(inode)->i_compr_blocks += diff;
>>  		stat_add_compr_blocks(inode, diff);
>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>> index 37c1147eb244..b8f01ee9d698 100644
>> --- a/fs/f2fs/file.c
>> +++ b/fs/f2fs/file.c
>> @@ -550,6 +550,7 @@ void f2fs_truncate_data_blocks_range(struct dnode_of_data *dn, int count)
>>  	bool compressed_cluster = false;
>>  	int cluster_index = 0, valid_blocks = 0;
>>  	int cluster_size = F2FS_I(dn->inode)->i_cluster_size;
>> +	bool released = !F2FS_I(dn->inode)->i_compr_blocks;
>>  
>>  	if (IS_INODE(dn->node_page) && f2fs_has_extra_attr(dn->inode))
>>  		base = get_extra_isize(dn->inode);
>> @@ -588,7 +589,9 @@ void f2fs_truncate_data_blocks_range(struct dnode_of_data *dn, int count)
>>  			clear_inode_flag(dn->inode, FI_FIRST_BLOCK_WRITTEN);
>>  
>>  		f2fs_invalidate_blocks(sbi, blkaddr);
>> -		nr_free++;
>> +
>> +		if (released && blkaddr != COMPRESS_ADDR)
>> +			nr_free++;
>>  	}
>>  
>>  	if (compressed_cluster)
>> @@ -3403,6 +3406,134 @@ static int f2fs_get_compress_blocks(struct file *filp, unsigned long arg)
>>  	return put_user(blocks, (u64 __user *)arg);
>>  }
>>  
>> +static int release_compress_blocks(struct dnode_of_data *dn, pgoff_t count)
>> +{
>> +	struct f2fs_sb_info *sbi = F2FS_I_SB(dn->inode);
>> +	unsigned int released_blocks = 0;
>> +	int cluster_size = F2FS_I(dn->inode)->i_cluster_size;
>> +
>> +	while (count) {
>> +		int compr_blocks = 0;
>> +		block_t blkaddr = f2fs_data_blkaddr(dn);
>> +		int i;
>> +
>> +		if (blkaddr != COMPRESS_ADDR) {
>> +			dn->ofs_in_node += cluster_size;
>> +			goto next;
>> +		}
>> +
>> +		for (i = 0; i < cluster_size; i++, dn->ofs_in_node++) {
>> +			blkaddr = f2fs_data_blkaddr(dn);
>> +
>> +			if (__is_valid_data_blkaddr(blkaddr)) {
>> +				compr_blocks++;
>> +				if (unlikely(!f2fs_is_valid_blkaddr(sbi, blkaddr,
>> +							DATA_GENERIC_ENHANCE)))
>> +					return -EFSCORRUPTED;
>> +			}
>> +
>> +			if (blkaddr != NEW_ADDR)
>> +				continue;
>> +
>> +			dn->data_blkaddr = NULL_ADDR;
>> +			f2fs_set_data_blkaddr(dn);
>> +		}
>> +
>> +		f2fs_i_compr_blocks_update(dn->inode, compr_blocks, false);
>> +		dec_valid_block_count(sbi, dn->inode,
>> +					cluster_size - compr_blocks);
>> +
>> +		released_blocks += cluster_size - compr_blocks;
>> +next:
>> +		count -= cluster_size;
>> +	}
>> +
>> +	return released_blocks;
>> +}
>> +
>> +static int f2fs_release_compress_blocks(struct file *filp, unsigned long arg)
>> +{
>> +	struct inode *inode = file_inode(filp);
>> +	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>> +	pgoff_t page_idx = 0, last_idx;
>> +	unsigned int released_blocks = 0;
>> +	int ret;
>> +
>> +	if (!f2fs_sb_has_compression(F2FS_I_SB(inode)))
>> +		return -EOPNOTSUPP;
>> +
>> +	if (!f2fs_compressed_file(inode))
>> +		return -EINVAL;
>> +
>> +	if (f2fs_readonly(sbi->sb))
>> +		return -EROFS;
>> +
>> +	ret = mnt_want_write_file(filp);
>> +	if (ret)
>> +		return ret;
>> +
>> +	if (!F2FS_I(inode)->i_compr_blocks)
>> +		goto out;
>> +
>> +	f2fs_balance_fs(F2FS_I_SB(inode), true);
>> +
>> +	inode_lock(inode);
>> +
>> +	if (!IS_IMMUTABLE(inode)) {
>> +		F2FS_I(inode)->i_flags |= F2FS_IMMUTABLE_FL;
>> +		f2fs_set_inode_flags(inode);
>> +		inode->i_ctime = current_time(inode);
>> +		f2fs_mark_inode_dirty_sync(inode, true);
>> +	}
>> +
>> +	down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
>> +	down_write(&F2FS_I(inode)->i_mmap_sem);
>> +
>> +	last_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
>> +
>> +	while (page_idx < last_idx) {
>> +		struct dnode_of_data dn;
>> +		pgoff_t end_offset, count;
>> +
>> +		set_new_dnode(&dn, inode, NULL, NULL, 0);
>> +		ret = f2fs_get_dnode_of_data(&dn, page_idx, LOOKUP_NODE);
>> +		if (ret) {
>> +			if (ret == -ENOENT) {
>> +				page_idx = f2fs_get_next_page_offset(&dn,
>> +								page_idx);
>> +				ret = 0;
>> +				continue;
>> +			}
>> +			break;
>> +		}
>> +
>> +		end_offset = ADDRS_PER_PAGE(dn.node_page, inode);
>> +		count = min(end_offset - dn.ofs_in_node, last_idx - page_idx);
>> +
>> +		ret = release_compress_blocks(&dn, count);
>> +
>> +		f2fs_put_dnode(&dn);
>> +
>> +		if (ret < 0)
>> +			break;
>> +
>> +		page_idx += count;
>> +		released_blocks += ret;
>> +	}
>> +
>> +	up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
>> +	up_write(&F2FS_I(inode)->i_mmap_sem);
>> +
>> +	inode_unlock(inode);
>> +out:
>> +	mnt_drop_write_file(filp);
>> +
>> +	if (!ret)
>> +		ret = put_user(released_blocks, (u64 __user *)arg);
>> +
>> +	return ret;
>> +}
>> +
>>  long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>>  {
>>  	if (unlikely(f2fs_cp_error(F2FS_I_SB(file_inode(filp)))))
>> @@ -3483,6 +3614,8 @@ long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>>  		return f2fs_set_volume_name(filp, arg);
>>  	case F2FS_IOC_GET_COMPRESS_BLOCKS:
>>  		return f2fs_get_compress_blocks(filp, arg);
>> +	case F2FS_IOC_RELEASE_COMPRESS_BLOCKS:
>> +		return f2fs_release_compress_blocks(filp, arg);
>>  	default:
>>  		return -ENOTTY;
>>  	}
>> @@ -3643,6 +3776,7 @@ long f2fs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>>  	case F2FS_IOC_GET_VOLUME_NAME:
>>  	case F2FS_IOC_SET_VOLUME_NAME:
>>  	case F2FS_IOC_GET_COMPRESS_BLOCKS:
>> +	case F2FS_IOC_RELEASE_COMPRESS_BLOCKS:
>>  		break;
>>  	default:
>>  		return -ENOIOCTLCMD;
>> -- 
>> 2.18.0.rc1
> .
>