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Date:   Wed, 4 Mar 2020 10:26:35 -0800
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <yuchao0@huawei.com>
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org, chao@kernel.org
Subject: Re: [PATCH v2] f2fs: introduce F2FS_IOC_RELEASE_COMPRESS_BLOCKS
Message-ID: <20200304182635.GA87370@google.com>
References: <20200227112621.126505-1-yuchao0@huawei.com>
 <20200227183052.GA55284@google.com>
 <8cb4552e-e6a2-e57b-1baa-40171e53e120@huawei.com>
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On 02/28, Chao Yu wrote:
> 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

I think that'd be doable.

> 
> 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
> > .
> >