[f2fs-dev] Reply: [PATCH -next 2/4] f2fs: extent cache: support extent for no-compressed file

[zhangqilong via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>]

> On 2022/9/21 15:57, Zhang Qilong wrote:
> > No-compressed file may suffer read performance issue due to it can't
> > use extent cache or the largest extent in inode can't covered other
> > parts of continuous blocks in readonly format f2fs image.
> >
> > Now it won't build extent cacge tree for no-compressed file in
> > readonly format f2fs image.
> >
> > For readonly format f2fs image, maybe the no-compressed file don't
> > have the largest extent, or it have more than one part which have
> 
> Why it can not have largest extent in f2fs_inode?

The following several situations may occur:
	1) Wrote w/o the extent when the filesystem is read-write fs.

    2) Largest extent have been drop after being re-wrote, or it have been split to smaller parts.

    3) The largest extent only covered one part of continuous blocks, like:
      |------parts 1(continuous blocks)-----|----not continuous---|---------------------parts 2 (continuous blocks)-----------|---------|
      The largest extent is part 2, but other parts (like part1, ) can't be mapped in readonly format f2fs image which should have been mapped.


Thanks,

> 
> Thanks,
> 
> > internally continuous blocks. So we add extent cache tree for the
> > no-compressed file in readonly format f2fs image.
> >
> > The cache policy is almost same with compressed file. The difference
> > is that, the no-compressed file part will set min-number of continuous
> > blocks F2FS_MIN_EXTENT_LEN in order to reduce cache fragmentation.
> >
> > Signed-off-by: Zhang Qilong <zhangqilong3@huawei.com>
> > ---
> >   fs/f2fs/extent_cache.c | 52
> ++++++++++++++++++++++++++++++++++--------
> >   1 file changed, 42 insertions(+), 10 deletions(-)
> >
> > diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c index
> > 387d53a61270..7e39381edca0 100644
> > --- a/fs/f2fs/extent_cache.c
> > +++ b/fs/f2fs/extent_cache.c
> > @@ -695,9 +695,12 @@ static void
> f2fs_update_extent_tree_range_compressed(struct inode *inode,
> >   	set_extent_info(&ei, fofs, blkaddr, llen);
> >   	ei.c_len = c_len;
> >
> > -	if (!__try_merge_extent_node(sbi, et, &ei, prev_en, next_en))
> > +	if (!__try_merge_extent_node(sbi, et, &ei, prev_en, next_en)) {
> > +		if (!c_len && llen < F2FS_MIN_EXTENT_LEN)
> > +			goto unlock_out;
> >   		__insert_extent_tree(sbi, et, &ei,
> >   				insert_p, insert_parent, leftmost);
> > +	}
> >   unlock_out:
> >   	write_unlock(&et->lock);
> >   }
> > @@ -726,24 +729,53 @@ static unsigned int
> f2fs_cluster_blocks_are_contiguous(struct dnode_of_data *dn)
> >   	return compressed ? i - 1 : i;
> >   }
> >
> > +/*
> > + * check whether normal file blocks are contiguous, and add extent
> > +cache
> > + * entry only if remained blocks are logically and physically contiguous.
> > + */
> > +static unsigned int f2fs_normal_blocks_are_contiguous(struct
> > +dnode_of_data *dn) {
> > +	int i = 0;
> > +	struct inode *inode = dn->inode;
> > +	block_t first_blkaddr = data_blkaddr(inode, dn->node_page,
> > +						dn->ofs_in_node);
> > +	unsigned int max_blocks = ADDRS_PER_PAGE(dn->node_page, inode)
> > +					- dn->ofs_in_node;
> > +
> > +	for (i = 1; i < max_blocks; i++) {
> > +		block_t blkaddr = data_blkaddr(inode, dn->node_page,
> > +				dn->ofs_in_node + i);
> > +
> > +		if (!__is_valid_data_blkaddr(blkaddr) ||
> > +				first_blkaddr + i != blkaddr)
> > +			return i;
> > +	}
> > +
> > +	return i;
> > +}
> > +
> >   void f2fs_readonly_update_extent_cache(struct dnode_of_data *dn,
> >   					pgoff_t index)
> >   {
> > -	unsigned int c_len = f2fs_cluster_blocks_are_contiguous(dn);
> > +	unsigned int c_len = 0;
> > +	unsigned int llen = 0;
> >   	block_t blkaddr;
> >
> > -	if (!c_len)
> > -		return;
> > -
> >   	blkaddr = f2fs_data_blkaddr(dn);
> > -	if (blkaddr == COMPRESS_ADDR)
> > -		blkaddr = data_blkaddr(dn->inode, dn->node_page,
> > +	if (f2fs_compressed_file(dn->inode)) {
> > +		c_len = f2fs_cluster_blocks_are_contiguous(dn);
> > +		if (!c_len)
> > +			return;
> > +		llen = F2FS_I(dn->inode)->i_cluster_size;
> > +		if (blkaddr == COMPRESS_ADDR)
> > +			blkaddr = data_blkaddr(dn->inode, dn->node_page,
> >   					dn->ofs_in_node + 1);
> > +	} else {
> > +		llen = f2fs_normal_blocks_are_contiguous(dn);
> > +	}
> >
> >   	f2fs_update_extent_tree_range_compressed(dn->inode,
> > -				index, blkaddr,
> > -				F2FS_I(dn->inode)->i_cluster_size,
> > -				c_len);
> > +				index, blkaddr, llen, c_len);
> >   }
> >   #endif
> >

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