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Date:   Tue, 27 Jul 2021 10:17:22 -0700
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <chao@kernel.org>
Cc:     Daeho Jeong <daeho43@gmail.com>, linux-kernel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net, kernel-team@android.com,
        Daeho Jeong <daehojeong@google.com>,
        Eric Biggers <ebiggers@google.com>
Subject: Re: [f2fs-dev] [PATCH v4] f2fs: change fiemap way in printing
 compression chunk
Message-ID: <YQA/orZ5wXjwWeyy@google.com>
References: <20210726041819.2059593-1-daeho43@gmail.com>
 <f9555521-8878-2d46-36f1-3032bb8bbc0a@kernel.org>
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In-Reply-To: <f9555521-8878-2d46-36f1-3032bb8bbc0a@kernel.org>
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On 07/27, Chao Yu wrote:
> On 2021/7/26 12:18, Daeho Jeong wrote:
> > From: Daeho Jeong <daehojeong@google.com>
> > 
> > When we print out a discontinuous compression chunk, it shows like a
> > continuous chunk now. To show it more correctly, I've changed the way of
> > printing fiemap info like below. Plus, eliminated NEW_ADDR(-1) in fiemap
> > info, since it is not in fiemap user api manual.
> > 
> > Let's assume 16KB compression cluster.
> > 
> > <before>
> >     Logical          Physical         Length           Flags
> > 0:  0000000000000000 00000002c091f000 0000000000004000 1008
> > 1:  0000000000004000 00000002c0920000 0000000000004000 1008
> >    ...
> > 9:  0000000000034000 0000000f8c623000 0000000000004000 1008
> > 10: 0000000000038000 000000101a6eb000 0000000000004000 1008
> > 
> > <after>
> > 0:  0000000000000000 00000002c091f000 0000000000004000 1008
> > 1:  0000000000004000 00000002c0920000 0000000000004000 1008
> >    ...
> > 9:  0000000000034000 0000000f8c623000 0000000000001000 1008
> > 10: 0000000000035000 000000101a6ea000 0000000000003000 1008
> > 11: 0000000000038000 000000101a6eb000 0000000000002000 1008
> > 12: 000000000003a000 00000002c3544000 0000000000002000 1008
> > 
> > Flags
> > 0x1000 => FIEMAP_EXTENT_MERGED
> > 0x0008 => FIEMAP_EXTENT_ENCODED
> > 
> > Signed-off-by: Daeho Jeong <daehojeong@google.com>
> > Tested-by: Eric Biggers <ebiggers@google.com>
> > 
> > ---
> > v4: initialized count_in_cluster
> > v3: fix the missing last extent flag issue
> > v2: changed the print format
> > ---
> >   fs/f2fs/data.c | 75 ++++++++++++++++++++++++++++----------------------
> >   1 file changed, 42 insertions(+), 33 deletions(-)
> > 
> > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > index 3a01a1b50104..1a716c3b5457 100644
> > --- a/fs/f2fs/data.c
> > +++ b/fs/f2fs/data.c
> > @@ -1843,8 +1843,9 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> >   	u64 logical = 0, phys = 0, size = 0;
> >   	u32 flags = 0;
> >   	int ret = 0;
> > -	bool compr_cluster = false;
> > +	bool compr_cluster = false, compr_appended;
> >   	unsigned int cluster_size = F2FS_I(inode)->i_cluster_size;
> > +	unsigned int count_in_cluster = 0;
> >   	loff_t maxbytes;
> >   	if (fieinfo->fi_flags & FIEMAP_FLAG_CACHE) {
> > @@ -1892,15 +1893,17 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> >   	map.m_next_pgofs = &next_pgofs;
> >   	map.m_seg_type = NO_CHECK_TYPE;
> > -	if (compr_cluster)
> > -		map.m_len = cluster_size - 1;
> > +	if (compr_cluster) {
> > +		map.m_lblk += 1;
> > +		map.m_len = cluster_size - count_in_cluster;
> > +	}
> >   	ret = f2fs_map_blocks(inode, &map, 0, F2FS_GET_BLOCK_FIEMAP);
> >   	if (ret)
> >   		goto out;
> >   	/* HOLE */
> > -	if (!(map.m_flags & F2FS_MAP_FLAGS)) {
> > +	if (!compr_cluster && !(map.m_flags & F2FS_MAP_FLAGS)) {
> >   		start_blk = next_pgofs;
> >   		if (blks_to_bytes(inode, start_blk) < blks_to_bytes(inode,
> > @@ -1910,6 +1913,14 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> >   		flags |= FIEMAP_EXTENT_LAST;
> >   	}
> > +	compr_appended = false;
> > +	/* In a case of compressed cluster, append this to the last extent */
> > +	if (compr_cluster && ((map.m_flags & F2FS_MAP_UNWRITTEN) ||
> > +			!(map.m_flags & F2FS_MAP_FLAGS))) {
> > +		compr_appended = true;
> > +		goto skip_fill;
> > +	}
> > +
> >   	if (size) {
> >   		flags |= FIEMAP_EXTENT_MERGED;
> >   		if (IS_ENCRYPTED(inode))
> > @@ -1926,38 +1937,36 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> >   	if (start_blk > last_blk)
> >   		goto out;
> > -	if (compr_cluster) {
> > -		compr_cluster = false;
> > -
> > -
> > -		logical = blks_to_bytes(inode, start_blk - 1);
> > -		phys = blks_to_bytes(inode, map.m_pblk);
> > -		size = blks_to_bytes(inode, cluster_size);
> > -
> > -		flags |= FIEMAP_EXTENT_ENCODED;
> > -
> > -		start_blk += cluster_size - 1;
> > -
> > -		if (start_blk > last_blk)
> > -			goto out;
> > -
> > -		goto prep_next;
> > -	}
> > -
> > +skip_fill:
> >   	if (map.m_pblk == COMPRESS_ADDR) {
> 
> Looks good, but one more thing I concern is how about detecting and
> returning -EFSCORRUPTED for below corrupted metadata cases:
> - [COMPRESS_ADDR, blkaddr, COMPRESS_ADDR, NEW_ADDR]
> - [blkaddr, COMPRESS_ADDR, NULL_ADDR, NULL_ADDR]

Do we really need to catch this in fiemap? What about giving the current
layout with warning message and setting NEED_FSCK?

> 
> Thanks,
> 
> >   		compr_cluster = true;
> > -		start_blk++;
> > -		goto prep_next;
> > -	}
> > -
> > -	logical = blks_to_bytes(inode, start_blk);
> > -	phys = blks_to_bytes(inode, map.m_pblk);
> > -	size = blks_to_bytes(inode, map.m_len);
> > -	flags = 0;
> > -	if (map.m_flags & F2FS_MAP_UNWRITTEN)
> > -		flags = FIEMAP_EXTENT_UNWRITTEN;
> > +		count_in_cluster = 1;
> > +	} else if (compr_appended) {
> > +		unsigned int appended_blks = cluster_size -
> > +						count_in_cluster + 1;
> > +		size += blks_to_bytes(inode, appended_blks);
> > +		start_blk += appended_blks;
> > +		compr_cluster = false;
> > +	} else {
> > +		logical = blks_to_bytes(inode, start_blk);
> > +		phys = __is_valid_data_blkaddr(map.m_pblk) ?
> > +			blks_to_bytes(inode, map.m_pblk) : 0;
> > +		size = blks_to_bytes(inode, map.m_len);
> > +		flags = 0;
> > +
> > +		if (compr_cluster) {
> > +			flags = FIEMAP_EXTENT_ENCODED;
> > +			count_in_cluster += map.m_len;
> > +			if (count_in_cluster == cluster_size) {
> > +				compr_cluster = false;
> > +				size += blks_to_bytes(inode, 1);
> > +			}
> > +		} else if (map.m_flags & F2FS_MAP_UNWRITTEN) {
> > +			flags = FIEMAP_EXTENT_UNWRITTEN;
> > +		}
> > -	start_blk += bytes_to_blks(inode, size);
> > +		start_blk += bytes_to_blks(inode, size);
> > +	}
> >   prep_next:
> >   	cond_resched();
> >