linux-kernel - Re: [PATCH] f2fs: fix to tag FIEMAP_EXTENT_DELALLOC in fiemap() for delay allocated extent

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Message-ID: <ZDROBJFxSUdGaqAa@google.com>
Date:   Mon, 10 Apr 2023 10:57:24 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <chao@...nel.org>
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] f2fs: fix to tag FIEMAP_EXTENT_DELALLOC in fiemap() for
 delay allocated extent

On 04/08, Chao Yu wrote:
> On 2023/4/8 4:59, Jaegeuk Kim wrote:
> > This breaks generic/009?
> 
> I guess it is as expected?
> 
> Please check description of fiemap ioctl manual from [1]:
> 
> FIEMAP_EXTENT_UNKNOWN
> The location of this extent is currently unknown. This may
> indicate the data is stored on an inaccessible volume or that
> no storage has been allocated for the file yet.
> 
> FIEMAP_EXTENT_DELALLOC
> This will also set FIEMAP_EXTENT_UNKNOWN.
> 
> Delayed allocation - while there is data for this extent, its
> physical location has not been allocated yet.
> 
> FIEMAP_EXTENT_UNWRITTEN
> Unwritten extent - the extent is allocated but its data has not
> been initialized. This indicates the extent’s data will be all
> zero if read through the filesystem but the contents are undefined
> if read directly from the device.
> 
> [1] https://www.kernel.org/doc/html/latest/filesystems/fiemap.html
> 
> According to its description, f2fs only support
> FIEMAP_EXTENT_{UNKNOWN, DELALLOC}, but not support
> FIEMAP_EXTENT_UNWRITTEN.

No, I don't think so.

> 
> So 009, 092, 094 .. which expects unwritten status from extent will
> fail.
> 
> How about disabling those testcase?
> 
> Thanks,
> 
> > 
> > On 04/05, Chao Yu wrote:
> > > xfstest generic/614 fails to run due below reason:
> > > 
> > > generic/614 1s ... [not run] test requires delayed allocation buffered writes
> > > 
> > > The root cause is f2fs tags wrong fiemap flag for delay allocated
> > > extent.
> > > 
> > > Quoted from fiemap.h:
> > > FIEMAP_EXTENT_UNKNOWN		0x00000002 /* Data location unknown. */
> > > FIEMAP_EXTENT_DELALLOC		0x00000004 /* Location still pending.
> > > 						    * Sets EXTENT_UNKNOWN. */
> > > FIEMAP_EXTENT_UNWRITTEN		0x00000800 /* Space allocated, but
> > > 						    * no data (i.e. zero). */
> > > 
> > > FIEMAP_EXTENT_UNWRITTEN means block address is preallocated, but w/o
> > > been written any data, which status f2fs is not supported now, for all
> > > NEW_ADDR block addresses, it means delay allocated blocks, so let's
> > > tag FIEMAP_EXTENT_DELALLOC instead.
> > > 
> > > Testcase:
> > > xfs_io -f -c 'pwrite 0 64k' /mnt/f2fs/file;
> > > filefrag -v /mnt/f2fs/file
> > > 
> > > Output:
> > > - Before
> > > Filesystem type is: f2f52010
> > > Fize of /mnt/f2fs/file is 65536 (16 blocks of 4096 bytes)
> > >   ext:     logical_offset:        physical_offset: length:   expected: flags:
> > >     0:        0..      15:          0..        15:     16:             last,unwritten,merged,eof
> > > /mnt/f2fs/file: 1 extent found
> > > 
> > > After:
> > > Filesystem type is: f2f52010
> > > File size of /mnt/f2fs/file is 65536 (16 blocks of 4096 bytes)
> > >   ext:     logical_offset:        physical_offset: length:   expected: flags:
> > >     0:        0..      15:          0..         0:      0:             last,unknown_loc,delalloc,eof
> > > /mnt/f2fs/file: 1 extent found
> > > 
> > > Fixes: 7f63eb77af7b ("f2fs: report unwritten area in f2fs_fiemap")
> > > Signed-off-by: Chao Yu <chao@...nel.org>
> > > ---
> > >   fs/f2fs/data.c | 7 +++++--
> > >   1 file changed, 5 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > > index 359de650772e..3afc9764743e 100644
> > > --- a/fs/f2fs/data.c
> > > +++ b/fs/f2fs/data.c
> > > @@ -1995,7 +1995,10 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> > >   	}
> > >   	if (size) {
> > > -		flags |= FIEMAP_EXTENT_MERGED;
> > > +		if (flags & FIEMAP_EXTENT_DELALLOC)
> > > +			phys = 0;
> > > +		else
> > > +			flags |= FIEMAP_EXTENT_MERGED;
> > >   		if (IS_ENCRYPTED(inode))
> > >   			flags |= FIEMAP_EXTENT_DATA_ENCRYPTED;
> > > @@ -2035,7 +2038,7 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> > >   				size += blks_to_bytes(inode, 1);
> > >   			}
> > >   		} else if (map.m_flags & F2FS_MAP_DELALLOC) {
> > > -			flags = FIEMAP_EXTENT_UNWRITTEN;
> > > +			flags = FIEMAP_EXTENT_DELALLOC;
> > >   		}
> > >   		start_blk += bytes_to_blks(inode, size);
> > > -- 
> > > 2.36.1