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Date: Mon, 21 Jun 2010 20:56:55 -0400 From: Chris Mason <chris.mason@...cle.com> To: Tao Ma <tao.ma@...cle.com> Cc: linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH RESEND] btrfs: Don't return extent in fiemap if we meet with a hole. On Mon, Jun 21, 2010 at 02:37:02PM +0800, Tao Ma wrote: > Hi Chris, > could you please consider merging this patch? It should be > trivial enough. It helps Jeff adding fiemap support to cp. Yes, I'll add this in, thanks! -chris > > Regards, > Tao > > From 909effe7240be30dbc9403dd8cbb326587c3cc02 Mon Sep 17 00:00:00 2001 > From: Tao Ma <tao.ma@...cle.com> > Date: Thu, 22 Apr 2010 12:38:57 +0800 > Subject: [PATCH RESEND] btrfs: Don't return extent in fiemap if we meet with a hole. > > Recently, my colleague Jeff tried to add fiemap support to cp(1). > http://www.mail-archive.com/bug-coreutils@gnu.org/msg19987.html > > He just meet with a strange issue with following command: > dd if=/dev/null of=/btrfs/sparse bs=1 seek=4096 > When we use fiemap to the file, btrfs returns an extent with len '4096' > and flag 'unwritten' while actually there is no data allocated. > > I just dived into this and to my surprise, it is done by btrfs > intentionally. I checked other file systems which support fiemap. > Actually with the file created by the script, ocfs2, ext3/4 and > xfs all return zero extent. And according to the documentation file > Documentation/filesystems/fiemap.txt, FIEMAP_EXTENT_UNWRITTEN should > be used when the extent is allocated but it's data has not been > initialized. So I think btrfs should work like other filesystems. > > Cc: Chris Mason <chris.mason@...cle.com> > Signed-off-by: Tao Ma <tao.ma@...cle.com> > Tested-by: Jeff Liu <jeff.liu@...cle.com> > --- > fs/btrfs/extent_io.c | 15 +++++++++------ > 1 files changed, 9 insertions(+), 6 deletions(-) > > diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c > index b177ed3..7eb4d77 100644 > --- a/fs/btrfs/extent_io.c > +++ b/fs/btrfs/extent_io.c > @@ -2951,7 +2951,7 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, > u64 disko = 0; > struct extent_map *em = NULL; > struct extent_state *cached_state = NULL; > - int end = 0; > + int end = 0, hole = 0; > u64 em_start = 0, em_len = 0; > unsigned long emflags; > ret = 0; > @@ -2978,12 +2978,13 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, > > disko = 0; > flags = 0; > + hole = 0; > > if (em->block_start == EXTENT_MAP_LAST_BYTE) { > end = 1; > flags |= FIEMAP_EXTENT_LAST; > } else if (em->block_start == EXTENT_MAP_HOLE) { > - flags |= FIEMAP_EXTENT_UNWRITTEN; > + hole = 1; > } else if (em->block_start == EXTENT_MAP_INLINE) { > flags |= (FIEMAP_EXTENT_DATA_INLINE | > FIEMAP_EXTENT_NOT_ALIGNED); > @@ -3015,10 +3016,12 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, > end = 1; > } > > - ret = fiemap_fill_next_extent(fieinfo, em_start, disko, > - em_len, flags); > - if (ret) > - goto out_free; > + if (!hole) { > + ret = fiemap_fill_next_extent(fieinfo, em_start, disko, > + em_len, flags); > + if (ret) > + goto out_free; > + } > } > out_free: > free_extent_map(em); > -- > 1.6.3.3.334.g916e1.dirty > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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