Btrfs devel - Jun 2010 - reflinked file size incorrect

Both `cp --reflink` and `bcp` sometimes round the file size up to the next
4k boundary, with the balance consisting of null bytes.  At first glance
this behavior occurs for source file size > 3916 bytes.  I have tried this
with stock btrfs from kernel 2.6.35-rc2 and 2.6.35-rc1 -- specifically,
Ubuntu 2.6.35-2.3~lucid1-server and 2.6.35-1.1~lucid1-server.
Any ideas?

$ rm -f abc; dd if=/dev/urandom of=abc bs=1 count=3917; \
  cp --reflink abc abc.1; ll abc*
3917 bytes (3.9 kB) copied, 0.0380613 s, 103 kB/s
-rw-r----- 1 root root 3917 2010-06-12 04:22 abc
-rw-r----- 1 root root 4096 2010-06-12 04:22 abc.1

$ rm -f abc; dd if=/dev/urandom of=abc bs=1 count=3916; \
  cp --reflink abc abc.1; ll abc*
3916 bytes (3.9 kB) copied, 0.0299729 s, 131 kB/s
-rw-r----- 1 root root 3916 2010-06-12 04:22 abc
-rw-r----- 1 root root 3916 2010-06-12 04:22 abc.1

$ rm -f abc; dd if=/dev/urandom of=abc bs=1 count=4097; \
  cp --reflink abc abc.1; ll abc*
4097 bytes (4.1 kB) copied, 0.0258441 s, 159 kB/s
-rw-r----- 1 root root 4097 2010-06-12 11:08 abc
-rw-r----- 1 root root 8192 2010-06-12 11:08 abc.1

$ uname -a
Linux allie 2.6.35-2-server #3~lucid1-Ubuntu SMP Thu Jun 10 17:52:32 UTC 2010
x86_64 GNU/Linux

Jim
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On Sat, 12 Jun 2010, Jim Ursetto wrote:
> Both `cp --reflink` and `bcp` sometimes round the file size up to the next
> 4k boundary, with the balance consisting of null bytes.  At first glance
> this behavior occurs for source file size > 3916 bytes.  I have tried
this
> with stock btrfs from kernel 2.6.35-rc2 and 2.6.35-rc1 -- specifically,
> Ubuntu 2.6.35-2.3~lucid1-server and 2.6.35-1.1~lucid1-server.
> Any ideas?
This bug is new in 2.6.35-rc1 from a22285a6 (Btrfs: Integrate metadata 
reservation with start_transaction).  Just sent a patch fixing this up to 
the list.

sage
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At 05:41pm on 2010 June 12, Sage Weil did write:
> This bug is new in 2.6.35-rc1 from a22285a6 (Btrfs: Integrate metadata 
> reservation with start_transaction).  Just sent a patch fixing this up to 
> the list.
Thank you, patch works perfectly.
Jim
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