Re: 2.6.9-mm1: LVM stopped working

[Laurent Riffard <laurent.riffard@free.fr>]

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Hello,

Lvm2 stopped working since 2.6.9-mm1 for me too : 2.6.9-rc4-mm1 was 
fine, 2.6.9-mm1 to 2.6.10-mm2 break lvm2. Reverting 
dio-handle-eof.patch on these kernel solves the problem.

I have a simple test case here.

With 2.6.9-rc4-mm1, "pvdisplay /dev/hda4" shows :
 --- Physical volume ---
 PV Name               /dev/hda4
 VG Name               vglinux1
 PV Size               19,07 GB / not usable 0
 Allocatable           yes
 PE Size (KByte)       4096
 Total PE              4882
 Free PE               3424
 Allocated PE          1458
 PV UUID               Kvi5oA-d8NL-DU0n-vJpt-TKb3-RmDP-nrZoaz

With later -mm kernel, "pvdisplay /dev/hda4" shows :
 No physical volume label read from /dev/hda4
 Failed to read physical volume "/dev/hda4"

I tracked down the problem to this code section in fs/direct-io.c (function direct_io_worker) :

  1012                 dio->total_pages = 0;
  1013                 if (user_addr & (PAGE_SIZE-1)) {
  1014                         dio->total_pages++;
  1015                         bytes -= PAGE_SIZE - (user_addr & (PAGE_SIZE - 1));
  1016                 }
  1017                 dio->total_pages += (bytes + PAGE_SIZE - 1) / PAGE_SIZE;
  1018                 dio->curr_user_address = user_addr;
  1019
  1020                 ret = do_direct_IO(dio);
  1021
  1022                 dio->result += bytes -
  1023                         ((dio->final_block_in_request - dio->block_in_file) <<
  1024                                         blkbits);

In my case, direct_io_worker is called to read 2048 bytes at the beginning of /dev/hda4 :
 user_addr=0xbfff9800 (half page aligned)
 bytes=2048 (half page)
So "bytes" is zeroed line 1015.
And dio->result is zeroed line 1023.
As a result, direct_io_worker returns 0.

Before dio-handle-eof.patch, line 1022 was :
	dio->result += iov[seg].iov_len -

What is the semantic of "bytes" line 1015 : bytes to read on the next page ?
Did I miss something ?

hope this helps... 
I will do some tests if needed.

-- 
laurent



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