Description of problem:

O_DIRECT doesn't work on LVM devices

Version-Release number of selected component (if applicable):

kernel-2.4.21-4.EL, O_DIRECT to a LVM device on a SCSI disk worked fine.
kernel-2.4.21-9.EL, kernel-2.4.21-15.EL,  kernel-2.4.21-18.EL seem to
disable varyio to LVM devices.
I.e. see mm/filemap.c
/* Only files on a varyio-capable block device are allowed to do
 * sector-aligned direct IO, and then only if the direct_sector_IO
 * method is present.  Otherwise we need to constrain the IO to fs
 * blocksize. */
This seems to be no longer true since kernel-2.4.21-9.EL for a LVM
device.

How reproducible:
anytime


Steps to Reproduce:

Using attached rawread to simulate O_DIRECT pread to /mnt/u1/<anyfile>
1.
/sbin/insmod /lib/modules/2.4.21-15.ELsmp/kernel/drivers/md/lvm-mod.o
/sbin/vgscan -v
/sbin/pvcreate /dev/sdj2
/sbin/vgcreate vgbde /dev/sdj2
/sbin/lvcreate -I512 -L3G -nlvgbde  -v vgbde
mkfs -t ext3 /dev/vgbde/lvgbde
mount -f ext3 /dev/vgbde/lvgbde /mnt/u1
.
2. rawread -f -z -t 4 -o 512 -s 8192 -r 1 => Errno = EINVAL
   rawread -f -z -t 4 -o 1024 -s 8192 -r 1 => Errno = EINVAL
   rawread -f -z -t 4 -o 2048 -s 8192 -r 1 => Errno = EINVAL
   rawread -f -z -t 4 -o 4096 -s 8192 -r 1 => OK, i.e. if offset is 
     FS blocksize multiple
  
Actual results:

9169  open("/mnt/u1/control01.ctl", O_RDONLY|O_DIRECT|O_LARGEFILE) = 15
9169  close(15)                         = 0
9169  open("/mnt3/bde/BDETST/control01.ctl",
O_RDWR|O_SYNC|O_DIRECT|O_LARGEFILE) = 15
9169  fcntl64(15, F_SETFD, FD_CLOEXEC)  = 0
9169  fcntl64(15, F_GETFL)              = 0xd002
(flags=O_RDWR|O_SYNC|O_DIRECT|O_LARGEFILE)
9169  fcntl64(15, F_SETLK, {type=F_WRLCK, whence=SEEK_SET, start=0,
len=0}) = 0
9169  gettimeofday({1093901803, 43850}, NULL) = 0
9169  pread(15, 0xbbb5e00, 8192, 512)   = -1 EINVAL (Invalid argument)

Expected results:

O_DIRECT pread/pwrite should work with 512 bytes aligned offset on LVM

Additional info: