Ext3: batched discard support

[Lukas Czerner <lczerner@redhat.com>]

Hello again,

I have composed a set of patches to add batched discard support for Ext3 file
system. Functionality is basically the same as in "batched discard support
for Ext4" (see http://www.spinics.net/lists/linux-ext4/msg19827.html ).

There are two patches:

[PATCH 1/2] Add discard/nodiscard mount option for ext3
 fs/ext3/super.c         |   14 +++++++++++++-
 include/linux/ext3_fs.h |    1 +
 2 files changed, 14 insertions(+), 1 deletions(-)

[PATCH 2/2] Add batched discard support for ext3
 fs/ext3/balloc.c        |  145 +++++++++++++++++++++++++++++++++++++++++++++++
 fs/ext3/super.c         |    1 +
 include/linux/ext3_fs.h |    1 +
 3 files changed, 147 insertions(+), 0 deletions(-)

The first one adds mount option to specify whether or not the discard should
be performed (default is nodiscard), and the second one adds discard support
itself.

Note that you will need one more patch for this to work "Add ioctl FITRIM" see
(http://www.spinics.net/lists/linux-ext4/msg19828.html) which adds ioctl to
issue discard itself.

Regards.

-Lukas

Signed-off-by: Lukas Czerner <lczerner@redhat.com>