block: enable by default support for large devices and files on 32-bit archs

Enable by default support for large devices and files (CONFIG_LBD):

- With 1TB disks being a commodity hardware it is quite easy to hit 2TB
  limitation while building RAIDs etc. and many distros have been using
  CONFIG_LBD=y by default already (at least Fedora 10 and openSUSE 11.1).

- This should also prevent a subtle ext4 filesystem compatibility issue:
  mke2fs.ext4 defaults to creating filesystems with huge_files feature
  enabled and such filesystems cannot be later mounted read-write on
  machines with CONFIG_LBD=n (it should be quite easy to hit this issue
  when trying to use filesystem created using distro kernel on system
  running the self-build kernel, think about USB disk enclosures & co.).

While at it:

- Clarify config option help text w.r.t. mounting ext4 filesystems
  (they can be mounted with CONFIG_LBD=n but in the read-only mode).

Cc: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/block/Kconfig b/block/Kconfig
index e7d12782bcfb5eccb56aee532b8c27fa81706499..2c39527aa7db026dc6c6b6c20fbe55024de46100 100644 (file)
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -26,6 +26,7 @@ if BLOCK
 config LBD
        bool "Support for large block devices and files"
        depends on !64BIT
+       default y
        help
          Enable block devices or files of size 2TB and larger.
 
@@ -38,11 +39,13 @@ config LBD
 
          The ext4 filesystem requires that this feature be enabled in
          order to support filesystems that have the huge_file feature
-         enabled.    Otherwise, it will refuse to mount any filesystems
-         that use the huge_file feature, which is enabled by default
-         by mke2fs.ext4.   The GFS2 filesystem also requires this feature.
+         enabled.  Otherwise, it will refuse to mount in the read-write
+         mode any filesystems that use the huge_file feature, which is
+         enabled by default by mke2fs.ext4.
 
-         If unsure, say N.
+         The GFS2 filesystem also requires this feature.
+
+         If unsure, say Y.
 
 config BLK_DEV_BSG
        bool "Block layer SG support v4 (EXPERIMENTAL)"