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    SubjectRe: [PATCH try #1] Kconfig: cleanup block/Kconfig help descriptions
    Nick,

    I am trying to configure a linux-2.6.28.7 kernel.

    Please explain why the switch for large block devices should be !64BIT.
    I have a 64BIT system and currently cannot generate files greater than
    2TB. Is this the problem? Should this be true for 64BIT systems?

    Thanks,
    don

    Nick Andrew wrote:
    > Modify the help descriptions of block/Kconfig for clarity, accuracy and consistency.
    >
    > Refactor the BLOCK description a bit. The wording "This permits ... to be
    > removed" isn't quite right; the block layer is removed when the option
    > is disabled, whereas most descriptions talk about what happens when the
    > option is enabled. Reformat the list of what is affected by disabling the
    > block layer.
    >
    > Add more examples of large block devices to LBD and strive for technical
    > accuracy; block devices of size _exactly_ 2TB require CONFIG_LBD,
    > not only "bigger than 2TB". Also try to say (perhaps not very clearly)
    > that the config option is only needed when you want to have individual
    > block devices of size >= 2TB, for example if you had 3 x 1TB disks in
    > your computer you'd have a total storage size of 3TB but you wouldn't
    > need the option unless you want to aggregate those disks into a RAID
    > or LVM.
    >
    > Improve terminology and grammar on BLK_DEV_IO_TRACE.
    >
    > I also added the boilerplate "If unsure, say N" to most options.
    >
    > Precisely say "2TB and larger" for LSF.
    >
    > Indent the help text for BLK_DEV_BSG by 2 spaces in accordance with
    > the standard.
    >
    > Signed-off-by: Nick Andrew <nick@nick-andrew.net>
    > ---
    > I'm not sure why LSF has "If unsure, say Y." I would have thought it
    > pretty uncommon to have such large files. Also if you need LSF, you
    > probably need LBD (can NFS handle 2TB+ files?). Is this a safety
    > feature? How often is Grandma going to mount a filesystem containing
    > 2TB+ sized files?
    >
    > Also the description for BLK_DEV_BSG is pretty obscure. Can anybody
    > suggest why you'd want to do this or what tools you can use or even
    > some documentation?
    >
    >
    > block/Kconfig | 65 +++++++++++++++++++++++++++++++++++++--------------------
    > 1 files changed, 42 insertions(+), 23 deletions(-)
    >
    >
    > diff --git a/block/Kconfig b/block/Kconfig
    > index 9bda7bc..a3d8509 100644
    > --- a/block/Kconfig
    > +++ b/block/Kconfig
    > @@ -5,14 +5,18 @@ menuconfig BLOCK
    > bool "Enable the block layer" if EMBEDDED
    > default y
    > help
    > - This permits the block layer to be removed from the kernel if it's not
    > - needed (on some embedded devices for example). If this option is
    > - disabled, then blockdev files will become unusable and some
    > - filesystems (such as ext3) will become unavailable.
    > + Provide block layer support for the kernel.
    >
    > - This option will also disable SCSI character devices and USB storage
    > - since they make use of various block layer definitions and
    > - facilities.
    > + Disable this option to remove the block layer support from the
    > + kernel. This may be useful for embedded devices.
    > +
    > + If this option is disabled:
    > +
    > + - block device files will become unusable
    > + - some filesystems (such as ext3) will become unavailable.
    > +
    > + Also, SCSI character devices and USB storage will be disabled since
    > + they make use of various block layer definitions and facilities.
    >
    > Say Y here unless you know you really don't want to mount disks and
    > suchlike.
    > @@ -23,9 +27,20 @@ config LBD
    > bool "Support for Large Block Devices"
    > depends on !64BIT
    > help
    > - Say Y here if you want to attach large (bigger than 2TB) discs to
    > - your machine, or if you want to have a raid or loopback device
    > - bigger than 2TB. Otherwise say N.
    > + Enable block devices of size 2TB and larger.
    > +
    > + This option is required to support the full capacity of large
    > + (2TB+) block devices, including RAID, disk, Network Block Device,
    > + Logical Volume Manager (LVM) and loopback.
    > +
    > + For example, RAID devices are frequently bigger than the capacity
    > + of the largest individual hard drive.
    > +
    > + This option is not required if you have individual disk drives
    > + which total 2TB+ and you are not aggregating the capacity into
    > + a large block device (e.g. using RAID or LVM).
    > +
    > + If unsure, say N.
    >
    > config BLK_DEV_IO_TRACE
    > bool "Support for tracing block io actions"
    > @@ -33,19 +48,21 @@ config BLK_DEV_IO_TRACE
    > select RELAY
    > select DEBUG_FS
    > help
    > - Say Y here, if you want to be able to trace the block layer actions
    > + Say Y here if you want to be able to trace the block layer actions
    > on a given queue. Tracing allows you to see any traffic happening
    > - on a block device queue. For more information (and the user space
    > - support tools needed), fetch the blktrace app from:
    > + on a block device queue. For more information (and the userspace
    > + support tools needed), fetch the blktrace tools from:
    >
    > git://brick.kernel.dk/data/git/blktrace.git
    >
    > + If unsure, say N.
    > +
    > config LSF
    > bool "Support for Large Single Files"
    > depends on !64BIT
    > help
    > - Say Y here if you want to be able to handle very large files (bigger
    > - than 2TB), otherwise say N.
    > + Say Y here if you want to be able to handle very large files (2TB
    > + and larger), otherwise say N.
    >
    > If unsure, say Y.
    >
    > @@ -53,14 +70,16 @@ config BLK_DEV_BSG
    > bool "Block layer SG support v4 (EXPERIMENTAL)"
    > depends on EXPERIMENTAL
    > ---help---
    > - Saying Y here will enable generic SG (SCSI generic) v4 support
    > - for any block device.
    > -
    > - Unlike SG v3 (aka block/scsi_ioctl.c drivers/scsi/sg.c), SG v4
    > - can handle complicated SCSI commands: tagged variable length cdbs
    > - with bidirectional data transfers and generic request/response
    > - protocols (e.g. Task Management Functions and SMP in Serial
    > - Attached SCSI).
    > + Saying Y here will enable generic SG (SCSI generic) v4 support
    > + for any block device.
    > +
    > + Unlike SG v3 (aka block/scsi_ioctl.c drivers/scsi/sg.c), SG v4
    > + can handle complicated SCSI commands: tagged variable length cdbs
    > + with bidirectional data transfers and generic request/response
    > + protocols (e.g. Task Management Functions and SMP in Serial
    > + Attached SCSI).
    > +
    > + If unsure, say N.
    >
    > endif # BLOCK
    >
    >
    > --
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