mmap on a block device

mmap on a block device

[Kaustubh Ashtekar]

Hello All,

Is it possible to mmap on a block device? I am writing my own kernel space
filesystem on Linux (academic project). I am writing a user space tool to
format the block device (again my own ramdisk driver). It would be much
simpler if I could just mmap the block device into my address space.

-Kaustubh
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mmap on a block device

[Rajat Sharma]

yes its fairly possible, go ahead and try it.

On Tue, Jun 7, 2011 at 9:57 AM, Kaustubh Ashtekar <ksashtekar@gmail.com> wrote:
> Hello All,
> Is it possible to mmap on a block device? I am writing my own kernel space
> filesystem on Linux (academic project). I am writing a user space tool to
> format the block device (again my own ramdisk driver). It would be much
> simpler if I could just mmap the block device into my address space.
> -Kaustubh
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>
>

mmap on a block device

[Kaustubh Ashtekar]

Done. mmap was successful.

Is it a good idea to mmap a block device. A block device being much bigger
than the available virtual address space, I will have to map it multiple
times while working on various parts of the block device.

BR,
Kaustubh

On Tue, Jun 7, 2011 at 11:47 AM, Rajat Sharma <fs.rajat@gmail.com> wrote:

> yes its fairly possible, go ahead and try it.
>
> On Tue, Jun 7, 2011 at 9:57 AM, Kaustubh Ashtekar <ksashtekar@gmail.com>
> wrote:
> > Hello All,
> > Is it possible to mmap on a block device? I am writing my own kernel
> space
> > filesystem on Linux (academic project). I am writing a user space tool to
> > format the block device (again my own ramdisk driver). It would be much
> > simpler if I could just mmap the block device into my address space.
> > -Kaustubh
> > _______________________________________________
> > Kernelnewbies mailing list
> > Kernelnewbies at kernelnewbies.org
> > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
> >
> >
>
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mmap on a block device

[Dave Hylands]

Hi Kaustubh,

Replying to all this time...

On Mon, Jun 6, 2011 at 11:44 PM, Kaustubh Ashtekar <ksashtekar@gmail.com> wrote:
> Done. mmap was successful.
> Is it a good idea to mmap a block device. A block device being much bigger
> than the available virtual address space, I will have to map it multiple
> times while working on various parts of the block device.

What it means to mmap any device is quite arbitrary and entirely up to
the driver writer.

All that mmaping means is to take some memory that the driver
allocated in kernel space and make that memory available into user
space. The contents of the memory is entirely up to the driver. Maybe
you put statistics in there? Maybe you make it map in the data storage
your block device is front-ending? It's up to the driver writer to
decide what goes there and whether it makes sense or not.

-- 
Dave Hylands
Shuswap, BC, Canada
http://www.davehylands.com