kmalloc question

kmalloc question

[Finney, Steve]

Is kmalloc (GFP_KERNEL) on a 32 bit HIGHMEM enabled MIPS kernel (BCM/Sibyte processor) guaranteed to allocate memory from the low, KSEG0/1 addressible region? I'm having trouble sorting through the slab.c code. On this processor, only 256 MB of DRAM is directly addressible; with more than 256 MB of RAM, there is 256 MB in zone 0, and the remainder in zone 2. Zone 1 is empty.

Thanks,
sf

kmalloc question

[Finney, Steve]

Is kmalloc (GFP_KERNEL) on a 32 bit HIGHMEM enabled MIPS kernel (BCM/Sibyte processor) guaranteed to allocate memory from the low, KSEG0/1 addressible region? I'm having trouble sorting through the slab.c code. On this processor, only 256 MB of DRAM is directly addressible; with more than 256 MB of RAM, there is 256 MB in zone 0, and the remainder in zone 2. Zone 1 is empty.

Thanks,
sf

Re: kmalloc question

[Ralf Baechle]

On Wed, Oct 08, 2003 at 03:06:50PM -1000, Finney, Steve wrote:

> Is kmalloc (GFP_KERNEL) on a 32 bit HIGHMEM enabled MIPS kernel (BCM/Sibyte processor) guaranteed to allocate memory from the low, KSEG0/1 addressible region? I'm having trouble sorting through the slab.c code. On this processor, only 256 MB of DRAM is directly addressible; with more than 256 MB of RAM, there is 256 MB in zone 0, and the remainder in zone 2. Zone 1 is empty.

Yes.

  Ralf

kmalloc question.

[Ganesh Patil]

where allocate kmalloc function memory?
-- 
Regards,
Ganesh Patil.

Re: kmalloc question.

[Theodore Tso]

On Jan 4, 2012, at 9:22 AM, Ganesh Patil wrote:

> where allocate kmalloc function memory?

Sorry, I can't parse your question.

-- Ted

Re: kmalloc question.

[Ganesh Patil]

Hello sir,

         I am B.E(computer)student from Pune university (India) .my
final year project is "File system level snapshot in ext4 "  so have
to take snapshot of particular file system and place somewhere(on same
filesystem or on another filesystem) .in snapshot we are going to copy
only inode of file in to another inode. as inode size in particular
filesystem   is fixed so we cant get inode from filesystem(if
filesystem filled more than half) so finally we come to decision that
we will create one structure which has fields same as that of original
inode. so we will allocate memory dynamically using kmalloc
function.but we require that allocated memory cant be destroy till we
manually not destroy it.because of that I am asking from where kmalloc
allocates memory block(from current file system,or from kernel
space(root filesystem) or from RAM(heap area)).

On 1/4/12, Theodore Tso <tytso@mit.edu> wrote:
>
> On Jan 4, 2012, at 9:22 AM, Ganesh Patil wrote:
>
>> where allocate kmalloc function memory?
>
> Sorry, I can't parse your question.
>
> -- Ted
>
>


-- 
Regards,
Ganesh Patil.

Re: kmalloc question.

[Ganesh Patil]

Thank you sir.

On 1/5/12, Amir Goldstein <amir73il@gmail.com> wrote:
> Hi Ganesh,
>
> I am glad to learn that ext4 snapshots has become a "hot" research subject
> in Pune.
> However, I must say:
> 1. this is not the place to ask such basic questions.
> 2. your question shows that you are missing a lot of background before you
> can
> approach this kind of project.
>
> The answer in kernel memory (slab), BTW, which has nothing to do with root
> filesystem.
>
> Amir.
>
> On Wed, Jan 4, 2012 at 5:50 PM, Ganesh Patil
> <patil.ganesh170@gmail.com>wrote:
>
>> Hello sir,
>>
>>         I am B.E(computer)student from Pune university (India) .my
>> final year project is "File system level snapshot in ext4 "  so have
>> to take snapshot of particular file system and place somewhere(on same
>> filesystem or on another filesystem) .in snapshot we are going to copy
>> only inode of file in to another inode. as inode size in particular
>> filesystem   is fixed so we cant get inode from filesystem(if
>> filesystem filled more than half) so finally we come to decision that
>> we will create one structure which has fields same as that of original
>> inode. so we will allocate memory dynamically using kmalloc
>> function.but we require that allocated memory cant be destroy till we
>> manually not destroy it.because of that I am asking from where kmalloc
>> allocates memory block(from current file system,or from kernel
>> space(root filesystem) or from RAM(heap area)).
>>
>> On 1/4/12, Theodore Tso <tytso@mit.edu> wrote:
>> >
>> > On Jan 4, 2012, at 9:22 AM, Ganesh Patil wrote:
>> >
>> >> where allocate kmalloc function memory?
>> >
>> > Sorry, I can't parse your question.
>> >
>> > -- Ted
>> >
>> >
>>
>>
>> --
>> Regards,
>> Ganesh Patil.
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>
>


-- 
Regards,
Ganesh Patil.

kmalloc question

[Andre.Messerschmidt]

Hi.

I always thought that it is save to use kmalloc in an interrupt handler as
long as you use GFP_ATOMIC. 
Now someone told me that it is not allowed to use these functions in any way
in an interrupt.

Can please someone clarify me here? 

regards
--
Andre Messerschmidt

Application Engineer
Infineon Technologies AG

Re: kmalloc question

[Alan Cox]

On Wed, 2002-06-05 at 06:25, Andre.Messerschmidt@infineon.com wrote:
> Hi.
> 
> I always thought that it is save to use kmalloc in an interrupt handler as
> long as you use GFP_ATOMIC. 
> Now someone told me that it is not allowed to use these functions in any way
> in an interrupt.
> 
> Can please someone clarify me here? 

GFP_ATOMIC is safe in an interrupt handler. You might get NULL back and
that it is your problem, but the kmalloc is safe