linux-ext4 - Re: Copying Data Blocks

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Date:	Tue, 6 Jan 2009 22:55:23 +0530
From:	"Rohit Sharma" <imreckless@...il.com>
To:	"Manish Katiyar" <mkatiyar@...il.com>
Cc:	"rishi agrawal" <postrishi@...il.com>,
	ext4 <linux-ext4@...r.kernel.org>,
	Kernelnewbies <kernelnewbies@...linux.org>
Subject: Re: Copying Data Blocks

We can find out no. of block currently being used by the donor inode,
The data we read from donor inode has to be in some buffer or page,
is there a way we can associate this buffer with the reciever inode
or write the contents of the buffer to the new inode.


On Tue, Jan 6, 2009 at 10:46 PM, Rohit Sharma <imreckless@...il.com> wrote:
> On Tue, Jan 6, 2009 at 10:43 PM, Manish Katiyar <mkatiyar@...il.com> wrote:
>> On Tue, Jan 6, 2009 at 10:15 PM, Rohit Sharma <imreckless@...il.com> wrote:
>>> On Tue, Jan 6, 2009 at 7:42 PM, rishi agrawal <postrishi@...il.com> wrote:
>>>> yes i suppose the donor inode is known
>>>> moreover the receiver inode's number is also known
>>>>
>>>> On Tue, Jan 6, 2009 at 6:54 PM, Manish Katiyar <mkatiyar@...il.com> wrote:
>>>>>
>>>>> On Tue, Jan 6, 2009 at 4:06 PM, Rohit Sharma <imreckless@...il.com> wrote:
>>>>> > I want to read data blocks from one inode
>>>>> > and copy it to other inode.
>>>>> >
>>>>> > I mean to copy data from data blocks associated with one inode
>>>>> > to the data blocks associated with other inode.
>>>>>
>>>>> Copying 4K chunk of data itself is a costly operation. and depending
>>>
>>> Yes its a costly operation, but if this can be done then
>>> we can definitely copy n blocks at a time.
>>>
>>>>> on the size of your donor inode this can be huge . Why do you want to
>>>>> do that ? Do you know the inode of the donor inode ?
>>>
>>> For physically relocating a file from one disk to other.
>>>
>>> Yes Manish, i know the donor inode and i will create the reciever inode.
>>
>> I am guessing .......will something like this work ?
>>
>> ino_t donor_inode_num;
>> struct inode *donor_inode = FS_iget(sb , donor_inode_num);
>> struct FS_inode_info * fsi = FSI(donor_inode) ;   // Do the regular
>> container_of stuff here
>>
>> for ( i = 0; i < (donor_inode->i_size + sb->s_blocksize -
>> 1)/sb->s_blocksize ; i ++ ) {
>>    // Do a memmove or memcpy here from fsi->i_data[i]
>> }
>>
>> I am not sure though how will you prevent the donor inode from being
>> changed/resized during this period.
>
> I am thinking of remounting ext2 in readonly mode, or i'll change the
> mount flags to readonly. But i m not sure if internally i can copy the
> data from one block to other.
>
>>
>> Thanks -
>> Manish
>>
>>
>>>
>>> Can we do that in kernel space.?
>>>>>
>>>>> thanks -
>>>>> Manish
>>>>> >
>>>>> > Is that possible in kernel space.?
>>>>> > --
>>>>> > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
>>>>> > the body of a message to majordomo@...r.kernel.org
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>>>>> >
>>>>> --
>>>>> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
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>>>>
>>>>
>>>>
>>>> --
>>>> Regards,
>>>> Rishi B. Agrawal
>>>>
>>>>
>>>
>>
>
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