From: "Rohit Sharma" Subject: Re: Copying Data Blocks Date: Tue, 6 Jan 2009 23:06:16 +0530 Message-ID: <2d08ef090901060936r1c9f4eddxc188b8ef943c71f5@mail.gmail.com> References: <2d08ef090901060236p46d4d396x797e4bceb24a2a34@mail.gmail.com> <5feb302e0901060612p4e114953pb6e297778aa7c0a4@mail.gmail.com> <2d08ef090901060845t85ac2b0i11c684a09d930608@mail.gmail.com> <2d08ef090901060916y4c49884dy4b44d6354b11ebb8@mail.gmail.com> <2d08ef090901060925p685506abkdc722c4099b485c7@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: "rishi agrawal" , ext4 , Kernelnewbies To: "Manish Katiyar" Return-path: Received: from wf-out-1314.google.com ([209.85.200.172]:30762 "EHLO wf-out-1314.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751009AbZAFRgR (ORCPT ); Tue, 6 Jan 2009 12:36:17 -0500 Received: by wf-out-1314.google.com with SMTP id 27so8242306wfd.4 for ; Tue, 06 Jan 2009 09:36:16 -0800 (PST) In-Reply-To: Content-Disposition: inline Sender: linux-ext4-owner@vger.kernel.org List-ID: On Tue, Jan 6, 2009 at 10:58 PM, Manish Katiyar wrote: > On Tue, Jan 6, 2009 at 10:55 PM, Rohit Sharma wrote: >> 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, > > Since we know the blocknumber of donor inode, it should be possible to > do a raw read and get the memory address of the data page using > sb_bread() and then accessing bh->b_data . Isn't it ? Yes that's the way we can read blocks but the major issue here is copying this content to newly allocated block. > > Thanks - > Manish > >> 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 wrote: >>> On Tue, Jan 6, 2009 at 10:43 PM, Manish Katiyar wrote: >>>> On Tue, Jan 6, 2009 at 10:15 PM, Rohit Sharma wrote: >>>>> On Tue, Jan 6, 2009 at 7:42 PM, rishi agrawal 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 wrote: >>>>>>> >>>>>>> On Tue, Jan 6, 2009 at 4:06 PM, Rohit Sharma 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@vger.kernel.org >>>>>>> > More majordomo info at http://vger.kernel.org/majordomo-info.html >>>>>>> > >>>>>>> -- >>>>>>> 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, >>>>>> Rishi B. Agrawal >>>>>> >>>>>> >>>>> >>>> >>> >> >