On Wed, Jan 7, 2009 at 12:44 PM, Manish Katiyar <mkatiyar@xxxxxxxxx> wrote: > On Wed, Jan 7, 2009 at 12:17 PM, Sandeep K Sinha > <sandeepksinha@xxxxxxxxx> wrote: >> Ok, Let me rephrase what rohit is exactly trying to question. >> >> There is an inode X which has say some N number of data blocks. >> Now, through his own kernel module and some changes to the file system, >> he wants to create a new inode Y in the FS and physically copy all the >> data from the old inode to the new inode. > > Errr....... I must be missing something..... I knew I was missing something.... so you want to move the blocks to another disk which is of low *priority*. Yes in that case copy is necessary. Apart from copy, you may also want to do some kind of readaheads for the source file. doing this in userspace is easy, but if you do this in kernel, even if you have done readahead you cannot hold kernel for that much time to copy all the data :-( thanks - Manish > . For this why do you need > to copy the data blocks ? if you just copy the old inode to new inode, > you have already copied the direct and indirect block pointers right ? > That will not take much time, and now if you free the old inode, you > have virtually changed the ownership of old blocks to the new inode. > > The problems i can see with this approach is that if the new inode is > not in the same block group as old inode, you have *kind of broken* > the ext2's intelligence of allocating the blocks in the same block > group. > > CMIIW . btw this thread is interesting :-) > > Thanks - > Manish. > >> >> And release the old inode and its data blocks and update the dentry >> with the new inode number. >> PS: The file system remains completely frozen in this time. >> >> >> On Wed, Jan 7, 2009 at 4:02 AM, Om <om.turyx@xxxxxxxxx> wrote: >>> Erik Mouw wrote: >>>> >>>> On Tue, 6 Jan 2009 23:16:14 +0530 "Rohit Sharma" <imreckless@xxxxxxxxx> >>>> wrote: >>>>> >>>>> On Tue, Jan 6, 2009 at 11:09 PM, Manish Katiyar <mkatiyar@xxxxxxxxx> >>>>> wrote: >>>>>> >>>>>> Apart from performance, is there anything else you are worried >>>>>> about ? >>>>> >>>>> Performance is only a bottleneck, >>>>> this can be done in user land >>>>> but kernel space solution will be more efficient. >>>> >>>> Hardly more efficient. Your main bottleneck will be IO from/to the >>>> device. If you are worried about copying between kernel and userland, >>>> you could use the tee(2) and splice(2) system calls. They are relatively >>>> new, so your system might not yet have manual pages for them. In that >>>> case, see http://linux.die.net/man/2/tee and >>>> http://linux.die.net/man/2/splice . >>> >>> Hm.. that is pretty enlightening... >>> Thanks, >>> Om. >>> >>> >>> -- >>> To unsubscribe from this list: send an email with >>> "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx >>> Please read the FAQ at http://kernelnewbies.org/FAQ >>> >>> >> >> >> >> -- >> Regards, >> Sandeep. >> >> >> >> >> >> >> "To learn is to change. Education is a process that changes the learner." >> >> -- >> To unsubscribe from this list: send an email with >> "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx >> Please read the FAQ at http://kernelnewbies.org/FAQ >> >> > -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
