On 12/29/11, Rajat Sharma <fs.rajat@xxxxxxxxx> wrote: > I would suggest that you go through the stackable FS documentation > maintained with wrapfs website: > > http://wrapfs.filesystems.org/docs/linux-stacking/index.html > > there is no replacement of fops, that again I would categorize as pure > "HACK". Here you build a stack of FS on top of existing one. so stack > fs appears as regular FS to VFS layer and as VFS to lower FS, it just > fits in between VFS and lower FS. To do it tranparent to applications > you need to mount wrapfs on the same mount point as lower fs so that > you hide direct exposure to lower FS and application can still assume > same file paths as lower FS. I am going through their documentation. I see this means I could intercept in between for filesystems on which I mount this file system and thus could do what I want to do. I can skip entire system calls I suppose. Also I am thinking of KProbes is it possible to skip system call using kprobes ? Thanks a lot for your help. > > Thanks, > Rajat > > On Thu, Dec 29, 2011 at 12:12 PM, Gaurav Saxena <grvsaxena419@xxxxxxxxx> > wrote: >> Hello Rajat, Thanks for your reply. >> >> On 12/28/11, Rajat Sharma <fs.rajat@xxxxxxxxx> wrote: >>> wrapfs needs the underlying filesystem to be already mounted and then >>> it attaches itself on top of this mount point. >> Ok That means it will replace the specific file system operations with >> its own operations ? And then call the specific operations from >> itself? Doesn't it then requires a different operation for each file >> system ? >>>Thats the whole idea of >>> stacking one to one VFS objects from wrapfs to underlying FS objects. >>> So it assumes that / to be already mounted. And you would want to >>> attach to a route volume as soon as possible, so entering wrapfs mount >>> entry in /etc/fstab just after / entry should be good enough. >> Do I need volumes for using wrapfs ? Or simple partitioning would >> suffice ? It sounds quite good I would look at this. >>> >>> Thanks, >>> Rajat >>> >>> On Wed, Dec 28, 2011 at 11:29 AM, Gaurav Saxena <grvsaxena419@xxxxxxxxx> >>> wrote: >>>> Hello Rajat Thanks for your reply. >>>> >>>> On Mon, Dec 26, 2011 at 11:23 AM, Rajat Sharma <fs.rajat@xxxxxxxxx> >>>> wrote: >>>>> Hi Gaurav, >>>>> >>>>> I would suggest to take a wrapfs source (a null stackable file-system) >>>>> and customize it for your need. Well Erez (wrapfs author) puts his >>>>> continuous efforts in stabilizing wrapfs and porting to new kernels >>>>> and he is approachable too. In-fact he has acknowledged on of my patch >>>>> and merged it into wrapfs tree. >>>> Is there a way to mount "/" on such file system ? Like I want to >>>> monitor / for changes like unlink or modified write. Would I be able >>>> to see such changes using wrapfs. As by default on the systems "/" >>>> would be mounted as ext4 filesystem. >>>>> >>>>> Agreed that you can do stuffs like patching system call table but I >>>>> (and most of us here) would categorize that as pure hack, as there >>>>> exist no framework provided by kernel to do that. Also any approach >>>>> you take to patch system call table won't be stable. >>>> Yes I agree with you I want to do this using a method which is not a >>>> hack, so that the support remains with all the versions of kernel >>>> rather than a trick that works in a limited way. >>>>> >>>>> Thanks, >>>>> Rajat >>>>> >>>>> On Sat, Dec 24, 2011 at 2:39 PM, Gaurav Saxena <grvsaxena419@xxxxxxxxx> >>>>> wrote: >>>>>> Hello all, >>>>>> >>>>>> I am writing an application which would create a backup for the system >>>>>> so that it could be restored as it is. For example I create a backup >>>>>> using my application. I just do nothing at time of backup so it would >>>>>> be fast. Now whenever I see any deletion I would save that file so >>>>>> that I could restore it. Also I would like to see for >>>>>> modification/rename. I cannot do this using inotify as I would be >>>>>> notified after actual deletion/write. I don't want to use SELinux >>>>>> because I want to implement this on existing installed system. I was >>>>>> earlier thinking of replacing system calls for open/unlink with my >>>>>> custom calls which will call my functions before actual work and then >>>>>> I would decide what to do I would also want to reject unlink request >>>>>> for some of the files. But as I now know that its not working in >>>>>> linux>3.0 . I had also seen dazuko which is not supporting linux>3.0 >>>>>> yet. Also there used to be a redirfs which used to work earlier but >>>>>> the latest kernel is not supported yet. I think a method could be to >>>>>> replace unlink in syscall table with my unlink function but I don't >>>>>> find any good method of doing that, as syscall table is no longer >>>>>> exported. I would like to implement this in a kernel module instead of >>>>>> modifying kernel code itself. Please suggest some method of doing >>>>>> that. >>>>>> Thanks to you all for your help. >>>>>> >>>>>> -- >>>>>> Thanks and Regards , >>>>>> Gaurav >>>>>> -- >>>>>> To unsubscribe from this list: send the line "unsubscribe >>>>>> linux-fsdevel" >>>>>> in >>>>>> the body of a message to majordomo@xxxxxxxxxxxxxxx >>>>>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>>> >>>> >>>> >>>> -- >>>> Thanks and Regards , >>>> Gaurav >>> >> >> >> -- >> Thanks and Regards , >> Gaurav > -- Thanks and Regards , Gaurav -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
