fiemap is broken for sparse file in ext4?
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From: Greg Freemyer on 11 Jun 2010 12:50 On Fri, Jun 11, 2010 at 11:46 AM, Eric Sandeen <sandeen(a)redhat.com> wrote: > Tao Ma wrote: > >>> What are you using to call fiemap? �Here it seems to be working: >> I just wrote a simple test program by calling ioctl. It is attached. >> btw, you need to call it immediately after dd so that we have a chance >> that ext4 don't have time to allocate extents. ;) > > OK I take it back, I do see it. �*cough* too many different filesystems > on this box ... ;) > > Yes, it does look like a bug. > > -Eric I'm not clear how this is supposed to work. Is this just a userspace bug in that FIEMAP_FLAG_SYNC is needed in the fiemap call, or is there a kernel bug as well? If fiemap is called with the FIEMAP_FLAG_SYNC flag is there currently a problem? Thanks Greg -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Eric Sandeen on 11 Jun 2010 13:00 Greg Freemyer wrote: > On Fri, Jun 11, 2010 at 11:46 AM, Eric Sandeen <sandeen(a)redhat.com> wrote: >> Tao Ma wrote: >> >>>> What are you using to call fiemap? Here it seems to be working: >>> I just wrote a simple test program by calling ioctl. It is attached. >>> btw, you need to call it immediately after dd so that we have a chance >>> that ext4 don't have time to allocate extents. ;) >> OK I take it back, I do see it. *cough* too many different filesystems >> on this box ... ;) >> >> Yes, it does look like a bug. >> >> -Eric > > I'm not clear how this is supposed to work. > > Is this just a userspace bug in that FIEMAP_FLAG_SYNC is needed in the > fiemap call, or is there a kernel bug as well? The flag is optional, though maybe filefrag should use it. Without it, we should get the proper logical offset and a delalloc-flagged extent returned > If fiemap is called with the FIEMAP_FLAG_SYNC flag is there currently a problem? yep, we should get one delalloc extent in the results and we don't. -Eric > Thanks > Greg -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Tao Ma on 11 Jun 2010 19:50 Hi Eric, Eric Sandeen wrote: > Greg Freemyer wrote: > >> On Fri, Jun 11, 2010 at 11:46 AM, Eric Sandeen <sandeen(a)redhat.com> wrote: >> >>> Tao Ma wrote: >>> >>> >>>>> What are you using to call fiemap? Here it seems to be working: >>>>> >>>> I just wrote a simple test program by calling ioctl. It is attached. >>>> btw, you need to call it immediately after dd so that we have a chance >>>> that ext4 don't have time to allocate extents. ;) >>>> >>> OK I take it back, I do see it. *cough* too many different filesystems >>> on this box ... ;) >>> >>> Yes, it does look like a bug. >>> >>> -Eric >>> >> I'm not clear how this is supposed to work. >> >> Is this just a userspace bug in that FIEMAP_FLAG_SYNC is needed in the >> fiemap call, or is there a kernel bug as well? >> > > The flag is optional, though maybe filefrag should use it. > > Without it, we should get the proper logical offset and a delalloc-flagged > extent returned > > >> If fiemap is called with the FIEMAP_FLAG_SYNC flag is there currently a problem? >> > > yep, we should get one delalloc extent in the results and we don't. > With FIEMAP_FLAG_SYNC set, my test shows that we get one extent without dealloc flags. So no problem with it. We have another different test result? ;) Regards, Tao -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Eric Sandeen on 11 Jun 2010 20:00
Tao Ma wrote: > Hi Eric, > Eric Sandeen wrote: >> Greg Freemyer wrote: >> >>> On Fri, Jun 11, 2010 at 11:46 AM, Eric Sandeen <sandeen(a)redhat.com> >>> wrote: >>> >>>> Tao Ma wrote: >>>> >>>> >>>>>> What are you using to call fiemap? Here it seems to be working: >>>>>> >>>>> I just wrote a simple test program by calling ioctl. It is attached. >>>>> btw, you need to call it immediately after dd so that we have a chance >>>>> that ext4 don't have time to allocate extents. ;) >>>>> >>>> OK I take it back, I do see it. *cough* too many different filesystems >>>> on this box ... ;) >>>> >>>> Yes, it does look like a bug. >>>> >>>> -Eric >>>> >>> I'm not clear how this is supposed to work. >>> >>> Is this just a userspace bug in that FIEMAP_FLAG_SYNC is needed in the >>> fiemap call, or is there a kernel bug as well? >>> >> >> The flag is optional, though maybe filefrag should use it. >> >> Without it, we should get the proper logical offset and a >> delalloc-flagged >> extent returned >> >> >>> If fiemap is called with the FIEMAP_FLAG_SYNC flag is there currently >>> a problem? >>> >> >> yep, we should get one delalloc extent in the results and we don't. >> > With FIEMAP_FLAG_SYNC set, my test shows that we get one extent without > dealloc flags. So no problem with it. > We have another different test result? ;) No, I misread. :( Calling with FIEMAP_FLAG_SYNC works as expected. -Eric > Regards, > Tao > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |