What happened to mount option "noextents"
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From: Peter Hallberg on 30 May 2010 08:30 On Ubuntu 9.04 it is possible to mount an ext4 file system with the mount option "noextents" but on Ubuntu 10.04 it gives the error message: Ext4: Unrecognized mount option "noextents" in dmesg. _________________________________________________________________ Surfa tryggt med Internet Explorer 8 http://www.microsoft.com/sverige/windows/internet-explorer/default.aspx-- 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: tytso on 30 May 2010 08:40 On Sun, May 30, 2010 at 02:07:06PM +0200, Peter Hallberg wrote: > > On Ubuntu 9.04 it is possible to mount an ext4 file system with the > mount option "noextents" but on Ubuntu 10.04 it gives the error > message: Ext4: Unrecognized mount option "noextents" in dmesg. Both the "extents" and "noexents" mount options were removed in newer kernels. If you want to turn on extents, the right answer is to use the "tune2fs -O extents" command. The "noextents" mount option didn't really make much sense, since it basically was either no-op (if extents were not enabled), and was mostly useless (if extents were enabled in the file system), since it basically meant, "create new files without using extents". But since the old files were still extents-based, it didn't make the file system any more compatible with ext3 file systems. Basically, since we couldn't think of a good use case where the mount options made sense, and ext4 has way too many mount options already, we decided to remove them. - Ted -- 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: Peter Hallberg on 30 May 2010 10:00 > Basically, since we couldn't think of a good use case where the mount > options made sense, and ext4 has way too many mount options already, we > decided to remove them. The ext2/3 Windows driver doesn't support extents yet so one common use would be to do a mount -o remount,noextents and make a dir and copy the files you want to read from Windows to it. I think mount -o remount is something that is well known, if you use tune2fs you would need to do research before you know if the change starts working right a way or after a reboot or if it is valid only until reboot or is static, with mount -o remount there is no risk that you forget to set the flag back to the right value. Also when I tryed tune2fs as you said, I got the following error message: peter(a)sanna:~$ sudo tune2fs -O ^extents /dev/mapper/sannavg-home tune2fs 1.41.4 (27-Jan-2009) Clearing filesystem feature 'extent' not supported. peter(a)sanna:~$ _________________________________________________________________ Klicka h�r! http://new.windowslivemobile.msn.com/SE-SE/windows-live-hotmail/default.aspx-- 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: Peter Hallberg on 30 May 2010 10:10 > Basically, since we couldn't think of a good use case where the mount > options made sense, and ext4 has way too many mount options already, we > decided to remove them. The ext2/3 Windows driver doesn't support extents yet so one common use would be to do a mount -o remount,noextents and make a dir and copy the files you want to read from Windows to it. I think mount -o remount is something that is well known, if you use tune2fs you would need to do research before you know if the change starts working right a way or after a reboot or if it is valid only until reboot or is static, with mount -o remount there is no risk that you forget to set the flag back to the right value. Also when I tryed tune2fs as you said, I got the following error message: peter(a)sanna:~$ sudo tune2fs -O ^extents /dev/mapper/sannavg-home tune2fs 1.41.4 (27-Jan-2009) Clearing filesystem feature 'extent' not supported. peter(a)sanna:~$ _________________________________________________________________ V�rfina smileys till Messenger h�r! http://springpack.msn.se-- 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: tytso on 30 May 2010 14:20
On Sun, May 30, 2010 at 03:52:10PM +0200, Peter Hallberg wrote: > > > Basically, since we couldn't think of a good use case where the mount > > options made sense, and ext4 has way too many mount options already, we > > decided to remove them. > > The ext2/3 Windows driver doesn't support extents yet so one common > use would be to do a mount -o remount,noextents and make a dir and > copy the files you want to read from Windows to it. I think mount -o > remount is something that is well known, if you use tune2fs you > would need to do research before you know if the change starts > working right a way or after a reboot or if it is valid only until > reboot or is static, with mount -o remount there is no risk that you > forget to set the flag back to the right value. Yeah, but.... it's a horrible interface to support. If one or more directories happen to be extent-mapped, then Windows won't be able to read it. And if there are other files that are created while the filesystem is remounted noextents, they will be created w/o extents, which means that fallocate won't work. The opportunities for hard-to-understand failures are very large, and especially for clueless Ubuntu users, it's just not something where I want to see whining on Launchpad because they read somewhere that they could do it, and it doesn't quite work right. This is more something where if someone wants to patch the kernel do something hacky like this, it's almost better because then it's not something where we have to worry about confused users wondering why something broke when they tried to use this interface. Something that works 80% of the time can be far worse than something that doesn't work at all. The real right answer is to fix the Windows driver to support extents. Or create a separate filesystem just for moving files from Linux to Windows --- or just write the files directly onto the Windows partition. > Also when I tryed tune2fs as you said, I got the following error message: > > peter(a)sanna:~$ sudo tune2fs -O ^extents /dev/mapper/sannavg-home > tune2fs 1.41.4 (27-Jan-2009) > Clearing filesystem feature 'extent' not supported. > peter(a)sanna:~$ Yes, right now you can only enable extents; it's not something you can disable. - Ted -- 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/ |