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Ext4 Developer Interlock Call: 07-9-07 Minutes

Attendees: Mingming Cao, Takashi Sato, Dave Kleikamp, Jose Santos, Andreas Dilger, Amit Arora, Suparna Bhattacharya, Aneesh Veetil, Ted T'so, Avantika Mathur

Minutes can be accessed at: http://ext4.wiki.kernel.org/index.php/Ext4_Developer%27s_Conference_Call


Preallocation and fallocate:

  • Amit will first be merging in Andreas' patch to fallocate, which allows initialized extents to be the full 32768 blocks. Uninitialized extents are limited to 32767 blocks. Amit will also add comments to this, and have the update patches ready by tomorrow.
  • The fallocate patches are already in the -mm tree. Ted will move the fallocate patches to the front of the patch-queue.
  • Once Amit has updated the preallocation, we will push fallocate patches and the ext4 preallocation patches to Linus' tree.
  • Once fallocate patches are merged in mainline, send patches to Ulrich for glibc changes.
  • Christoph Hellwig thinks there should be a separate system call for deallocate functionality.
  • Mingming discussed an error case in current preallocation. If the entire filesystem is full, When an uninitialized extent is written to, there is no space to store the metadata blocks needed to split it into unintialized and initialized extents. Andreas' proposed solution is to fallback to writing zeroes out to the preallocated blocks. This issue can be resolved as a bug fix after preallocation is in mainline.
  • Mingming asked about implementing preallocation in ext2/3. It was decided that this is not desirable, as it is an advanced change, and our current focus is ext4.

Nanosecond Timestamps:

  • Negative timestamps: Temporary solution will be to round small negative timestamps within a close range to the epoch to zero. Large negative timestamps would be converted to positive. This can later be fixed to have signed timestamps.

Delayed Allocation:

  • We will try to push the delalloc feature for ext4 to mainline.
  • It is currently below the unstable patch marker in the queue, because of possible vfs implementation of delalloc.
  • After the rest of the ext4 patches are pushed; then we will work to push delalloc. These can even be included after 2.6.23-rc1, since there are no major format changes.
  • If later there is a vfs level delalloc implemented, we can then take out support for delalloc from within ext4.

Inode Version:

  • Trond has requested a flag in the superblock indicating i_version as on or off, rather than using a mount option.
  • Plan is to remove the last i_version patch, which supports disabling i_version through a mount option. Mingming will remove this patch from the path queue. The issue can be resolved once the feature is in mainline.


  • Aneesh will resend a patch witha fix to the block reservation; to be added to the patch queue.
  • Aneesh had ported the mballoc patches to the current patch queue. The patch was too large to send to the mailing list. He has found some issues with the patches, and will work on fixing those before requesting review.
  • Aneesh suggested adding 'from: author' to each patch to capture who the real author of each feature is.


  • Now that version 1.40 is out, Ted will focus on merging in the extetns support patches, and trying to have full exents support.
  • Ted will also start merging other small patches, such as large number of subdirectory support, and nanosecond timestamps.
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