On Wed, May 09, 2007 at 09:31:02PM +0530, Amit K. Arora wrote: > I have the updated patches ready which take care of Andrew's comments. > Will run some tests and post them soon. > > But, before submitting these patches, I think it will be better to finalize > on certain things which might be worth some discussion here: > > 1) Should the file size change when preallocation is done beyond EOF ? > - Andreas and Chris Wedgwood are in favor of not changing the > file size in this case. I also tend to agree with them. Does anyone > has an argument in favor of changing the filesize ? > If not, I will remove the code which changes the filesize, before I > resubmit the concerned ext4 patch. I think there needs to be both. If we don't have a mechanism to atomically change the file size with the preallocation, then applications that use stat() to work out if they need to preallocate more space will end up racing. > 2) For FA_UNALLOCATE mode, should the file system allow unallocation > of normal (non-preallocated) blocks (blocks allocated via > regular write/truncate operations) also (i.e. work as punch()) ? Yes. That is the current XFS implementation for XFS_IOC_UNRESVSP, and what i did for FA_UNALLOCATE as well. > - Though FA_UNALLOCATE mode is yet to be implemented on ext4, still > we need to finalize on the convention here as a general guideline > to all the filesystems that implement fallocate. > > 3) If above is true, the file size will need to be changed > for "unallocation" when block holding the EOF gets unallocated. No - we punch a hole. If you want the filesize to change, then you use ftruncate() to remove the blocks at EOF and change the file size atomically. > 4) Should we update mtime & ctime on a successfull allocation/ > unallocation ? > - David Chinner raised this question in following post: > http://lkml.org/lkml/2007/4/29/407 > I think it makes sense to update the [mc]time for a successfull > preallocation/unallocation. Does anyone feel otherwise ? > It will be interesting to know how XFS behaves currently. Does XFS > update [mc]time for preallocation ? No, XFS does *not* update a/m/ctime on prealloc/punch unless the file size changes. If the filesize changes, it behaves exactly the same way that ftruncate() behaves. Cheers, Dave. -- Dave Chinner Principal Engineer SGI Australian Software Group - To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
