On Wed, 2006-12-13 at 15:31 +0530, Amit K. Arora wrote: > On Tue, Dec 12, 2006 at 04:20:38PM -0800, Mingming Cao wrote: > > On Tue, 2006-12-12 at 11:53 +0530, Amit K. Arora wrote: > > Supporting preallocation for extent based files seems fairly > > straightforward. I agree we should look at this first. After get this > > done, it probably worth re-consider whether to support preallocation for > > non-extent based files on ext4. I could imagine user upgrade from ext3 > > to ext4, and expecting to use preallocation on those existing files.... I disagree here. Why add the complexity for what is going to be a rare case? In cases where a user is going to benefit from preallocation, she'll probably also benefit from extents, and would be better off making a copy of the file, thus converting it to extents. > I gave a thought on this initially. But, I was not sure how we should > implement preallocation in a non-extent based file. Using extents we can > mark a set of blocks as unitialized, but how will we do this for > non-extent based files ? If we do not have a way to mark blocks > uninitialized, when someone will try to read from a preallocated block, > it will return junk/stale data instead of zeroes. If anything, the block-based preallocation could initialize all of the data to zero. It would be slow, but it would still provide the correct function and result in contiguous allocation. Shaggy -- David Kleikamp IBM Linux Technology Center - 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
