Ah okay, I now see how it works. Thanks a lot for your response. Regards, Aastha.
On 25 February 2013 18:27, Josef Bacik <jba...@fusionio.com> wrote: > On Mon, Feb 25, 2013 at 08:15:40AM -0700, Aastha Mehta wrote: >> Thanks again Josef. >> >> I understood that cow_file_range is called for a regular file. Just to >> clarify, in cow_file_range is cow done at the time of reserving >> extents in the extent btree for the io to be done in this delalloc? I >> see the following comment above find_free_extent() which is called >> while trying to reserve extents: >> >> /* >> * walks the btree of allocated extents and find a hole of a given size. >> * The key ins is changed to record the hole: >> * ins->objectid == block start >> * ins->flags = BTRFS_EXTENT_ITEM_KEY >> * ins->offset == number of blocks >> * Any available blocks before search_start are skipped. >> */ >> >> This seems to be the only place where a cow might be done, because a >> key is being inserted into an extent which modifies it. >> > > The key isn't inserted at this time, it's just returned with those values for > us > to do as we please. There is no update of the btree until > insert_reserved_extent/btrfs_mark_extent_written in btrfs_finish_ordered_io. > Thanks, > > Josef -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
