Jan Kara wrote: >> On Tue, Jul 28, 2009 at 05:28:05PM -0700, Curt Wohlgemuth wrote: ... >> 2) We can modify the ext4_ext_convert_to_initialized() to be more >> aggressive about initializing data blocks if we know we are doing DIO, >> since zero'ing an aligned 16 to 32 blocks and then waiting for the >> journal commit once is cheaper than converting the extent one block at >> a time and waiting for the journal commit after each block write. > Definitely. I'm not following the discussion too much in detail but > what seems to me is the following could work: > The direct IO path would first send all the data to disk to the > desired location (get_block wouldn't do any conversion, just map blocks). > When this is done, we convert all the touched extents to initialized ones > from ext4_direct_IO, update i_size if needed, and wait for transaction > commit. > > Honza This is all about right, but it's tricky, because right now, get_block is called in the direct IO path from get_more_blocks(), and it's called with create == 0 unless OWN_LOCKING is specified. If we do get_block w/ create == 0 and find prealloc'd blocks, then we're given back unmapped buffer heads. This looks like a hole, and so DIO falls back to buffered. Right now the only way to get create == 1 sent to get_blocks via directio is to do OWN_LOCKING, which implies... we have to do our own locking, and it'll take some time to get it right I think. -Eric -- 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
