On Wed, Jan 09 2008, Andi Kleen wrote: > Jens Axboe <jens.axboe@xxxxxxxxxx> writes: > > > > So how does it work? Instead of punting IO to a thread and passing it > > through the page cache, we instead attempt to send the IO directly to the > > Great -- something like this was needed for a long time. > > > - The file block mappings must not change while loop is using the file. > > This means that we have to ensure exclusive access to the file and > > this is the bit that is currently missing in the implementation. It > > would be nice if we could just do this via open(), ideas welcome... > > get_write_access()/put_write_access() will block other writers. > > But as pointed out by others that is not enough for this. Yeah, basically allowing O_RDONLY | O_DIRECT opens should be ok, but we can't allow writes and we can't allow page cache to exist for this file outside of loop. > I suppose you could use a white list like a special flag for file systems > (like ext2/ext3) that do not reallocate blocks. Irk, but yeah we probably need something like that for now until Chris proposes his API addition. -- Jens Axboe - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
