On Mon, Mar 17, 2014 at 01:28:04AM +0000, Al Viro wrote: > but that is unsafe - consider a situation when you are writing 20Kb from e.g. > 0.5Kb offset from the beginning of last (4Kb) block. You have 6 blocks > affected, right? One old, five new. And you want the last half-kilobyte s/the last/all but the first/, sorry. Basically, we want to get from OOOOOOOO (8 sectors of old data) to ONNNNNNN|NNNNNNNN|NNNNNNNN|NNNNNNNN|NNNNNNNN|NZZZZZZZ (1 sector of old data, 40 sectors of new data, 7 sectors of zeroes). We want the last 7 sectors zeroed out, but we do *not* want that to happen to the one sector of old data. OTOH, if the file had been 4K shorter (and all blocks had been new) we would want ZNNNNNNN|NNNNNNNN|NNNNNNNN|NNNNNNNN|NNNNNNNN|NZZZZZZZ. IOW, it's not just the last block we want to know about. There's simply not enough bandwidth in that interface to pass the information we would need for such mixed block runs... -- 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
