---- 在 星期一, 2021-03-29 23:13:52 Miklos Szeredi <miklos@xxxxxxxxxx> 撰写 ---- > On Mon, Mar 8, 2021 at 12:17 PM Chengguang Xu <cgxu519@xxxxxxxxxxxx> wrote: > > > > Currently copy-up will copy whole lower file to upper > > regardless of the data range which is needed for further > > operation. This patch avoids unnecessary copy when truncate > > size is smaller than the file size. > > This doesn't look right. If copy up succeeds, resulting in a > truncated file, then we should return success there and then. Doing > the truncate again and failing (unlikely, but I wouldn't think it > impossible) wouldn't be nice. > > But need to be careful, because we could possibly have other attribute > change requests besides ATTR_SIZE, in which case optimizing the > truncate away and returning success wouldn't be correct. OK, I'll modify in V2. > > Minor issue: this patch doesn't optimize the truncate to zero case. > That's not a bug, but I'm curious if that is an oversight or > deliberate. > I overlooked that case because all our cases use O_TRUNC flag on open time when truncate to zero size. How about specify O_TRUNC flag when calling copy-up function for this case? Thanks, Chengguang
