> -----Original Message----- > From: linux-fsdevel-owner@xxxxxxxxxxxxxxx [mailto:linux-fsdevel- > owner@xxxxxxxxxxxxxxx] On Behalf Of Pádraig Brady > Sent: Monday, November 28, 2011 4:55 PM > To: Dave Chinner > Cc: Theodore Tso; Christoph Hellwig; linux-fsdevel@xxxxxxxxxxxxxxx > Subject: Re: fallocate vs ENOSPC > > On 11/28/2011 05:10 AM, Dave Chinner wrote: > > Quite frankly, if system utilities like cp and tar start to abuse > > fallocate() by default so they can get "upfront ENOSPC detection", > > then I will seriously consider making XFS use delayed allocation for > > fallocate rather than unwritten extents so we don't lose the past 15 > > years worth of IO and aging optimisations that delayed allocation > > provides us with.... > > For the record I was considering fallocate() for these reasons. > > 1. Improved file layout for subsequent access > 2. Immediate indication of ENOSPC > 3. Efficient writing of NUL portions > > You lucidly detailed issues with 1. which I suppose could be somewhat > mitigated by not fallocating < say 1MB, though I suppose file systems > could be smarter here and not preallocate small chunks (or when > otherwise not appropriate). We can already get ENOSPC from a write() > after an fallocate() in certain edge cases, so it would probably make > sense to expand those cases. > Just out of curiosity, how is it going to work with sparse files? By default, cp uses --sparse=auto. And for sparse files, it avoids some disk allocation automatically. With fallocate(), do you plan to change the semantics? Cheers, Tao > cheers, > Pádraig. > -- > 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 ��.n��������+%������w��{.n�����{���)�� jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
