| Message ID | 159885400575.3608006.17716724192510967135.stgit@magnolia (mailing list archive) |
|---|---|
| Headers | show |
| Series | xfs: widen timestamps to deal with y2038 | expand |
On Mon, Aug 31, 2020 at 9:08 AM Darrick J. Wong <darrick.wong@oracle.com> wrote: > > Hi all, > > This series performs some refactoring of our timestamp and inode > encoding functions, then retrofits the timestamp union to handle > timestamps as a 64-bit nanosecond counter. Next, it adds bit shifting > to the non-root dquot timer fields to boost their effective size to 34 > bits. These two changes enable correct time handling on XFS through the > year 2486. > > On a current V5 filesystem, inodes timestamps are a signed 32-bit > seconds counter, with 0 being the Unix epoch. Quota timers are an > unsigned 32-bit seconds counter, with 0 also being the Unix epoch. > > This means that inode timestamps can range from: > -(2^31-1) (13 Dec 1901) through (2^31-1) (19 Jan 2038). > > And quota timers can range from: > 0 (1 Jan 1970) through (2^32-1) (7 Feb 2106). > > With the bigtime encoding turned on, inode timestamps are an unsigned > 64-bit nanoseconds counter, with 0 being the 1901 epoch. Quota timers > are a 34-bit unsigned second counter right shifted two bits, with 0 > being the Unix epoch, and capped at the maximum inode timestamp value. > > This means that inode timestamps can range from: > 0 (13 Dec 1901) through (2^64-1 / 1e9) (2 Jul 2486) > > Quota timers could theoretically range from: > 0 (1 Jan 1970) through (((2^34-1) + (2^31-1)) & ~3) (16 Jun 2582). > > But with the capping in place, the quota timers maximum is: > max((2^64-1 / 1e9) - (2^31-1), (((2^34-1) + (2^31-1)) & ~3) (2 Jul 2486). > > v2: rebase to 5.9, having landed the quota refactoring > v3: various suggestions by Amir and Dave > v4: drop the timestamp unions, add "is bigtime?" predicates everywhere > v5: reintroduce timestamp unions as *legacy* timestamp unions I went over the relevant patches briefly. I do not have time for thorough re-review and seems like you have enough reviewers already, but wanted to say that IMO v5 is "approachable" for novice xfs developers and I can follow the conversions easily, so that's probably a good thing ;-) Thanks, Amir.
On Mon, Aug 31, 2020 at 11:07:14AM +0300, Amir Goldstein wrote: > On Mon, Aug 31, 2020 at 9:08 AM Darrick J. Wong <darrick.wong@oracle.com> wrote: > > > > Hi all, > > > > This series performs some refactoring of our timestamp and inode > > encoding functions, then retrofits the timestamp union to handle > > timestamps as a 64-bit nanosecond counter. Next, it adds bit shifting > > to the non-root dquot timer fields to boost their effective size to 34 > > bits. These two changes enable correct time handling on XFS through the > > year 2486. > > > > On a current V5 filesystem, inodes timestamps are a signed 32-bit > > seconds counter, with 0 being the Unix epoch. Quota timers are an > > unsigned 32-bit seconds counter, with 0 also being the Unix epoch. > > > > This means that inode timestamps can range from: > > -(2^31-1) (13 Dec 1901) through (2^31-1) (19 Jan 2038). > > > > And quota timers can range from: > > 0 (1 Jan 1970) through (2^32-1) (7 Feb 2106). > > > > With the bigtime encoding turned on, inode timestamps are an unsigned > > 64-bit nanoseconds counter, with 0 being the 1901 epoch. Quota timers > > are a 34-bit unsigned second counter right shifted two bits, with 0 > > being the Unix epoch, and capped at the maximum inode timestamp value. > > > > This means that inode timestamps can range from: > > 0 (13 Dec 1901) through (2^64-1 / 1e9) (2 Jul 2486) > > > > Quota timers could theoretically range from: > > 0 (1 Jan 1970) through (((2^34-1) + (2^31-1)) & ~3) (16 Jun 2582). > > > > But with the capping in place, the quota timers maximum is: > > max((2^64-1 / 1e9) - (2^31-1), (((2^34-1) + (2^31-1)) & ~3) (2 Jul 2486). > > > > v2: rebase to 5.9, having landed the quota refactoring > > v3: various suggestions by Amir and Dave > > v4: drop the timestamp unions, add "is bigtime?" predicates everywhere > > v5: reintroduce timestamp unions as *legacy* timestamp unions > > I went over the relevant patches briefly. > I do not have time for thorough re-review and seems like you have enough > reviewers already, but wanted to say that IMO v5 is "approachable" for > novice xfs developers and I can follow the conversions easily, so that's > probably a good thing ;-) <nod> Thanks for the review! Good to see you at LPC last week too! --D > Thanks, > Amir.