On Thu, Jul 11, 2024 at 11:58:59AM -0400, Jeff Layton wrote: > On Thu, 2024-07-11 at 08:09 -0700, Darrick J. Wong wrote: > > On Thu, Jul 11, 2024 at 07:08:10AM -0400, Jeff Layton wrote: > > > Enable multigrain timestamps, which should ensure that there is an > > > apparent change to the timestamp whenever it has been written after > > > being actively observed via getattr. > > > > > > Also, anytime the mtime changes, the ctime must also change, and those > > > are now the only two options for xfs_trans_ichgtime. Have that function > > > unconditionally bump the ctime, and ASSERT that XFS_ICHGTIME_CHG is > > > always set. > > > > > > Finally, stop setting STATX_CHANGE_COOKIE in getattr, since the ctime > > > should give us better semantics now. > > > > Following up on "As long as the fs isn't touching i_ctime_nsec directly, > > you shouldn't need to worry about this" from: > > https://lore.kernel.org/linux-xfs/cae5c28f172ac57b7eaaa98a00b23f342f01ba64.camel@xxxxxxxxxx/ > > > > xfs /does/ touch i_ctime_nsec directly when it's writing inodes to disk. > > From xfs_inode_to_disk, see: > > > > to->di_ctime = xfs_inode_to_disk_ts(ip, inode_get_ctime(inode)); > > > > AFAICT, inode_get_ctime itself remains unchanged, and still returns > > inode->__i_ctime, right? In which case it's returning a raw timespec64, > > which can include the QUERIED flag in tv_nsec, right? > > > > No, in the first patch in the series, inode_get_ctime becomes this: > > #define I_CTIME_QUERIED ((u32)BIT(31)) > > static inline time64_t inode_get_ctime_sec(const struct inode *inode) > { > return inode->i_ctime_sec; > } > > static inline long inode_get_ctime_nsec(const struct inode *inode) > { > return inode->i_ctime_nsec & ~I_CTIME_QUERIED; > } > > static inline struct timespec64 inode_get_ctime(const struct inode *inode) > { > struct timespec64 ts = { .tv_sec = inode_get_ctime_sec(inode), > .tv_nsec = inode_get_ctime_nsec(inode) }; > > return ts; > } Doh! I forgot that this has already been soaking in the vfs tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/include/linux/fs.h?h=next-20240711&id=3aa63a569c64e708df547a8913c84e64a06e7853 > ...which should ensure that you never store the QUERIED bit. So yep, we're fine here. Sorry about the noise; this was the very subtle clue in the diff that the change had already been applied: static inline struct timespec64 inode_get_ctime(const struct inode *inode) @@ -1626,13 +1637,7 @@ static inline struct timespec64 inode_get_ctime(const struct inode *inode) return ts; } (Doh doh doh doh doh...) > > Now let's look at the consumer: > > > > static inline xfs_timestamp_t > > xfs_inode_to_disk_ts( > > struct xfs_inode *ip, > > const struct timespec64 tv) > > { > > struct xfs_legacy_timestamp *lts; > > xfs_timestamp_t ts; > > > > if (xfs_inode_has_bigtime(ip)) > > return cpu_to_be64(xfs_inode_encode_bigtime(tv)); > > > > lts = (struct xfs_legacy_timestamp *)&ts; > > lts->t_sec = cpu_to_be32(tv.tv_sec); > > lts->t_nsec = cpu_to_be32(tv.tv_nsec); > > > > return ts; > > } > > > > For the !bigtime case (aka before we added y2038 support) the queried > > flag gets encoded into the tv_nsec field since xfs doesn't filter the > > queried flag. > > > > For the bigtime case, the timespec is turned into an absolute nsec count > > since the xfs epoch (which is the minimum timestamp possible under the > > old encoding scheme): > > > > static inline uint64_t xfs_inode_encode_bigtime(struct timespec64 tv) > > { > > return xfs_unix_to_bigtime(tv.tv_sec) * NSEC_PER_SEC + tv.tv_nsec; > > } > > > > Here we'd also be mixing in the QUERIED flag, only now we've encoded a > > time that's a second in the future. I think the solution is to add a: > > > > static inline struct timespec64 > > inode_peek_ctime(const struct inode *inode) > > { > > return (struct timespec64){ > > .tv_sec = inode->__i_ctime.tv_sec, > > .tv_nsec = inode->__i_ctime.tv_nsec & ~I_CTIME_QUERIED, > > }; > > } > > > > similar to what inode_peek_iversion does for iversion; and then > > xfs_inode_to_disk can do: > > > > to->di_ctime = xfs_inode_to_disk_ts(ip, inode_peek_ctime(inode)); > > > > which would prevent I_CTIME_QUERIED from going out to disk. > > > > At load time, xfs_inode_from_disk uses inode_set_ctime_to_ts so I think > > xfs won't accidentally introduce QUERIED when it's loading an inode from > > disk. > > > > > > Also already done in this patchset: > > struct timespec64 inode_set_ctime_to_ts(struct inode *inode, struct timespec64 ts) > { > inode->i_ctime_sec = ts.tv_sec; > inode->i_ctime_nsec = ts.tv_nsec & ~I_CTIME_QUERIED; > trace_inode_set_ctime_to_ts(inode, &ts); > return ts; > } > EXPORT_SYMBOL(inode_set_ctime_to_ts); > > Basically, we never want to store or fetch the QUERIED flag from disk, > and since it's in an unused bit, we can just universally mask it off > when dealing with "external" users of it. > > One caveat -- I am using the sign bit for the QUERIED flag, so I'm > assuming that no one should ever pass inode_set_ctime_to_ts a negative > tv_nsec value. > > Maybe I should add a WARN_ON_ONCE here to check for that? It seems > nonsensical, but you never know... Well in theory filesystems should validate incoming timestamps and reject tv_nsec with the high bit set, but I'd bet there's a filesystem out there that allows negative nanoseconds, even if the kernel will never pass it such a thing. ;) > > > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> > > > --- > > > fs/xfs/libxfs/xfs_trans_inode.c | 6 +++--- > > > fs/xfs/xfs_iops.c | 10 +++------- > > > fs/xfs/xfs_super.c | 2 +- > > > 3 files changed, 7 insertions(+), 11 deletions(-) > > > > > > diff --git a/fs/xfs/libxfs/xfs_trans_inode.c b/fs/xfs/libxfs/xfs_trans_inode.c > > > index 69fc5b981352..1f3639bbf5f0 100644 > > > --- a/fs/xfs/libxfs/xfs_trans_inode.c > > > +++ b/fs/xfs/libxfs/xfs_trans_inode.c > > > @@ -62,12 +62,12 @@ xfs_trans_ichgtime( > > > ASSERT(tp); > > > xfs_assert_ilocked(ip, XFS_ILOCK_EXCL); > > > > > > - tv = current_time(inode); > > > + /* If the mtime changes, then ctime must also change */ > > > + ASSERT(flags & XFS_ICHGTIME_CHG); > > > > > > + tv = inode_set_ctime_current(inode); > > > if (flags & XFS_ICHGTIME_MOD) > > > inode_set_mtime_to_ts(inode, tv); > > > - if (flags & XFS_ICHGTIME_CHG) > > > - inode_set_ctime_to_ts(inode, tv); > > > if (flags & XFS_ICHGTIME_CREATE) > > > ip->i_crtime = tv; And as I mentioned elsewhere in this thread, 6.11 contains a change to make it so that xfs_trans_ichgtime can set the access time. That breaks the old assertion that XFS_ICHGTIME_CHG is always set, but I think we can work around that easily. if (flags & XFS_ICHGTIME_CHG) tv = inode_set_ctime_current(inode); else tv = current_time(inode); --D > > > } > > > diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c > > > index a00dcbc77e12..d25872f818fa 100644 > > > --- a/fs/xfs/xfs_iops.c > > > +++ b/fs/xfs/xfs_iops.c > > > @@ -592,8 +592,9 @@ xfs_vn_getattr( > > > stat->gid = vfsgid_into_kgid(vfsgid); > > > stat->ino = ip->i_ino; > > > stat->atime = inode_get_atime(inode); > > > - stat->mtime = inode_get_mtime(inode); > > > - stat->ctime = inode_get_ctime(inode); > > > + > > > + fill_mg_cmtime(stat, request_mask, inode); > > > + > > > stat->blocks = XFS_FSB_TO_BB(mp, ip->i_nblocks + ip->i_delayed_blks); > > > > > > if (xfs_has_v3inodes(mp)) { > > > @@ -603,11 +604,6 @@ xfs_vn_getattr( > > > } > > > } > > > > > > - if ((request_mask & STATX_CHANGE_COOKIE) && IS_I_VERSION(inode)) { > > > - stat->change_cookie = inode_query_iversion(inode); > > > - stat->result_mask |= STATX_CHANGE_COOKIE; > > > - } > > > - > > > /* > > > * Note: If you add another clause to set an attribute flag, please > > > * update attributes_mask below. > > > diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c > > > index 27e9f749c4c7..210481b03fdb 100644 > > > --- a/fs/xfs/xfs_super.c > > > +++ b/fs/xfs/xfs_super.c > > > @@ -2052,7 +2052,7 @@ static struct file_system_type xfs_fs_type = { > > > .init_fs_context = xfs_init_fs_context, > > > .parameters = xfs_fs_parameters, > > > .kill_sb = xfs_kill_sb, > > > - .fs_flags = FS_REQUIRES_DEV | FS_ALLOW_IDMAP, > > > + .fs_flags = FS_REQUIRES_DEV | FS_ALLOW_IDMAP | FS_MGTIME, > > > }; > > > MODULE_ALIAS_FS("xfs"); > > > > > > > > > -- > > > 2.45.2 > > > > > -- > Jeff Layton <jlayton@xxxxxxxxxx>
