On 25 Mar 2022 at 03:10, Darrick J. Wong wrote: > On Fri, Mar 25, 2022 at 08:37:19AM +1100, Dave Chinner wrote: >> On Mon, Mar 21, 2022 at 10:47:39AM +0530, Chandan Babu R wrote: >> > XFS_SB_FEAT_INCOMPAT_NREXT64 incompat feature bit will be set on filesystems >> > which support large per-inode extent counters. This commit defines the new >> > incompat feature bit and the corresponding per-fs feature bit (along with >> > inline functions to work on it). >> > >> > Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx> >> > Signed-off-by: Chandan Babu R <chandan.babu@xxxxxxxxxx> >> > --- >> > fs/xfs/libxfs/xfs_format.h | 1 + >> > fs/xfs/libxfs/xfs_sb.c | 3 +++ >> > fs/xfs/xfs_mount.h | 2 ++ >> > 3 files changed, 6 insertions(+) >> > >> > diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h >> > index b5e9256d6d32..64ff0c310696 100644 >> > --- a/fs/xfs/libxfs/xfs_format.h >> > +++ b/fs/xfs/libxfs/xfs_format.h >> > @@ -372,6 +372,7 @@ xfs_sb_has_ro_compat_feature( >> > #define XFS_SB_FEAT_INCOMPAT_META_UUID (1 << 2) /* metadata UUID */ >> > #define XFS_SB_FEAT_INCOMPAT_BIGTIME (1 << 3) /* large timestamps */ >> > #define XFS_SB_FEAT_INCOMPAT_NEEDSREPAIR (1 << 4) /* needs xfs_repair */ >> > +#define XFS_SB_FEAT_INCOMPAT_NREXT64 (1 << 5) /* large extent counters */ >> > #define XFS_SB_FEAT_INCOMPAT_ALL \ >> > (XFS_SB_FEAT_INCOMPAT_FTYPE| \ >> > XFS_SB_FEAT_INCOMPAT_SPINODES| \ >> > diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c >> > index f4e84aa1d50a..bd632389ae92 100644 >> > --- a/fs/xfs/libxfs/xfs_sb.c >> > +++ b/fs/xfs/libxfs/xfs_sb.c >> > @@ -124,6 +124,9 @@ xfs_sb_version_to_features( >> > features |= XFS_FEAT_BIGTIME; >> > if (sbp->sb_features_incompat & XFS_SB_FEAT_INCOMPAT_NEEDSREPAIR) >> > features |= XFS_FEAT_NEEDSREPAIR; >> > + if (sbp->sb_features_incompat & XFS_SB_FEAT_INCOMPAT_NREXT64) >> > + features |= XFS_FEAT_NREXT64; >> > + >> >> Shouldn't enabling the feature be the last patch in the series, once >> all the infrastructure to support the feature is in place? i.e. if >> someone does a bisect on a XFS_FEAT_NREXT64 enabled filesystem, they >> can land in the middle of this series where the fs tries to use >> XFS_FEAT_NREXT64 but the functionality is not complete. > > The last patch of the series does exactly that, by adding NREXT64 to > XFS_SB_FEAT_INCOMPAT_ALL. > If a bisection lands on the current patch, the "Unknown incompat feature" check would cause the filesystem mount to fail. Hence, I think the code is safe since it does not allow partially implemented NREXT64 feature to be executed. -- chandan
