Commit 8e2c84df authored Apr 24, 2014 by Brian Foster Committed by Dave Chinner Apr 24, 2014

xfs: reserve v5 superblock read-only compat. feature bit for finobt



Reserve a v5 read-only compatibility feature bit for the finobt and
create the xfs_sb_version_hasfinobt() helper to determine whether
an fs has the feature enabled.

The finobt does not change existing on-disk structures, but must
remain consistent with the ialloc btree. Modifications from older
kernels would violate that constrant. Therefore, we restrict older
kernels to read-only mounts of finobt-enabled filesystems.

Note that this does not yet enable the ability to rw mount a finobt
fs (by setting the feature bit in the XFS_SB_FEAT_RO_COMPAT_ALL
mask).

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

parent 57bd3dbe

fs/xfs/xfs_sb.h

+7 −0

Original line number	Diff line number	Diff line
		@@ -587,6 +587,7 @@ xfs_sb_has_compat_feature(
		return (sbp->sb_features_compat & feature) != 0;
		}

		#define XFS_SB_FEAT_RO_COMPAT_FINOBT (1 << 0) /* free inode btree */
		#define XFS_SB_FEAT_RO_COMPAT_ALL 0
		#define XFS_SB_FEAT_RO_COMPAT_UNKNOWN ~XFS_SB_FEAT_RO_COMPAT_ALL
		static inline bool
		@@ -641,6 +642,12 @@ static inline int xfs_sb_version_hasftype(struct xfs_sb *sbp)
		(sbp->sb_features2 & XFS_SB_VERSION2_FTYPE));
		}

		static inline int xfs_sb_version_hasfinobt(xfs_sb_t *sbp)
		{
		return (XFS_SB_VERSION_NUM(sbp) == XFS_SB_VERSION_5) &&
		(sbp->sb_features_ro_compat & XFS_SB_FEAT_RO_COMPAT_FINOBT);
		}

		/*
		* end of superblock version macros
		*/