xfs: remove bitfield based superblock updates

When we log changes to the superblock, we first have to write them
to the on-disk buffer, and then log that. Right now we have a
complex bitfield based arrangement to only write the modified field
to the buffer before we log it.

This used to be necessary as a performance optimisation because we
logged the superblock buffer in every extent or inode allocation or
freeing, and so performance was extremely important. We haven't done
this for years, however, ever since the lazy superblock counters
pulled the superblock logging out of the transaction commit
fast path.

Hence we have a bunch of complexity that is not necessary that makes
writing the in-core superblock to disk much more complex than it
needs to be. We only need to log the superblock now during
management operations (e.g. during mount, unmount or quota control
operations) so it is not a performance critical path anymore.

As such, remove the complex field based logging mechanism and
replace it with a simple conversion function similar to what we use
for all other on-disk structures.

This means we always log the entirity of the superblock, but again
because we rarely modify the superblock this is not an issue for log
bandwidth or CPU time. Indeed, if we do log the superblock
frequently, delayed logging will minimise the impact of this
overhead.

[Fixed gquota/pquota inode sharing regression noticed by bfoster.]

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

1 files changed, 96 insertions, 181 deletions

diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
index 752915fa775a..115a7cd3a6fb 100644
--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c
@@ -40,69 +40,6 @@
  * Physical superblock buffer manipulations. Shared with libxfs in userspace.
  */
 
-static const struct {
-	short offset;
-	short type;	/* 0 = integer
-			 * 1 = binary / string (no translation)
-			 */
-} xfs_sb_info[] = {
-	{ offsetof(xfs_sb_t, sb_magicnum),	0 },
-	{ offsetof(xfs_sb_t, sb_blocksize),	0 },
-	{ offsetof(xfs_sb_t, sb_dblocks),	0 },
-	{ offsetof(xfs_sb_t, sb_rblocks),	0 },
-	{ offsetof(xfs_sb_t, sb_rextents),	0 },
-	{ offsetof(xfs_sb_t, sb_uuid),		1 },
-	{ offsetof(xfs_sb_t, sb_logstart),	0 },
-	{ offsetof(xfs_sb_t, sb_rootino),	0 },
-	{ offsetof(xfs_sb_t, sb_rbmino),	0 },
-	{ offsetof(xfs_sb_t, sb_rsumino),	0 },
-	{ offsetof(xfs_sb_t, sb_rextsize),	0 },
-	{ offsetof(xfs_sb_t, sb_agblocks),	0 },
-	{ offsetof(xfs_sb_t, sb_agcount),	0 },
-	{ offsetof(xfs_sb_t, sb_rbmblocks),	0 },
-	{ offsetof(xfs_sb_t, sb_logblocks),	0 },
-	{ offsetof(xfs_sb_t, sb_versionnum),	0 },
-	{ offsetof(xfs_sb_t, sb_sectsize),	0 },
-	{ offsetof(xfs_sb_t, sb_inodesize),	0 },
-	{ offsetof(xfs_sb_t, sb_inopblock),	0 },
-	{ offsetof(xfs_sb_t, sb_fname[0]),	1 },
-	{ offsetof(xfs_sb_t, sb_blocklog),	0 },
-	{ offsetof(xfs_sb_t, sb_sectlog),	0 },
-	{ offsetof(xfs_sb_t, sb_inodelog),	0 },
-	{ offsetof(xfs_sb_t, sb_inopblog),	0 },
-	{ offsetof(xfs_sb_t, sb_agblklog),	0 },
-	{ offsetof(xfs_sb_t, sb_rextslog),	0 },
-	{ offsetof(xfs_sb_t, sb_inprogress),	0 },
-	{ offsetof(xfs_sb_t, sb_imax_pct),	0 },
-	{ offsetof(xfs_sb_t, sb_icount),	0 },
-	{ offsetof(xfs_sb_t, sb_ifree),		0 },
-	{ offsetof(xfs_sb_t, sb_fdblocks),	0 },
-	{ offsetof(xfs_sb_t, sb_frextents),	0 },
-	{ offsetof(xfs_sb_t, sb_uquotino),	0 },
-	{ offsetof(xfs_sb_t, sb_gquotino),	0 },
-	{ offsetof(xfs_sb_t, sb_qflags),	0 },
-	{ offsetof(xfs_sb_t, sb_flags),		0 },
-	{ offsetof(xfs_sb_t, sb_shared_vn),	0 },
-	{ offsetof(xfs_sb_t, sb_inoalignmt),	0 },
-	{ offsetof(xfs_sb_t, sb_unit),		0 },
-	{ offsetof(xfs_sb_t, sb_width),		0 },
-	{ offsetof(xfs_sb_t, sb_dirblklog),	0 },
-	{ offsetof(xfs_sb_t, sb_logsectlog),	0 },
-	{ offsetof(xfs_sb_t, sb_logsectsize),	0 },
-	{ offsetof(xfs_sb_t, sb_logsunit),	0 },
-	{ offsetof(xfs_sb_t, sb_features2),	0 },
-	{ offsetof(xfs_sb_t, sb_bad_features2),	0 },
-	{ offsetof(xfs_sb_t, sb_features_compat),	0 },
-	{ offsetof(xfs_sb_t, sb_features_ro_compat),	0 },
-	{ offsetof(xfs_sb_t, sb_features_incompat),	0 },
-	{ offsetof(xfs_sb_t, sb_features_log_incompat),	0 },
-	{ offsetof(xfs_sb_t, sb_crc),		0 },
-	{ offsetof(xfs_sb_t, sb_pad),		0 },
-	{ offsetof(xfs_sb_t, sb_pquotino),	0 },
-	{ offsetof(xfs_sb_t, sb_lsn),		0 },
-	{ sizeof(xfs_sb_t),			0 }
-};
-
 /*
  * Reference counting access wrappers to the perag structures.
  * Because we never free per-ag structures, the only thing we
@@ -461,58 +398,49 @@ xfs_sb_from_disk(
 	__xfs_sb_from_disk(to, from, true);
 }
 
-static inline void
+static void
 xfs_sb_quota_to_disk(
-	xfs_dsb_t	*to,
-	xfs_sb_t	*from,
-	__int64_t	*fields)
+	struct xfs_dsb	*to,
+	struct xfs_sb	*from)
 {
 	__uint16_t	qflags = from->sb_qflags;
 
+	to->sb_uquotino = cpu_to_be64(from->sb_uquotino);
+	if (xfs_sb_version_has_pquotino(from)) {
+		to->sb_qflags = cpu_to_be16(from->sb_qflags);
+		to->sb_gquotino = cpu_to_be64(from->sb_gquotino);
+		to->sb_pquotino = cpu_to_be64(from->sb_pquotino);
+		return;
+	}
+
 	/*
-	 * We need to do these manipilations only if we are working
-	 * with an older version of on-disk superblock.
+	 * The in-core version of sb_qflags do not have XFS_OQUOTA_*
+	 * flags, whereas the on-disk version does.  So, convert incore
+	 * XFS_{PG}QUOTA_* flags to on-disk XFS_OQUOTA_* flags.
 	 */
-	if (xfs_sb_version_has_pquotino(from))
-		return;
+	qflags &= ~(XFS_PQUOTA_ENFD | XFS_PQUOTA_CHKD |
+			XFS_GQUOTA_ENFD | XFS_GQUOTA_CHKD);
 
-	if (*fields & XFS_SB_QFLAGS) {
-		/*
-		 * The in-core version of sb_qflags do not have
-		 * XFS_OQUOTA_* flags, whereas the on-disk version
-		 * does.  So, convert incore XFS_{PG}QUOTA_* flags
-		 * to on-disk XFS_OQUOTA_* flags.
-		 */
-		qflags &= ~(XFS_PQUOTA_ENFD | XFS_PQUOTA_CHKD |
-				XFS_GQUOTA_ENFD | XFS_GQUOTA_CHKD);
-
-		if (from->sb_qflags &
-				(XFS_PQUOTA_ENFD | XFS_GQUOTA_ENFD))
-			qflags |= XFS_OQUOTA_ENFD;
-		if (from->sb_qflags &
-				(XFS_PQUOTA_CHKD | XFS_GQUOTA_CHKD))
-			qflags |= XFS_OQUOTA_CHKD;
-		to->sb_qflags = cpu_to_be16(qflags);
-		*fields &= ~XFS_SB_QFLAGS;
-	}
+	if (from->sb_qflags &
+			(XFS_PQUOTA_ENFD | XFS_GQUOTA_ENFD))
+		qflags |= XFS_OQUOTA_ENFD;
+	if (from->sb_qflags &
+			(XFS_PQUOTA_CHKD | XFS_GQUOTA_CHKD))
+		qflags |= XFS_OQUOTA_CHKD;
+	to->sb_qflags = cpu_to_be16(qflags);
 
 	/*
-	 * GQUOTINO and PQUOTINO cannot be used together in versions of
-	 * superblock that do not have pquotino. from->sb_flags tells us which
-	 * quota is active and should be copied to disk. If neither are active,
-	 * make sure we write NULLFSINO to the sb_gquotino field as a quota
-	 * inode value of "0" is invalid when the XFS_SB_VERSION_QUOTA feature
-	 * bit is set.
+	 * GQUOTINO and PQUOTINO cannot be used together in versions
+	 * of superblock that do not have pquotino. from->sb_flags
+	 * tells us which quota is active and should be copied to
+	 * disk. If neither are active, we should NULL the inode.
 	 *
-	 * Note that we don't need to handle the sb_uquotino or sb_pquotino here
-	 * as they do not require any translation. Hence the main sb field loop
-	 * will write them appropriately from the in-core superblock.
+	 * In all cases, the separate pquotino must remain 0 because it
+	 * it beyond the "end" of the valid non-pquotino superblock.
 	 */
-	if ((*fields & XFS_SB_GQUOTINO) &&
-				(from->sb_qflags & XFS_GQUOTA_ACCT))
+	if (from->sb_qflags & XFS_GQUOTA_ACCT)
 		to->sb_gquotino = cpu_to_be64(from->sb_gquotino);
-	else if ((*fields & XFS_SB_PQUOTINO) &&
-				(from->sb_qflags & XFS_PQUOTA_ACCT))
+	else if (from->sb_qflags & XFS_PQUOTA_ACCT)
 		to->sb_gquotino = cpu_to_be64(from->sb_pquotino);
 	else {
 		/*
@@ -526,63 +454,72 @@ xfs_sb_quota_to_disk(
 			to->sb_gquotino = cpu_to_be64(NULLFSINO);
 	}
 
-	*fields &= ~(XFS_SB_PQUOTINO | XFS_SB_GQUOTINO);
+	to->sb_pquotino = 0;
 }
 
-/*
- * Copy in core superblock to ondisk one.
- *
- * The fields argument is mask of superblock fields to copy.
- */
 void
 xfs_sb_to_disk(
-	xfs_dsb_t	*to,
-	xfs_sb_t	*from,
-	__int64_t	fields)
+	struct xfs_dsb	*to,
+	struct xfs_sb	*from)
 {
-	xfs_caddr_t	to_ptr = (xfs_caddr_t)to;
-	xfs_caddr_t	from_ptr = (xfs_caddr_t)from;
-	xfs_sb_field_t	f;
-	int		first;
-	int		size;
-
-	ASSERT(fields);
-	if (!fields)
-		return;
+	xfs_sb_quota_to_disk(to, from);
+
+	to->sb_magicnum = cpu_to_be32(from->sb_magicnum);
+	to->sb_blocksize = cpu_to_be32(from->sb_blocksize);
+	to->sb_dblocks = cpu_to_be64(from->sb_dblocks);
+	to->sb_rblocks = cpu_to_be64(from->sb_rblocks);
+	to->sb_rextents = cpu_to_be64(from->sb_rextents);
+	memcpy(&to->sb_uuid, &from->sb_uuid, sizeof(to->sb_uuid));
+	to->sb_logstart = cpu_to_be64(from->sb_logstart);
+	to->sb_rootino = cpu_to_be64(from->sb_rootino);
+	to->sb_rbmino = cpu_to_be64(from->sb_rbmino);
+	to->sb_rsumino = cpu_to_be64(from->sb_rsumino);
+	to->sb_rextsize = cpu_to_be32(from->sb_rextsize);
+	to->sb_agblocks = cpu_to_be32(from->sb_agblocks);
+	to->sb_agcount = cpu_to_be32(from->sb_agcount);
+	to->sb_rbmblocks = cpu_to_be32(from->sb_rbmblocks);
+	to->sb_logblocks = cpu_to_be32(from->sb_logblocks);
+	to->sb_versionnum = cpu_to_be16(from->sb_versionnum);
+	to->sb_sectsize = cpu_to_be16(from->sb_sectsize);
+	to->sb_inodesize = cpu_to_be16(from->sb_inodesize);
+	to->sb_inopblock = cpu_to_be16(from->sb_inopblock);
+	memcpy(&to->sb_fname, &from->sb_fname, sizeof(to->sb_fname));
+	to->sb_blocklog = from->sb_blocklog;
+	to->sb_sectlog = from->sb_sectlog;
+	to->sb_inodelog = from->sb_inodelog;
+	to->sb_inopblog = from->sb_inopblog;
+	to->sb_agblklog = from->sb_agblklog;
+	to->sb_rextslog = from->sb_rextslog;
+	to->sb_inprogress = from->sb_inprogress;
+	to->sb_imax_pct = from->sb_imax_pct;
+	to->sb_icount = cpu_to_be64(from->sb_icount);
+	to->sb_ifree = cpu_to_be64(from->sb_ifree);
+	to->sb_fdblocks = cpu_to_be64(from->sb_fdblocks);
+	to->sb_frextents = cpu_to_be64(from->sb_frextents);
 
-	/* We should never write the crc here, it's updated in the IO path */
-	fields &= ~XFS_SB_CRC;
-
-	xfs_sb_quota_to_disk(to, from, &fields);
-	while (fields) {
-		f = (xfs_sb_field_t)xfs_lowbit64((__uint64_t)fields);
-		first = xfs_sb_info[f].offset;
-		size = xfs_sb_info[f + 1].offset - first;
-
-		ASSERT(xfs_sb_info[f].type == 0 || xfs_sb_info[f].type == 1);
-
-		if (size == 1 || xfs_sb_info[f].type == 1) {
-			memcpy(to_ptr + first, from_ptr + first, size);
-		} else {
-			switch (size) {
-			case 2:
-				*(__be16 *)(to_ptr + first) =
-				      cpu_to_be16(*(__u16 *)(from_ptr + first));
-				break;
-			case 4:
-				*(__be32 *)(to_ptr + first) =
-				      cpu_to_be32(*(__u32 *)(from_ptr + first));
-				break;
-			case 8:
-				*(__be64 *)(to_ptr + first) =
-				      cpu_to_be64(*(__u64 *)(from_ptr + first));
-				break;
-			default:
-				ASSERT(0);
-			}
-		}
 
-		fields &= ~(1LL << f);
+	to->sb_flags = from->sb_flags;
+	to->sb_shared_vn = from->sb_shared_vn;
+	to->sb_inoalignmt = cpu_to_be32(from->sb_inoalignmt);
+	to->sb_unit = cpu_to_be32(from->sb_unit);
+	to->sb_width = cpu_to_be32(from->sb_width);
+	to->sb_dirblklog = from->sb_dirblklog;
+	to->sb_logsectlog = from->sb_logsectlog;
+	to->sb_logsectsize = cpu_to_be16(from->sb_logsectsize);
+	to->sb_logsunit = cpu_to_be32(from->sb_logsunit);
+	to->sb_features2 = cpu_to_be32(from->sb_features2);
+	to->sb_bad_features2 = cpu_to_be32(from->sb_bad_features2);
+
+	if (xfs_sb_version_hascrc(from)) {
+		to->sb_features_compat = cpu_to_be32(from->sb_features_compat);
+		to->sb_features_ro_compat =
+				cpu_to_be32(from->sb_features_ro_compat);
+		to->sb_features_incompat =
+				cpu_to_be32(from->sb_features_incompat);
+		to->sb_features_log_incompat =
+				cpu_to_be32(from->sb_features_log_incompat);
+		to->sb_pad = 0;
+		to->sb_lsn = cpu_to_be64(from->sb_lsn);
 	}
 }
 
@@ -823,35 +760,13 @@ xfs_initialize_perag_data(
  * access.
  */
 void
-xfs_mod_sb(xfs_trans_t *tp, __int64_t fields)
+xfs_mod_sb(
+	struct xfs_trans	*tp)
 {
-	xfs_buf_t	*bp;
-	int		first;
-	int		last;
-	xfs_mount_t	*mp;
-	xfs_sb_field_t	f;
-
-	ASSERT(fields);
-	if (!fields)
-		return;
-	mp = tp->t_mountp;
-	bp = xfs_trans_getsb(tp, mp, 0);
-	first = sizeof(xfs_sb_t);
-	last = 0;
-
-	/* translate/copy */
-
-	xfs_sb_to_disk(XFS_BUF_TO_SBP(bp), &mp->m_sb, fields);
-
-	/* find modified range */
-	f = (xfs_sb_field_t)xfs_highbit64((__uint64_t)fields);
-	ASSERT((1LL << f) & XFS_SB_MOD_BITS);
-	last = xfs_sb_info[f + 1].offset - 1;
-
-	f = (xfs_sb_field_t)xfs_lowbit64((__uint64_t)fields);
-	ASSERT((1LL << f) & XFS_SB_MOD_BITS);
-	first = xfs_sb_info[f].offset;
+	struct xfs_mount	*mp = tp->t_mountp;
+	struct xfs_buf		*bp = xfs_trans_getsb(tp, mp, 0);
 
+	xfs_sb_to_disk(XFS_BUF_TO_SBP(bp), &mp->m_sb);
 	xfs_trans_buf_set_type(tp, bp, XFS_BLFT_SB_BUF);
-	xfs_trans_log_buf(tp, bp, first, last);
+	xfs_trans_log_buf(tp, bp, 0, sizeof(struct xfs_dsb));
 }