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xfs: remove bitfield based superblock updates
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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 <[email protected]>
Reviewed-by: Brian Foster <[email protected]>
Signed-off-by: Dave Chinner <[email protected]>
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@dchinner
Dave Chinner authored and dchinner committed Jan 21, 2015
1 parent 97bf6af commit 4d11a40
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Showing 11 changed files with 130 additions and 246 deletions.
2 changes: 1 addition & 1 deletion fs/xfs/libxfs/xfs_attr_leaf.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -403,7 +403,7 @@ xfs_sbversion_add_attr2(xfs_mount_t *mp, xfs_trans_t *tp)
if (!xfs_sb_version_hasattr2(&mp->m_sb)) {
xfs_sb_version_addattr2(&mp->m_sb);
spin_unlock(&mp->m_sb_lock);
xfs_mod_sb(tp, XFS_SB_VERSIONNUM | XFS_SB_FEATURES2);
xfs_mod_sb(tp);
} else
spin_unlock(&mp->m_sb_lock);
}
Expand Down
14 changes: 6 additions & 8 deletions fs/xfs/libxfs/xfs_bmap.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1221,22 +1221,20 @@ xfs_bmap_add_attrfork(
goto bmap_cancel;
if (!xfs_sb_version_hasattr(&mp->m_sb) ||
(!xfs_sb_version_hasattr2(&mp->m_sb) && version == 2)) {
__int64_t sbfields = 0;
bool mod_sb = false;

spin_lock(&mp->m_sb_lock);
if (!xfs_sb_version_hasattr(&mp->m_sb)) {
xfs_sb_version_addattr(&mp->m_sb);
sbfields |= XFS_SB_VERSIONNUM;
mod_sb = true;
}
if (!xfs_sb_version_hasattr2(&mp->m_sb) && version == 2) {
xfs_sb_version_addattr2(&mp->m_sb);
sbfields |= (XFS_SB_VERSIONNUM | XFS_SB_FEATURES2);
mod_sb = true;
}
if (sbfields) {
spin_unlock(&mp->m_sb_lock);
xfs_mod_sb(tp, sbfields);
} else
spin_unlock(&mp->m_sb_lock);
spin_unlock(&mp->m_sb_lock);
if (mod_sb)
xfs_mod_sb(tp);
}

error = xfs_bmap_finish(&tp, &flist, &committed);
Expand Down
277 changes: 96 additions & 181 deletions fs/xfs/libxfs/xfs_sb.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down Expand Up @@ -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 {
/*
Expand All @@ -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);
}
}

Expand Down Expand Up @@ -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));
}
10 changes: 5 additions & 5 deletions fs/xfs/libxfs/xfs_sb.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -27,11 +27,11 @@ extern struct xfs_perag *xfs_perag_get_tag(struct xfs_mount *, xfs_agnumber_t,
extern void xfs_perag_put(struct xfs_perag *pag);
extern int xfs_initialize_perag_data(struct xfs_mount *, xfs_agnumber_t);

extern void xfs_sb_calc_crc(struct xfs_buf *);
extern void xfs_mod_sb(struct xfs_trans *, __int64_t);
extern void xfs_sb_mount_common(struct xfs_mount *, struct xfs_sb *);
extern void xfs_sb_from_disk(struct xfs_sb *, struct xfs_dsb *);
extern void xfs_sb_to_disk(struct xfs_dsb *, struct xfs_sb *, __int64_t);
extern void xfs_sb_calc_crc(struct xfs_buf *bp);
extern void xfs_mod_sb(struct xfs_trans *tp);
extern void xfs_sb_mount_common(struct xfs_mount *mp, struct xfs_sb *sbp);
extern void xfs_sb_from_disk(struct xfs_sb *to, struct xfs_dsb *from);
extern void xfs_sb_to_disk(struct xfs_dsb *to, struct xfs_sb *from);
extern void xfs_sb_quota_from_disk(struct xfs_sb *sbp);

#endif /* __XFS_SB_H__ */
6 changes: 2 additions & 4 deletions fs/xfs/xfs_fsops.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -541,7 +541,7 @@ xfs_growfs_data_private(
saved_error = error;
continue;
}
xfs_sb_to_disk(XFS_BUF_TO_SBP(bp), &mp->m_sb, XFS_SB_ALL_BITS);
xfs_sb_to_disk(XFS_BUF_TO_SBP(bp), &mp->m_sb);

error = xfs_bwrite(bp);
xfs_buf_relse(bp);
Expand Down Expand Up @@ -780,9 +780,7 @@ xfs_fs_log_dummy(
xfs_trans_cancel(tp, 0);
return error;
}

/* log the UUID because it is an unchanging field */
xfs_mod_sb(tp, XFS_SB_UUID);
xfs_mod_sb(tp);
xfs_trans_set_sync(tp);
return xfs_trans_commit(tp, 0);
}
Expand Down
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