Re: [PATCH 6/7] xfs: replace xfs_mod_incore_sb_batched

Brian Foster
2015-02-05T14:10:54Z

On Thu, Feb 05, 2015 at 07:54:08AM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> Introduce helper functions for modifying fields in the superblock
> into xfs_trans.c, the only caller of xfs_mod_incore_sb_batch(). We
> can then use these directly in xfs_trans_unreserve_and_mod_sb() and
> so remove another user of the xfs_mode_incore_sb() API without
> losing any functionality or scalability of the transaction commit
> code..
>
> Based on a patch from Christoph Hellwig.
>
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
> fs/xfs/xfs_mount.c | 51 --------------
> fs/xfs/xfs_mount.h | 11 ---
> fs/xfs/xfs_trans.c | 198 ++++++++++++++++++++++++++++++++++-------------------
> 3 files changed, 126 insertions(+), 134 deletions(-)
>
> diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
> index 284f528..9499e88 100644
> --- a/fs/xfs/xfs_mount.c
> +++ b/fs/xfs/xfs_mount.c
> @@ -1354,57 +1354,6 @@ xfs_mod_incore_sb(
> }
>
> /*
> - * Change more than one field in the in-core superblock structure at a time.
> - *
> - * The fields and changes to those fields are specified in the array of
> - * xfs_mod_sb structures passed in. Either all of the specified deltas
> - * will be applied or none of them will. If any modified field dips below 0,
> - * then all modifications will be backed out and EINVAL will be returned.
> - *
> - * Note that this function may not be used for the superblock values that
> - * are tracked with the in-memory per-cpu counters - a direct call to
> - * xfs_mod_incore_sb is required for these.
> - */
> -int
> -xfs_mod_incore_sb_batch(
> - struct xfs_mount *mp,
> - xfs_mod_sb_t *msb,
> - uint nmsb,
> - int rsvd)
> -{
> - xfs_mod_sb_t *msbp;
> - int error = 0;
> -
> - /*
> - * Loop through the array of mod structures and apply each individually.
> - * If any fail, then back out all those which have already been applied.
> - * Do all of this within the scope of the m_sb_lock so that all of the
> - * changes will be atomic.
> - */
> - spin_lock(&mp->m_sb_lock);
> - for (msbp = msb; msbp < (msb + nmsb); msbp++) {
> - ASSERT(msbp->msb_field < XFS_SBS_ICOUNT ||
> - msbp->msb_field > XFS_SBS_FDBLOCKS);
> -
> - error = xfs_mod_incore_sb_unlocked(mp, msbp->msb_field,
> - msbp->msb_delta, rsvd);
> - if (error)
> - goto unwind;
> - }
> - spin_unlock(&mp->m_sb_lock);
> - return 0;
> -
> -unwind:
> - while (--msbp >= msb) {
> - error = xfs_mod_incore_sb_unlocked(mp, msbp->msb_field,
> - -msbp->msb_delta, rsvd);
> - ASSERT(error == 0);
> - }
> - spin_unlock(&mp->m_sb_lock);
> - return error;
> -}
> -
> -/*
> * xfs_getsb() is called to obtain the buffer for the superblock.
> * The buffer is returned locked and read in from disk.
> * The buffer should be released with a call to xfs_brelse().
> diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
> index 8970489..66f28c1 100644
> --- a/fs/xfs/xfs_mount.h
> +++ b/fs/xfs/xfs_mount.h
> @@ -249,15 +249,6 @@ xfs_daddr_to_agbno(struct xfs_mount *mp, xfs_daddr_t d)
> }
>
> /*
> - * This structure is for use by the xfs_mod_incore_sb_batch() routine.
> - * xfs_growfs can specify a few fields which are more than int limit
> - */
> -typedef struct xfs_mod_sb {
> - xfs_sb_field_t msb_field; /* Field to modify, see below */
> - int64_t msb_delta; /* Change to make to specified field */
> -} xfs_mod_sb_t;
> -
> -/*
> * Per-ag incore structure, copies of information in agf and agi, to improve the
> * performance of allocation group selection.
> */
> @@ -314,8 +305,6 @@ extern int xfs_initialize_perag(xfs_mount_t *mp, xfs_agnumber_t agcount,
>
> extern void xfs_unmountfs(xfs_mount_t *);
> extern int xfs_mod_incore_sb(xfs_mount_t *, xfs_sb_field_t, int64_t, int);
> -extern int xfs_mod_incore_sb_batch(xfs_mount_t *, xfs_mod_sb_t *,
> - uint, int);
> extern int xfs_mod_icount(struct xfs_mount *mp, int64_t delta);
> extern int xfs_mod_ifree(struct xfs_mount *mp, int64_t delta);
> extern int xfs_mod_fdblocks(struct xfs_mount *mp, int64_t delta,
> diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
> index 4e4bc5a..220ef2c 100644
> --- a/fs/xfs/xfs_trans.c
> +++ b/fs/xfs/xfs_trans.c
> @@ -485,6 +485,54 @@ xfs_trans_apply_sb_deltas(
> sizeof(sbp->sb_frextents) - 1);
> }
>
> +STATIC int
> +xfs_sb_mod8(
> + uint8_t *field,
> + int8_t delta)
> +{
> + int8_t counter = *field;
> +
> + counter += delta;
> + if (counter < 0) {
> + ASSERT(0);
> + return -EINVAL;
> + }
> + *field = counter;
> + return 0;
> +}
> +
> +STATIC int
> +xfs_sb_mod32(
> + uint32_t *field,
> + int32_t delta)
> +{
> + int32_t counter = *field;
> +
> + counter += delta;
> + if (counter < 0) {
> + ASSERT(0);
> + return -EINVAL;
> + }
> + *field = counter;
> + return 0;
> +}
> +
> +STATIC int
> +xfs_sb_mod64(
> + uint64_t *field,
> + int64_t delta)
> +{
> + int64_t counter = *field;
> +
> + counter += delta;
> + if (counter < 0) {
> + ASSERT(0);
> + return -EINVAL;
> + }
> + *field = counter;
> + return 0;
> +}
> +
> /*
> * xfs_trans_unreserve_and_mod_sb() is called to release unused reservations
> * and apply superblock counter changes to the in-core superblock. The
> @@ -492,13 +540,6 @@ xfs_trans_apply_sb_deltas(
> * applied to the in-core superblock. The idea is that that has already been
> * done.
> *
> - * This is done efficiently with a single call to xfs_mod_incore_sb_batch().
> - * However, we have to ensure that we only modify each superblock field only
> - * once because the application of the delta values may not be atomic. That can
> - * lead to ENOSPC races occurring if we have two separate modifcations of the
> - * free space counter to put back the entire reservation and then take away
> - * what we used.
> - *
> * If we are not logging superblock counters, then the inode allocated/free and
> * used block counts are not updated in the on disk superblock. In this case,
> * XFS_TRANS_SB_DIRTY will not be set when the transaction is updated but we
> @@ -506,20 +547,15 @@ xfs_trans_apply_sb_deltas(
> */
> void
> xfs_trans_unreserve_and_mod_sb(
> - xfs_trans_t *tp)
> + struct xfs_trans *tp)
> {
> - xfs_mod_sb_t msb[9]; /* If you add cases, add entries */
> - xfs_mod_sb_t *msbp;
> - xfs_mount_t *mp = tp->t_mountp;
> - /* REFERENCED */
> - int error;
> - bool rsvd = (tp->t_flags & XFS_TRANS_RESERVE) != 0;
> - int64_t blkdelta = 0;
> - int64_t rtxdelta = 0;
> - int64_t idelta = 0;
> - int64_t ifreedelta = 0;
> -
> - msbp = msb;
> + struct xfs_mount *mp = tp->t_mountp;
> + bool rsvd = (tp->t_flags & XFS_TRANS_RESERVE) != 0;
> + int64_t blkdelta = 0;
> + int64_t rtxdelta = 0;
> + int64_t idelta = 0;
> + int64_t ifreedelta = 0;
> + int error;
>
> /* calculate deltas */
> if (tp->t_blk_res > 0)
> @@ -560,72 +596,90 @@ xfs_trans_unreserve_and_mod_sb(
> goto out_undo_icount;
> }
>
> + if (rtxdelta == 0 && !(tp->t_flags & XFS_TRANS_SB_DIRTY))
> + return;
> +
> /* apply remaining deltas */
> + spin_lock(&mp->m_sb_lock);
> if (rtxdelta) {
> - error = xfs_mod_frextents(mp, rtxdelta);
> + error = xfs_sb_mod64(&mp->m_sb.sb_frextents, rtxdelta);

Any reason why we don't continue to use the xfs_mod_frextents() function
introduced in the previous patch? Seems like we should be consistent one
way or the other.

Brian

> if (error)
> goto out_undo_ifree;
> }
>
> - if (tp->t_flags & XFS_TRANS_SB_DIRTY) {
> - if (tp->t_dblocks_delta != 0) {
> - msbp->msb_field = XFS_SBS_DBLOCKS;
> - msbp->msb_delta = tp->t_dblocks_delta;
> - msbp++;
> - }
> - if (tp->t_agcount_delta != 0) {
> - msbp->msb_field = XFS_SBS_AGCOUNT;
> - msbp->msb_delta = tp->t_agcount_delta;
> - msbp++;
> - }
> - if (tp->t_imaxpct_delta != 0) {
> - msbp->msb_field = XFS_SBS_IMAX_PCT;
> - msbp->msb_delta = tp->t_imaxpct_delta;
> - msbp++;
> - }
> - if (tp->t_rextsize_delta != 0) {
> - msbp->msb_field = XFS_SBS_REXTSIZE;
> - msbp->msb_delta = tp->t_rextsize_delta;
> - msbp++;
> - }
> - if (tp->t_rbmblocks_delta != 0) {
> - msbp->msb_field = XFS_SBS_RBMBLOCKS;
> - msbp->msb_delta = tp->t_rbmblocks_delta;
> - msbp++;
> - }
> - if (tp->t_rblocks_delta != 0) {
> - msbp->msb_field = XFS_SBS_RBLOCKS;
> - msbp->msb_delta = tp->t_rblocks_delta;
> - msbp++;
> - }
> - if (tp->t_rextents_delta != 0) {
> - msbp->msb_field = XFS_SBS_REXTENTS;
> - msbp->msb_delta = tp->t_rextents_delta;
> - msbp++;
> - }
> - if (tp->t_rextslog_delta != 0) {
> - msbp->msb_field = XFS_SBS_REXTSLOG;
> - msbp->msb_delta = tp->t_rextslog_delta;
> - msbp++;
> - }
> - }
> -
> - /*
> - * If we need to change anything, do it.
> - */
> - if (msbp > msb) {
> - error = xfs_mod_incore_sb_batch(tp->t_mountp, msb,
> - (uint)(msbp - msb), rsvd);
> + if (tp->t_dblocks_delta != 0) {
> + error = xfs_sb_mod64(&mp->m_sb.sb_dblocks, tp->t_dblocks_delta);
> if (error)
> goto out_undo_frextents;
> }
> -
> + if (tp->t_agcount_delta != 0) {
> + error = xfs_sb_mod32(&mp->m_sb.sb_agcount, tp->t_agcount_delta);
> + if (error)
> + goto out_undo_dblocks;
> + }
> + if (tp->t_imaxpct_delta != 0) {
> + error = xfs_sb_mod8(&mp->m_sb.sb_imax_pct, tp->t_imaxpct_delta);
> + if (error)
> + goto out_undo_agcount;
> + }
> + if (tp->t_rextsize_delta != 0) {
> + error = xfs_sb_mod32(&mp->m_sb.sb_rextsize,
> + tp->t_rextsize_delta);
> + if (error)
> + goto out_undo_imaxpct;
> + }
> + if (tp->t_rbmblocks_delta != 0) {
> + error = xfs_sb_mod32(&mp->m_sb.sb_rbmblocks,
> + tp->t_rbmblocks_delta);
> + if (error)
> + goto out_undo_rextsize;
> + }
> + if (tp->t_rblocks_delta != 0) {
> + error = xfs_sb_mod64(&mp->m_sb.sb_rblocks, tp->t_rblocks_delta);
> + if (error)
> + goto out_undo_rbmblocks;
> + }
> + if (tp->t_rextents_delta != 0) {
> + error = xfs_sb_mod64(&mp->m_sb.sb_rextents,
> + tp->t_rextents_delta);
> + if (error)
> + goto out_undo_rblocks;
> + }
> + if (tp->t_rextslog_delta != 0) {
> + error = xfs_sb_mod8(&mp->m_sb.sb_rextslog,
> + tp->t_rextslog_delta);
> + if (error)
> + goto out_undo_rextents;
> + }
> + spin_unlock(&mp->m_sb_lock);
> return;
>
> +out_undo_rextents:
> + if (tp->t_rextents_delta)
> + xfs_sb_mod64(&mp->m_sb.sb_rextents, -tp->t_rextents_delta);
> +out_undo_rblocks:
> + if (tp->t_rblocks_delta)
> + xfs_sb_mod64(&mp->m_sb.sb_rblocks, -tp->t_rblocks_delta);
> +out_undo_rbmblocks:
> + if (tp->t_rbmblocks_delta)
> + xfs_sb_mod32(&mp->m_sb.sb_rbmblocks, -tp->t_rbmblocks_delta);
> +out_undo_rextsize:
> + if (tp->t_rextsize_delta)
> + xfs_sb_mod32(&mp->m_sb.sb_rextsize, -tp->t_rextsize_delta);
> +out_undo_imaxpct:
> + if (tp->t_rextsize_delta)
> + xfs_sb_mod8(&mp->m_sb.sb_imax_pct, -tp->t_imaxpct_delta);
> +out_undo_agcount:
> + if (tp->t_agcount_delta)
> + xfs_sb_mod32(&mp->m_sb.sb_agcount, -tp->t_agcount_delta);
> +out_undo_dblocks:
> + if (tp->t_dblocks_delta)
> + xfs_sb_mod64(&mp->m_sb.sb_dblocks, -tp->t_dblocks_delta);
> out_undo_frextents:
> if (rtxdelta)
> - xfs_mod_frextents(mp, -rtxdelta);
> + xfs_sb_mod64(&mp->m_sb.sb_frextents, -rtxdelta);
> out_undo_ifree:
> + spin_unlock(&mp->m_sb_lock);
> if (ifreedelta)
> xfs_mod_ifree(mp, -ifreedelta);
> out_undo_icount:
> --
> 2.0.0
>
> _______________________________________________
> xfs mailing list
> xfs@oss.sgi.com
> http://oss.sgi.com/mailman/listinfo/xfs