From a47587389e98820ea194fd16cd658491f8e4ee31 Mon Sep 17 00:00:00 2001 From: Javen Wu Date: Fri, 24 Aug 2012 19:24:48 -0700 Subject: [PATCH] Drop spill buffer reference When calling sa_update() and friends it is possible that a spill buffer will be needed to accomidate the update. When this happens a hold is taken on the new dbuf and that hold must be released before calling dmu_tx_commit(). Failing to release the hold will cause a copy of the dbuf to be made in dbuf_sync_leaf(). This is done to ensure further updates to the dbuf never sneak in to the syncing txg. This could be left to the sa_update() caller. But then the caller would need to be aware of this internal SA implementation detail. It is therefore preferable to handle this all internally in the SA implementation. Signed-off-by: Brian Behlendorf Closes #503 Closes #513 --- module/zfs/sa.c | 24 ++++++++++++++++++++++-- 1 file changed, 22 insertions(+), 2 deletions(-) diff --git a/module/zfs/sa.c b/module/zfs/sa.c index 32b4c5b08..a26e5ebdd 100644 --- a/module/zfs/sa.c +++ b/module/zfs/sa.c @@ -1773,12 +1773,14 @@ sa_bulk_update_impl(sa_handle_t *hdl, sa_bulk_attr_t *bulk, int count, int error; sa_os_t *sa = hdl->sa_os->os_sa; dmu_object_type_t bonustype; - - bonustype = SA_BONUSTYPE_FROM_DB(SA_GET_DB(hdl, SA_BONUS)); + dmu_buf_t *saved_spill; ASSERT(hdl); ASSERT(MUTEX_HELD(&hdl->sa_lock)); + bonustype = SA_BONUSTYPE_FROM_DB(SA_GET_DB(hdl, SA_BONUS)); + saved_spill = hdl->sa_spill; + /* sync out registration table if necessary */ if (sa->sa_need_attr_registration) sa_attr_register_sync(hdl, tx); @@ -1787,6 +1789,24 @@ sa_bulk_update_impl(sa_handle_t *hdl, sa_bulk_attr_t *bulk, int count, if (error == 0 && !IS_SA_BONUSTYPE(bonustype) && sa->sa_update_cb) sa->sa_update_cb(hdl, tx); + /* + * If saved_spill is NULL and current sa_spill is not NULL that + * means we increased the refcount of the spill buffer through + * sa_get_spill() or dmu_spill_hold_by_dnode(). Therefore we + * must release the hold before calling dmu_tx_commit() to avoid + * making a copy of this buffer in dbuf_sync_leaf() due to the + * reference count now being greater than 1. + */ + if (!saved_spill && hdl->sa_spill) { + if (hdl->sa_spill_tab) { + sa_idx_tab_rele(hdl->sa_os, hdl->sa_spill_tab); + hdl->sa_spill_tab = NULL; + } + + dmu_buf_rele((dmu_buf_t *)hdl->sa_spill, NULL); + hdl->sa_spill = NULL; + } + return (error); }