Fix stack dbuf_hold_impl()
This commit preserves the recursive function dbuf_hold_impl() but moves
the local variables and function arguments to the heap to minimize
the stack frame size. Enough space is initially allocated on the
stack for 20 levels of recursion. This technique was based on commit
34229a2f2a which reduced stack usage of
traverse_visitbp().
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This commit is contained in:
Brian Behlendorf
parent
5ac1241a95
commit
fc5bb51f08
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@ -36,6 +36,29 @@
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#include <sys/sa.h>
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#include <sys/sa_impl.h>
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struct dbuf_hold_impl_data {
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/* Function arguments */
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dnode_t *dh_dn;
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uint8_t dh_level;
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uint64_t dh_blkid;
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int dh_fail_sparse;
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void *dh_tag;
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dmu_buf_impl_t **dh_dbp;
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/* Local variables */
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dmu_buf_impl_t *dh_db;
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dmu_buf_impl_t *dh_parent;
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blkptr_t *dh_bp;
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int dh_err;
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dbuf_dirty_record_t *dh_dr;
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arc_buf_contents_t dh_type;
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int dh_depth;
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};
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static void __dbuf_hold_impl_init(struct dbuf_hold_impl_data *dh,
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dnode_t *dn, uint8_t level, uint64_t blkid, int fail_sparse,
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void *tag, dmu_buf_impl_t **dbp, int depth);
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static int __dbuf_hold_impl(struct dbuf_hold_impl_data *dh);
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static void dbuf_destroy(dmu_buf_impl_t *db);
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static int dbuf_undirty(dmu_buf_impl_t *db, dmu_tx_t *tx);
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static void dbuf_write(dbuf_dirty_record_t *dr, arc_buf_t *data, dmu_tx_t *tx);
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@ -1586,7 +1609,7 @@ dbuf_clear(dmu_buf_impl_t *db)
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static int
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dbuf_findbp(dnode_t *dn, int level, uint64_t blkid, int fail_sparse,
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dmu_buf_impl_t **parentp, blkptr_t **bpp)
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dmu_buf_impl_t **parentp, blkptr_t **bpp, struct dbuf_hold_impl_data *dh)
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{
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int nlevels, epbs;
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@ -1623,8 +1646,17 @@ dbuf_findbp(dnode_t *dn, int level, uint64_t blkid, int fail_sparse,
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return (ENOENT);
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} else if (level < nlevels-1) {
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/* this block is referenced from an indirect block */
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int err = dbuf_hold_impl(dn, level+1,
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blkid >> epbs, fail_sparse, NULL, parentp);
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int err;
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if (dh == NULL) {
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err = dbuf_hold_impl(dn, level+1, blkid >> epbs,
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fail_sparse, NULL, parentp);
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}
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else {
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__dbuf_hold_impl_init(dh + 1, dn, dh->dh_level + 1,
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blkid >> epbs, fail_sparse, NULL,
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parentp, dh->dh_depth + 1);
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err = __dbuf_hold_impl(dh + 1);
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}
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if (err)
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return (err);
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err = dbuf_read(*parentp, NULL,
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@ -1823,7 +1855,7 @@ dbuf_prefetch(dnode_t *dn, uint64_t blkid)
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return;
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}
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if (dbuf_findbp(dn, 0, blkid, TRUE, &db, &bp) == 0) {
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if (dbuf_findbp(dn, 0, blkid, TRUE, &db, &bp, NULL) == 0) {
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if (bp && !BP_IS_HOLE(bp)) {
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int priority = dn->dn_type == DMU_OT_DDT_ZAP ?
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ZIO_PRIORITY_DDT_PREFETCH : ZIO_PRIORITY_ASYNC_READ;
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@ -1850,98 +1882,142 @@ dbuf_prefetch(dnode_t *dn, uint64_t blkid)
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}
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}
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#define DBUF_HOLD_IMPL_MAX_DEPTH 20
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/*
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* Returns with db_holds incremented, and db_mtx not held.
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* Note: dn_struct_rwlock must be held.
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*/
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int
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dbuf_hold_impl(dnode_t *dn, uint8_t level, uint64_t blkid, int fail_sparse,
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void *tag, dmu_buf_impl_t **dbp)
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static int
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__dbuf_hold_impl(struct dbuf_hold_impl_data *dh)
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{
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dmu_buf_impl_t *db, *parent = NULL;
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ASSERT3S(dh->dh_depth, <, DBUF_HOLD_IMPL_MAX_DEPTH);
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dh->dh_parent = NULL;
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ASSERT(blkid != DMU_BONUS_BLKID);
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ASSERT(RW_LOCK_HELD(&dn->dn_struct_rwlock));
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ASSERT3U(dn->dn_nlevels, >, level);
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ASSERT(dh->dh_blkid != DMU_BONUS_BLKID);
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ASSERT(RW_LOCK_HELD(&dh->dh_dn->dn_struct_rwlock));
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ASSERT3U(dh->dh_dn->dn_nlevels, >, dh->dh_level);
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*dbp = NULL;
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*(dh->dh_dbp) = NULL;
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top:
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/* dbuf_find() returns with db_mtx held */
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db = dbuf_find(dn, level, blkid);
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dh->dh_db = dbuf_find(dh->dh_dn, dh->dh_level, dh->dh_blkid);
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if (db == NULL) {
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blkptr_t *bp = NULL;
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int err;
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if (dh->dh_db == NULL) {
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dh->dh_bp = NULL;
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ASSERT3P(parent, ==, NULL);
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err = dbuf_findbp(dn, level, blkid, fail_sparse, &parent, &bp);
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if (fail_sparse) {
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if (err == 0 && bp && BP_IS_HOLE(bp))
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err = ENOENT;
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if (err) {
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if (parent)
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dbuf_rele(parent, NULL);
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return (err);
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ASSERT3P(dh->dh_parent, ==, NULL);
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dh->dh_err = dbuf_findbp(dh->dh_dn, dh->dh_level, dh->dh_blkid,
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dh->dh_fail_sparse, &dh->dh_parent,
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&dh->dh_bp, dh);
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if (dh->dh_fail_sparse) {
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if (dh->dh_err == 0 && dh->dh_bp && BP_IS_HOLE(dh->dh_bp))
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dh->dh_err = ENOENT;
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if (dh->dh_err) {
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if (dh->dh_parent)
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dbuf_rele(dh->dh_parent, NULL);
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return (dh->dh_err);
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}
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}
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if (err && err != ENOENT)
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return (err);
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db = dbuf_create(dn, level, blkid, parent, bp);
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if (dh->dh_err && dh->dh_err != ENOENT)
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return (dh->dh_err);
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dh->dh_db = dbuf_create(dh->dh_dn, dh->dh_level, dh->dh_blkid,
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dh->dh_parent, dh->dh_bp);
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}
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if (db->db_buf && refcount_is_zero(&db->db_holds)) {
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arc_buf_add_ref(db->db_buf, db);
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if (db->db_buf->b_data == NULL) {
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dbuf_clear(db);
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if (parent) {
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dbuf_rele(parent, NULL);
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parent = NULL;
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if (dh->dh_db->db_buf && refcount_is_zero(&dh->dh_db->db_holds)) {
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arc_buf_add_ref(dh->dh_db->db_buf, dh->dh_db);
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if (dh->dh_db->db_buf->b_data == NULL) {
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dbuf_clear(dh->dh_db);
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if (dh->dh_parent) {
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dbuf_rele(dh->dh_parent, NULL);
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dh->dh_parent = NULL;
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}
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goto top;
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}
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ASSERT3P(db->db.db_data, ==, db->db_buf->b_data);
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ASSERT3P(dh->dh_db->db.db_data, ==, dh->dh_db->db_buf->b_data);
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}
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ASSERT(db->db_buf == NULL || arc_referenced(db->db_buf));
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ASSERT(dh->dh_db->db_buf == NULL || arc_referenced(dh->dh_db->db_buf));
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/*
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* If this buffer is currently syncing out, and we are are
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* still referencing it from db_data, we need to make a copy
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* of it in case we decide we want to dirty it again in this txg.
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*/
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if (db->db_level == 0 && db->db_blkid != DMU_BONUS_BLKID &&
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dn->dn_object != DMU_META_DNODE_OBJECT &&
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db->db_state == DB_CACHED && db->db_data_pending) {
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dbuf_dirty_record_t *dr = db->db_data_pending;
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if (dh->dh_db->db_level == 0 &&
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dh->dh_db->db_blkid != DMU_BONUS_BLKID &&
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dh->dh_dn->dn_object != DMU_META_DNODE_OBJECT &&
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dh->dh_db->db_state == DB_CACHED && dh->dh_db->db_data_pending) {
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dh->dh_dr = dh->dh_db->db_data_pending;
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if (dr->dt.dl.dr_data == db->db_buf) {
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arc_buf_contents_t type = DBUF_GET_BUFC_TYPE(db);
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if (dh->dh_dr->dt.dl.dr_data == dh->dh_db->db_buf) {
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dh->dh_type = DBUF_GET_BUFC_TYPE(dh->dh_db);
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dbuf_set_data(db,
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arc_buf_alloc(dn->dn_objset->os_spa,
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db->db.db_size, db, type));
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bcopy(dr->dt.dl.dr_data->b_data, db->db.db_data,
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db->db.db_size);
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dbuf_set_data(dh->dh_db,
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arc_buf_alloc(dh->dh_dn->dn_objset->os_spa,
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dh->dh_db->db.db_size, dh->dh_db, dh->dh_type));
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bcopy(dh->dh_dr->dt.dl.dr_data->b_data,
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dh->dh_db->db.db_data, dh->dh_db->db.db_size);
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}
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}
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(void) refcount_add(&db->db_holds, tag);
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dbuf_update_data(db);
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DBUF_VERIFY(db);
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mutex_exit(&db->db_mtx);
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(void) refcount_add(&dh->dh_db->db_holds, dh->dh_tag);
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dbuf_update_data(dh->dh_db);
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DBUF_VERIFY(dh->dh_db);
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mutex_exit(&dh->dh_db->db_mtx);
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/* NOTE: we can't rele the parent until after we drop the db_mtx */
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if (parent)
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dbuf_rele(parent, NULL);
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if (dh->dh_parent)
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dbuf_rele(dh->dh_parent, NULL);
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ASSERT3P(DB_DNODE(db), ==, dn);
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ASSERT3U(db->db_blkid, ==, blkid);
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ASSERT3U(db->db_level, ==, level);
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*dbp = db;
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ASSERT3P(DB_DNODE(dh->dh_db), ==, dh->dh_dn);
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ASSERT3U(dh->dh_db->db_blkid, ==, dh->dh_blkid);
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ASSERT3U(dh->dh_db->db_level, ==, dh->dh_level);
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*(dh->dh_dbp) = dh->dh_db;
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return (0);
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}
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/*
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* The following code preserves the recursive function dbuf_hold_impl()
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* but moves the local variables AND function arguments to the heap to
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* minimize the stack frame size. Enough space is initially allocated
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* on the stack for 20 levels of recursion.
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*/
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int
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dbuf_hold_impl(dnode_t *dn, uint8_t level, uint64_t blkid, int fail_sparse,
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void *tag, dmu_buf_impl_t **dbp)
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{
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struct dbuf_hold_impl_data *dh;
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int error;
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dh = kmem_zalloc(sizeof(struct dbuf_hold_impl_data) *
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DBUF_HOLD_IMPL_MAX_DEPTH, KM_SLEEP);
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__dbuf_hold_impl_init(dh, dn, level, blkid, fail_sparse, tag, dbp, 0);
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error = __dbuf_hold_impl(dh);
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kmem_free(dh, sizeof(struct dbuf_hold_impl_data) *
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DBUF_HOLD_IMPL_MAX_DEPTH);
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return (error);
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}
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static void
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__dbuf_hold_impl_init(struct dbuf_hold_impl_data *dh,
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dnode_t *dn, uint8_t level, uint64_t blkid, int fail_sparse,
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void *tag, dmu_buf_impl_t **dbp, int depth)
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{
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dh->dh_dn = dn;
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dh->dh_level = level;
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dh->dh_blkid = blkid;
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dh->dh_fail_sparse = fail_sparse;
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dh->dh_tag = tag;
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dh->dh_dbp = dbp;
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dh->dh_depth = depth;
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}
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dmu_buf_impl_t *
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dbuf_hold(dnode_t *dn, uint64_t blkid, void *tag)
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{
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