Fix stack traverse_visitbp()
Due to limited stack space recursive functions are frowned upon in the Linux kernel. However, they often are the most elegant solution to a problem. The following code preserves the recursive function traverse_visitbp() 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 change does ugly-up-the-code but it reduces the worst case usage from roughly 4160 bytes to 960 bytes on x86_64 archs. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This commit is contained in:
Brian Behlendorf
parent
da6b4005c9
commit
6656bf5621
@ -59,6 +59,31 @@ typedef struct traverse_data {
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void *td_arg;
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} traverse_data_t;
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typedef struct traverse_visitbp_data {
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/* Function arguments */
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traverse_data_t *tv_td;
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const dnode_phys_t *tv_dnp;
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arc_buf_t *tv_pbuf;
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blkptr_t *tv_bp;
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const zbookmark_t *tv_zb;
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/* Local variables */
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prefetch_data_t *tv_pd;
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zbookmark_t tv_czb;
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arc_buf_t *tv_buf;
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boolean_t tv_hard;
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objset_phys_t *tv_osp;
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dnode_phys_t *tv_ldnp;
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blkptr_t *tv_cbp;
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uint32_t tv_flags;
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int tv_err;
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int tv_lasterr;
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int tv_i;
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int tv_epb;
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int tv_depth;
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} traverse_visitbp_data_t;
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static inline int traverse_visitbp(traverse_data_t *td, const
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dnode_phys_t *dnp, arc_buf_t *pbuf, blkptr_t *bp, const zbookmark_t *zb);
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static int traverse_dnode(traverse_data_t *td, const dnode_phys_t *dnp,
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arc_buf_t *buf, uint64_t objset, uint64_t object);
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@ -128,137 +153,191 @@ traverse_zil(traverse_data_t *td, zil_header_t *zh)
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zil_free(zilog);
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}
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static int
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traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp,
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arc_buf_t *pbuf, blkptr_t *bp, const zbookmark_t *zb)
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{
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zbookmark_t czb;
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int err = 0, lasterr = 0;
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arc_buf_t *buf = NULL;
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prefetch_data_t *pd = td->td_pfd;
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boolean_t hard = td->td_flags & TRAVERSE_HARD;
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#define TRAVERSE_VISITBP_MAX_DEPTH 20
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if (bp->blk_birth == 0) {
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err = td->td_func(td->td_spa, NULL, NULL, pbuf, zb, dnp,
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td->td_arg);
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return (err);
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static void
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__traverse_visitbp_init(traverse_visitbp_data_t *tv,
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traverse_data_t *td, const dnode_phys_t *dnp,
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arc_buf_t *pbuf, blkptr_t *bp, const zbookmark_t *zb, int depth)
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{
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tv->tv_td = td;
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tv->tv_dnp = dnp;
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tv->tv_pbuf = pbuf;
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tv->tv_bp = bp;
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tv->tv_zb = zb;
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tv->tv_err = 0;
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tv->tv_lasterr = 0;
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tv->tv_buf = NULL;
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tv->tv_pd = td->td_pfd;
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tv->tv_hard = td->td_flags & TRAVERSE_HARD;
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tv->tv_flags = ARC_WAIT;
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tv->tv_depth = depth;
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}
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static noinline int
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__traverse_visitbp(traverse_visitbp_data_t *tv)
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{
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ASSERT3S(tv->tv_depth, <, TRAVERSE_VISITBP_MAX_DEPTH);
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if (tv->tv_bp->blk_birth == 0) {
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tv->tv_err = tv->tv_td->td_func(tv->tv_td->td_spa, NULL, NULL,
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tv->tv_pbuf, tv->tv_zb, tv->tv_dnp, tv->tv_td->td_arg);
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return (tv->tv_err);
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}
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if (bp->blk_birth <= td->td_min_txg)
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if (tv->tv_bp->blk_birth <= tv->tv_td->td_min_txg)
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return (0);
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if (pd && !pd->pd_exited &&
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((pd->pd_flags & TRAVERSE_PREFETCH_DATA) ||
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BP_GET_TYPE(bp) == DMU_OT_DNODE || BP_GET_LEVEL(bp) > 0)) {
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mutex_enter(&pd->pd_mtx);
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ASSERT(pd->pd_blks_fetched >= 0);
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while (pd->pd_blks_fetched == 0 && !pd->pd_exited)
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cv_wait(&pd->pd_cv, &pd->pd_mtx);
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pd->pd_blks_fetched--;
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cv_broadcast(&pd->pd_cv);
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mutex_exit(&pd->pd_mtx);
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if (tv->tv_pd && !tv->tv_pd->pd_exited &&
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((tv->tv_pd->pd_flags & TRAVERSE_PREFETCH_DATA) ||
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BP_GET_TYPE(tv->tv_bp) == DMU_OT_DNODE ||
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BP_GET_LEVEL(tv->tv_bp) > 0)) {
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mutex_enter(&tv->tv_pd->pd_mtx);
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ASSERT(tv->tv_pd->pd_blks_fetched >= 0);
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while (tv->tv_pd->pd_blks_fetched == 0 && !tv->tv_pd->pd_exited)
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cv_wait(&tv->tv_pd->pd_cv, &tv->tv_pd->pd_mtx);
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tv->tv_pd->pd_blks_fetched--;
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cv_broadcast(&tv->tv_pd->pd_cv);
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mutex_exit(&tv->tv_pd->pd_mtx);
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}
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if (td->td_flags & TRAVERSE_PRE) {
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err = td->td_func(td->td_spa, NULL, bp, pbuf, zb, dnp,
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td->td_arg);
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if (err == TRAVERSE_VISIT_NO_CHILDREN)
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if (tv->tv_td->td_flags & TRAVERSE_PRE) {
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tv->tv_err = tv->tv_td->td_func(tv->tv_td->td_spa, NULL,
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tv->tv_bp, tv->tv_pbuf, tv->tv_zb, tv->tv_dnp,
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tv->tv_td->td_arg);
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if (tv->tv_err == TRAVERSE_VISIT_NO_CHILDREN)
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return (0);
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if (err)
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return (err);
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if (tv->tv_err)
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return (tv->tv_err);
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}
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if (BP_GET_LEVEL(bp) > 0) {
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uint32_t flags = ARC_WAIT;
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int i;
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blkptr_t *cbp;
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int epb = BP_GET_LSIZE(bp) >> SPA_BLKPTRSHIFT;
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if (BP_GET_LEVEL(tv->tv_bp) > 0) {
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tv->tv_epb = BP_GET_LSIZE(tv->tv_bp) >> SPA_BLKPTRSHIFT;
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err = dsl_read(NULL, td->td_spa, bp, pbuf,
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arc_getbuf_func, &buf,
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ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, zb);
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if (err)
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return (err);
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tv->tv_err = dsl_read(NULL, tv->tv_td->td_spa, tv->tv_bp,
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tv->tv_pbuf, arc_getbuf_func, &tv->tv_buf,
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ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL,
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&tv->tv_flags, tv->tv_zb);
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if (tv->tv_err)
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return (tv->tv_err);
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/* recursively visitbp() blocks below this */
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cbp = buf->b_data;
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for (i = 0; i < epb; i++, cbp++) {
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SET_BOOKMARK(&czb, zb->zb_objset, zb->zb_object,
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zb->zb_level - 1,
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zb->zb_blkid * epb + i);
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err = traverse_visitbp(td, dnp, buf, cbp, &czb);
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if (err) {
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if (!hard)
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tv->tv_cbp = tv->tv_buf->b_data;
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for (tv->tv_i = 0; tv->tv_i < tv->tv_epb;
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tv->tv_i++, tv->tv_cbp++) {
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SET_BOOKMARK(&tv->tv_czb, tv->tv_zb->zb_objset,
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tv->tv_zb->zb_object, tv->tv_zb->zb_level - 1,
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tv->tv_zb->zb_blkid * tv->tv_epb + tv->tv_i);
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__traverse_visitbp_init(tv + 1, tv->tv_td,
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tv->tv_dnp, tv->tv_buf, tv->tv_cbp,
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&tv->tv_czb, tv->tv_depth + 1);
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tv->tv_err = __traverse_visitbp(tv + 1);
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if (tv->tv_err) {
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if (!tv->tv_hard)
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break;
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lasterr = err;
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tv->tv_lasterr = tv->tv_err;
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}
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}
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} else if (BP_GET_TYPE(bp) == DMU_OT_DNODE) {
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uint32_t flags = ARC_WAIT;
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int i;
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int epb = BP_GET_LSIZE(bp) >> DNODE_SHIFT;
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} else if (BP_GET_TYPE(tv->tv_bp) == DMU_OT_DNODE) {
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tv->tv_epb = BP_GET_LSIZE(tv->tv_bp) >> DNODE_SHIFT;
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err = dsl_read(NULL, td->td_spa, bp, pbuf,
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arc_getbuf_func, &buf,
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ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, zb);
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if (err)
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return (err);
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tv->tv_err = dsl_read(NULL, tv->tv_td->td_spa, tv->tv_bp,
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tv->tv_pbuf, arc_getbuf_func, &tv->tv_buf,
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ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL,
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&tv->tv_flags, tv->tv_zb);
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if (tv->tv_err)
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return (tv->tv_err);
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/* recursively visitbp() blocks below this */
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dnp = buf->b_data;
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for (i = 0; i < epb; i++, dnp++) {
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err = traverse_dnode(td, dnp, buf, zb->zb_objset,
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zb->zb_blkid * epb + i);
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if (err) {
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if (!hard)
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tv->tv_dnp = tv->tv_buf->b_data;
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for (tv->tv_i = 0; tv->tv_i < tv->tv_epb;
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tv->tv_i++, tv->tv_dnp++) {
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tv->tv_err = traverse_dnode(tv->tv_td, tv->tv_dnp,
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tv->tv_buf, tv->tv_zb->zb_objset,
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tv->tv_zb->zb_blkid * tv->tv_epb + tv->tv_i);
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if (tv->tv_err) {
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if (!tv->tv_hard)
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break;
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lasterr = err;
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tv->tv_lasterr = tv->tv_err;
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}
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}
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} else if (BP_GET_TYPE(bp) == DMU_OT_OBJSET) {
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uint32_t flags = ARC_WAIT;
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objset_phys_t *osp;
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dnode_phys_t *dnp;
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} else if (BP_GET_TYPE(tv->tv_bp) == DMU_OT_OBJSET) {
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err = dsl_read_nolock(NULL, td->td_spa, bp,
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arc_getbuf_func, &buf,
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ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, zb);
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if (err)
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return (err);
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tv->tv_err = dsl_read_nolock(NULL, tv->tv_td->td_spa,
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tv->tv_bp, arc_getbuf_func, &tv->tv_buf,
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ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL,
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&tv->tv_flags, tv->tv_zb);
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if (tv->tv_err)
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return (tv->tv_err);
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osp = buf->b_data;
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dnp = &osp->os_meta_dnode;
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err = traverse_dnode(td, dnp, buf, zb->zb_objset,
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DMU_META_DNODE_OBJECT);
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if (err && hard) {
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lasterr = err;
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err = 0;
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tv->tv_osp = tv->tv_buf->b_data;
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tv->tv_ldnp = &tv->tv_osp->os_meta_dnode;
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tv->tv_err = traverse_dnode(tv->tv_td, tv->tv_ldnp, tv->tv_buf,
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tv->tv_zb->zb_objset, DMU_META_DNODE_OBJECT);
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if (tv->tv_err && tv->tv_hard) {
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tv->tv_lasterr = tv->tv_err;
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tv->tv_err = 0;
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}
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if (err == 0 && arc_buf_size(buf) >= sizeof (objset_phys_t)) {
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dnp = &osp->os_userused_dnode;
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err = traverse_dnode(td, dnp, buf, zb->zb_objset,
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if (tv->tv_err == 0 &&
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arc_buf_size(tv->tv_buf) >= sizeof (objset_phys_t)) {
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tv->tv_ldnp = &tv->tv_osp->os_userused_dnode;
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tv->tv_err = traverse_dnode(tv->tv_td, tv->tv_ldnp,
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tv->tv_buf, tv->tv_zb->zb_objset,
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DMU_USERUSED_OBJECT);
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}
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if (err && hard) {
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lasterr = err;
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err = 0;
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if (tv->tv_err && tv->tv_hard) {
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tv->tv_lasterr = tv->tv_err;
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tv->tv_err = 0;
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}
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if (err == 0 && arc_buf_size(buf) >= sizeof (objset_phys_t)) {
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dnp = &osp->os_groupused_dnode;
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err = traverse_dnode(td, dnp, buf, zb->zb_objset,
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if (tv->tv_err == 0 &&
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arc_buf_size(tv->tv_buf) >= sizeof (objset_phys_t)) {
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tv->tv_ldnp = &tv->tv_osp->os_groupused_dnode;
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tv->tv_err = traverse_dnode(tv->tv_td, tv->tv_ldnp,
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tv->tv_buf, tv->tv_zb->zb_objset,
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DMU_GROUPUSED_OBJECT);
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}
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}
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if (buf)
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(void) arc_buf_remove_ref(buf, &buf);
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if (tv->tv_buf)
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(void) arc_buf_remove_ref(tv->tv_buf, &tv->tv_buf);
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if (err == 0 && lasterr == 0 && (td->td_flags & TRAVERSE_POST)) {
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err = td->td_func(td->td_spa, NULL, bp, pbuf, zb, dnp,
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td->td_arg);
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if (tv->tv_err == 0 && tv->tv_lasterr == 0 &&
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(tv->tv_td->td_flags & TRAVERSE_POST)) {
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tv->tv_err = tv->tv_td->td_func(tv->tv_td->td_spa, NULL,
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tv->tv_bp, tv->tv_pbuf, tv->tv_zb, tv->tv_dnp,
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tv->tv_td->td_arg);
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}
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return (err != 0 ? err : lasterr);
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return (tv->tv_err != 0 ? tv->tv_err : tv->tv_lasterr);
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}
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/*
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* Due to limited stack space recursive functions are frowned upon in
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* the Linux kernel. However, they often are the most elegant solution
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* to a problem. The following code preserves the recursive function
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* traverse_visitbp() but moves the local variables AND function
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* arguments to the heap to minimize the stack frame size. Enough
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* space is initially allocated on the stack for 16 levels of recursion.
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* This change does ugly-up-the-code but it reduces the worst case
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* usage from roughly 2496 bytes to 576 bytes on x86_64 archs.
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*/
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static int
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traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp,
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arc_buf_t *pbuf, blkptr_t *bp, const zbookmark_t *zb)
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{
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traverse_visitbp_data_t *tv;
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int error;
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tv = kmem_zalloc(sizeof(traverse_visitbp_data_t) *
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TRAVERSE_VISITBP_MAX_DEPTH, KM_SLEEP);
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__traverse_visitbp_init(tv, td, dnp, pbuf, bp, zb, 0);
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error = __traverse_visitbp(tv);
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kmem_free(tv, sizeof(traverse_visitbp_data_t) *
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TRAVERSE_VISITBP_MAX_DEPTH);
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return (error);
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}
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static int
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