diff --git a/.topdeps b/.topdeps new file mode 100644 index 000000000000..1f7391f92b6a --- /dev/null +++ b/.topdeps @@ -0,0 +1 @@ +master diff --git a/.topmsg b/.topmsg new file mode 100644 index 000000000000..0c9201a1a884 --- /dev/null +++ b/.topmsg @@ -0,0 +1,13 @@ +From: Brian Behlendorf +Subject: [PATCH] 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 diff --git a/module/zfs/dmu_traverse.c b/module/zfs/dmu_traverse.c index 429c76ae11f1..2cf10df828a2 100644 --- a/module/zfs/dmu_traverse.c +++ b/module/zfs/dmu_traverse.c @@ -57,6 +57,33 @@ struct traverse_data { void *td_arg; }; +struct traverse_visitbp_data { + /* Function arguments */ + struct traverse_data *tv_td; + const dnode_phys_t *tv_dnp; + arc_buf_t *tv_pbuf; + blkptr_t *tv_bp; + const zbookmark_t *tv_zb; + /* Local variables */ + struct prefetch_data *tv_pd; + zbookmark_t tv_czb; + arc_buf_t *tv_buf; + boolean_t tv_hard; + objset_phys_t *tv_osp; + dnode_phys_t *tv_ldnp; + blkptr_t *tv_cbp; + uint32_t tv_flags; + int tv_err; + int tv_lasterr; + int tv_i; + int tv_epb; +#ifdef DEBUG + int tv_depth; +#endif +}; + +static inline int traverse_visitbp(struct traverse_data *td, const + dnode_phys_t *dnp, arc_buf_t *pbuf, blkptr_t *bp, const zbookmark_t *zb); static int traverse_dnode(struct traverse_data *td, const dnode_phys_t *dnp, arc_buf_t *buf, uint64_t objset, uint64_t object); @@ -128,137 +155,191 @@ traverse_zil(struct traverse_data *td, zil_header_t *zh) zil_free(zilog); } -static int -traverse_visitbp(struct traverse_data *td, const dnode_phys_t *dnp, - arc_buf_t *pbuf, blkptr_t *bp, const zbookmark_t *zb) +#define TRAVERSE_VISITBP_MAX_DEPTH 20 + +static void +__traverse_visitbp_init(struct traverse_visitbp_data *tv, + struct traverse_data *td, const dnode_phys_t *dnp, + arc_buf_t *pbuf, blkptr_t *bp, const zbookmark_t *zb, int depth) { - zbookmark_t czb; - int err = 0, lasterr = 0; - arc_buf_t *buf = NULL; - struct prefetch_data *pd = td->td_pfd; - boolean_t hard = td->td_flags & TRAVERSE_HARD; + tv->tv_td = td; + tv->tv_dnp = dnp; + tv->tv_pbuf = pbuf; + tv->tv_bp = bp; + tv->tv_zb = zb; + tv->tv_err = 0; + tv->tv_lasterr = 0; + tv->tv_buf = NULL; + tv->tv_pd = td->td_pfd; + tv->tv_hard = td->td_flags & TRAVERSE_HARD; + tv->tv_flags = ARC_WAIT; + tv->tv_depth = depth; +} - if (bp->blk_birth == 0) { - err = td->td_func(td->td_spa, NULL, NULL, pbuf, zb, dnp, - td->td_arg); - return (err); +static noinline int +__traverse_visitbp(struct traverse_visitbp_data *tv) +{ + ASSERT3S(tv->tv_depth, <, TRAVERSE_VISITBP_MAX_DEPTH); + + if (tv->tv_bp->blk_birth == 0) { + tv->tv_err = tv->tv_td->td_func(tv->tv_td->td_spa, NULL, NULL, + tv->tv_pbuf, tv->tv_zb, tv->tv_dnp, tv->tv_td->td_arg); + return (tv->tv_err); } - if (bp->blk_birth <= td->td_min_txg) + if (tv->tv_bp->blk_birth <= tv->tv_td->td_min_txg) return (0); - if (pd && !pd->pd_exited && - ((pd->pd_flags & TRAVERSE_PREFETCH_DATA) || - BP_GET_TYPE(bp) == DMU_OT_DNODE || BP_GET_LEVEL(bp) > 0)) { - mutex_enter(&pd->pd_mtx); - ASSERT(pd->pd_blks_fetched >= 0); - while (pd->pd_blks_fetched == 0 && !pd->pd_exited) - cv_wait(&pd->pd_cv, &pd->pd_mtx); - pd->pd_blks_fetched--; - cv_broadcast(&pd->pd_cv); - mutex_exit(&pd->pd_mtx); + if (tv->tv_pd && !tv->tv_pd->pd_exited && + ((tv->tv_pd->pd_flags & TRAVERSE_PREFETCH_DATA) || + BP_GET_TYPE(tv->tv_bp) == DMU_OT_DNODE || + BP_GET_LEVEL(tv->tv_bp) > 0)) { + mutex_enter(&tv->tv_pd->pd_mtx); + ASSERT(tv->tv_pd->pd_blks_fetched >= 0); + while (tv->tv_pd->pd_blks_fetched == 0 && !tv->tv_pd->pd_exited) + cv_wait(&tv->tv_pd->pd_cv, &tv->tv_pd->pd_mtx); + tv->tv_pd->pd_blks_fetched--; + cv_broadcast(&tv->tv_pd->pd_cv); + mutex_exit(&tv->tv_pd->pd_mtx); } - if (td->td_flags & TRAVERSE_PRE) { - err = td->td_func(td->td_spa, NULL, bp, pbuf, zb, dnp, - td->td_arg); - if (err) - return (err); + if (tv->tv_td->td_flags & TRAVERSE_PRE) { + tv->tv_err = tv->tv_td->td_func(tv->tv_td->td_spa, NULL, + tv->tv_bp, tv->tv_pbuf, tv->tv_zb, tv->tv_dnp, + tv->tv_td->td_arg); + if (tv->tv_err) + return (tv->tv_err); } - if (BP_GET_LEVEL(bp) > 0) { - uint32_t flags = ARC_WAIT; - int i; - blkptr_t *cbp; - int epb = BP_GET_LSIZE(bp) >> SPA_BLKPTRSHIFT; + if (BP_GET_LEVEL(tv->tv_bp) > 0) { + tv->tv_epb = BP_GET_LSIZE(tv->tv_bp) >> SPA_BLKPTRSHIFT; - err = dsl_read(NULL, td->td_spa, bp, pbuf, - arc_getbuf_func, &buf, - ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, zb); - if (err) - return (err); + tv->tv_err = dsl_read(NULL, tv->tv_td->td_spa, tv->tv_bp, + tv->tv_pbuf, arc_getbuf_func, &tv->tv_buf, + ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, + &tv->tv_flags, tv->tv_zb); + if (tv->tv_err) + return (tv->tv_err); /* recursively visitbp() blocks below this */ - cbp = buf->b_data; - for (i = 0; i < epb; i++, cbp++) { - SET_BOOKMARK(&czb, zb->zb_objset, zb->zb_object, - zb->zb_level - 1, - zb->zb_blkid * epb + i); - err = traverse_visitbp(td, dnp, buf, cbp, &czb); - if (err) { - if (!hard) + tv->tv_cbp = tv->tv_buf->b_data; + for (tv->tv_i = 0; tv->tv_i < tv->tv_epb; + tv->tv_i++, tv->tv_cbp++) { + SET_BOOKMARK(&tv->tv_czb, tv->tv_zb->zb_objset, + tv->tv_zb->zb_object, tv->tv_zb->zb_level - 1, + tv->tv_zb->zb_blkid * tv->tv_epb + tv->tv_i); + __traverse_visitbp_init(tv + 1, tv->tv_td, + tv->tv_dnp, tv->tv_buf, tv->tv_cbp, + &tv->tv_czb, tv->tv_depth + 1); + tv->tv_err = __traverse_visitbp(tv + 1); + if (tv->tv_err) { + if (!tv->tv_hard) break; - lasterr = err; + tv->tv_lasterr = tv->tv_err; } } - } else if (BP_GET_TYPE(bp) == DMU_OT_DNODE) { - uint32_t flags = ARC_WAIT; - int i; - int epb = BP_GET_LSIZE(bp) >> DNODE_SHIFT; + } else if (BP_GET_TYPE(tv->tv_bp) == DMU_OT_DNODE) { + tv->tv_epb = BP_GET_LSIZE(tv->tv_bp) >> DNODE_SHIFT; - err = dsl_read(NULL, td->td_spa, bp, pbuf, - arc_getbuf_func, &buf, - ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, zb); - if (err) - return (err); + tv->tv_err = dsl_read(NULL, tv->tv_td->td_spa, tv->tv_bp, + tv->tv_pbuf, arc_getbuf_func, &tv->tv_buf, + ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, + &tv->tv_flags, tv->tv_zb); + if (tv->tv_err) + return (tv->tv_err); /* recursively visitbp() blocks below this */ - dnp = buf->b_data; - for (i = 0; i < epb; i++, dnp++) { - err = traverse_dnode(td, dnp, buf, zb->zb_objset, - zb->zb_blkid * epb + i); - if (err) { - if (!hard) + tv->tv_dnp = tv->tv_buf->b_data; + for (tv->tv_i = 0; tv->tv_i < tv->tv_epb; + tv->tv_i++, tv->tv_dnp++) { + tv->tv_err = traverse_dnode(tv->tv_td, tv->tv_dnp, + tv->tv_buf, tv->tv_zb->zb_objset, + tv->tv_zb->zb_blkid * tv->tv_epb + tv->tv_i); + if (tv->tv_err) { + if (!tv->tv_hard) break; - lasterr = err; + tv->tv_lasterr = tv->tv_err; } } - } else if (BP_GET_TYPE(bp) == DMU_OT_OBJSET) { - uint32_t flags = ARC_WAIT; - objset_phys_t *osp; - dnode_phys_t *dnp; - - err = dsl_read_nolock(NULL, td->td_spa, bp, - arc_getbuf_func, &buf, - ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, zb); - if (err) - return (err); - - osp = buf->b_data; - traverse_zil(td, &osp->os_zil_header); - - dnp = &osp->os_meta_dnode; - err = traverse_dnode(td, dnp, buf, zb->zb_objset, - DMU_META_DNODE_OBJECT); - if (err && hard) { - lasterr = err; - err = 0; + } else if (BP_GET_TYPE(tv->tv_bp) == DMU_OT_OBJSET) { + + tv->tv_err = dsl_read_nolock(NULL, tv->tv_td->td_spa, + tv->tv_bp, arc_getbuf_func, &tv->tv_buf, + ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, + &tv->tv_flags, tv->tv_zb); + if (tv->tv_err) + return (tv->tv_err); + + tv->tv_osp = tv->tv_buf->b_data; + traverse_zil(tv->tv_td, &tv->tv_osp->os_zil_header); + + tv->tv_ldnp = &tv->tv_osp->os_meta_dnode; + tv->tv_err = traverse_dnode(tv->tv_td, tv->tv_ldnp, tv->tv_buf, + tv->tv_zb->zb_objset, DMU_META_DNODE_OBJECT); + if (tv->tv_err && tv->tv_hard) { + tv->tv_lasterr = tv->tv_err; + tv->tv_err = 0; } - if (err == 0 && arc_buf_size(buf) >= sizeof (objset_phys_t)) { - dnp = &osp->os_userused_dnode; - err = traverse_dnode(td, dnp, buf, zb->zb_objset, + if (tv->tv_err == 0 && + arc_buf_size(tv->tv_buf) >= sizeof (objset_phys_t)) { + tv->tv_ldnp = &tv->tv_osp->os_userused_dnode; + tv->tv_err = traverse_dnode(tv->tv_td, tv->tv_ldnp, + tv->tv_buf, tv->tv_zb->zb_objset, DMU_USERUSED_OBJECT); } - if (err && hard) { - lasterr = err; - err = 0; + if (tv->tv_err && tv->tv_hard) { + tv->tv_lasterr = tv->tv_err; + tv->tv_err = 0; } - if (err == 0 && arc_buf_size(buf) >= sizeof (objset_phys_t)) { - dnp = &osp->os_groupused_dnode; - err = traverse_dnode(td, dnp, buf, zb->zb_objset, + if (tv->tv_err == 0 && + arc_buf_size(tv->tv_buf) >= sizeof (objset_phys_t)) { + tv->tv_ldnp = &tv->tv_osp->os_groupused_dnode; + tv->tv_err = traverse_dnode(tv->tv_td, tv->tv_ldnp, + tv->tv_buf, tv->tv_zb->zb_objset, DMU_GROUPUSED_OBJECT); } } - if (buf) - (void) arc_buf_remove_ref(buf, &buf); + if (tv->tv_buf) + (void) arc_buf_remove_ref(tv->tv_buf, &tv->tv_buf); - if (err == 0 && lasterr == 0 && (td->td_flags & TRAVERSE_POST)) { - err = td->td_func(td->td_spa, NULL, bp, pbuf, zb, dnp, - td->td_arg); + if (tv->tv_err == 0 && tv->tv_lasterr == 0 && + (tv->tv_td->td_flags & TRAVERSE_POST)) { + tv->tv_err = tv->tv_td->td_func(tv->tv_td->td_spa, NULL, + tv->tv_bp, tv->tv_pbuf, tv->tv_zb, tv->tv_dnp, + tv->tv_td->td_arg); } - return (err != 0 ? err : lasterr); + return (tv->tv_err != 0 ? tv->tv_err : tv->tv_lasterr); +} + +/* + * 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 16 levels of recursion. + * This change does ugly-up-the-code but it reduces the worst case + * usage from roughly 2496 bytes to 576 bytes on x86_64 archs. + */ +static int +traverse_visitbp(struct traverse_data *td, const dnode_phys_t *dnp, + arc_buf_t *pbuf, blkptr_t *bp, const zbookmark_t *zb) +{ + struct traverse_visitbp_data *tv; + int error; + + tv = kmem_zalloc(sizeof(struct traverse_visitbp_data) * + TRAVERSE_VISITBP_MAX_DEPTH, KM_SLEEP); + __traverse_visitbp_init(tv, td, dnp, pbuf, bp, zb, 0); + + error = __traverse_visitbp(tv); + + kmem_free(tv, sizeof(struct traverse_visitbp_data) * + TRAVERSE_VISITBP_MAX_DEPTH); + + return (error); } static int