From 410d8c4e1531fca810da0080ce5b19278f26a582 Mon Sep 17 00:00:00 2001 From: Ned Bass Date: Thu, 29 Jul 2010 18:30:39 -0700 Subject: [PATCH] Reduce dsl_scan_visitbp stack usage by moving blkptr_t to heap Github issue 22 reported a stack overrun when the zfs module was loaded, possibly related to the presence of existing zpools created under zfs-fuse. The stack trace showed 9 levels of recursion between dsl_scan_visitbp() and dsl_scan_recurse(). To reduce stack overhead in that code path, this commit moves the 128 byte blkptr_t data strucutre in dsl_scan_visitbp() to the heap. Signed-off-by: Brian Behlendorf --- module/zfs/dsl_scan.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-) diff --git a/module/zfs/dsl_scan.c b/module/zfs/dsl_scan.c index 23c37c7ccf..14e61a3632 100644 --- a/module/zfs/dsl_scan.c +++ b/module/zfs/dsl_scan.c @@ -789,18 +789,21 @@ dsl_scan_visitbp(blkptr_t *bp, const zbookmark_t *zb, { dsl_pool_t *dp = scn->scn_dp; arc_buf_t *buf = NULL; - blkptr_t bp_toread = *bp; + blkptr_t *bp_toread; + + bp_toread = kmem_alloc(sizeof (blkptr_t), KM_SLEEP); + *bp_toread = *bp; /* ASSERT(pbuf == NULL || arc_released(pbuf)); */ if (dsl_scan_check_pause(scn, zb)) - return; + goto out; if (dsl_scan_check_resume(scn, dnp, zb)) - return; + goto out; if (bp->blk_birth == 0) - return; + goto out; scn->scn_visited_this_txg++; @@ -811,7 +814,7 @@ dsl_scan_visitbp(blkptr_t *bp, const zbookmark_t *zb, pbuf, bp); if (bp->blk_birth <= scn->scn_phys.scn_cur_min_txg) - return; + goto out; if (BP_GET_TYPE(bp) != DMU_OT_USERGROUP_USED) { /* @@ -826,12 +829,12 @@ dsl_scan_visitbp(blkptr_t *bp, const zbookmark_t *zb, * it (original untranslated -> translations from * deleted snap -> now). */ - bp_toread = *bp; + *bp_toread = *bp; } - if (dsl_scan_recurse(scn, ds, ostype, dnp, &bp_toread, zb, tx, + if (dsl_scan_recurse(scn, ds, ostype, dnp, bp_toread, zb, tx, &buf) != 0) - return; + goto out; /* * If dsl_scan_ddt() has aready visited this block, it will have @@ -841,7 +844,7 @@ dsl_scan_visitbp(blkptr_t *bp, const zbookmark_t *zb, if (ddt_class_contains(dp->dp_spa, scn->scn_phys.scn_ddt_class_max, bp)) { ASSERT(buf == NULL); - return; + goto out; } /* @@ -856,6 +859,8 @@ dsl_scan_visitbp(blkptr_t *bp, const zbookmark_t *zb, } if (buf) (void) arc_buf_remove_ref(buf, &buf); +out: + kmem_free(bp_toread, sizeof(blkptr_t)); } static void