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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 <behlendorf1@llnl.gov>
This commit is contained in:
Ned Bass 2010-07-29 18:30:39 -07:00 committed by Brian Behlendorf
parent 911d2e0df4
commit 410d8c4e15
1 changed files with 14 additions and 9 deletions
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23
module/zfs/dsl_scan.c
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@ -789,18 +789,21 @@ dsl_scan_visitbp(blkptr_t *bp, const zbookmark_t *zb,
{ {
dsl_pool_t *dp = scn->scn_dp; dsl_pool_t *dp = scn->scn_dp;
arc_buf_t *buf = NULL; 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)); */ /* ASSERT(pbuf == NULL || arc_released(pbuf)); */
if (dsl_scan_check_pause(scn, zb)) if (dsl_scan_check_pause(scn, zb))
return; goto out;
if (dsl_scan_check_resume(scn, dnp, zb)) if (dsl_scan_check_resume(scn, dnp, zb))
return; goto out;
if (bp->blk_birth == 0) if (bp->blk_birth == 0)
return; goto out;
scn->scn_visited_this_txg++; scn->scn_visited_this_txg++;
@ -811,7 +814,7 @@ dsl_scan_visitbp(blkptr_t *bp, const zbookmark_t *zb,
pbuf, bp); pbuf, bp);
if (bp->blk_birth <= scn->scn_phys.scn_cur_min_txg) if (bp->blk_birth <= scn->scn_phys.scn_cur_min_txg)
return; goto out;
if (BP_GET_TYPE(bp) != DMU_OT_USERGROUP_USED) { 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 * it (original untranslated -> translations from
* deleted snap -> now). * 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) &buf) != 0)
return; goto out;
/* /*
* If dsl_scan_ddt() has aready visited this block, it will have * 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, if (ddt_class_contains(dp->dp_spa,
scn->scn_phys.scn_ddt_class_max, bp)) { scn->scn_phys.scn_ddt_class_max, bp)) {
ASSERT(buf == NULL); ASSERT(buf == NULL);
return; goto out;
} }
/* /*
@ -856,6 +859,8 @@ dsl_scan_visitbp(blkptr_t *bp, const zbookmark_t *zb,
} }
if (buf) if (buf)
(void) arc_buf_remove_ref(buf, &buf); (void) arc_buf_remove_ref(buf, &buf);
out:
kmem_free(bp_toread, sizeof(blkptr_t));
} }
static void static void