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Remove recursion from dsl_dir_willuse_space()

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Remove recursion from dsl_dir_willuse_space() to reduce stack usage.
Issues with stack overflow were observed in zfs recv of zvols,
likelihood of an overflow is proportional to the depth of the dataset
as dsl_dir_willuse_space() recurses to parent datasets.

Signed-off-by: Andrew Barnes <barnes333@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2069
This commit is contained in:
Andrew Barnes 2014-01-20 15:39:28 +11:00 committed by Brian Behlendorf
parent 0ad85ed91e
commit 1ba1615925
1 changed files with 17 additions and 11 deletions
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14
module/zfs/dsl_dir.c
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@ -808,6 +808,10 @@ dsl_dir_tempreserve_clear(void *tr_cookie, dmu_tx_t *tx)
* or free space, for example when dirtying data. Be conservative; it's okay
* to write less space or free more, but we don't want to write more or free
* less than the amount specified.
*
* NOTE: The behavior of this function is identical to the Illumos / FreeBSD
* version however it has been adjusted to use an iterative rather then
* recursive algorithm to minimize stack usage.
*/
void
dsl_dir_willuse_space(dsl_dir_t *dd, int64_t space, dmu_tx_t *tx)
@ -815,20 +819,22 @@ dsl_dir_willuse_space(dsl_dir_t *dd, int64_t space, dmu_tx_t *tx)
int64_t parent_space;
uint64_t est_used;
do {
mutex_enter(&dd->dd_lock);
if (space > 0)
dd->dd_space_towrite[tx->tx_txg & TXG_MASK] += space;
est_used = dsl_dir_space_towrite(dd) + dd->dd_phys->dd_used_bytes;
est_used = dsl_dir_space_towrite(dd) +
dd->dd_phys->dd_used_bytes;
parent_space = parent_delta(dd, est_used, space);
mutex_exit(&dd->dd_lock);
/* Make sure that we clean up dd_space_to* */
dsl_dir_dirty(dd, tx);
/* XXX this is potentially expensive and unnecessary... */
if (parent_space && dd->dd_parent)
dsl_dir_willuse_space(dd->dd_parent, parent_space, tx);
dd = dd->dd_parent;
space = parent_space;
} while (space && dd);
}
/* call from syncing context when we actually write/free space for this dd */