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Fix self-healing IO prior to dsl_pool_init() completion

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Async writes triggered by a self-healing IO may be issued before the
pool finishes the process of initialization.  This results in a NULL
dereference of `spa->spa_dsl_pool` in vdev_queue_max_async_writes().

George Wilson recommended addressing this issue by initializing the
passed `dsl_pool_t **` prior to dmu_objset_open_impl().  Since the
caller is passing the `spa->spa_dsl_pool` this has the effect of
ensuring it's initialized.

However, since this depends on the caller knowing they must pass
the `spa->spa_dsl_pool` an additional NULL check was added to
vdev_queue_max_async_writes().  This guards against any future
restructuring of the code which might result in dsl_pool_init()
being called differently.

Signed-off-by: GeLiXin <47034221@qq.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #4652
This commit is contained in:
GeLiXin
2016-05-21 11:34:06 +08:00
committed by Brian Behlendorf
parent 92547bc45c
commit b7faa7aabd
2 changed files with 23 additions and 6 deletions
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module/zfs/vdev_queue.c
+12 -3
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@@ -249,20 +249,29 @@ static int
vdev_queue_max_async_writes(spa_t *spa)
{
int writes;
uint64_t dirty = spa->spa_dsl_pool->dp_dirty_total;
uint64_t dirty = 0;
dsl_pool_t *dp = spa_get_dsl(spa);
uint64_t min_bytes = zfs_dirty_data_max *
zfs_vdev_async_write_active_min_dirty_percent / 100;
uint64_t max_bytes = zfs_dirty_data_max *
zfs_vdev_async_write_active_max_dirty_percent / 100;
/*
* Async writes may occur before the assignment of the spa's
* dsl_pool_t if a self-healing zio is issued prior to the
* completion of dmu_objset_open_impl().
*/
if (dp == NULL)
return (zfs_vdev_async_write_max_active);
/*
* Sync tasks correspond to interactive user actions. To reduce the
* execution time of those actions we push data out as fast as possible.
*/
if (spa_has_pending_synctask(spa)) {
if (spa_has_pending_synctask(spa))
return (zfs_vdev_async_write_max_active);
}
dirty = dp->dp_dirty_total;
if (dirty < min_bytes)
return (zfs_vdev_async_write_min_active);
if (dirty > max_bytes)