* Vlastimil Babka [off-list ref] [211215 11:43]:

On 12/1/21 15:29, Liam Howlett wrote:

quoted

From: "Liam R. Howlett" <redacted>

The maple tree code was added to find the unmapped area in a previous
commit and was checked against what the rbtree returned, but the actual
result was never used.  Start using the maple tree implementation and
remove the rbtree code.

Nice cleanup. But...

quoted

Add kernel documentation comment for these functions.

Signed-off-by: Liam R. Howlett <redacted>

quoted

 
 	/* Adjust search length to account for worst case alignment overhead */
 	length = info->length + info->align_mask;
 	if (length < info->length)
 		return -ENOMEM;
 
-	rcu_read_lock();
-	mas_empty_area_rev(&mas, info->low_limit, info->high_limit - 1,
-			   length);
-	rcu_read_unlock();

Why is RCU locking being removed as part of this? Ditton in
unmapped_area_topdown()

It is not needed with the mmap_lock() being used in the maple tree.  But
I should either be consistent and keep it everywhere or not have it in
the earlier patch.  I will fix this, maybe I should have left them in
everywhere.