lkml.org 
[lkml]   [2018]   [Jun]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [PATCH -mm -V3 03/21] mm, THP, swap: Support PMD swap mapping in swap_duplicate()
Hi,

The series up to and including this patch doesn't build. For this patch we
need:

diff --git a/mm/swap_state.c b/mm/swap_state.c
index c6b3eab73fde..2f2d07627113 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -433,7 +433,7 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
/*
* Swap entry may have been freed since our caller observed it.
*/
- err = swapcache_prepare(entry);
+ err = swapcache_prepare(entry, false);
if (err == -EEXIST) {
radix_tree_preload_end();
/*

On Wed, May 23, 2018 at 04:26:07PM +0800, Huang, Ying wrote:
> @@ -3516,11 +3512,39 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage)

Two comments about this part of __swap_duplicate as long as you're moving it to
another function:

} else if (count || has_cache) {
if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX) /* #1 */
count += usage;
else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX) /* #2 */
err = -EINVAL;
#1: __swap_duplicate_locked might use

VM_BUG_ON(usage != SWAP_HAS_CACHE && usage != 1);

to document the unstated assumption that usage is 1 (otherwise count could
overflow).

#2: We've masked off SWAP_HAS_CACHE and COUNT_CONTINUED, and already checked
for SWAP_MAP_BAD, so I think condition #2 always fails and can just be removed.

> +#ifdef CONFIG_THP_SWAP
> +static int __swap_duplicate_cluster(swp_entry_t *entry, unsigned char usage)
...
> + } else {
> + for (i = 0; i < SWAPFILE_CLUSTER; i++) {
> +retry:
> + err = __swap_duplicate_locked(si, offset + i, 1);

I guess usage is assumed to be 1 at this point (__swap_duplicate_locked makes
the same assumption). Maybe make this explicit with

err = __swap_duplicate_locked(si, offset + i, usage);

, use 'usage' in cluster_set_count and __swap_entry_free too, and then
earlier have a

VM_BUG_ON(usage != SWAP_HAS_CACHE && usage != 1);

?

> +#else
> +static inline int __swap_duplicate_cluster(swp_entry_t *entry,

This doesn't need inline.


Not related to your changes, but while we're here, the comment with
SWAP_HAS_CONT in swap_count() could be deleted: I don't think there ever was a
SWAP_HAS_CONT.

The rest looks ok up to this point.

\
 
 \ /
  Last update: 2018-06-11 22:44    [W:0.188 / U:0.116 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site