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Subject[PATCH v2 04/10] erofs: fix up inplace I/O pointer for big pcluster
Date
From: Gao Xiang <hsiangkao@redhat.com>

When picking up inplace I/O pages, it should be traversed in reverse
order in aligned with the traversal order of file-backed online pages.
Also, index should be updated together when preloading compressed pages.

Previously, only page-sized pclustersize was supported so no problem
at all. Also rename `compressedpages' to `icpage_ptr' to reflect its
functionality.

Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
---
fs/erofs/zdata.c | 28 ++++++++++++++--------------
1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 7f572086b4e3..03f106ead8d2 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -204,7 +204,8 @@ struct z_erofs_collector {

struct z_erofs_pcluster *pcl, *tailpcl;
struct z_erofs_collection *cl;
- struct page **compressedpages;
+ /* a pointer used to pick up inplace I/O pages */
+ struct page **icpage_ptr;
z_erofs_next_pcluster_t owned_head;

enum z_erofs_collectmode mode;
@@ -238,17 +239,19 @@ static void preload_compressed_pages(struct z_erofs_collector *clt,
enum z_erofs_cache_alloctype type,
struct list_head *pagepool)
{
- const struct z_erofs_pcluster *pcl = clt->pcl;
- struct page **pages = clt->compressedpages;
- pgoff_t index = pcl->obj.index + (pages - pcl->compressed_pages);
+ struct z_erofs_pcluster *pcl = clt->pcl;
bool standalone = true;
gfp_t gfp = (mapping_gfp_mask(mc) & ~__GFP_DIRECT_RECLAIM) |
__GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN;
+ struct page **pages;
+ pgoff_t index;

if (clt->mode < COLLECT_PRIMARY_FOLLOWED)
return;

- for (; pages < pcl->compressed_pages + pcl->pclusterpages; ++pages) {
+ pages = pcl->compressed_pages;
+ index = pcl->obj.index;
+ for (; index < pcl->obj.index + pcl->pclusterpages; ++index, ++pages) {
struct page *page;
compressed_page_t t;
struct page *newpage = NULL;
@@ -360,16 +363,14 @@ int erofs_try_to_free_cached_page(struct address_space *mapping,
}

/* page_type must be Z_EROFS_PAGE_TYPE_EXCLUSIVE */
-static inline bool z_erofs_try_inplace_io(struct z_erofs_collector *clt,
- struct page *page)
+static bool z_erofs_try_inplace_io(struct z_erofs_collector *clt,
+ struct page *page)
{
struct z_erofs_pcluster *const pcl = clt->pcl;

- while (clt->compressedpages <
- pcl->compressed_pages + pcl->pclusterpages) {
- if (!cmpxchg(clt->compressedpages++, NULL, page))
+ while (clt->icpage_ptr > pcl->compressed_pages)
+ if (!cmpxchg(--clt->icpage_ptr, NULL, page))
return true;
- }
return false;
}

@@ -576,9 +577,8 @@ static int z_erofs_collector_begin(struct z_erofs_collector *clt,
z_erofs_pagevec_ctor_init(&clt->vector, Z_EROFS_NR_INLINE_PAGEVECS,
clt->cl->pagevec, clt->cl->vcnt);

- clt->compressedpages = clt->pcl->compressed_pages;
- if (clt->mode <= COLLECT_PRIMARY) /* cannot do in-place I/O */
- clt->compressedpages += clt->pcl->pclusterpages;
+ /* since file-backed online pages are traversed in reverse order */
+ clt->icpage_ptr = clt->pcl->compressed_pages + clt->pcl->pclusterpages;
return 0;
}

--
2.20.1
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