erofs: rework online page handling

Since all decompressed offsets have been integrated to bvecs[], this
patch avoids all sub-indexes so that page->private only includes a
part count and an eio flag, thus in the future folio->private can have
the same meaning.

In addition, PG_error will not be used anymore after this patch and
we're heading to use page->private (later folio->private) and
page->mapping  (later folio->mapping) only.

Acked-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20220715154203.48093-9-hsiangkao@linux.alibaba.com

1 files changed, 19 insertions, 49 deletions

diff --git a/fs/erofs/zdata.h b/fs/erofs/zdata.h
index 5d236c8b40c5..75f6fd435388 100644
--- a/fs/erofs/zdata.h
+++ b/fs/erofs/zdata.h
@@ -109,6 +109,8 @@ struct z_erofs_decompressqueue {
 		struct completion done;
 		struct work_struct work;
 	} u;
+
+	bool eio;
 };
 
 static inline bool z_erofs_is_inline_pcluster(struct z_erofs_pcluster *pcl)
@@ -123,38 +125,17 @@ static inline unsigned int z_erofs_pclusterpages(struct z_erofs_pcluster *pcl)
 	return pcl->pclusterpages;
 }
 
-#define Z_EROFS_ONLINEPAGE_COUNT_BITS   2
-#define Z_EROFS_ONLINEPAGE_COUNT_MASK   ((1 << Z_EROFS_ONLINEPAGE_COUNT_BITS) - 1)
-#define Z_EROFS_ONLINEPAGE_INDEX_SHIFT  (Z_EROFS_ONLINEPAGE_COUNT_BITS)
-
 /*
- * waiters (aka. ongoing_packs): # to unlock the page
- * sub-index: 0 - for partial page, >= 1 full page sub-index
+ * bit 31: I/O error occurred on this page
+ * bit 0 - 30: remaining parts to complete this page
  */
-typedef atomic_t z_erofs_onlinepage_t;
-
-/* type punning */
-union z_erofs_onlinepage_converter {
-	z_erofs_onlinepage_t *o;
-	unsigned long *v;
-};
-
-static inline unsigned int z_erofs_onlinepage_index(struct page *page)
-{
-	union z_erofs_onlinepage_converter u;
-
-	DBG_BUGON(!PagePrivate(page));
-	u.v = &page_private(page);
-
-	return atomic_read(u.o) >> Z_EROFS_ONLINEPAGE_INDEX_SHIFT;
-}
+#define Z_EROFS_PAGE_EIO			(1 << 31)
 
 static inline void z_erofs_onlinepage_init(struct page *page)
 {
 	union {
-		z_erofs_onlinepage_t o;
+		atomic_t o;
 		unsigned long v;
-	/* keep from being unlocked in advance */
 	} u = { .o = ATOMIC_INIT(1) };
 
 	set_page_private(page, u.v);
@@ -162,45 +143,34 @@ static inline void z_erofs_onlinepage_init(struct page *page)
 	SetPagePrivate(page);
 }
 
-static inline void z_erofs_onlinepage_fixup(struct page *page,
-	uintptr_t index, bool down)
+static inline void z_erofs_onlinepage_split(struct page *page)
 {
-	union z_erofs_onlinepage_converter u = { .v = &page_private(page) };
-	int orig, orig_index, val;
-
-repeat:
-	orig = atomic_read(u.o);
-	orig_index = orig >> Z_EROFS_ONLINEPAGE_INDEX_SHIFT;
-	if (orig_index) {
-		if (!index)
-			return;
+	atomic_inc((atomic_t *)&page->private);
+}
 
-		DBG_BUGON(orig_index != index);
-	}
+static inline void z_erofs_page_mark_eio(struct page *page)
+{
+	int orig;
 
-	val = (index << Z_EROFS_ONLINEPAGE_INDEX_SHIFT) |
-		((orig & Z_EROFS_ONLINEPAGE_COUNT_MASK) + (unsigned int)down);
-	if (atomic_cmpxchg(u.o, orig, val) != orig)
-		goto repeat;
+	do {
+		orig = atomic_read((atomic_t *)&page->private);
+	} while (atomic_cmpxchg((atomic_t *)&page->private, orig,
+				orig | Z_EROFS_PAGE_EIO) != orig);
 }
 
 static inline void z_erofs_onlinepage_endio(struct page *page)
 {
-	union z_erofs_onlinepage_converter u;
 	unsigned int v;
 
 	DBG_BUGON(!PagePrivate(page));
-	u.v = &page_private(page);
-
-	v = atomic_dec_return(u.o);
-	if (!(v & Z_EROFS_ONLINEPAGE_COUNT_MASK)) {
+	v = atomic_dec_return((atomic_t *)&page->private);
+	if (!(v & ~Z_EROFS_PAGE_EIO)) {
 		set_page_private(page, 0);
 		ClearPagePrivate(page);
-		if (!PageError(page))
+		if (!(v & Z_EROFS_PAGE_EIO))
 			SetPageUptodate(page);
 		unlock_page(page);
 	}
-	erofs_dbg("%s, page %p value %x", __func__, page, atomic_read(u.o));
 }
 
 #define Z_EROFS_VMAP_ONSTACK_PAGES	\