erofs: record the longest decompressed size in this round

Currently, `pcl->length' records the longest decompressed length
as long as the pcluster itself isn't reclaimed.  However, such
number is unneeded for the general cases since it doesn't indicate
the exact decompressed size in this round.

Instead, let's record the decompressed size for this round instead,
thus `pcl->nr_pages' can be completely dropped and pageofs_out is
also designed to be kept in sync with `pcl->length'.

Acked-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20220715154203.48093-16-hsiangkao@linux.alibaba.com

1 files changed, 27 insertions, 51 deletions

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index d4db2c1d53a6..0ef672372a69 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -482,7 +482,6 @@ static int z_erofs_lookup_pcluster(struct z_erofs_decompress_frontend *fe)
 {
 	struct erofs_map_blocks *map = &fe->map;
 	struct z_erofs_pcluster *pcl = fe->pcl;
-	unsigned int length;
 
 	/* to avoid unexpected loop formed by corrupted images */
 	if (fe->owned_head == &pcl->next || pcl == fe->tailpcl) {
@@ -495,24 +494,6 @@ static int z_erofs_lookup_pcluster(struct z_erofs_decompress_frontend *fe)
 		return -EFSCORRUPTED;
 	}
 
-	length = READ_ONCE(pcl->length);
-	if (length & Z_EROFS_PCLUSTER_FULL_LENGTH) {
-		if ((map->m_llen << Z_EROFS_PCLUSTER_LENGTH_BIT) > length) {
-			DBG_BUGON(1);
-			return -EFSCORRUPTED;
-		}
-	} else {
-		unsigned int llen = map->m_llen << Z_EROFS_PCLUSTER_LENGTH_BIT;
-
-		if (map->m_flags & EROFS_MAP_FULL_MAPPED)
-			llen |= Z_EROFS_PCLUSTER_FULL_LENGTH;
-
-		while (llen > length &&
-		       length != cmpxchg_relaxed(&pcl->length, length, llen)) {
-			cpu_relax();
-			length = READ_ONCE(pcl->length);
-		}
-	}
 	mutex_lock(&pcl->lock);
 	/* used to check tail merging loop due to corrupted images */
 	if (fe->owned_head == Z_EROFS_PCLUSTER_TAIL)
@@ -543,9 +524,8 @@ static int z_erofs_register_pcluster(struct z_erofs_decompress_frontend *fe)
 
 	atomic_set(&pcl->obj.refcount, 1);
 	pcl->algorithmformat = map->m_algorithmformat;
-	pcl->length = (map->m_llen << Z_EROFS_PCLUSTER_LENGTH_BIT) |
-		(map->m_flags & EROFS_MAP_FULL_MAPPED ?
-			Z_EROFS_PCLUSTER_FULL_LENGTH : 0);
+	pcl->length = 0;
+	pcl->partial = true;
 
 	/* new pclusters should be claimed as type 1, primary and followed */
 	pcl->next = fe->owned_head;
@@ -703,7 +683,7 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
 	bool tight = true, exclusive;
 
 	enum z_erofs_cache_alloctype cache_strategy;
-	unsigned int cur, end, spiltted, index;
+	unsigned int cur, end, spiltted;
 	int err = 0;
 
 	/* register locked file pages as online pages in pack */
@@ -806,12 +786,17 @@ retry:
 	/* bump up the number of spiltted parts of a page */
 	++spiltted;
 
-	/* also update nr_pages */
-	index = page->index - (map->m_la >> PAGE_SHIFT);
-	fe->pcl->nr_pages = max_t(pgoff_t, fe->pcl->nr_pages, index + 1);
+	if ((map->m_flags & EROFS_MAP_FULL_MAPPED) &&
+	    fe->pcl->length == map->m_llen)
+		fe->pcl->partial = false;
+	if (fe->pcl->length < offset + end - map->m_la) {
+		fe->pcl->length = offset + end - map->m_la;
+		fe->pcl->pageofs_out = map->m_la & ~PAGE_MASK;
+	}
 next_part:
-	/* can be used for verification */
+	/* shorten the remaining extent to update progress */
 	map->m_llen = offset + cur - map->m_la;
+	map->m_flags &= ~EROFS_MAP_FULL_MAPPED;
 
 	end = cur;
 	if (end > 0)
@@ -858,7 +843,7 @@ struct z_erofs_decompress_backend {
 	struct page **compressed_pages;
 
 	struct page **pagepool;
-	unsigned int onstack_used;
+	unsigned int onstack_used, nr_pages;
 };
 
 static int z_erofs_do_decompressed_bvec(struct z_erofs_decompress_backend *be,
@@ -867,7 +852,7 @@ static int z_erofs_do_decompressed_bvec(struct z_erofs_decompress_backend *be,
 	unsigned int pgnr = (bvec->offset + be->pcl->pageofs_out) >> PAGE_SHIFT;
 	struct page *oldpage;
 
-	DBG_BUGON(pgnr >= be->pcl->nr_pages);
+	DBG_BUGON(pgnr >= be->nr_pages);
 	oldpage = be->decompressed_pages[pgnr];
 	be->decompressed_pages[pgnr] = bvec->page;
 
@@ -955,24 +940,23 @@ static int z_erofs_decompress_pcluster(struct z_erofs_decompress_backend *be,
 	struct erofs_sb_info *const sbi = EROFS_SB(be->sb);
 	struct z_erofs_pcluster *pcl = be->pcl;
 	unsigned int pclusterpages = z_erofs_pclusterpages(pcl);
-	unsigned int i, inputsize, outputsize, llen, nr_pages;
-	struct page *page;
+	unsigned int i, inputsize;
 	int err2;
-	bool overlapped, partial;
+	struct page *page;
+	bool overlapped;
 
-	DBG_BUGON(!READ_ONCE(pcl->nr_pages));
 	mutex_lock(&pcl->lock);
-	nr_pages = pcl->nr_pages;
+	be->nr_pages = PAGE_ALIGN(pcl->length + pcl->pageofs_out) >> PAGE_SHIFT;
 
 	/* allocate (de)compressed page arrays if cannot be kept on stack */
 	be->decompressed_pages = NULL;
 	be->compressed_pages = NULL;
 	be->onstack_used = 0;
-	if (nr_pages <= Z_EROFS_ONSTACK_PAGES) {
+	if (be->nr_pages <= Z_EROFS_ONSTACK_PAGES) {
 		be->decompressed_pages = be->onstack_pages;
-		be->onstack_used = nr_pages;
+		be->onstack_used = be->nr_pages;
 		memset(be->decompressed_pages, 0,
-		       sizeof(struct page *) * nr_pages);
+		       sizeof(struct page *) * be->nr_pages);
 	}
 
 	if (pclusterpages + be->onstack_used <= Z_EROFS_ONSTACK_PAGES)
@@ -980,7 +964,7 @@ static int z_erofs_decompress_pcluster(struct z_erofs_decompress_backend *be,
 
 	if (!be->decompressed_pages)
 		be->decompressed_pages =
-			kvcalloc(nr_pages, sizeof(struct page *),
+			kvcalloc(be->nr_pages, sizeof(struct page *),
 				 GFP_KERNEL | __GFP_NOFAIL);
 	if (!be->compressed_pages)
 		be->compressed_pages =
@@ -997,15 +981,6 @@ static int z_erofs_decompress_pcluster(struct z_erofs_decompress_backend *be,
 	if (err)
 		goto out;
 
-	llen = pcl->length >> Z_EROFS_PCLUSTER_LENGTH_BIT;
-	if (nr_pages << PAGE_SHIFT >= pcl->pageofs_out + llen) {
-		outputsize = llen;
-		partial = !(pcl->length & Z_EROFS_PCLUSTER_FULL_LENGTH);
-	} else {
-		outputsize = (nr_pages << PAGE_SHIFT) - pcl->pageofs_out;
-		partial = true;
-	}
-
 	if (z_erofs_is_inline_pcluster(pcl))
 		inputsize = pcl->tailpacking_size;
 	else
@@ -1018,10 +993,10 @@ static int z_erofs_decompress_pcluster(struct z_erofs_decompress_backend *be,
 					.pageofs_in = pcl->pageofs_in,
 					.pageofs_out = pcl->pageofs_out,
 					.inputsize = inputsize,
-					.outputsize = outputsize,
+					.outputsize = pcl->length,
 					.alg = pcl->algorithmformat,
 					.inplace_io = overlapped,
-					.partial_decoding = partial
+					.partial_decoding = pcl->partial,
 				 }, be->pagepool);
 
 out:
@@ -1046,7 +1021,7 @@ out:
 	    be->compressed_pages >= be->onstack_pages + Z_EROFS_ONSTACK_PAGES)
 		kvfree(be->compressed_pages);
 
-	for (i = 0; i < nr_pages; ++i) {
+	for (i = 0; i < be->nr_pages; ++i) {
 		page = be->decompressed_pages[i];
 		if (!page)
 			continue;
@@ -1064,7 +1039,8 @@ out:
 	if (be->decompressed_pages != be->onstack_pages)
 		kvfree(be->decompressed_pages);
 
-	pcl->nr_pages = 0;
+	pcl->length = 0;
+	pcl->partial = true;
 	pcl->bvset.nextpage = NULL;
 	pcl->vcnt = 0;