[PATCH 3/4] erofs: specify accurate nr_iovecs for compressed bios

[Gao Xiang]

Use more accurate compressed page count
instead of BIO_MAX_PAGES unconditionally.

Signed-off-by: Gao Xiang <hsiangkao at redhat.com>
---
 fs/erofs/zdata.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index d483e9fee41c..bb20f73f10e0 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -135,6 +135,8 @@ struct z_erofs_decompress_frontend {
 	struct z_erofs_collector clt;
 	struct erofs_map_blocks map;
 
+	unsigned int compressedblock_total;
+
 	/* used for applying cache strategy on the fly */
 	bool backmost;
 	erofs_off_t headoffset;
@@ -622,6 +624,7 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
 
 	preload_compressed_pages(clt, MNGD_MAPPING(sbi),
 				 cache_strategy, pagepool);
+	fe->compressedblock_total += BIT(clt->pcl->clusterbits);
 
 hitted:
 	/*
@@ -1151,7 +1154,7 @@ static void move_to_bypass_jobqueue(struct z_erofs_pcluster *pcl,
 }
 
 static void z_erofs_submit_queue(struct super_block *sb,
-				 z_erofs_next_pcluster_t owned_head,
+				 struct z_erofs_decompress_frontend *f,
 				 struct list_head *pagepool,
 				 struct z_erofs_decompressqueue *fgq,
 				 bool *force_fg)
@@ -1160,10 +1163,12 @@ static void z_erofs_submit_queue(struct super_block *sb,
 	z_erofs_next_pcluster_t qtail[NR_JOBQUEUES];
 	struct z_erofs_decompressqueue *q[NR_JOBQUEUES];
 	void *bi_private;
+	z_erofs_next_pcluster_t owned_head = f->clt.owned_head;
 	/* since bio will be NULL, no need to initialize last_index */
 	pgoff_t last_index;
 	unsigned int nr_bios = 0;
 	struct bio *bio = NULL;
+	int cblks = f->compressedblock_total;
 
 	bi_private = jobqueueset_init(sb, q, fgq, force_fg);
 	qtail[JQ_BYPASS] = &q[JQ_BYPASS]->head;
@@ -1207,8 +1212,8 @@ static void z_erofs_submit_queue(struct super_block *sb,
 			}
 
 			if (!bio) {
-				bio = bio_alloc(GFP_NOIO, BIO_MAX_PAGES);
-
+				bio = bio_alloc(GFP_NOIO,
+						min(cblks, BIO_MAX_PAGES));
 				bio->bi_end_io = z_erofs_decompressqueue_endio;
 				bio_set_dev(bio, sb->s_bdev);
 				bio->bi_iter.bi_sector = (sector_t)cur <<
@@ -1221,6 +1226,7 @@ static void z_erofs_submit_queue(struct super_block *sb,
 			if (bio_add_page(bio, page, PAGE_SIZE, 0) < PAGE_SIZE)
 				goto submit_bio_retry;
 
+			--cblks;
 			last_index = cur;
 			bypass = false;
 		} while (++cur < end);
@@ -1234,6 +1240,8 @@ static void z_erofs_submit_queue(struct super_block *sb,
 	if (bio)
 		submit_bio(bio);
 
+	DBG_BUGON(cblks);
+
 	/*
 	 * although background is preferred, no one is pending for submission.
 	 * don't issue workqueue for decompression but drop it directly instead.
@@ -1246,14 +1254,14 @@ static void z_erofs_submit_queue(struct super_block *sb,
 }
 
 static void z_erofs_runqueue(struct super_block *sb,
-			     struct z_erofs_collector *clt,
+			     struct z_erofs_decompress_frontend *f,
 			     struct list_head *pagepool, bool force_fg)
 {
 	struct z_erofs_decompressqueue io[NR_JOBQUEUES];
 
-	if (clt->owned_head == Z_EROFS_PCLUSTER_TAIL)
+	if (f->clt.owned_head == Z_EROFS_PCLUSTER_TAIL)
 		return;
-	z_erofs_submit_queue(sb, clt->owned_head, pagepool, io, &force_fg);
+	z_erofs_submit_queue(sb, f, pagepool, io, &force_fg);
 
 	/* handle bypass queue (no i/o pclusters) immediately */
 	z_erofs_decompress_queue(&io[JQ_BYPASS], pagepool);
@@ -1284,7 +1292,7 @@ static int z_erofs_readpage(struct file *file, struct page *page)
 	(void)z_erofs_collector_end(&f.clt);
 
 	/* if some compressed cluster ready, need submit them anyway */
-	z_erofs_runqueue(inode->i_sb, &f.clt, &pagepool, true);
+	z_erofs_runqueue(inode->i_sb, &f, &pagepool, true);
 
 	if (err)
 		erofs_err(inode->i_sb, "failed to read, err [%d]", err);
@@ -1343,7 +1351,7 @@ static void z_erofs_readahead(struct readahead_control *rac)
 
 	(void)z_erofs_collector_end(&f.clt);
 
-	z_erofs_runqueue(inode->i_sb, &f.clt, &pagepool, sync);
+	z_erofs_runqueue(inode->i_sb, &f, &pagepool, sync);
 
 	if (f.map.mpage)
 		put_page(f.map.mpage);
-- 
2.18.1