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

From: Gao Xiang
Date: Fri Sep 18 2020 - 09:55:27 EST


Use more accurate compressed page count
instead of BIO_MAX_PAGES unconditionally.

Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxx>
---
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