Re: [f2fs-dev] [PATCH v2] f2fs: compress: fix overwrite may reduce compress ratio unproperly

[Chao Yu <chao@kernel.org>]

On 2021/10/14 21:12, Fengnan Chang wrote:
> when overwrite only first block of cluster, since cluster is not full, it
> will call f2fs_write_raw_pages when f2fs_write_multi_pages, and cause the
> whole cluster become uncompressed eventhough data can be compressed.
> this may will make random write bench score reduce a lot.
> 
> root# dd if=/dev/zero of=./fio-test bs=1M count=1
> 
> root# sync
> 
> root# echo 3 > /proc/sys/vm/drop_caches
> 
> root# f2fs_io get_cblocks ./fio-test
> 
> root# dd if=/dev/zero of=./fio-test bs=4K count=1 oflag=direct conv=notrunc
> 
> w/o patch:
> root# f2fs_io get_cblocks ./fio-test
> 189
> 
> w/ patch:
> root# f2fs_io get_cblocks ./fio-test
> 192
> 
> Signed-off-by: Fengnan Chang <changfengnan@vivo.com>
> ---
>   fs/f2fs/compress.c | 12 ++++++++++++
>   fs/f2fs/data.c     |  7 +++++++
>   fs/f2fs/f2fs.h     |  1 +
>   3 files changed, 20 insertions(+)
> 
> diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
> index c1bf9ad4c220..c4f36ead6f17 100644
> --- a/fs/f2fs/compress.c
> +++ b/fs/f2fs/compress.c
> @@ -857,6 +857,18 @@ void f2fs_end_read_compressed_page(struct page *page, bool failed,
>   		f2fs_decompress_cluster(dic);
>   }
>   
> +bool is_page_same_cluster(struct compress_ctx *cc, struct pagevec *pvec, int index)

Fengnan,

It needs add f2fs prefix for non-static symbol to avoid global namespace
pollution.

Anyway, how about this?

---
  fs/f2fs/compress.c | 19 +++++++++++++++++++
  fs/f2fs/data.c     |  7 ++++---
  fs/f2fs/f2fs.h     |  2 ++
  3 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
index c1bf9ad4c220..15d9b89d4df0 100644
--- a/fs/f2fs/compress.c
+++ b/fs/f2fs/compress.c
@@ -881,6 +881,25 @@ bool f2fs_cluster_can_merge_page(struct compress_ctx *cc, pgoff_t index)
  	return is_page_in_cluster(cc, index);
  }

+bool f2fs_all_cluster_page_loaded(struct compress_ctx *cc, struct pagevec *pvec,
+						int index, int nr_pages)
+{
+	unsigned long pgidx;
+	int i;
+
+	if (nr_pages - index < cc->cluster_size)
+		return false;
+
+	pgidx = pvec->pages[index]->index;
+
+	for (i = 1; i < cc->cluster_size; i++) {
+		if (pvec->pages[index + i]->index != pgidx + i)
+			return false;
+	}
+
+	return true;
+}
+
  static bool cluster_has_invalid_data(struct compress_ctx *cc)
  {
  	loff_t i_size = i_size_read(cc->inode);
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 14fe5c6216cc..b0665f69c093 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -3075,9 +3075,10 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
  						done = 1;
  						break;
  					} else if (ret2 &&
-						!f2fs_compress_write_end(inode,
-								fsdata, page->index,
-								1)) {
+						(!f2fs_compress_write_end(inode,
+							fsdata, page->index, 1) ||
+						!f2fs_all_cluster_page_loaded(&cc,
+							&pvec, i, nr_pages))) {
  						retry = 1;
  						break;
  					}
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 7a32c2127945..b8da34198ce0 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -4047,6 +4047,8 @@ void f2fs_end_read_compressed_page(struct page *page, bool failed,
  							block_t blkaddr);
  bool f2fs_cluster_is_empty(struct compress_ctx *cc);
  bool f2fs_cluster_can_merge_page(struct compress_ctx *cc, pgoff_t index);
+bool f2fs_all_cluster_page_loaded(struct compress_ctx *cc, struct pagevec *pvec,
+						int index, int nr_pages);
  bool f2fs_sanity_check_cluster(struct dnode_of_data *dn);
  void f2fs_compress_ctx_add_page(struct compress_ctx *cc, struct page *page);
  int f2fs_write_multi_pages(struct compress_ctx *cc,
-- 
2.32.0




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