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Date:   Tue, 1 Jun 2021 10:27:22 -0700
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <chao@kernel.org>
Cc:     Chao Yu <yuchao0@huawei.com>, linux-kernel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH v6] f2fs: compress: add compress_inode to
 cache compressed blocks
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References: <20210520115150.4718-1-chao@kernel.org>
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On 06/01, Jaegeuk Kim wrote:
> On 05/26, Chao Yu wrote:
> > On 2021/5/26 21:26, Jaegeuk Kim wrote:
> > > On 05/26, Chao Yu wrote:
> > > > On 2021/5/25 22:01, Jaegeuk Kim wrote:
> > > > > On 05/25, Chao Yu wrote:
> > > > > > On 2021/5/25 21:02, Jaegeuk Kim wrote:
> > > > > > > On 05/25, Jaegeuk Kim wrote:
> > > > > > > > On 05/25, Chao Yu wrote:
> > > > > > > > > Also, and queue this?
> > > > > > > > 
> > > > > > > > Easy to get this?
> > > > > > > 
> > > > > > > need GFP_NOFS?
> > > > > > 
> > > > > > Not sure, I use __GFP_IO intentionally here to avoid __GFP_RECLAIM from
> > > > > > GFP_NOFS, because in low memory case, I don't want to instead page cache
> > > > > > of normal file with page cache of sbi->compress_inode.
> > > > > > 
> > > > > > What is memory size in your vm?
> > > > > 
> > > > > 4GB. If I set GFP_NOFS, I don't see the error anymore, at least.
> > > > 
> > > > I applied below patch and don't see the warning message anymore.
> > > > 
> > > > ---
> > > >   fs/f2fs/compress.c | 2 +-
> > > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > > > 
> > > > diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
> > > > index 701dd0f6f4ec..ed5b7fabc604 100644
> > > > --- a/fs/f2fs/compress.c
> > > > +++ b/fs/f2fs/compress.c
> > > > @@ -1703,7 +1703,7 @@ void f2fs_cache_compressed_page(struct f2fs_sb_info *sbi, struct page *page,
> > > >   	avail_ram = si.totalram - si.totalhigh;
> > > > 
> > > >   	/* free memory is lower than watermark, deny caching compress page */
> > > > -	if (free_ram <= sbi->compress_watermark / 100 * avail_ram)
> > 
> > This is buggy, because sbi->compress_watermark equals to 20, so that
> > sbi->compress_watermark / 100 * avail_ram always be zero...
> > 
> > After this change, if free ram is lower, we may just skip caching
> > compressed blocks here.
> 
> Can we move this in f2fs_available_free_memory()?

Testing this.

---
 fs/f2fs/compress.c | 14 +-------------
 fs/f2fs/node.c     | 11 ++++++++++-
 fs/f2fs/node.h     |  1 +
 3 files changed, 12 insertions(+), 14 deletions(-)

diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
index 9fd62a0a646b..455561826c7d 100644
--- a/fs/f2fs/compress.c
+++ b/fs/f2fs/compress.c
@@ -1688,8 +1688,6 @@ void f2fs_cache_compressed_page(struct f2fs_sb_info *sbi, struct page *page,
 {
 	struct page *cpage;
 	int ret;
-	struct sysinfo si;
-	unsigned long free_ram, avail_ram;
 
 	if (!test_opt(sbi, COMPRESS_CACHE))
 		return;
@@ -1697,17 +1695,7 @@ void f2fs_cache_compressed_page(struct f2fs_sb_info *sbi, struct page *page,
 	if (!f2fs_is_valid_blkaddr(sbi, blkaddr, DATA_GENERIC_ENHANCE_READ))
 		return;
 
-	si_meminfo(&si);
-	free_ram = si.freeram;
-	avail_ram = si.totalram - si.totalhigh;
-
-	/* free memory is lower than watermark, deny caching compress page */
-	if (free_ram <= sbi->compress_watermark / 100 * avail_ram)
-		return;
-
-	/* cached page count exceed threshold, deny caching compress page */
-	if (COMPRESS_MAPPING(sbi)->nrpages >=
-			free_ram / 100 * sbi->compress_percent)
+	if (!f2fs_available_free_memory(sbi, COMPRESS_PAGE))
 		return;
 
 	cpage = find_get_page(COMPRESS_MAPPING(sbi), blkaddr);
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 3a8f7afa5059..67093416ce9c 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -45,7 +45,7 @@ bool f2fs_available_free_memory(struct f2fs_sb_info *sbi, int type)
 	struct f2fs_nm_info *nm_i = NM_I(sbi);
 	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
 	struct sysinfo val;
-	unsigned long avail_ram;
+	unsigned long avail_ram, free_ram;
 	unsigned long mem_size = 0;
 	bool res = false;
 
@@ -56,6 +56,7 @@ bool f2fs_available_free_memory(struct f2fs_sb_info *sbi, int type)
 
 	/* only uses low memory */
 	avail_ram = val.totalram - val.totalhigh;
+	free_ram = val.freeram;
 
 	/*
 	 * give 25%, 25%, 50%, 50%, 50% memory for each components respectively
@@ -97,6 +98,14 @@ bool f2fs_available_free_memory(struct f2fs_sb_info *sbi, int type)
 		mem_size = (atomic_read(&dcc->discard_cmd_cnt) *
 				sizeof(struct discard_cmd)) >> PAGE_SHIFT;
 		res = mem_size < (avail_ram * nm_i->ram_thresh / 100);
+	} else if (type == COMPRESS_PAGE) {
+		/*
+		 * free memory is lower than watermark or cached page count
+		 * exceed threshold, deny caching compress page.
+		 */
+		res = (free_ram > avail_ram * sbi->compress_watermark / 100) &&
+			(COMPRESS_MAPPING(sbi)->nrpages <
+			 free_ram * sbi->compress_percent / 100);
 	} else {
 		if (!sbi->sb->s_bdi->wb.dirty_exceeded)
 			return true;
diff --git a/fs/f2fs/node.h b/fs/f2fs/node.h
index d85e8659cfda..84d45385d1f2 100644
--- a/fs/f2fs/node.h
+++ b/fs/f2fs/node.h
@@ -148,6 +148,7 @@ enum mem_type {
 	EXTENT_CACHE,	/* indicates extent cache */
 	INMEM_PAGES,	/* indicates inmemory pages */
 	DISCARD_CACHE,	/* indicates memory of cached discard cmds */
+	COMPRESS_PAGE,	/* indicates memory of cached compressed pages */
 	BASE_CHECK,	/* check kernel status */
 };
 
-- 
2.32.0.rc0.204.g9fa02ecfa5-goog