linux-kernel - [PATCH] f2fs: avoid false positive of free secs check

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Date:   Mon, 27 Nov 2017 14:54:59 +0800
From:   Yunlong Song <yunlong.song@...wei.com>
To:     <jaegeuk@...nel.org>, <chao@...nel.org>, <yuchao0@...wei.com>,
        <yunlong.song@...oud.com>, <yunlong.song@...wei.com>
CC:     <miaoxie@...wei.com>, <bintian.wang@...wei.com>,
        <linux-fsdevel@...r.kernel.org>,
        <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH] f2fs: avoid false positive of free secs check

Sometimes f2fs_gc is called with no target victim (e.g. xfstest
generic/027, ndirty_node:545 ndiry_dent:1 ndirty_imeta:513 rsvd_segs:21
free_segs:27, has_not_enough_free_secs will return true). This patch
first merges pages and then converts into sections.

Signed-off-by: Yunlong Song <yunlong.song@...wei.com>
---
 fs/f2fs/f2fs.h    |  9 ---------
 fs/f2fs/segment.c | 12 +++++++-----
 fs/f2fs/segment.h | 13 +++++++++----
 3 files changed, 16 insertions(+), 18 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index ca6b0c9..e89cff7 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1675,15 +1675,6 @@ static inline int get_dirty_pages(struct inode *inode)
 	return atomic_read(&F2FS_I(inode)->dirty_pages);
 }
 
-static inline int get_blocktype_secs(struct f2fs_sb_info *sbi, int block_type)
-{
-	unsigned int pages_per_sec = sbi->segs_per_sec * sbi->blocks_per_seg;
-	unsigned int segs = (get_pages(sbi, block_type) + pages_per_sec - 1) >>
-						sbi->log_blocks_per_seg;
-
-	return segs / sbi->segs_per_sec;
-}
-
 static inline block_t valid_user_blocks(struct f2fs_sb_info *sbi)
 {
 	return sbi->total_valid_block_count;
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index c117e09..603f805 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -171,17 +171,19 @@ static unsigned long __find_rev_next_zero_bit(const unsigned long *addr,
 
 bool need_SSR(struct f2fs_sb_info *sbi)
 {
-	int node_secs = get_blocktype_secs(sbi, F2FS_DIRTY_NODES);
-	int dent_secs = get_blocktype_secs(sbi, F2FS_DIRTY_DENTS);
-	int imeta_secs = get_blocktype_secs(sbi, F2FS_DIRTY_IMETA);
+	s64 node_pages = get_pages(sbi, F2FS_DIRTY_NODES);
+	s64 dent_pages = get_pages(sbi, F2FS_DIRTY_DENTS);
+	s64 imeta_pages = get_pages(sbi, F2FS_DIRTY_IMETA);
 
 	if (test_opt(sbi, LFS))
 		return false;
 	if (sbi->gc_thread && sbi->gc_thread->gc_urgent)
 		return true;
 
-	return free_sections(sbi) <= (node_secs + 2 * dent_secs + imeta_secs +
-			SM_I(sbi)->min_ssr_sections + reserved_sections(sbi));
+	return free_sections(sbi) <=
+		(PAGE2SEC(sbi, node_pages + imeta_pages) +
+		PAGE2SEC(sbi, 2 * dent_pages) +
+		SM_I(sbi)->min_ssr_sections + reserved_sections(sbi));
 }
 
 void register_inmem_page(struct inode *inode, struct page *page)
diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
index d1d394c..723d79e 100644
--- a/fs/f2fs/segment.h
+++ b/fs/f2fs/segment.h
@@ -115,6 +115,10 @@
 #define SECTOR_TO_BLOCK(sectors)					\
 	((sectors) >> F2FS_LOG_SECTORS_PER_BLOCK)
 
+#define PAGE2SEC(sbi, pages)				\
+	((((pages) + BLKS_PER_SEC(sbi) - 1)		\
+	>> sbi->log_blocks_per_seg) / sbi->segs_per_sec)
+
 /*
  * indicate a block allocation direction: RIGHT and LEFT.
  * RIGHT means allocating new sections towards the end of volume.
@@ -527,9 +531,9 @@ static inline bool has_curseg_enough_space(struct f2fs_sb_info *sbi)
 static inline bool has_not_enough_free_secs(struct f2fs_sb_info *sbi,
 					int freed, int needed)
 {
-	int node_secs = get_blocktype_secs(sbi, F2FS_DIRTY_NODES);
-	int dent_secs = get_blocktype_secs(sbi, F2FS_DIRTY_DENTS);
-	int imeta_secs = get_blocktype_secs(sbi, F2FS_DIRTY_IMETA);
+	s64 node_pages = get_pages(sbi, F2FS_DIRTY_NODES);
+	s64 dent_pages = get_pages(sbi, F2FS_DIRTY_DENTS);
+	s64 imeta_pages = get_pages(sbi, F2FS_DIRTY_IMETA);
 
 	if (unlikely(is_sbi_flag_set(sbi, SBI_POR_DOING)))
 		return false;
@@ -538,7 +542,8 @@ static inline bool has_not_enough_free_secs(struct f2fs_sb_info *sbi,
 			has_curseg_enough_space(sbi))
 		return false;
 	return (free_sections(sbi) + freed) <=
-		(node_secs + 2 * dent_secs + imeta_secs +
+		(PAGE2SEC(sbi, node_pages + imeta_pages) +
+		PAGE2SEC(sbi, 2 * dent_pages) +
 		reserved_sections(sbi) + needed);
 }
 
-- 
1.8.5.2