Re: [PATCH] f2fs: avoid false positive of free secs check

[Yunlong Song]

SSR can make hot/warm/cold nodes written together, so why should we account
them different?

On 2017/11/29 19:56, Chao Yu wrote:

On 2017/11/27 14:54, Yunlong Song wrote:

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.

I don't think this could be right, IMO, instead, it would be better to
account dirty hot/warm/cold nodes or imeta separately, as actually, they
will use different section, but currently, our calculation way is based
on that they could be written to same section.

Thanks,

Signed-off-by: Yunlong Song <yunlong.s...@huawei.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);
  }

.

--
Thanks,
Yunlong Song