f2fs: flush dirty nat entries when exceeding threshold

When testing f2fs with xfstest, generic/251 is stuck for long time,
the case uses below serials to obtain fresh released space in device,
in order to prepare for following fstrim test.

1. rm -rf /mnt/dir
2. mkdir /mnt/dir/
3. cp -axT `pwd`/ /mnt/dir/
4. goto 1

During preparing step, all nat entries will be cached in nat cache,
most of them are dirty entries with invalid blkaddr, which means
nodes related to these entries have been truncated, and they could
be reused after the dirty entries been checkpointed.

However, there was no checkpoint been triggered, so nid allocators
(e.g. mkdir, creat) will run into long journey of iterating all NAT
pages, looking for free nids in alloc_nid->build_free_nids.

Here, in f2fs_balance_fs_bg we give another chance to do checkpoint
to flush nat entries for reusing them in free nid cache when dirty
entry count exceeds 10% of max count.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/node.h b/fs/f2fs/node.h
index d4d1f636fe1c36c923ebcd68da46249161ccafc8..bd119c0edf93cc8e3a4c694f7072c57625e0703e 100644 (file)
--- a/fs/f2fs/node.h
+++ b/fs/f2fs/node.h
@@ -25,6 +25,9 @@
 /* control the memory footprint threshold (10MB per 1GB ram) */
 #define DEF_RAM_THRESHOLD      10
 
+/* control dirty nats ratio threshold (default: 10% over max nid count) */
+#define DEF_DIRTY_NAT_RATIO_THRESHOLD          10
+
 /* vector size for gang look-up from nat cache that consists of radix tree */
 #define NATVEC_SIZE    64
 #define SETVEC_SIZE    32
@@ -117,6 +120,12 @@ static inline void raw_nat_from_node_info(struct f2fs_nat_entry *raw_ne,
        raw_ne->version = ni->version;
 }
 
+static inline bool excess_dirty_nats(struct f2fs_sb_info *sbi)
+{
+       return NM_I(sbi)->dirty_nat_cnt >= NM_I(sbi)->max_nid *
+                                       DEF_DIRTY_NAT_RATIO_THRESHOLD / 100;
+}
+
 enum mem_type {
        FREE_NIDS,      /* indicates the free nid list */
        NAT_ENTRIES,    /* indicates the cached nat entry */

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index e16235bbdd7df002eb74a2f90fd0135989f5286a..53baf4a420dcea7b4d0a006c1fbbb5ee85f546c6 100644 (file)
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -291,8 +291,9 @@ void f2fs_balance_fs_bg(struct f2fs_sb_info *sbi)
 
        /* checkpoint is the only way to shrink partial cached entries */
        if (!available_free_memory(sbi, NAT_ENTRIES) ||
-                       excess_prefree_segs(sbi) ||
                        !available_free_memory(sbi, INO_ENTRIES) ||
+                       excess_prefree_segs(sbi) ||
+                       excess_dirty_nats(sbi) ||
                        (is_idle(sbi) && f2fs_time_over(sbi, CP_TIME))) {
                if (test_opt(sbi, DATA_FLUSH))
                        sync_dirty_inodes(sbi, FILE_INODE);