Hi Chao,
On Sat, Jan 16, 2016 at 05:36:40PM +0800, Chao Yu wrote:
> 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 preparing 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, we give another chance to f2fs_balance_fs_bg to do checkpoint
> to flush nat entries for reusing in free nid cache when dirty entry
> count exceeds 10% of max count.
>
> Signed-off-by: Chao Yu <chao2...@samsung.com>
> ---
> fs/f2fs/node.h | 8 ++++++++
> fs/f2fs/segment.c | 3 ++-
> 2 files changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/fs/f2fs/node.h b/fs/f2fs/node.h
> index d4d1f63..630c62d 100644
> --- a/fs/f2fs/node.h
> +++ b/fs/f2fs/node.h
> @@ -25,6 +25,8 @@
> /* control the memory footprint threshold (10MB per 1GB ram) */
> #define DEF_RAM_THRESHOLD 10
>
> +#define DEF_DIRTY_NAT_THRESHOLD 10 /* 10% over max nid */
> +
> /* vector size for gang look-up from nat cache that consists of radix tree */
> #define NATVEC_SIZE 64
> #define SETVEC_SIZE 32
> @@ -117,6 +119,12 @@ 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_THRESHOLD / 100;
Need to add a sysfs entry?
Thanks,
> +}
> +
> 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 5904a41..68800e6 100644
> --- 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);
> --
> 2.6.3
>
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