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SubjectRe: [f2fs-dev] [PATCH 1/2] f2fs: avoid down_write on nat_tree_lock during checkpoint
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On 2021/12/15 2:24, Jaegeuk Kim wrote:
> Let's cache nat entry if there's no lock contention only.
>
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
> fs/f2fs/node.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index 556fcd8457f3..b1bc7d76da3b 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -430,6 +430,10 @@ static void cache_nat_entry(struct f2fs_sb_info *sbi, nid_t nid,
> struct f2fs_nm_info *nm_i = NM_I(sbi);
> struct nat_entry *new, *e;
>
> + /* Let's mitigate lock contention of nat_tree_lock during checkpoint */
> + if (rwsem_is_locked(&sbi->cp_global_sem))

Why not down_write_trylock(nat_tree_lock)? cp_global_sem lock coverage is larger than
nat_tree_lock's in f2fs_write_checkpoint().

Thanks,

> + return;
> +
> new = __alloc_nat_entry(sbi, nid, false);
> if (!new)
> return;

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