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Date: Wed, 1 Mar 2017 21:09:14 +0800
From: Kinglong Mee <kinglongmee@...il.com>
To: Chao Yu <yuchao0@...wei.com>, jaegeuk@...nel.org
Cc: chao@...nel.org, linux-kernel@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net,
Kinglong Mee <kinglongmee@...il.com>
Subject: Re: [f2fs-dev] [PATCH RFC] f2fs: combine nat_bits and free_nid_bitmap
cache
On 3/1/2017 17:10, Chao Yu wrote:
> Both nat_bits cache and free_nid_bitmap cache provide same functionality
> as a intermediate cache between free nid cache and disk, but with
> different granularity of indicating free nid range, and different
> persistence policy. nat_bits cache provides better persistence ability,
> and free_nid_bitmap provides better granularity.
>
> In this patch we combine advantage of both caches, so finally policy of
> the intermediate cache would be:
> - init: load free nid status from nat_bits into free_nid_bitmap
> - lookup: scan free_nid_bitmap before load NAT blocks
Why not scan the full_nat_bits/empty_nat_bits before load NAT blocks here?
If after an objects shrinker, the cached free nid will be empty quickly.
thanks,
Kinglong Mee
> - update: update free_nid_bitmap in real-time
> - persistence: udpate and persist nat_bits in checkpoint
>
> Signed-off-by: Chao Yu <yuchao0@...wei.com>
> ---
> fs/f2fs/node.c | 109 +++++++++++++++++++++------------------------------------
> 1 file changed, 39 insertions(+), 70 deletions(-)
>
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index 1a759d45b7e4..6c027b6833f4 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -338,9 +338,6 @@ static void set_node_addr(struct f2fs_sb_info *sbi, struct node_info *ni,
> set_nat_flag(e, IS_CHECKPOINTED, false);
> __set_nat_cache_dirty(nm_i, e);
>
> - if (enabled_nat_bits(sbi, NULL) && new_blkaddr == NEW_ADDR)
> - clear_bit_le(NAT_BLOCK_OFFSET(ni->nid), nm_i->empty_nat_bits);
> -
> /* update fsync_mark if its inode nat entry is still alive */
> if (ni->nid != ni->ino)
> e = __lookup_nat_cache(nm_i, ni->ino);
> @@ -1920,58 +1917,6 @@ static void scan_free_nid_bits(struct f2fs_sb_info *sbi)
> up_read(&nm_i->nat_tree_lock);
> }
>
> -static int scan_nat_bits(struct f2fs_sb_info *sbi)
> -{
> - struct f2fs_nm_info *nm_i = NM_I(sbi);
> - struct page *page;
> - unsigned int i = 0;
> - nid_t nid;
> -
> - if (!enabled_nat_bits(sbi, NULL))
> - return -EAGAIN;
> -
> - down_read(&nm_i->nat_tree_lock);
> -check_empty:
> - i = find_next_bit_le(nm_i->empty_nat_bits, nm_i->nat_blocks, i);
> - if (i >= nm_i->nat_blocks) {
> - i = 0;
> - goto check_partial;
> - }
> -
> - for (nid = i * NAT_ENTRY_PER_BLOCK; nid < (i + 1) * NAT_ENTRY_PER_BLOCK;
> - nid++) {
> - if (unlikely(nid >= nm_i->max_nid))
> - break;
> - add_free_nid(sbi, nid, true);
> - }
> -
> - if (nm_i->nid_cnt[FREE_NID_LIST] >= MAX_FREE_NIDS)
> - goto out;
> - i++;
> - goto check_empty;
> -
> -check_partial:
> - i = find_next_zero_bit_le(nm_i->full_nat_bits, nm_i->nat_blocks, i);
> - if (i >= nm_i->nat_blocks) {
> - disable_nat_bits(sbi, true);
> - up_read(&nm_i->nat_tree_lock);
> - return -EINVAL;
> - }
> -
> - nid = i * NAT_ENTRY_PER_BLOCK;
> - page = get_current_nat_page(sbi, nid);
> - scan_nat_page(sbi, page, nid);
> - f2fs_put_page(page, 1);
> -
> - if (nm_i->nid_cnt[FREE_NID_LIST] < MAX_FREE_NIDS) {
> - i++;
> - goto check_partial;
> - }
> -out:
> - up_read(&nm_i->nat_tree_lock);
> - return 0;
> -}
> -
> static void __build_free_nids(struct f2fs_sb_info *sbi, bool sync, bool mount)
> {
> struct f2fs_nm_info *nm_i = NM_I(sbi);
> @@ -1993,21 +1938,6 @@ static void __build_free_nids(struct f2fs_sb_info *sbi, bool sync, bool mount)
>
> if (nm_i->nid_cnt[FREE_NID_LIST])
> return;
> -
> - /* try to find free nids with nat_bits */
> - if (!scan_nat_bits(sbi) && nm_i->nid_cnt[FREE_NID_LIST])
> - return;
> - }
> -
> - /* find next valid candidate */
> - if (enabled_nat_bits(sbi, NULL)) {
> - int idx = find_next_zero_bit_le(nm_i->full_nat_bits,
> - nm_i->nat_blocks, 0);
> -
> - if (idx >= nm_i->nat_blocks)
> - set_sbi_flag(sbi, SBI_NEED_FSCK);
> - else
> - nid = idx * NAT_ENTRY_PER_BLOCK;
> }
>
> /* readahead nat pages to be scanned */
> @@ -2590,6 +2520,41 @@ static int __get_nat_bitmaps(struct f2fs_sb_info *sbi)
> return 0;
> }
>
> +inline void load_free_nid_bitmap(struct f2fs_sb_info *sbi)
> +{
> + struct f2fs_nm_info *nm_i = NM_I(sbi);
> + unsigned int i = 0;
> + nid_t nid, last_nid;
> +
> + for (i = 0; i < nm_i->nat_blocks; i++) {
> + i = find_next_bit_le(nm_i->empty_nat_bits, nm_i->nat_blocks, i);
> + if (i >= nm_i->nat_blocks)
> + break;
> +
> + set_bit_le(i, nm_i->nat_block_bitmap);
> +
> + nid = i * NAT_ENTRY_PER_BLOCK;
> + last_nid = (i + 1) * NAT_ENTRY_PER_BLOCK;
> +
> + for (; nid < last_nid; nid++)
> + update_free_nid_bitmap(sbi, nid, true, true);
> + }
> +
> + for (i = 0; i < nm_i->nat_blocks; i++) {
> + i = find_next_bit_le(nm_i->full_nat_bits, nm_i->nat_blocks, i);
> + if (i >= nm_i->nat_blocks)
> + break;
> +
> + set_bit_le(i, nm_i->nat_block_bitmap);
> +
> + nid = i * NAT_ENTRY_PER_BLOCK;
> + last_nid = (i + 1) * NAT_ENTRY_PER_BLOCK;
> +
> + for (; nid < last_nid; nid++)
> + update_free_nid_bitmap(sbi, nid, false, true);
> + }
> +}
> +
> static int init_node_manager(struct f2fs_sb_info *sbi)
> {
> struct f2fs_super_block *sb_raw = F2FS_RAW_SUPER(sbi);
> @@ -2672,6 +2637,10 @@ int init_free_nid_cache(struct f2fs_sb_info *sbi)
>
> spin_lock_init(&nm_i->free_nid_lock);
>
> + /* load free nid status from nat_bits table */
> + if (enabled_nat_bits(sbi, NULL))
> + load_free_nid_bitmap(sbi);
> +
> return 0;
> }
>
>
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