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Date: Thu, 2 Mar 2017 09:35:41 +0800
From: Chao Yu <yuchao0@...wei.com>
To: Kinglong Mee <kinglongmee@...il.com>, <jaegeuk@...nel.org>
CC: <chao@...nel.org>, <linux-kernel@...r.kernel.org>,
<linux-f2fs-devel@...ts.sourceforge.net>
Subject: Re: [f2fs-dev] [PATCH RFC] f2fs: combine nat_bits and free_nid_bitmap
cache
On 2017/3/1 21:09, Kinglong Mee wrote:
> 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.
Since after this patch, all nids status (free or used) of
full_nat_bits/empty_nat_bits will be loaded into free_nid_bitmap, so we can just
check free_nid_bitmap instead of both cache before loading NAT blocks.
Thanks,
>
> 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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