Re: [f2fs-dev] [PATCH 2/3] f2fs: add bitmaps for empty or full NAT blocks

From: Chao Yu
Date: Tue Feb 28 2017 - 05:39:54 EST

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In reply to: Jaegeuk Kim: "Re: [f2fs-dev] [PATCH 2/3] f2fs: add bitmaps for empty or full NAT blocks"
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On 2017/2/28 6:19, Jaegeuk Kim wrote:
> On 02/27, Chao Yu wrote:
>> On 2017/2/26 2:34, Jaegeuk Kim wrote:
>>> On 02/25, Chao Yu wrote:
>>>> On 2017/2/24 6:54, Jaegeuk Kim wrote:
>>>>> On 02/23, Chao Yu wrote:
>>>>>> On 2017/2/14 10:06, Jaegeuk Kim wrote:
>>> ...
>>>>>
>>>>>>> +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 target = FREE_NID_PAGES * NAT_ENTRY_PER_BLOCK;
>>>>>>> + nid_t nid;
>>>>>>> +
>>>>>>> + if (!is_set_ckpt_flags(sbi, CP_NAT_BITS_FLAG))
>>>>>>> + 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] >= target)
>>>>>>> + 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);
>>>>>>
>>>>>> Can this happen in real world? Should be a bug in somewhere?
>>>>>
>>>>> It happens, since current design handles full_nat_bits optionally in order
>>>>> to avoid scanning a whole NAT page to set it back as 1 from 0.
>>>>
>>>> All 0 value in full_nat_bits means the NAT block has at least one free nid,
>>>> right? so if we traverse all such NAT blocks, and still haven't collect enough
>>>> *target* number of free nids, we don't have to disable nat bit cache, we can
>>>> just break out here.
>>>
>>> No, I'm seeing this case:
>>> 1. mount with full=0, empty=0, which indicates some free nids.
>>> 2. allocate all there-in free nids, but still full=0, empty=0.
>>> 3. allocate more free nids.
>>> ...
>>> ... checkpoint makes full=1, empty=0
>>>
>>> If there is no checkpoint and it consumes all the free nids, we can see all 0
>>> value in full_nat_bits which is quite impossible. In that case, I'd prefer
>>> to stop nat_bits and give fsck.f2fs to revive it back.
>>
>> Yeah, I can understand that, but what I concern is when there is few free nids
>> (< target), we still try to load nids of 8 NAT blocks until ending the loop of
>> caching free nids, so it will be very easy to enter the case of disabling
>> nid_bits cache here, so how about doing more check?
>>
>> if (i >= nm_i->nat_blocks &&
>
> This indicates full_nat_bits consists of all zeros, which means, whatever in
> the next time, we need to return -EINVAL. If we do not disable it here, there is
> no way to turn any bit into zero.

We can expect late checkpoint will refresh full_nat_bits, __update_nat_bits will
turn bit to one or zero there.

>
> BTW, I'm trying to freeze all the patches for a pull request, so let me have
> another patch for any pending issues which are not urgent for now as I think.

Got it. I will send you patch if I find explicit bug. :)

Thanks,

>
> Thanks,
>
>> nm_i->nid_cnt[FREE_NID_LIST] != nm_i->available_nids)
>> disable_nat_bits
>>
>> Thanks,
>>
>>>
>>> Thanks,
>>>
>>>>
>>>> Thanks,
>>>>
>>>>>
>>>>>>
>>>>>>> + 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] < target) {
>>>>>>> + 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);
>>>>>>> struct curseg_info *curseg = CURSEG_I(sbi, CURSEG_HOT_DATA);
>>>>>>> @@ -1854,6 +1911,20 @@ static void __build_free_nids(struct f2fs_sb_info *sbi, bool sync)
>>>>>>> if (!sync && !available_free_memory(sbi, FREE_NIDS))
>>>>>>> return;
>>>>>>>
>>>>>>> + /* try to find free nids with nat_bits */
>>>>>>> + if (!mount && !scan_nat_bits(sbi) && nm_i->nid_cnt[FREE_NID_LIST])
>>>>>>> + return;
>>>>>>> +
>>>>>>> + /* find next valid candidate */
>>>>>>
>>>>>> This is just for mount case?
>>>>>
>>>>> Yup, it reuses free nids in dirty NAT blocks, so that we can make them as full
>>>>> NAT pages.
>>>>>
>>>>> Thanks,
>>>>>
>>>>>>
>>>>>>> + if (is_set_ckpt_flags(sbi, CP_NAT_BITS_FLAG)) {
>>>>>>> + 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 */
>>>>>>> ra_meta_pages(sbi, NAT_BLOCK_OFFSET(nid), FREE_NID_PAGES,
>>>>>>> META_NAT, true);
>>>>>>> @@ -1896,10 +1967,10 @@ static void __build_free_nids(struct f2fs_sb_info *sbi, bool sync)
>>>>>>> nm_i->ra_nid_pages, META_NAT, false);
>>>>>>> }
>>>>>>>
>>>>>>> -void build_free_nids(struct f2fs_sb_info *sbi, bool sync)
>>>>>>> +void build_free_nids(struct f2fs_sb_info *sbi, bool sync, bool mount)
>>>>>>> {
>>>>>>> mutex_lock(&NM_I(sbi)->build_lock);
>>>>>>> - __build_free_nids(sbi, sync);
>>>>>>> + __build_free_nids(sbi, sync, mount);
>>>>>>> mutex_unlock(&NM_I(sbi)->build_lock);
>>>>>>> }
>>>>>>>
>>>>>>> @@ -1941,7 +2012,7 @@ bool alloc_nid(struct f2fs_sb_info *sbi, nid_t *nid)
>>>>>>> spin_unlock(&nm_i->nid_list_lock);
>>>>>>>
>>>>>>> /* Let's scan nat pages and its caches to get free nids */
>>>>>>> - build_free_nids(sbi, true);
>>>>>>> + build_free_nids(sbi, true, false);
>>>>>>> goto retry;
>>>>>>> }
>>>>>>>
>>>>>>> @@ -2233,8 +2304,39 @@ static void __adjust_nat_entry_set(struct nat_entry_set *nes,
>>>>>>> list_add_tail(&nes->set_list, head);
>>>>>>> }
>>>>>>>
>>>>>>> +void __update_nat_bits(struct f2fs_sb_info *sbi, nid_t start_nid,
>>>>>>> + struct page *page)
>>>>>>> +{
>>>>>>> + struct f2fs_nm_info *nm_i = NM_I(sbi);
>>>>>>> + unsigned int nat_index = start_nid / NAT_ENTRY_PER_BLOCK;
>>>>>>> + struct f2fs_nat_block *nat_blk = page_address(page);
>>>>>>> + int valid = 0;
>>>>>>> + int i;
>>>>>>> +
>>>>>>> + if (!is_set_ckpt_flags(sbi, CP_NAT_BITS_FLAG))
>>>>>>> + return;
>>>>>>> +
>>>>>>> + for (i = 0; i < NAT_ENTRY_PER_BLOCK; i++) {
>>>>>>> + if (start_nid == 0 && i == 0)
>>>>>>> + valid++;
>>>>>>> + if (nat_blk->entries[i].block_addr)
>>>>>>> + valid++;
>>>>>>> + }
>>>>>>> + if (valid == 0) {
>>>>>>> + test_and_set_bit_le(nat_index, nm_i->empty_nat_bits);
>>>>>>> + test_and_clear_bit_le(nat_index, nm_i->full_nat_bits);
>>>>>>
>>>>>> set_bit_le/clear_bit_le
>>>>>>
>>>>>>> + return;
>>>>>>> + }
>>>>>>> +
>>>>>>> + test_and_clear_bit_le(nat_index, nm_i->empty_nat_bits);
>>>>>>
>>>>>> ditto
>>>>>>
>>>>>>> + if (valid == NAT_ENTRY_PER_BLOCK)
>>>>>>> + test_and_set_bit_le(nat_index, nm_i->full_nat_bits);
>>>>>>> + else
>>>>>>> + test_and_clear_bit_le(nat_index, nm_i->full_nat_bits);
>>>>>>
>>>>>> ditto
>>>>>>
>>>>>>> +}
>>>>>>> +
>>>>>>> static void __flush_nat_entry_set(struct f2fs_sb_info *sbi,
>>>>>>> - struct nat_entry_set *set)
>>>>>>> + struct nat_entry_set *set, struct cp_control *cpc)
>>>>>>> {
>>>>>>> struct curseg_info *curseg = CURSEG_I(sbi, CURSEG_HOT_DATA);
>>>>>>> struct f2fs_journal *journal = curseg->journal;
>>>>>>> @@ -2249,7 +2351,8 @@ static void __flush_nat_entry_set(struct f2fs_sb_info *sbi,
>>>>>>> * #1, flush nat entries to journal in current hot data summary block.
>>>>>>> * #2, flush nat entries to nat page.
>>>>>>> */
>>>>>>> - if (!__has_cursum_space(journal, set->entry_cnt, NAT_JOURNAL))
>>>>>>> + if (cpc->reason == CP_UMOUNT ||
>>>>>>
>>>>>> if ((cpc->reason == CP_UMOUNT && is_set_ckpt_flags(sbi, CP_NAT_BITS_FLAG)) ||
>>>>>>
>>>>>>> + !__has_cursum_space(journal, set->entry_cnt, NAT_JOURNAL))
>>>>>>> to_journal = false;
>>>>>>>
>>>>>>> if (to_journal) {
>>>>>>> @@ -2289,10 +2392,12 @@ static void __flush_nat_entry_set(struct f2fs_sb_info *sbi,
>>>>>>> }
>>>>>>> }
>>>>>>>
>>>>>>> - if (to_journal)
>>>>>>> + if (to_journal) {
>>>>>>> up_write(&curseg->journal_rwsem);
>>>>>>> - else
>>>>>>> + } else {
>>>>>>> + __update_nat_bits(sbi, start_nid, page);
>>>>>>> f2fs_put_page(page, 1);
>>>>>>> + }
>>>>>>>
>>>>>>> f2fs_bug_on(sbi, set->entry_cnt);
>>>>>>>
>>>>>>> @@ -2303,7 +2408,7 @@ static void __flush_nat_entry_set(struct f2fs_sb_info *sbi,
>>>>>>> /*
>>>>>>> * This function is called during the checkpointing process.
>>>>>>> */
>>>>>>> -void flush_nat_entries(struct f2fs_sb_info *sbi)
>>>>>>> +void flush_nat_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>>>>>>> {
>>>>>>> struct f2fs_nm_info *nm_i = NM_I(sbi);
>>>>>>> struct curseg_info *curseg = CURSEG_I(sbi, CURSEG_HOT_DATA);
>>>>>>> @@ -2324,7 +2429,8 @@ void flush_nat_entries(struct f2fs_sb_info *sbi)
>>>>>>> * entries, remove all entries from journal and merge them
>>>>>>> * into nat entry set.
>>>>>>> */
>>>>>>> - if (!__has_cursum_space(journal, nm_i->dirty_nat_cnt, NAT_JOURNAL))
>>>>>>> + if (cpc->reason == CP_UMOUNT ||
>>>>>>
>>>>>> if ((cpc->reason == CP_UMOUNT && is_set_ckpt_flags(sbi, CP_NAT_BITS_FLAG)) ||
>>>>>>
>>>>>>> + !__has_cursum_space(journal, nm_i->dirty_nat_cnt, NAT_JOURNAL))
>>>>>>> remove_nats_in_journal(sbi);
>>>>>>>
>>>>>>> while ((found = __gang_lookup_nat_set(nm_i,
>>>>>>> @@ -2338,27 +2444,72 @@ void flush_nat_entries(struct f2fs_sb_info *sbi)
>>>>>>>
>>>>>>> /* flush dirty nats in nat entry set */
>>>>>>> list_for_each_entry_safe(set, tmp, &sets, set_list)
>>>>>>> - __flush_nat_entry_set(sbi, set);
>>>>>>> + __flush_nat_entry_set(sbi, set, cpc);
>>>>>>>
>>>>>>> up_write(&nm_i->nat_tree_lock);
>>>>>>>
>>>>>>> f2fs_bug_on(sbi, nm_i->dirty_nat_cnt);
>>>>>>> }
>>>>>>>
>>>>>>> +static int __get_nat_bitmaps(struct f2fs_sb_info *sbi)
>>>>>>> +{
>>>>>>> + struct f2fs_checkpoint *ckpt = F2FS_CKPT(sbi);
>>>>>>> + struct f2fs_nm_info *nm_i = NM_I(sbi);
>>>>>>> + unsigned int nat_bits_bytes = nm_i->nat_blocks / BITS_PER_BYTE;
>>>>>>> + unsigned int i;
>>>>>>> + __u64 cp_ver = le64_to_cpu(ckpt->checkpoint_ver);
>>>>>>
>>>>>> __u64 cp_ver = cur_cp_version(ckpt);
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>>> + size_t crc_offset = le32_to_cpu(ckpt->checksum_offset);
>>>>>>> + __u64 crc = le32_to_cpu(*((__le32 *)
>>>>>>> + ((unsigned char *)ckpt + crc_offset)));
>>>>>>> + block_t nat_bits_addr;
>>>>>>> +
>>>>>>> + if (!is_set_ckpt_flags(sbi, CP_NAT_BITS_FLAG))
>>>>>>> + return 0;
>>>>>>> +
>>>>>>> + nm_i->nat_bits_blocks = F2FS_BYTES_TO_BLK((nat_bits_bytes << 1) + 8 +
>>>>>>> + F2FS_BLKSIZE - 1);
>>>>>>> + nm_i->nat_bits = kzalloc(nm_i->nat_bits_blocks << F2FS_BLKSIZE_BITS,
>>>>>>> + GFP_KERNEL);
>>>>>>> + if (!nm_i->nat_bits)
>>>>>>> + return -ENOMEM;
>>>>>>> +
>>>>>>> + nat_bits_addr = __start_cp_addr(sbi) + sbi->blocks_per_seg -
>>>>>>> + nm_i->nat_bits_blocks;
>>>>>>> + for (i = 0; i < nm_i->nat_bits_blocks; i++) {
>>>>>>> + struct page *page = get_meta_page(sbi, nat_bits_addr++);
>>>>>>> +
>>>>>>> + memcpy(nm_i->nat_bits + (i << F2FS_BLKSIZE_BITS),
>>>>>>> + page_address(page), F2FS_BLKSIZE);
>>>>>>> + f2fs_put_page(page, 1);
>>>>>>> + }
>>>>>>> +
>>>>>>> + cp_ver |= (crc << 32);
>>>>>>> + if (cpu_to_le64(cp_ver) != *(__le64 *)nm_i->nat_bits) {
>>>>>>> + disable_nat_bits(sbi, true);
>>>>>>> + return 0;
>>>>>>> + }
>>>>>>> +
>>>>>>> + nm_i->full_nat_bits = nm_i->nat_bits + 8;
>>>>>>> + nm_i->empty_nat_bits = nm_i->full_nat_bits + nat_bits_bytes;
>>>>>>> +
>>>>>>> + f2fs_msg(sbi->sb, KERN_NOTICE, "Found nat_bits in checkpoint");
>>>>>>> + return 0;
>>>>>>> +}
>>>>>>> +
>>>>>>> static int init_node_manager(struct f2fs_sb_info *sbi)
>>>>>>> {
>>>>>>> struct f2fs_super_block *sb_raw = F2FS_RAW_SUPER(sbi);
>>>>>>> struct f2fs_nm_info *nm_i = NM_I(sbi);
>>>>>>> unsigned char *version_bitmap;
>>>>>>> - unsigned int nat_segs, nat_blocks;
>>>>>>> + unsigned int nat_segs;
>>>>>>> + int err;
>>>>>>>
>>>>>>> nm_i->nat_blkaddr = le32_to_cpu(sb_raw->nat_blkaddr);
>>>>>>>
>>>>>>> /* segment_count_nat includes pair segment so divide to 2. */
>>>>>>> nat_segs = le32_to_cpu(sb_raw->segment_count_nat) >> 1;
>>>>>>> - nat_blocks = nat_segs << le32_to_cpu(sb_raw->log_blocks_per_seg);
>>>>>>> -
>>>>>>> - nm_i->max_nid = NAT_ENTRY_PER_BLOCK * nat_blocks;
>>>>>>> + nm_i->nat_blocks = nat_segs << le32_to_cpu(sb_raw->log_blocks_per_seg);
>>>>>>> + nm_i->max_nid = NAT_ENTRY_PER_BLOCK * nm_i->nat_blocks;
>>>>>>>
>>>>>>> /* not used nids: 0, node, meta, (and root counted as valid node) */
>>>>>>> nm_i->available_nids = nm_i->max_nid - sbi->total_valid_node_count -
>>>>>>> @@ -2392,6 +2543,10 @@ static int init_node_manager(struct f2fs_sb_info *sbi)
>>>>>>> if (!nm_i->nat_bitmap)
>>>>>>> return -ENOMEM;
>>>>>>>
>>>>>>> + err = __get_nat_bitmaps(sbi);
>>>>>>> + if (err)
>>>>>>> + return err;
>>>>>>> +
>>>>>>> #ifdef CONFIG_F2FS_CHECK_FS
>>>>>>> nm_i->nat_bitmap_mir = kmemdup(version_bitmap, nm_i->bitmap_size,
>>>>>>> GFP_KERNEL);
>>>>>>> @@ -2414,7 +2569,7 @@ int build_node_manager(struct f2fs_sb_info *sbi)
>>>>>>> if (err)
>>>>>>> return err;
>>>>>>>
>>>>>>> - build_free_nids(sbi, true);
>>>>>>> + build_free_nids(sbi, true, true);
>>>>>>> return 0;
>>>>>>> }
>>>>>>>
>>>>>>> @@ -2473,6 +2628,7 @@ void destroy_node_manager(struct f2fs_sb_info *sbi)
>>>>>>> up_write(&nm_i->nat_tree_lock);
>>>>>>>
>>>>>>> kfree(nm_i->nat_bitmap);
>>>>>>> + kfree(nm_i->nat_bits);
>>>>>>> #ifdef CONFIG_F2FS_CHECK_FS
>>>>>>> kfree(nm_i->nat_bitmap_mir);
>>>>>>> #endif
>>>>>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>>>>>> index df2ff5cfe8f4..8e1ec248c653 100644
>>>>>>> --- a/fs/f2fs/segment.c
>>>>>>> +++ b/fs/f2fs/segment.c
>>>>>>> @@ -386,7 +386,7 @@ void f2fs_balance_fs_bg(struct f2fs_sb_info *sbi)
>>>>>>> if (!available_free_memory(sbi, FREE_NIDS))
>>>>>>> try_to_free_nids(sbi, MAX_FREE_NIDS);
>>>>>>> else
>>>>>>> - build_free_nids(sbi, false);
>>>>>>> + build_free_nids(sbi, false, false);
>>>>>>>
>>>>>>> if (!is_idle(sbi))
>>>>>>> return;
>>>>>>> diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
>>>>>>> index f0748524ca8c..1c92ace2e8f8 100644
>>>>>>> --- a/include/linux/f2fs_fs.h
>>>>>>> +++ b/include/linux/f2fs_fs.h
>>>>>>> @@ -114,6 +114,7 @@ struct f2fs_super_block {
>>>>>>> /*
>>>>>>> * For checkpoint
>>>>>>> */
>>>>>>> +#define CP_NAT_BITS_FLAG 0x00000080
>>>>>>> #define CP_CRC_RECOVERY_FLAG 0x00000040
>>>>>>> #define CP_FASTBOOT_FLAG 0x00000020
>>>>>>> #define CP_FSCK_FLAG 0x00000010
>>>>>>>
>>>>>>
>>>>>>
>>>>>> ------------------------------------------------------------------------------
>>>>>> Check out the vibrant tech community on one of the world's most
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>>>>>> _______________________________________________
>>>>>> Linux-f2fs-devel mailing list
>>>>>> Linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx
>>>>>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
>>>>>
>>>>> .
>>>>>
>>>>
>>>>
>>>> ------------------------------------------------------------------------------
>>>> Check out the vibrant tech community on one of the world's most
>>>> engaging tech sites, SlashDot.org! http://sdm.link/slashdot
>>>> _______________________________________________
>>>> Linux-f2fs-devel mailing list
>>>> Linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx
>>>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
>>>
>>> .
>>>
>>
>>
>> ------------------------------------------------------------------------------
>> Check out the vibrant tech community on one of the world's most
>> engaging tech sites, SlashDot.org! http://sdm.link/slashdot
>> _______________________________________________
>> Linux-f2fs-devel mailing list
>> Linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx
>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
>
> .
>

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