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

From: Jaegeuk Kim
Date: Thu Feb 23 2017 - 17:55:11 EST

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In reply to: Chao Yu: "Re: [f2fs-dev] [PATCH 2/3] f2fs: add bitmaps for empty or full NAT blocks"
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On 02/23, Chao Yu wrote:
> On 2017/2/14 10:06, Jaegeuk Kim wrote:
> > This patches adds bitmaps to represent empty or full NAT blocks containing
> > free nid entries.
> >
> > If we can find valid crc|cp_ver in the last block of checkpoint pack, we'll
> > use these bitmaps when building free nids. In order to avoid checkpointing
> > burden, up-to-date bitmaps will be flushed only during umount time. So,
> > normally we can get this gain, but when power-cut happens, we rely on fsck.f2fs
> > which recovers this bitmap again.
> >
> > After this patch, we build free nids from nid #0 at mount time to make more
> > full NAT blocks, but in runtime, we check empty NAT blocks to load free nids
> > without loading any NAT pages from disk.
> >
> > Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
> > ---
> > fs/f2fs/checkpoint.c | 29 +++++++-
> > fs/f2fs/debug.c | 1 +
> > fs/f2fs/f2fs.h | 23 +++++-
> > fs/f2fs/node.c | 188 +++++++++++++++++++++++++++++++++++++++++++-----
> > fs/f2fs/segment.c | 2 +-
> > include/linux/f2fs_fs.h | 1 +
> > 6 files changed, 224 insertions(+), 20 deletions(-)
> >
> > diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> > index 042f8d9afe44..783c5c3f16a4 100644
> > --- a/fs/f2fs/checkpoint.c
> > +++ b/fs/f2fs/checkpoint.c
> > @@ -1024,6 +1024,10 @@ static void update_ckpt_flags(struct f2fs_sb_info *sbi, struct cp_control *cpc)
> >
> > spin_lock(&sbi->cp_lock);
> >
> > + if (ckpt->cp_pack_total_block_count >
> > + sbi->blocks_per_seg - NM_I(sbi)->nat_bits_blocks)
> > + disable_nat_bits(sbi, false);
>
> I think we need to drop nat full/empty bitmap only if there is no enough space
> in CP area while doing umount, otherwise we can keep this in memory.

Yup.

>
> > +
> > if (cpc->reason == CP_UMOUNT)
> > __set_ckpt_flags(ckpt, CP_UMOUNT_FLAG);
> > else
> > @@ -1136,6 +1140,29 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
> >
> > start_blk = __start_cp_next_addr(sbi);
> >
> > + /* write nat bits */

...

> > +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.

>
> > + 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
> >
>
>
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Next message: Logan Gunthorpe: "Re: [PATCH v2 3/4] switchtec: Add sysfs attributes to the Switchtec driver"
Previous message: Pavel Machek: "Re: [PATCH 1/4] v4l2: device_register_subdev_nodes: allow calling multiple times"
In reply to: Chao Yu: "Re: [f2fs-dev] [PATCH 2/3] f2fs: add bitmaps for empty or full NAT blocks"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]