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Message-ID: <ce9df2e1-b438-5303-d246-fb28b451c2ee@huawei.com>
Date: Tue, 15 Nov 2016 14:40:45 +0800
From: Chao Yu <yuchao0@...wei.com>
To: Jaegeuk Kim <jaegeuk@...nel.org>
CC: <linux-f2fs-devel@...ts.sourceforge.net>,
<linux-kernel@...r.kernel.org>, <chao@...nel.org>
Subject: Re: [PATCH v2] f2fs: don't wait writeback for datas during checkpoint
Hi Jaegeuk,
On 2016/11/15 7:32, Jaegeuk Kim wrote:
> Hi Chao,
>
> On Mon, Nov 14, 2016 at 07:04:12PM +0800, Chao Yu wrote:
>> Normally, while committing checkpoint, we will wait on all pages to be
>> writebacked no matter the page is data or metadata, so in scenario where
>> there are lots of data IO being submitted with metadata, we may suffer
>> long latency for waiting writeback during checkpoint.
>>
>> Indeed, we only care about persistence for pages with metadata, but not
>> pages with data, as file system consistent are only related to metadate,
>> so in order to avoid encountering long latency in above scenario, let's
>> recognize and reference metadata in submitted IOs, wait writeback only
>> for metadatas.
>
> Hmm, another concern comes, which is related to GCed data like below scenario.
>
> 1. Write data X
> 2. Sync
> 3. Move data X by GC
> 4. Checkpoint
> 5. Power-cut
>
> In this case, we should guarantee data X which was migrated by GC during #3.
> If we don't care about end_io in #4 Checkpoint, we can lose the data after
> #5 Power-cut.
>
> Any idea?
Yes, good catch. :)
What about tagging these GCed page as cold data through set_cold_data, and clear
the tag in end_io, then we can keep reference count and wait on writeback for them?
Thanks,
>
> Thanks,
>
>>
>> Signed-off-by: Chao Yu <yuchao0@...wei.com>
>> ---
>> fs/f2fs/checkpoint.c | 2 +-
>> fs/f2fs/data.c | 36 ++++++++++++++++++++++++++++++++----
>> fs/f2fs/debug.c | 7 ++++---
>> fs/f2fs/f2fs.h | 8 +++++---
>> 4 files changed, 42 insertions(+), 11 deletions(-)
>>
>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
>> index 7bece59..bdf8a50 100644
>> --- a/fs/f2fs/checkpoint.c
>> +++ b/fs/f2fs/checkpoint.c
>> @@ -1003,7 +1003,7 @@ static void wait_on_all_pages_writeback(struct f2fs_sb_info *sbi)
>> for (;;) {
>> prepare_to_wait(&sbi->cp_wait, &wait, TASK_UNINTERRUPTIBLE);
>>
>> - if (!atomic_read(&sbi->nr_wb_bios))
>> + if (!get_pages(sbi, F2FS_WB_META))
>> break;
>>
>> io_schedule_timeout(5*HZ);
>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>> index 66d2aee..f52cec3 100644
>> --- a/fs/f2fs/data.c
>> +++ b/fs/f2fs/data.c
>> @@ -29,6 +29,26 @@
>> #include "trace.h"
>> #include <trace/events/f2fs.h>
>>
>> +static bool f2fs_is_meta_data(struct page *page)
>> +{
>> + struct address_space *mapping = page->mapping;
>> + struct f2fs_sb_info *sbi;
>> + struct inode *inode;
>> +
>> + /* it is bounce page of encrypted regular inode */
>> + if (!mapping)
>> + return false;
>> +
>> + inode = mapping->host;
>> + sbi = F2FS_I_SB(inode);
>> +
>> + if ((inode->i_ino == F2FS_META_INO(sbi) &&
>> + page->index < MAIN_BLKADDR(sbi)) ||
>> + inode->i_ino == F2FS_NODE_INO(sbi) ||
>> + S_ISDIR(inode->i_mode))
>> + return true;
>> + return false;
>> +}
>> static void f2fs_read_end_io(struct bio *bio)
>> {
>> struct bio_vec *bvec;
>> @@ -73,6 +93,7 @@ static void f2fs_write_end_io(struct bio *bio)
>>
>> bio_for_each_segment_all(bvec, bio, i) {
>> struct page *page = bvec->bv_page;
>> + bool is_meta = f2fs_is_meta_data(page);
>>
>> fscrypt_pullback_bio_page(&page, true);
>>
>> @@ -80,9 +101,10 @@ static void f2fs_write_end_io(struct bio *bio)
>> mapping_set_error(page->mapping, -EIO);
>> f2fs_stop_checkpoint(sbi, true);
>> }
>> + dec_page_count(sbi, is_meta ? F2FS_WB_META : F2FS_WB_DATA);
>> end_page_writeback(page);
>> }
>> - if (atomic_dec_and_test(&sbi->nr_wb_bios) &&
>> + if (!get_pages(sbi, F2FS_WB_META) &&
>> wq_has_sleeper(&sbi->cp_wait))
>> wake_up(&sbi->cp_wait);
>>
>> @@ -111,7 +133,6 @@ static inline void __submit_bio(struct f2fs_sb_info *sbi,
>> struct bio *bio, enum page_type type)
>> {
>> if (!is_read_io(bio_op(bio))) {
>> - atomic_inc(&sbi->nr_wb_bios);
>> if (f2fs_sb_mounted_blkzoned(sbi->sb) &&
>> current->plug && (type == DATA || type == NODE))
>> blk_finish_plug(current->plug);
>> @@ -272,6 +293,15 @@ void f2fs_submit_page_mbio(struct f2fs_io_info *fio)
>> verify_block_addr(sbi, fio->old_blkaddr);
>> verify_block_addr(sbi, fio->new_blkaddr);
>>
>> + bio_page = fio->encrypted_page ? fio->encrypted_page : fio->page;
>> +
>> + if (!is_read) {
>> + bool is_meta;
>> +
>> + is_meta = f2fs_is_meta_data(bio_page);
>> + inc_page_count(sbi, is_meta ? F2FS_WB_META : F2FS_WB_DATA);
>> + }
>> +
>> down_write(&io->io_rwsem);
>>
>> if (io->bio && (io->last_block_in_bio != fio->new_blkaddr - 1 ||
>> @@ -284,8 +314,6 @@ void f2fs_submit_page_mbio(struct f2fs_io_info *fio)
>> io->fio = *fio;
>> }
>>
>> - bio_page = fio->encrypted_page ? fio->encrypted_page : fio->page;
>> -
>> if (bio_add_page(io->bio, bio_page, PAGE_SIZE, 0) <
>> PAGE_SIZE) {
>> __submit_merged_bio(io);
>> diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
>> index 2fdf233..f2d87de 100644
>> --- a/fs/f2fs/debug.c
>> +++ b/fs/f2fs/debug.c
>> @@ -50,7 +50,8 @@ static void update_general_status(struct f2fs_sb_info *sbi)
>> si->ndirty_files = sbi->ndirty_inode[FILE_INODE];
>> si->ndirty_all = sbi->ndirty_inode[DIRTY_META];
>> si->inmem_pages = get_pages(sbi, F2FS_INMEM_PAGES);
>> - si->wb_bios = atomic_read(&sbi->nr_wb_bios);
>> + si->nr_wb_meta = get_pages(sbi, F2FS_WB_META);
>> + si->nr_wb_data = get_pages(sbi, F2FS_WB_DATA);
>> si->total_count = (int)sbi->user_block_count / sbi->blocks_per_seg;
>> si->rsvd_segs = reserved_segments(sbi);
>> si->overp_segs = overprovision_segments(sbi);
>> @@ -313,8 +314,8 @@ static int stat_show(struct seq_file *s, void *v)
>> seq_printf(s, " - Inner Struct Count: tree: %d(%d), node: %d\n",
>> si->ext_tree, si->zombie_tree, si->ext_node);
>> seq_puts(s, "\nBalancing F2FS Async:\n");
>> - seq_printf(s, " - inmem: %4d, wb_bios: %4d\n",
>> - si->inmem_pages, si->wb_bios);
>> + seq_printf(s, " - inmem: %4d, wb_meta: %4d, wb_data: %4d\n",
>> + si->inmem_pages, si->nr_wb_meta, si->nr_wb_data);
>> seq_printf(s, " - nodes: %4d in %4d\n",
>> si->ndirty_node, si->node_pages);
>> seq_printf(s, " - dents: %4d in dirs:%4d (%4d)\n",
>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>> index 23a937f..4df301c 100644
>> --- a/fs/f2fs/f2fs.h
>> +++ b/fs/f2fs/f2fs.h
>> @@ -682,6 +682,8 @@ enum count_type {
>> F2FS_DIRTY_META,
>> F2FS_INMEM_PAGES,
>> F2FS_DIRTY_IMETA,
>> + F2FS_WB_META,
>> + F2FS_WB_DATA,
>> NR_COUNT_TYPE,
>> };
>>
>> @@ -849,7 +851,6 @@ struct f2fs_sb_info {
>> block_t discard_blks; /* discard command candidats */
>> block_t last_valid_block_count; /* for recovery */
>> u32 s_next_generation; /* for NFS support */
>> - atomic_t nr_wb_bios; /* # of writeback bios */
>>
>> /* # of pages, see count_type */
>> atomic_t nr_pages[NR_COUNT_TYPE];
>> @@ -1263,7 +1264,8 @@ static inline void inc_page_count(struct f2fs_sb_info *sbi, int count_type)
>> {
>> atomic_inc(&sbi->nr_pages[count_type]);
>>
>> - if (count_type == F2FS_DIRTY_DATA || count_type == F2FS_INMEM_PAGES)
>> + if (count_type == F2FS_DIRTY_DATA || count_type == F2FS_INMEM_PAGES ||
>> + count_type == F2FS_WB_META || count_type == F2FS_WB_DATA)
>> return;
>>
>> set_sbi_flag(sbi, SBI_IS_DIRTY);
>> @@ -2219,7 +2221,7 @@ struct f2fs_stat_info {
>> unsigned int ndirty_dirs, ndirty_files, ndirty_all;
>> int nats, dirty_nats, sits, dirty_sits, free_nids, alloc_nids;
>> int total_count, utilization;
>> - int bg_gc, wb_bios;
>> + int bg_gc, nr_wb_meta, nr_wb_data;
>> int inline_xattr, inline_inode, inline_dir, orphans;
>> unsigned int valid_count, valid_node_count, valid_inode_count, discard_blks;
>> unsigned int bimodal, avg_vblocks;
>> --
>> 2.8.2.311.gee88674
>
> .
>
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