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Date: Wed, 18 May 2016 09:17:00 +0800
From: Chao Yu <yuchao0@...wei.com>
To: Jaegeuk Kim <jaegeuk@...nel.org>, <linux-kernel@...r.kernel.org>,
<linux-fsdevel@...r.kernel.org>,
<linux-f2fs-devel@...ts.sourceforge.net>
Subject: Re: [f2fs-dev] [PATCH] f2fs: use bio count instead of F2FS_WRITEBACK
page count
Hi Jaegeuk,
On 2016/5/18 8:44, Jaegeuk Kim wrote:
> This can reduce page counting overhead.
We change to increase one reference for one bio, but block layer can split or
merge bios by itself, and write_end will be called per bio, so the reference may
be maintained incorrectly?
Thanks,
>
> Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> ---
> fs/f2fs/checkpoint.c | 2 +-
> fs/f2fs/data.c | 26 +++++++++++++++-----------
> fs/f2fs/debug.c | 6 +++---
> fs/f2fs/f2fs.h | 4 ++--
> fs/f2fs/super.c | 2 +-
> 5 files changed, 22 insertions(+), 18 deletions(-)
>
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> index d04113b..447e2a9 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -914,7 +914,7 @@ static void wait_on_all_pages_writeback(struct f2fs_sb_info *sbi)
> for (;;) {
> prepare_to_wait(&sbi->cp_wait, &wait, TASK_UNINTERRUPTIBLE);
>
> - if (!get_pages(sbi, F2FS_WRITEBACK))
> + if (!atomic_read(&sbi->nr_wb_bios))
> break;
>
> io_schedule_timeout(5*HZ);
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 1013836..faef666 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -71,10 +71,9 @@ static void f2fs_write_end_io(struct bio *bio)
> f2fs_stop_checkpoint(sbi);
> }
> end_page_writeback(page);
> - dec_page_count(sbi, F2FS_WRITEBACK);
> }
> -
> - if (!get_pages(sbi, F2FS_WRITEBACK) && wq_has_sleeper(&sbi->cp_wait))
> + if (atomic_dec_and_test(&sbi->nr_wb_bios) &&
> + wq_has_sleeper(&sbi->cp_wait))
> wake_up(&sbi->cp_wait);
>
> bio_put(bio);
> @@ -98,6 +97,14 @@ static struct bio *__bio_alloc(struct f2fs_sb_info *sbi, block_t blk_addr,
> return bio;
> }
>
> +static inline void __submit_bio(struct f2fs_sb_info *sbi, int rw,
> + struct bio *bio)
> +{
> + if (!is_read_io(rw))
> + atomic_inc(&sbi->nr_wb_bios);
> + submit_bio(rw, bio);
> +}
> +
> static void __submit_merged_bio(struct f2fs_bio_info *io)
> {
> struct f2fs_io_info *fio = &io->fio;
> @@ -110,7 +117,7 @@ static void __submit_merged_bio(struct f2fs_bio_info *io)
> else
> trace_f2fs_submit_write_bio(io->sbi->sb, fio, io->bio);
>
> - submit_bio(fio->rw, io->bio);
> + __submit_bio(io->sbi, fio->rw, io->bio);
> io->bio = NULL;
> }
>
> @@ -228,7 +235,7 @@ int f2fs_submit_page_bio(struct f2fs_io_info *fio)
> return -EFAULT;
> }
>
> - submit_bio(fio->rw, bio);
> + __submit_bio(fio->sbi, fio->rw, bio);
> return 0;
> }
>
> @@ -248,9 +255,6 @@ void f2fs_submit_page_mbio(struct f2fs_io_info *fio)
>
> down_write(&io->io_rwsem);
>
> - if (!is_read)
> - inc_page_count(sbi, F2FS_WRITEBACK);
> -
> if (io->bio && (io->last_block_in_bio != fio->new_blkaddr - 1 ||
> io->fio.rw != fio->rw))
> __submit_merged_bio(io);
> @@ -1047,7 +1051,7 @@ got_it:
> */
> if (bio && (last_block_in_bio != block_nr - 1)) {
> submit_and_realloc:
> - submit_bio(READ, bio);
> + __submit_bio(F2FS_I_SB(inode), READ, bio);
> bio = NULL;
> }
> if (bio == NULL) {
> @@ -1090,7 +1094,7 @@ set_error_page:
> goto next_page;
> confused:
> if (bio) {
> - submit_bio(READ, bio);
> + __submit_bio(F2FS_I_SB(inode), READ, bio);
> bio = NULL;
> }
> unlock_page(page);
> @@ -1100,7 +1104,7 @@ next_page:
> }
> BUG_ON(pages && !list_empty(pages));
> if (bio)
> - submit_bio(READ, bio);
> + __submit_bio(F2FS_I_SB(inode), READ, bio);
> return 0;
> }
>
> diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
> index 37615b2..a188973 100644
> --- a/fs/f2fs/debug.c
> +++ b/fs/f2fs/debug.c
> @@ -48,7 +48,7 @@ static void update_general_status(struct f2fs_sb_info *sbi)
> si->ndirty_dirs = sbi->ndirty_inode[DIR_INODE];
> si->ndirty_files = sbi->ndirty_inode[FILE_INODE];
> si->inmem_pages = get_pages(sbi, F2FS_INMEM_PAGES);
> - si->wb_pages = get_pages(sbi, F2FS_WRITEBACK);
> + si->wb_bios = atomic_read(&sbi->nr_wb_bios);
> si->total_count = (int)sbi->user_block_count / sbi->blocks_per_seg;
> si->rsvd_segs = reserved_segments(sbi);
> si->overp_segs = overprovision_segments(sbi);
> @@ -299,8 +299,8 @@ 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: %4d\n",
> - si->inmem_pages, si->wb_pages);
> + seq_printf(s, " - inmem: %4d, wb_bios: %4d\n",
> + si->inmem_pages, si->wb_bios);
> seq_printf(s, " - nodes: %4d in %4d\n",
> si->ndirty_node, si->node_pages);
> seq_printf(s, " - dents: %4d in dirs:%4d\n",
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 1351178..bc45a2c 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -650,7 +650,6 @@ struct f2fs_sm_info {
> * dirty dentry blocks, dirty node blocks, and dirty meta blocks.
> */
> enum count_type {
> - F2FS_WRITEBACK,
> F2FS_DIRTY_DENTS,
> F2FS_DIRTY_DATA,
> F2FS_DIRTY_NODES,
> @@ -813,6 +812,7 @@ 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 */
> atomic_t nr_pages[NR_COUNT_TYPE]; /* # of pages, see count_type */
>
> struct f2fs_mount_info mount_opt; /* mount options */
> @@ -2017,7 +2017,7 @@ struct f2fs_stat_info {
> int ndirty_dent, ndirty_dirs, ndirty_data, ndirty_files;
> int nats, dirty_nats, sits, dirty_sits, fnids;
> int total_count, utilization;
> - int bg_gc, inmem_pages, wb_pages;
> + int bg_gc, inmem_pages, wb_bios;
> int inline_xattr, inline_inode, inline_dir, orphans;
> unsigned int valid_count, valid_node_count, valid_inode_count;
> unsigned int bimodal, avg_vblocks;
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 9df6d72..c21e662 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -649,7 +649,7 @@ static void f2fs_put_super(struct super_block *sb)
> mutex_unlock(&sbi->umount_mutex);
>
> /* our cp_error case, we can wait for any writeback page */
> - if (get_pages(sbi, F2FS_WRITEBACK))
> + if (atomic_read(&sbi->nr_wb_bios))
> f2fs_flush_merged_bios(sbi);
>
> iput(sbi->node_inode);
>
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