Re: [f2fs-dev] [PATCH 1/2] f2fs: support aligned pinned file

From: Chao Yu
Date: Thu Oct 24 2019 - 04:21:45 EST

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Hi Jaegeuk,

On 2019/10/23 1:16, Jaegeuk Kim wrote:
> This patch supports 2MB-aligned pinned file, which can guarantee no GC at all
> by allocating fully valid 2MB segment.
>
> Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
> ---
> fs/f2fs/f2fs.h | 4 +++-
> fs/f2fs/file.c | 39 ++++++++++++++++++++++++++++++++++-----
> fs/f2fs/recovery.c | 2 +-
> fs/f2fs/segment.c | 21 ++++++++++++++++++++-
> fs/f2fs/segment.h | 2 ++
> fs/f2fs/super.c | 1 +
> fs/f2fs/sysfs.c | 2 ++
> 7 files changed, 63 insertions(+), 8 deletions(-)
>
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index ca342f4c7db1..c681f51e351b 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -890,6 +890,7 @@ enum {
> CURSEG_WARM_NODE, /* direct node blocks of normal files */
> CURSEG_COLD_NODE, /* indirect node blocks */
> NO_CHECK_TYPE,
> + CURSEG_COLD_DATA_PINNED,/* cold data for pinned file */
> };
>
> struct flush_cmd {
> @@ -1301,6 +1302,7 @@ struct f2fs_sb_info {
>
> /* threshold for gc trials on pinned files */
> u64 gc_pin_file_threshold;
> + struct rw_semaphore pin_sem;
>
> /* maximum # of trials to find a victim segment for SSR and GC */
> unsigned int max_victim_search;
> @@ -3116,7 +3118,7 @@ void f2fs_release_discard_addrs(struct f2fs_sb_info *sbi);
> int f2fs_npages_for_summary_flush(struct f2fs_sb_info *sbi, bool for_ra);
> void allocate_segment_for_resize(struct f2fs_sb_info *sbi, int type,
> unsigned int start, unsigned int end);
> -void f2fs_allocate_new_segments(struct f2fs_sb_info *sbi);
> +void f2fs_allocate_new_segments(struct f2fs_sb_info *sbi, int type);
> int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range);
> bool f2fs_exist_trim_candidates(struct f2fs_sb_info *sbi,
> struct cp_control *cpc);
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 29bc0a542759..f6c038e8a6a7 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -1545,12 +1545,41 @@ static int expand_inode_data(struct inode *inode, loff_t offset,
> if (off_end)
> map.m_len++;
>
> - if (f2fs_is_pinned_file(inode))
> - map.m_seg_type = CURSEG_COLD_DATA;
> + if (!map.m_len)
> + return 0;
> +
> + if (f2fs_is_pinned_file(inode)) {
> + block_t len = (map.m_len >> sbi->log_blocks_per_seg) <<
> + sbi->log_blocks_per_seg;
> + block_t done = 0;
> +
> + if (map.m_len % sbi->blocks_per_seg)
> + len += sbi->blocks_per_seg;
>
> - err = f2fs_map_blocks(inode, &map, 1, (f2fs_is_pinned_file(inode) ?
> - F2FS_GET_BLOCK_PRE_DIO :
> - F2FS_GET_BLOCK_PRE_AIO));
> + map.m_len = sbi->blocks_per_seg;
> +next_alloc:
> + mutex_lock(&sbi->gc_mutex);
> + err = f2fs_gc(sbi, true, false, NULL_SEGNO);
> + if (err && err != -ENODATA && err != -EAGAIN)
> + goto out_err;

To grab enough free space?

Shouldn't we call

if (has_not_enough_free_secs(sbi, 0, 0)) {
mutex_lock(&sbi->gc_mutex);
f2fs_gc(sbi, false, false, NULL_SEGNO);
}

> +
> + down_write(&sbi->pin_sem);
> + map.m_seg_type = CURSEG_COLD_DATA_PINNED;
> + f2fs_allocate_new_segments(sbi, CURSEG_COLD_DATA);
> + err = f2fs_map_blocks(inode, &map, 1, F2FS_GET_BLOCK_PRE_DIO);
> + up_write(&sbi->pin_sem);
> +
> + done += map.m_len;
> + len -= map.m_len;
> + map.m_lblk += map.m_len;
> + if (!err && len)
> + goto next_alloc;
> +
> + map.m_len = done;
> + } else {
> + err = f2fs_map_blocks(inode, &map, 1, F2FS_GET_BLOCK_PRE_AIO);
> + }
> +out_err:
> if (err) {
> pgoff_t last_off;
>
> diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
> index 783773e4560d..76477f71d4ee 100644
> --- a/fs/f2fs/recovery.c
> +++ b/fs/f2fs/recovery.c
> @@ -711,7 +711,7 @@ static int recover_data(struct f2fs_sb_info *sbi, struct list_head *inode_list,
> f2fs_put_page(page, 1);
> }
> if (!err)
> - f2fs_allocate_new_segments(sbi);
> + f2fs_allocate_new_segments(sbi, NO_CHECK_TYPE);
> return err;
> }
>
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 25c750cd0272..253d72c2663c 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -2690,7 +2690,7 @@ void allocate_segment_for_resize(struct f2fs_sb_info *sbi, int type,
> up_read(&SM_I(sbi)->curseg_lock);
> }
>
> -void f2fs_allocate_new_segments(struct f2fs_sb_info *sbi)
> +void f2fs_allocate_new_segments(struct f2fs_sb_info *sbi, int type)
> {
> struct curseg_info *curseg;
> unsigned int old_segno;
> @@ -2699,6 +2699,9 @@ void f2fs_allocate_new_segments(struct f2fs_sb_info *sbi)
> down_write(&SIT_I(sbi)->sentry_lock);
>
> for (i = CURSEG_HOT_DATA; i <= CURSEG_COLD_DATA; i++) {
> + if (type != NO_CHECK_TYPE && i != type)
> + continue;
> +
> curseg = CURSEG_I(sbi, i);
> old_segno = curseg->segno;
> SIT_I(sbi)->s_ops->allocate_segment(sbi, i, true);
> @@ -3068,6 +3071,19 @@ void f2fs_allocate_data_block(struct f2fs_sb_info *sbi, struct page *page,
> {
> struct sit_info *sit_i = SIT_I(sbi);
> struct curseg_info *curseg = CURSEG_I(sbi, type);
> + bool put_pin_sem = false;
> +
> + if (type == CURSEG_COLD_DATA) {
> + /* GC during CURSEG_COLD_DATA_PINNED allocation */
> + if (down_read_trylock(&sbi->pin_sem)) {
> + put_pin_sem = true;
> + } else {
> + type = CURSEG_WARM_DATA;
> + curseg = CURSEG_I(sbi, type);

It will mix pending cold data into warm area... rather than recovering curseg to
write pointer of last cold segment?

I know maybe that fallocate aligned address could be corner case, but I guess
there should be some better solutions can handle race case more effectively.

One solution could be: allocating a virtual log header to select free segment as
2m-aligned space target.

Thanks,

> + }
> + } else if (type == CURSEG_COLD_DATA_PINNED) {
> + type = CURSEG_COLD_DATA;
> + }
>
> down_read(&SM_I(sbi)->curseg_lock);
>
> @@ -3133,6 +3149,9 @@ void f2fs_allocate_data_block(struct f2fs_sb_info *sbi, struct page *page,
> mutex_unlock(&curseg->curseg_mutex);
>
> up_read(&SM_I(sbi)->curseg_lock);
> +
> + if (put_pin_sem)
> + up_read(&sbi->pin_sem);
> }
>
> static void update_device_state(struct f2fs_io_info *fio)
> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
> index 325781a1ae4d..a95467b202ea 100644
> --- a/fs/f2fs/segment.h
> +++ b/fs/f2fs/segment.h
> @@ -313,6 +313,8 @@ struct sit_entry_set {
> */
> static inline struct curseg_info *CURSEG_I(struct f2fs_sb_info *sbi, int type)
> {
> + if (type == CURSEG_COLD_DATA_PINNED)
> + type = CURSEG_COLD_DATA;
> return (struct curseg_info *)(SM_I(sbi)->curseg_array + type);
> }
>
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index f320fd11db48..c02a47ce551b 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -2853,6 +2853,7 @@ static void init_sb_info(struct f2fs_sb_info *sbi)
> spin_lock_init(&sbi->dev_lock);
>
> init_rwsem(&sbi->sb_lock);
> + init_rwsem(&sbi->pin_sem);
> }
>
> static int init_percpu_info(struct f2fs_sb_info *sbi)
> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
> index b558b64a4c9c..f164959e4224 100644
> --- a/fs/f2fs/sysfs.c
> +++ b/fs/f2fs/sysfs.c
> @@ -154,6 +154,8 @@ static ssize_t features_show(struct f2fs_attr *a,
> if (f2fs_sb_has_casefold(sbi))
> len += snprintf(buf + len, PAGE_SIZE - len, "%s%s",
> len ? ", " : "", "casefold");
> + len += snprintf(buf + len, PAGE_SIZE - len, "%s%s",
> + len ? ", " : "", "pin_file");
> len += snprintf(buf + len, PAGE_SIZE - len, "\n");
> return len;
> }
>

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