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Date: Mon, 11 Apr 2022 13:20:30 -0700
From: Jaegeuk Kim <jaegeuk@...nel.org>
To: Chao Yu <chao@...nel.org>
Cc: linux-f2fs-devel@...ts.sourceforge.net,
linux-kernel@...r.kernel.org, Chao Yu <chao.yu@...o.com>
Subject: Re: [PATCH v3] f2fs: give priority to select unpinned section for
foreground GC
On 04/06, Chao Yu wrote:
> Previously, during foreground GC, if victims contain data of pinned file,
> it will fail migration of the data, and meanwhile i_gc_failures of that
> pinned file may increase, and when it exceeds threshold, GC will unpin
> the file, result in breaking pinfile's semantics.
>
> In order to mitigate such condition, let's record and skip section which
> has pinned file's data and give priority to select unpinned one.
>
> Signed-off-by: Chao Yu <chao.yu@...o.com>
> ---
> v3:
> - check pin status before pinning section in pin_section().
> fs/f2fs/gc.c | 56 ++++++++++++++++++++++++++++++++++++++++++++---
> fs/f2fs/segment.c | 7 ++++++
> fs/f2fs/segment.h | 2 ++
> 3 files changed, 62 insertions(+), 3 deletions(-)
>
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index 6a7e4148ff9d..df23824ae3c2 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -646,6 +646,37 @@ static void release_victim_entry(struct f2fs_sb_info *sbi)
> f2fs_bug_on(sbi, !list_empty(&am->victim_list));
> }
>
> +static void pin_section(struct f2fs_sb_info *sbi, unsigned int segno)
Need f2fs_...?
> +{
> + struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
> + unsigned int secno = GET_SEC_FROM_SEG(sbi, segno);
> +
> + if (test_bit(secno, dirty_i->pinned_secmap))
> + return;
> + set_bit(secno, dirty_i->pinned_secmap);
> + dirty_i->pinned_secmap_cnt++;
> +}
> +
> +static bool pinned_section_exists(struct dirty_seglist_info *dirty_i)
> +{
> + return dirty_i->pinned_secmap_cnt;
> +}
> +
> +static bool section_is_pinned(struct dirty_seglist_info *dirty_i,
> + unsigned int secno)
> +{
> + return pinned_section_exists(dirty_i) &&
> + test_bit(secno, dirty_i->pinned_secmap);
> +}
> +
> +static void unpin_all_sections(struct f2fs_sb_info *sbi)
> +{
> + unsigned int bitmap_size = f2fs_bitmap_size(MAIN_SECS(sbi));
> +
> + memset(DIRTY_I(sbi)->pinned_secmap, 0, bitmap_size);
> + DIRTY_I(sbi)->pinned_secmap_cnt = 0;
> +}
> +
> /*
> * This function is called from two paths.
> * One is garbage collection and the other is SSR segment selection.
> @@ -787,6 +818,9 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi,
> if (gc_type == BG_GC && test_bit(secno, dirty_i->victim_secmap))
> goto next;
>
> + if (gc_type == FG_GC && section_is_pinned(dirty_i, secno))
> + goto next;
> +
> if (is_atgc) {
> add_victim_entry(sbi, &p, segno);
> goto next;
> @@ -1202,8 +1236,10 @@ static int move_data_block(struct inode *inode, block_t bidx,
> }
>
> if (f2fs_is_pinned_file(inode)) {
> - if (gc_type == FG_GC)
> + if (gc_type == FG_GC) {
> f2fs_pin_file_control(inode, true);
> + pin_section(F2FS_I_SB(inode), segno);
Do we need to check unpinning the inode?
if (!f2fs_pin_file_control())
f2fs_set_pin_section();
> + }
> err = -EAGAIN;
> goto out;
> }
> @@ -1352,8 +1388,10 @@ static int move_data_page(struct inode *inode, block_t bidx, int gc_type,
> goto out;
> }
> if (f2fs_is_pinned_file(inode)) {
> - if (gc_type == FG_GC)
> + if (gc_type == FG_GC) {
> f2fs_pin_file_control(inode, true);
> + pin_section(F2FS_I_SB(inode), segno);
> + }
> err = -EAGAIN;
> goto out;
> }
> @@ -1485,6 +1523,7 @@ static int gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
> gc_type == FG_GC) {
> f2fs_pin_file_control(inode, true);
> iput(inode);
> + pin_section(sbi, segno);
We don't have this code.
> return submitted;
> }
>
> @@ -1766,9 +1805,17 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
> ret = -EINVAL;
> goto stop;
> }
> +retry:
> ret = __get_victim(sbi, &segno, gc_type);
> - if (ret)
> + if (ret) {
> + /* allow to search victim from sections has pinned data */
> + if (ret == -ENODATA && gc_type == FG_GC &&
> + pinned_section_exists(DIRTY_I(sbi))) {
> + unpin_all_sections(sbi);
> + goto retry;
> + }
> goto stop;
> + }
>
> seg_freed = do_garbage_collect(sbi, segno, &gc_list, gc_type, force);
> if (gc_type == FG_GC &&
> @@ -1811,6 +1858,9 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
> SIT_I(sbi)->last_victim[ALLOC_NEXT] = 0;
> SIT_I(sbi)->last_victim[FLUSH_DEVICE] = init_segno;
>
> + if (gc_type == FG_GC && pinned_section_exists(DIRTY_I(sbi)))
> + unpin_all_sections(sbi);
> +
> trace_f2fs_gc_end(sbi->sb, ret, total_freed, sec_freed,
> get_pages(sbi, F2FS_DIRTY_NODES),
> get_pages(sbi, F2FS_DIRTY_DENTS),
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 012524db7437..1c20d7c9eca3 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -4736,6 +4736,12 @@ static int init_victim_secmap(struct f2fs_sb_info *sbi)
> dirty_i->victim_secmap = f2fs_kvzalloc(sbi, bitmap_size, GFP_KERNEL);
> if (!dirty_i->victim_secmap)
> return -ENOMEM;
> +
> + dirty_i->pinned_secmap = f2fs_kvzalloc(sbi, bitmap_size, GFP_KERNEL);
> + if (!dirty_i->pinned_secmap)
> + return -ENOMEM;
> +
> + dirty_i->pinned_secmap_cnt = 0;
> return 0;
> }
>
> @@ -5324,6 +5330,7 @@ static void destroy_victim_secmap(struct f2fs_sb_info *sbi)
> {
> struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
>
> + kvfree(dirty_i->pinned_secmap);
> kvfree(dirty_i->victim_secmap);
> }
>
> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
> index 5c94caf0c0a1..fd6f246e649c 100644
> --- a/fs/f2fs/segment.h
> +++ b/fs/f2fs/segment.h
> @@ -294,6 +294,8 @@ struct dirty_seglist_info {
> struct mutex seglist_lock; /* lock for segment bitmaps */
> int nr_dirty[NR_DIRTY_TYPE]; /* # of dirty segments */
> unsigned long *victim_secmap; /* background GC victims */
> + unsigned long *pinned_secmap; /* pinned victims from foreground GC */
> + unsigned int pinned_secmap_cnt; /* count of victims which has pinned data */
> };
>
> /* victim selection function for cleaning and SSR */
> --
> 2.32.0
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