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Date: Thu, 26 Apr 2018 09:54:49 -0600
From: Jaegeuk Kim <jaegeuk@...nel.org>
To: Chao Yu <yuchao0@...wei.com>
Cc: linux-f2fs-devel@...ts.sourceforge.net,
linux-kernel@...r.kernel.org, chao@...nel.org
Subject: Re: [PATCH v2] f2fs: avoid stucking GC due to atomic write
On 04/24, Chao Yu wrote:
> f2fs doesn't allow abuse on atomic write class interface, so except
> limiting in-mem pages' total memory usage capacity, we need to limit
> atomic-write usage as well when filesystem is seriously fragmented,
> otherwise we may run into infinite loop during foreground GC because
> target blocks in victim segment are belong to atomic opened file for
> long time.
How about using fi->i_gc_failure likewise pin_file?
>
> Now, we will detect failure due to atomic write in foreground GC, if
> the count exceeds threshold, we will drop all atomic written data in
> cache, by this, I expect it can keep our system running safely to
> prevent Dos attack.
>
> In addition, his patch adds to show GC skip information in debugfs,
> now it just shows count of skipped caused by atomic write.
>
> Signed-off-by: Chao Yu <yuchao0@...wei.com>
> ---
> v2:
> - add to show skip info in debugfs.
> fs/f2fs/debug.c | 8 ++++++++
> fs/f2fs/f2fs.h | 2 ++
> fs/f2fs/file.c | 5 +++++
> fs/f2fs/gc.c | 29 +++++++++++++++++++++++++----
> fs/f2fs/gc.h | 3 +++
> fs/f2fs/segment.c | 1 +
> fs/f2fs/segment.h | 2 ++
> 7 files changed, 46 insertions(+), 4 deletions(-)
>
> diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
> index 0fbd674c66fb..607b258a9b61 100644
> --- a/fs/f2fs/debug.c
> +++ b/fs/f2fs/debug.c
> @@ -104,6 +104,10 @@ static void update_general_status(struct f2fs_sb_info *sbi)
> si->avail_nids = NM_I(sbi)->available_nids;
> si->alloc_nids = NM_I(sbi)->nid_cnt[PREALLOC_NID];
> si->bg_gc = sbi->bg_gc;
> + si->skipped_atomic_files[BG_GC] =
> + sbi->gc_thread->skipped_atomic_files[BG_GC];
> + si->skipped_atomic_files[FG_GC] =
> + sbi->gc_thread->skipped_atomic_files[FG_GC];
> si->util_free = (int)(free_user_blocks(sbi) >> sbi->log_blocks_per_seg)
> * 100 / (int)(sbi->user_block_count >> sbi->log_blocks_per_seg)
> / 2;
> @@ -341,6 +345,10 @@ static int stat_show(struct seq_file *s, void *v)
> si->bg_data_blks);
> seq_printf(s, " - node blocks : %d (%d)\n", si->node_blks,
> si->bg_node_blks);
> + seq_printf(s, "Skipped : atomic write %llu (%llu)\n",
> + si->skipped_atomic_files[BG_GC] +
> + si->skipped_atomic_files[FG_GC],
> + si->skipped_atomic_files[BG_GC]);
> seq_puts(s, "\nExtent Cache:\n");
> seq_printf(s, " - Hit Count: L1-1:%llu L1-2:%llu L2:%llu\n",
> si->hit_largest, si->hit_cached,
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 75d3b4875429..c2b92cb377c6 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -2254,6 +2254,7 @@ enum {
> FI_EXTRA_ATTR, /* indicate file has extra attribute */
> FI_PROJ_INHERIT, /* indicate file inherits projectid */
> FI_PIN_FILE, /* indicate file should not be gced */
> + FI_ATOMIC_REVOKE_REQUEST,/* indicate atomic committed data has been dropped */
> };
>
> static inline void __mark_inode_dirty_flag(struct inode *inode,
> @@ -3010,6 +3011,7 @@ struct f2fs_stat_info {
> int bg_node_segs, bg_data_segs;
> int tot_blks, data_blks, node_blks;
> int bg_data_blks, bg_node_blks;
> + unsigned long long skipped_atomic_files[2];
> int curseg[NR_CURSEG_TYPE];
> int cursec[NR_CURSEG_TYPE];
> int curzone[NR_CURSEG_TYPE];
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index a352804af244..0cfa65c21d3f 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -1702,6 +1702,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
> skip_flush:
> set_inode_flag(inode, FI_HOT_DATA);
> set_inode_flag(inode, FI_ATOMIC_FILE);
> + clear_inode_flag(inode, FI_ATOMIC_REVOKE_REQUEST);
> f2fs_update_time(F2FS_I_SB(inode), REQ_TIME);
>
> F2FS_I(inode)->inmem_task = current;
> @@ -1750,6 +1751,10 @@ static int f2fs_ioc_commit_atomic_write(struct file *filp)
> ret = f2fs_do_sync_file(filp, 0, LLONG_MAX, 1, false);
> }
> err_out:
> + if (is_inode_flag_set(inode, FI_ATOMIC_REVOKE_REQUEST)) {
> + clear_inode_flag(inode, FI_ATOMIC_REVOKE_REQUEST);
> + ret = -EINVAL;
> + }
> up_write(&F2FS_I(inode)->dio_rwsem[WRITE]);
> inode_unlock(inode);
> mnt_drop_write_file(filp);
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index 2febb84b2fd6..ec6cb7b417a1 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -135,6 +135,9 @@ int init_gc_context(struct f2fs_sb_info *sbi)
>
> init_rwsem(&gc_th->gc_rwsem);
>
> + gc_th->skipped_atomic_files[BG_GC] = 0;
> + gc_th->skipped_atomic_files[FG_GC] = 0;
> +
> sbi->gc_thread = gc_th;
>
> return 0;
> @@ -629,7 +632,7 @@ static bool is_alive(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
> * This can be used to move blocks, aka LBAs, directly on disk.
> */
> static void move_data_block(struct inode *inode, block_t bidx,
> - unsigned int segno, int off)
> + int gc_type, unsigned int segno, int off)
> {
> struct f2fs_io_info fio = {
> .sbi = F2FS_I_SB(inode),
> @@ -656,8 +659,10 @@ static void move_data_block(struct inode *inode, block_t bidx,
> if (!check_valid_map(F2FS_I_SB(inode), segno, off))
> goto out;
>
> - if (f2fs_is_atomic_file(inode))
> + if (f2fs_is_atomic_file(inode)) {
> + GC_I(F2FS_I_SB(inode))->skipped_atomic_files[gc_type]++;
> goto out;
> + }
>
> if (f2fs_is_pinned_file(inode)) {
> f2fs_pin_file_control(inode, true);
> @@ -763,8 +768,10 @@ static void move_data_page(struct inode *inode, block_t bidx, int gc_type,
> if (!check_valid_map(F2FS_I_SB(inode), segno, off))
> goto out;
>
> - if (f2fs_is_atomic_file(inode))
> + if (f2fs_is_atomic_file(inode)) {
> + GC_I(F2FS_I_SB(inode))->skipped_atomic_files[gc_type]++;
> goto out;
> + }
> if (f2fs_is_pinned_file(inode)) {
> if (gc_type == FG_GC)
> f2fs_pin_file_control(inode, true);
> @@ -926,7 +933,8 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
> start_bidx = start_bidx_of_node(nofs, inode)
> + ofs_in_node;
> if (f2fs_post_read_required(inode))
> - move_data_block(inode, start_bidx, segno, off);
> + move_data_block(inode, start_bidx, gc_type,
> + segno, off);
> else
> move_data_page(inode, start_bidx, gc_type,
> segno, off);
> @@ -1043,6 +1051,9 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
> .ilist = LIST_HEAD_INIT(gc_list.ilist),
> .iroot = RADIX_TREE_INIT(gc_list.iroot, GFP_NOFS),
> };
> + unsigned long long last_skipped =
> + GC_I(sbi)->skipped_atomic_files[FG_GC];
> + unsigned int skipped_round = 0, round = 0;
>
> trace_f2fs_gc_begin(sbi->sb, sync, background,
> get_pages(sbi, F2FS_DIRTY_NODES),
> @@ -1094,11 +1105,21 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
> sec_freed++;
> total_freed += seg_freed;
>
> + if (gc_type == FG_GC) {
> + if (GC_I(sbi)->skipped_atomic_files[FG_GC] > last_skipped)
> + skipped_round++;
> + last_skipped = GC_I(sbi)->skipped_atomic_files[FG_GC];
> + round++;
> + }
> +
> if (gc_type == FG_GC)
> sbi->cur_victim_sec = NULL_SEGNO;
>
> if (!sync) {
> if (has_not_enough_free_secs(sbi, sec_freed, 0)) {
> + if (skipped_round > MAX_SKIP_ATOMIC_COUNT &&
> + skipped_round * 2 >= round)
> + drop_inmem_pages_all(sbi);
> segno = NULL_SEGNO;
> goto gc_more;
> }
> diff --git a/fs/f2fs/gc.h b/fs/f2fs/gc.h
> index 9a5b273328c2..9aa341cc4347 100644
> --- a/fs/f2fs/gc.h
> +++ b/fs/f2fs/gc.h
> @@ -40,6 +40,9 @@ struct f2fs_gc_kthread {
> unsigned int gc_idle;
> unsigned int gc_urgent;
> unsigned int gc_wake;
> +
> + /* for skip statistic */
> + unsigned long long skipped_atomic_files[2];
> };
>
> struct gc_inode_list {
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index f787eea1b2f6..ce108a909d66 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -293,6 +293,7 @@ void drop_inmem_pages_all(struct f2fs_sb_info *sbi)
> spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
>
> if (inode) {
> + set_inode_flag(inode, FI_ATOMIC_REVOKE_REQUEST);
> drop_inmem_pages(inode);
> iput(inode);
> }
> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
> index 492ad0c86fa9..7702b054689c 100644
> --- a/fs/f2fs/segment.h
> +++ b/fs/f2fs/segment.h
> @@ -215,6 +215,8 @@ struct segment_allocation {
> #define IS_DUMMY_WRITTEN_PAGE(page) \
> (page_private(page) == (unsigned long)DUMMY_WRITTEN_PAGE)
>
> +#define MAX_SKIP_ATOMIC_COUNT 16
> +
> struct inmem_pages {
> struct list_head list;
> struct page *page;
> --
> 2.15.0.55.gc2ece9dc4de6
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