Re: [PATCH v2] f2fs: avoid stucking GC due to atomic write

From: Chao Yu
Date: Thu Apr 26 2018 - 21:51:45 EST

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In reply to: Jaegeuk Kim: "Re: [PATCH v2] f2fs: avoid stucking GC due to atomic write"
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On 2018/4/26 23:54, Jaegeuk Kim wrote:
> 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?

OK, how about changing it to array fi->i_gc_failure[MAX_GC_FAILURE], and change
the type to unsigned long long to avoid overflow?

enum {
GC_FAILURE_PIN,
GC_FAILURE_ATOMIC,
MAX_GC_FAILURE
}

Thanks,

>
>>
>> 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@xxxxxxxxxx>
>> ---
>> 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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