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f2fs: fix to avoid REQ_TIME and CP_TIME collision

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Lei Li reported a issue: if foreground operations are frequent, background
checkpoint may be always skipped due to below check, result in losing more
data after sudden power-cut.

f2fs_balance_fs_bg()
...
	if (!is_idle(sbi, REQ_TIME) &&
		(!excess_dirty_nats(sbi) && !excess_dirty_nodes(sbi)))
		return;

E.g:
cp_interval = 5 second
idle_interval = 2 second
foreground operation interval = 1 second (append 1 byte per second into file)

In such case, no matter when it calls f2fs_balance_fs_bg(), is_idle(, REQ_TIME)
returns false, result in skipping background checkpoint.

This patch changes as below to make trigger condition being more reasonable:
- trigger sync_fs() if dirty_{nats,nodes} and prefree segs exceeds threshold;
- skip triggering sync_fs() if there is any background inflight IO or there is
foreground operation recently and meanwhile cp_rwsem is being held by someone;

Reported-by: Lei Li <noctis.akm@gmail.com>
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This commit is contained in:
Chao Yu 2020-11-25 10:57:36 +08:00 committed by Jaegeuk Kim
parent 8769918bf0
commit 493720a485
2 changed files with 38 additions and 24 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

19
fs/f2fs/f2fs.h
View file

@ -2400,24 +2400,31 @@ static inline void *f2fs_kmem_cache_alloc(struct kmem_cache *cachep,
return entry;
}
static inline bool is_idle(struct f2fs_sb_info *sbi, int type)
static inline bool is_inflight_io(struct f2fs_sb_info *sbi, int type)
{
if (sbi->gc_mode == GC_URGENT_HIGH)
return true;
if (get_pages(sbi, F2FS_RD_DATA) || get_pages(sbi, F2FS_RD_NODE) ||
get_pages(sbi, F2FS_RD_META) || get_pages(sbi, F2FS_WB_DATA) ||
get_pages(sbi, F2FS_WB_CP_DATA) ||
get_pages(sbi, F2FS_DIO_READ) ||
get_pages(sbi, F2FS_DIO_WRITE))
return false;
return true;
if (type != DISCARD_TIME && SM_I(sbi) && SM_I(sbi)->dcc_info &&
atomic_read(&SM_I(sbi)->dcc_info->queued_discard))
return false;
return true;
if (SM_I(sbi) && SM_I(sbi)->fcc_info &&
atomic_read(&SM_I(sbi)->fcc_info->queued_flush))
return true;
return false;
}
static inline bool is_idle(struct f2fs_sb_info *sbi, int type)
{
if (sbi->gc_mode == GC_URGENT_HIGH)
return true;
if (is_inflight_io(sbi, type))
return false;
if (sbi->gc_mode == GC_URGENT_LOW &&

25
fs/f2fs/segment.c
View file

@ -529,17 +529,25 @@ void f2fs_balance_fs_bg(struct f2fs_sb_info *sbi, bool from_bg)
else
f2fs_build_free_nids(sbi, false, false);
if (!is_idle(sbi, REQ_TIME) &&
(!excess_dirty_nats(sbi) && !excess_dirty_nodes(sbi)))
if (excess_dirty_nats(sbi) || excess_dirty_nodes(sbi) ||
excess_prefree_segs(sbi))
goto do_sync;
/* there is background inflight IO or foreground operation recently */
if (is_inflight_io(sbi, REQ_TIME) ||
(!f2fs_time_over(sbi, REQ_TIME) && rwsem_is_locked(&sbi->cp_rwsem)))
return;
/* exceed periodical checkpoint timeout threshold */
if (f2fs_time_over(sbi, CP_TIME))
goto do_sync;
/* checkpoint is the only way to shrink partial cached entries */
if (!f2fs_available_free_memory(sbi, NAT_ENTRIES) ||
!f2fs_available_free_memory(sbi, INO_ENTRIES) ||
excess_prefree_segs(sbi) ||
excess_dirty_nats(sbi) ||
excess_dirty_nodes(sbi) ||
f2fs_time_over(sbi, CP_TIME)) {
if (f2fs_available_free_memory(sbi, NAT_ENTRIES) ||
f2fs_available_free_memory(sbi, INO_ENTRIES))
return;
do_sync:
if (test_opt(sbi, DATA_FLUSH) && from_bg) {
struct blk_plug plug;
@ -553,7 +561,6 @@ void f2fs_balance_fs_bg(struct f2fs_sb_info *sbi, bool from_bg)
}
f2fs_sync_fs(sbi->sb, true);
stat_inc_bg_cp_count(sbi->stat_info);
}
}
static int __submit_flush_wait(struct f2fs_sb_info *sbi,