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Date: Thu, 19 Apr 2018 20:27:57 -0700
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 3/5] f2fs: avoid stucking GC due to atomic write
On 04/20, Chao Yu wrote:
> On 2018/4/20 11:12, Jaegeuk Kim wrote:
> > On 04/18, 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.
> >>
> >> 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.
> >>
> >> Signed-off-by: Chao Yu <yuchao0@...wei.com>
> >> ---
> >> fs/f2fs/f2fs.h | 1 +
> >> fs/f2fs/file.c | 5 +++++
> >> fs/f2fs/gc.c | 27 +++++++++++++++++++++++----
> >> fs/f2fs/gc.h | 3 +++
> >> fs/f2fs/segment.c | 1 +
> >> fs/f2fs/segment.h | 2 ++
> >> 6 files changed, 35 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> >> index c1c3a1d11186..3453288d6a71 100644
> >> --- a/fs/f2fs/f2fs.h
> >> +++ b/fs/f2fs/f2fs.h
> >> @@ -2249,6 +2249,7 @@ 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,
> >> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> >> index 7c90ded5a431..cddd9aee1bb2 100644
> >> --- a/fs/f2fs/file.c
> >> +++ b/fs/f2fs/file.c
> >> @@ -1698,6 +1698,7 @@ 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;
> >> @@ -1746,6 +1747,10 @@ 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 bfb7a4a3a929..495876ca62b6 100644
> >> --- a/fs/f2fs/gc.c
> >> +++ b/fs/f2fs/gc.c
> >> @@ -135,6 +135,8 @@ int start_gc_thread(struct f2fs_sb_info *sbi)
> >> gc_th->gc_urgent = 0;
> >> gc_th->gc_wake= 0;
> >>
> >> + gc_th->atomic_file = 0;
> >> +
> >> sbi->gc_thread = gc_th;
> >> init_waitqueue_head(&sbi->gc_thread->gc_wait_queue_head);
> >> sbi->gc_thread->f2fs_gc_task = kthread_run(gc_thread_func, sbi,
> >> @@ -603,7 +605,7 @@ 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),
> >> @@ -630,8 +632,10 @@ 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)) {
> >> + F2FS_I_SB(inode)->gc_thread->atomic_file++;
> >> goto out;
> >> + }
> >>
> >> if (f2fs_is_pinned_file(inode)) {
> >> f2fs_pin_file_control(inode, true);
> >> @@ -737,8 +741,10 @@ 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)) {
> >> + F2FS_I_SB(inode)->gc_thread->atomic_file++;
> >> goto out;
> >> + }
> >> if (f2fs_is_pinned_file(inode)) {
> >> if (gc_type == FG_GC)
> >> f2fs_pin_file_control(inode, true);
> >> @@ -900,7 +906,8 @@ 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_encrypted_file(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);
> >> @@ -1017,6 +1024,8 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
> >> .ilist = LIST_HEAD_INIT(gc_list.ilist),
> >> .iroot = RADIX_TREE_INIT(GFP_NOFS),
> >> };
> >> + unsigned int last_atomic_file = sbi->gc_thread->atomic_file;
> >> + unsigned int skipped_round = 0, round = 0;
> >>
> >> trace_f2fs_gc_begin(sbi->sb, sync, background,
> >> get_pages(sbi, F2FS_DIRTY_NODES),
> >> @@ -1068,11 +1077,21 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
> >> sec_freed++;
> >> total_freed += seg_freed;
> >>
> >> + if (gc_type == FG_GC) {
> >> + if (sbi->gc_thread->atomic_file > last_atomic_file)
> >> + skipped_round++;
> >> + last_atomic_file = sbi->gc_thread->atomic_file;
> >
> > How about resetting ->atomic_file to zero?
>
> Since we will show this stat number through sysfs entry, it'd better to keep its
> data?
Alright, but we need to manage overflow?
>
> Thanks,
>
> >
> >> + 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 b0045d4c8d1e..bc1d21d46ae7 100644
> >> --- a/fs/f2fs/gc.h
> >> +++ b/fs/f2fs/gc.h
> >> @@ -39,6 +39,9 @@ struct f2fs_gc_kthread {
> >> unsigned int gc_idle;
> >> unsigned int gc_urgent;
> >> unsigned int gc_wake;
> >> +
> >> + /* for stuck statistic */
> >> + unsigned int atomic_file;
> >> };
> >>
> >> struct gc_inode_list {
> >> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> >> index d809f731bfd1..831cefa088bc 100644
> >> --- a/fs/f2fs/segment.c
> >> +++ b/fs/f2fs/segment.c
> >> @@ -287,6 +287,7 @@ 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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