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Date: Tue, 18 Sep 2018 10:14:21 +0800
From: Chao Yu <yuchao0@...wei.com>
To: Jaegeuk Kim <jaegeuk@...nel.org>
CC: Chao Yu <chao@...nel.org>,
<linux-f2fs-devel@...ts.sourceforge.net>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] f2fs: submit cached bio to avoid endless PageWriteback
On 2018/9/18 10:02, Jaegeuk Kim wrote:
> On 09/18, Chao Yu wrote:
>> On 2018/9/18 9:37, Jaegeuk Kim wrote:
>>> On 09/18, Chao Yu wrote:
>>>> On 2018/9/18 9:04, Jaegeuk Kim wrote:
>>>>> On 09/13, Chao Yu wrote:
>>>>>> From: Chao Yu <yuchao0@...wei.com>
>>>>>>
>>>>>> When migrating encrypted block from background GC thread, we only add
>>>>>> them into f2fs inner bio cache, but forget to submit the cached bio, it
>>>>>> may cause potential deadlock when we are waiting page writebacked, fix
>>>>>> it.
>>>>>>
>>>>>> Signed-off-by: Chao Yu <yuchao0@...wei.com>
>>>>>> ---
>>>>>> v3:
>>>>>> clean up codes suggested by Jaegeuk.
>>>>>> fs/f2fs/f2fs.h | 2 +-
>>>>>> fs/f2fs/gc.c | 71 +++++++++++++++++++++++++++++++++++---------------
>>>>>> fs/f2fs/node.c | 13 ++++++---
>>>>>> 3 files changed, 61 insertions(+), 25 deletions(-)
>>>>>>
>>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>>> index b676b82312e0..917b2ca76aac 100644
>>>>>> --- a/fs/f2fs/f2fs.h
>>>>>> +++ b/fs/f2fs/f2fs.h
>>>>>> @@ -2869,7 +2869,7 @@ struct page *f2fs_new_node_page(struct dnode_of_data *dn, unsigned int ofs);
>>>>>> void f2fs_ra_node_page(struct f2fs_sb_info *sbi, nid_t nid);
>>>>>> struct page *f2fs_get_node_page(struct f2fs_sb_info *sbi, pgoff_t nid);
>>>>>> struct page *f2fs_get_node_page_ra(struct page *parent, int start);
>>>>>> -void f2fs_move_node_page(struct page *node_page, int gc_type);
>>>>>> +int f2fs_move_node_page(struct page *node_page, int gc_type);
>>>>>> int f2fs_fsync_node_pages(struct f2fs_sb_info *sbi, struct inode *inode,
>>>>>> struct writeback_control *wbc, bool atomic,
>>>>>> unsigned int *seq_id);
>>>>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>>>>>> index a4c1a419611d..f57622cfe058 100644
>>>>>> --- a/fs/f2fs/gc.c
>>>>>> +++ b/fs/f2fs/gc.c
>>>>>> @@ -461,7 +461,7 @@ static int check_valid_map(struct f2fs_sb_info *sbi,
>>>>>> * On validity, copy that node with cold status, otherwise (invalid node)
>>>>>> * ignore that.
>>>>>> */
>>>>>> -static void gc_node_segment(struct f2fs_sb_info *sbi,
>>>>>> +static int gc_node_segment(struct f2fs_sb_info *sbi,
>>>>>> struct f2fs_summary *sum, unsigned int segno, int gc_type)
>>>>>> {
>>>>>> struct f2fs_summary *entry;
>>>>>> @@ -469,6 +469,7 @@ static void gc_node_segment(struct f2fs_sb_info *sbi,
>>>>>> int off;
>>>>>> int phase = 0;
>>>>>> bool fggc = (gc_type == FG_GC);
>>>>>> + int submitted = 0;
>>>>>>
>>>>>> start_addr = START_BLOCK(sbi, segno);
>>>>>>
>>>>>> @@ -482,10 +483,11 @@ static void gc_node_segment(struct f2fs_sb_info *sbi,
>>>>>> nid_t nid = le32_to_cpu(entry->nid);
>>>>>> struct page *node_page;
>>>>>> struct node_info ni;
>>>>>> + int err;
>>>>>>
>>>>>> /* stop BG_GC if there is not enough free sections. */
>>>>>> if (gc_type == BG_GC && has_not_enough_free_secs(sbi, 0, 0))
>>>>>> - return;
>>>>>> + return submitted;
>>>>>>
>>>>>> if (check_valid_map(sbi, segno, off) == 0)
>>>>>> continue;
>>>>>> @@ -522,7 +524,9 @@ static void gc_node_segment(struct f2fs_sb_info *sbi,
>>>>>> continue;
>>>>>> }
>>>>>>
>>>>>> - f2fs_move_node_page(node_page, gc_type);
>>>>>> + err = f2fs_move_node_page(node_page, gc_type);
>>>>>> + if (!err && gc_type == FG_GC)
>>>>>> + submitted++;
>>>>>> stat_inc_node_blk_count(sbi, 1, gc_type);
>>>>>> }
>>>>>>
>>>>>> @@ -531,6 +535,7 @@ static void gc_node_segment(struct f2fs_sb_info *sbi,
>>>>>>
>>>>>> if (fggc)
>>>>>> atomic_dec(&sbi->wb_sync_req[NODE]);
>>>>>> + return submitted;
>>>>>> }
>>>>>>
>>>>>> /*
>>>>>> @@ -666,7 +671,7 @@ static int ra_data_block(struct inode *inode, pgoff_t index)
>>>>>> * Move data block via META_MAPPING while keeping locked data page.
>>>>>> * This can be used to move blocks, aka LBAs, directly on disk.
>>>>>> */
>>>>>> -static void move_data_block(struct inode *inode, block_t bidx,
>>>>>> +static int move_data_block(struct inode *inode, block_t bidx,
>>>>>> int gc_type, unsigned int segno, int off)
>>>>>
>>>>> We don't need to submit IOs in this case.
>>>>
>>>> Actually, previously, we missed to submit IOs for encrypted block only in
>>>> BGGC, so we fix to submit for this case, all other codes are cleanups. Right?
>>>
>>> The move_data_block migrates encrypted blocks all the time with meta page IOs.
>>> I don't know what you're saying about BGGC.
>>
>> In move_data_block(), we use f2fs_submit_page_write() to add encrypted page
>> in to sbi->write_io[META].bio cache, so before exit GC, we need to submit
>> this cache by f2fs_submit_merged_write(), otherwise bio with encrypted page
>> will be cached in sbi->write_io[META].bio for long time, since we only
>> submmit this bio cache in foreground GC.
>>
>> if (gc_type == FG_GC)
>> f2fs_submit_merged_write(sbi,
>> (type == SUM_TYPE_NODE) ? NODE : DATA);
>
> Does this issue pending META IOs? I think META won't block any NODE/DATA
> pages. Moreover checkpoint or reading the moved block make the IOs be flushed,
> so it doesn't hurt the consistency.
I just guess below endless waiting for page writeback is cased by this case
-000|__switch_to()
-001|__schedule()
-002|need_resched(inline)
-002|schedule()
-003|schedule_timeout()
-004|get_current(inline)
-004|io_schedule_timeout()
-005|bit_wait_io()
-006|__wait_on_bit()
-007|wait_on_page_bit()
-008|PageWriteback(inline)
-008|wait_on_page_writeback(inline)
-008|__filemap_fdatawait_range()
-009|filemap_fdatawait_keep_errors()
-010|sync_inodes_sb()
-011|__sync_filesystem(inline)
-011|sync_filesystem()
-012|generic_shutdown_super()
-013|kill_block_super()
-014|kill_f2fs_super()
-015|deactivate_locked_super()
-016|deactivate_super()
-017|mnt_free_id(inline)
-017|cleanup_mnt()
-018|__cleanup_mnt()
-019|task_work_run()
-020|do_notify_resume()
-021|work_pending(asm)
-->|exception
-022|NUX:0x539E58(asm)
---|end of frame
>
>>
>>>
>>>>
>>>> Thanks,
>>>>
>>>>>
>>>>>> {
>>>>>> struct f2fs_io_info fio = {
>>>>>> @@ -685,25 +690,29 @@ static void move_data_block(struct inode *inode, block_t bidx,
>>>>>> struct node_info ni;
>>>>>> struct page *page, *mpage;
>>>>>> block_t newaddr;
>>>>>> - int err;
>>>>>> + int err = 0;
>>>>>> bool lfs_mode = test_opt(fio.sbi, LFS);
>>>>>>
>>>>>> /* do not read out */
>>>>>> page = f2fs_grab_cache_page(inode->i_mapping, bidx, false);
>>>>>> if (!page)
>>>>>> - return;
>>>>>> + return -ENOMEM;
>>>>>>
>>>>>> - if (!check_valid_map(F2FS_I_SB(inode), segno, off))
>>>>>> + if (!check_valid_map(F2FS_I_SB(inode), segno, off)) {
>>>>>> + err = -ENOENT;
>>>>>> goto out;
>>>>>> + }
>>>>>>
>>>>>> if (f2fs_is_atomic_file(inode)) {
>>>>>> F2FS_I(inode)->i_gc_failures[GC_FAILURE_ATOMIC]++;
>>>>>> F2FS_I_SB(inode)->skipped_atomic_files[gc_type]++;
>>>>>> + err = -EAGAIN;
>>>>>> goto out;
>>>>>> }
>>>>>>
>>>>>> if (f2fs_is_pinned_file(inode)) {
>>>>>> f2fs_pin_file_control(inode, true);
>>>>>> + err = -EAGAIN;
>>>>>> goto out;
>>>>>> }
>>>>>>
>>>>>> @@ -714,6 +723,7 @@ static void move_data_block(struct inode *inode, block_t bidx,
>>>>>>
>>>>>> if (unlikely(dn.data_blkaddr == NULL_ADDR)) {
>>>>>> ClearPageUptodate(page);
>>>>>> + err = -ENOENT;
>>>>>> goto put_out;
>>>>>> }
>>>>>>
>>>>>> @@ -796,6 +806,7 @@ static void move_data_block(struct inode *inode, block_t bidx,
>>>>>> fio.new_blkaddr = newaddr;
>>>>>> f2fs_submit_page_write(&fio);
>>>>>> if (fio.retry) {
>>>>>> + err = -EAGAIN;
>>>>>> if (PageWriteback(fio.encrypted_page))
>>>>>> end_page_writeback(fio.encrypted_page);
>>>>>> goto put_page_out;
>>>>>> @@ -819,34 +830,42 @@ static void move_data_block(struct inode *inode, block_t bidx,
>>>>>> f2fs_put_dnode(&dn);
>>>>>> out:
>>>>>> f2fs_put_page(page, 1);
>>>>>> + return err;
>>>>>> }
>>>>>>
>>>>>> -static void move_data_page(struct inode *inode, block_t bidx, int gc_type,
>>>>>> +static int move_data_page(struct inode *inode, block_t bidx, int gc_type,
>>>>>> unsigned int segno, int off)
>>>>>> {
>>>>>> struct page *page;
>>>>>> + int err = 0;
>>>>>>
>>>>>> page = f2fs_get_lock_data_page(inode, bidx, true);
>>>>>> if (IS_ERR(page))
>>>>>> - return;
>>>>>> + return PTR_ERR(page);
>>>>>>
>>>>>> - if (!check_valid_map(F2FS_I_SB(inode), segno, off))
>>>>>> + if (!check_valid_map(F2FS_I_SB(inode), segno, off)) {
>>>>>> + err = -ENOENT;
>>>>>> goto out;
>>>>>> + }
>>>>>>
>>>>>> if (f2fs_is_atomic_file(inode)) {
>>>>>> F2FS_I(inode)->i_gc_failures[GC_FAILURE_ATOMIC]++;
>>>>>> F2FS_I_SB(inode)->skipped_atomic_files[gc_type]++;
>>>>>> + err = -EAGAIN;
>>>>>> goto out;
>>>>>> }
>>>>>> if (f2fs_is_pinned_file(inode)) {
>>>>>> if (gc_type == FG_GC)
>>>>>> f2fs_pin_file_control(inode, true);
>>>>>> + err = -EAGAIN;
>>>>>> goto out;
>>>>>> }
>>>>>>
>>>>>> if (gc_type == BG_GC) {
>>>>>> - if (PageWriteback(page))
>>>>>> + if (PageWriteback(page)) {
>>>>>> + err = -EAGAIN;
>>>>>> goto out;
>>>>>> + }
>>>>>> set_page_dirty(page);
>>>>>> set_cold_data(page);
>>>>>> } else {
>>>>>> @@ -864,7 +883,6 @@ static void move_data_page(struct inode *inode, block_t bidx, int gc_type,
>>>>>> .io_type = FS_GC_DATA_IO,
>>>>>> };
>>>>>> bool is_dirty = PageDirty(page);
>>>>>> - int err;
>>>>>>
>>>>>> retry:
>>>>>> set_page_dirty(page);
>>>>>> @@ -889,6 +907,7 @@ static void move_data_page(struct inode *inode, block_t bidx, int gc_type,
>>>>>> }
>>>>>> out:
>>>>>> f2fs_put_page(page, 1);
>>>>>> + return err;
>>>>>> }
>>>>>>
>>>>>> /*
>>>>>> @@ -898,7 +917,7 @@ static void move_data_page(struct inode *inode, block_t bidx, int gc_type,
>>>>>> * If the parent node is not valid or the data block address is different,
>>>>>> * the victim data block is ignored.
>>>>>> */
>>>>>> -static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>>>>> +static int gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>>>>> struct gc_inode_list *gc_list, unsigned int segno, int gc_type)
>>>>>> {
>>>>>> struct super_block *sb = sbi->sb;
>>>>>> @@ -906,6 +925,7 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>>>>> block_t start_addr;
>>>>>> int off;
>>>>>> int phase = 0;
>>>>>> + int submitted = 0;
>>>>>>
>>>>>> start_addr = START_BLOCK(sbi, segno);
>>>>>>
>>>>>> @@ -922,7 +942,7 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>>>>>
>>>>>> /* stop BG_GC if there is not enough free sections. */
>>>>>> if (gc_type == BG_GC && has_not_enough_free_secs(sbi, 0, 0))
>>>>>> - return;
>>>>>> + return submitted;
>>>>>>
>>>>>> if (check_valid_map(sbi, segno, off) == 0)
>>>>>> continue;
>>>>>> @@ -994,6 +1014,7 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>>>>> if (inode) {
>>>>>> struct f2fs_inode_info *fi = F2FS_I(inode);
>>>>>> bool locked = false;
>>>>>> + int err;
>>>>>>
>>>>>> if (S_ISREG(inode->i_mode)) {
>>>>>> if (!down_write_trylock(&fi->i_gc_rwsem[READ]))
>>>>>> @@ -1013,12 +1034,16 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>>>>> start_bidx = f2fs_start_bidx_of_node(nofs, inode)
>>>>>> + ofs_in_node;
>>>>>> if (f2fs_post_read_required(inode))
>>>>>> - move_data_block(inode, start_bidx, gc_type,
>>>>>> - segno, off);
>>>>>> + err = move_data_block(inode, start_bidx,
>>>>>> + gc_type, segno, off);
>>>>>> else
>>>>>> - move_data_page(inode, start_bidx, gc_type,
>>>>>> + err = move_data_page(inode, start_bidx, gc_type,
>>>>>> segno, off);
>>>>>>
>>>>>> + if (!err && (gc_type == FG_GC ||
>>>>>> + f2fs_post_read_required(inode)))
>>>>>> + submitted++;
>>>>>> +
>>>>>> if (locked) {
>>>>>> up_write(&fi->i_gc_rwsem[WRITE]);
>>>>>> up_write(&fi->i_gc_rwsem[READ]);
>>>>>> @@ -1030,6 +1055,8 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>>>>>
>>>>>> if (++phase < 5)
>>>>>> goto next_step;
>>>>>> +
>>>>>> + return submitted;
>>>>>> }
>>>>>>
>>>>>> static int __get_victim(struct f2fs_sb_info *sbi, unsigned int *victim,
>>>>>> @@ -1057,6 +1084,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>>>>>> int seg_freed = 0;
>>>>>> unsigned char type = IS_DATASEG(get_seg_entry(sbi, segno)->type) ?
>>>>>> SUM_TYPE_DATA : SUM_TYPE_NODE;
>>>>>> + int submitted = 0;
>>>>>>
>>>>>> /* readahead multi ssa blocks those have contiguous address */
>>>>>> if (sbi->segs_per_sec > 1)
>>>>>> @@ -1100,10 +1128,11 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>>>>>> * - lock_page(sum_page)
>>>>>> */
>>>>>> if (type == SUM_TYPE_NODE)
>>>>>> - gc_node_segment(sbi, sum->entries, segno, gc_type);
>>>>>> - else
>>>>>> - gc_data_segment(sbi, sum->entries, gc_list, segno,
>>>>>> + submitted += gc_node_segment(sbi, sum->entries, segno,
>>>>>> gc_type);
>>>>>> + else
>>>>>> + submitted += gc_data_segment(sbi, sum->entries, gc_list,
>>>>>> + segno, gc_type);
>>>>>>
>>>>>> stat_inc_seg_count(sbi, type, gc_type);
>>>>>>
>>>>>> @@ -1114,7 +1143,7 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
>>>>>> f2fs_put_page(sum_page, 0);
>>>>>> }
>>>>>>
>>>>>> - if (gc_type == FG_GC)
>>>>>> + if (submitted)
>>>>>> f2fs_submit_merged_write(sbi,
>>>>>> (type == SUM_TYPE_NODE) ? NODE : DATA);
>>>>>>
>>>>>> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
>>>>>> index fa2381c0bc47..214dd6326b4b 100644
>>>>>> --- a/fs/f2fs/node.c
>>>>>> +++ b/fs/f2fs/node.c
>>>>>> @@ -1584,8 +1584,10 @@ static int __write_node_page(struct page *page, bool atomic, bool *submitted,
>>>>>> return AOP_WRITEPAGE_ACTIVATE;
>>>>>> }
>>>>>>
>>>>>> -void f2fs_move_node_page(struct page *node_page, int gc_type)
>>>>>> +int f2fs_move_node_page(struct page *node_page, int gc_type)
>>>>>> {
>>>>>> + int err = 0;
>>>>>> +
>>>>>> if (gc_type == FG_GC) {
>>>>>> struct writeback_control wbc = {
>>>>>> .sync_mode = WB_SYNC_ALL,
>>>>>> @@ -1597,12 +1599,16 @@ void f2fs_move_node_page(struct page *node_page, int gc_type)
>>>>>> f2fs_wait_on_page_writeback(node_page, NODE, true);
>>>>>>
>>>>>> f2fs_bug_on(F2FS_P_SB(node_page), PageWriteback(node_page));
>>>>>> - if (!clear_page_dirty_for_io(node_page))
>>>>>> + if (!clear_page_dirty_for_io(node_page)) {
>>>>>> + err = -EAGAIN;
>>>>>> goto out_page;
>>>>>> + }
>>>>>>
>>>>>> if (__write_node_page(node_page, false, NULL,
>>>>>> - &wbc, false, FS_GC_NODE_IO, NULL))
>>>>>> + &wbc, false, FS_GC_NODE_IO, NULL)) {
>>>>>> + err = -EAGAIN;
>>>>>> unlock_page(node_page);
>>>>>> + }
>>>>>> goto release_page;
>>>>>> } else {
>>>>>> /* set page dirty and write it */
>>>>>> @@ -1613,6 +1619,7 @@ void f2fs_move_node_page(struct page *node_page, int gc_type)
>>>>>> unlock_page(node_page);
>>>>>> release_page:
>>>>>> f2fs_put_page(node_page, 0);
>>>>>> + return err;
>>>>>> }
>>>>>>
>>>>>> static int f2fs_write_node_page(struct page *page,
>>>>>> --
>>>>>> 2.18.0
>>>>>
>>>>> .
>>>>>
>>>
>>> .
>>>
>
> .
>
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