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Message-ID: <ab15ea97-0ad8-ce85-3f3c-197ecc0c4e16@kernel.org>
Date: Fri, 21 Sep 2018 21:47:30 +0800
From: Chao Yu <chao@...nel.org>
To: Chao Yu <yuchao0@...wei.com>, Jaegeuk Kim <jaegeuk@...nel.org>
Cc: 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 10:14, Chao Yu wrote:
> 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.
It may cause long latency before someone flushes the meta IO, how about flushing
IO like other flows, like writepages?
Or is there any benefit that we still cache meta IO after GC?
>
> I just guess below endless waiting for page writeback is cased by this case
Any thoughts?
>
> -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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