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Message-ID: <20180926002033.GB3829@jaegeuk-macbookpro.roam.corp.google.com>
Date: Tue, 25 Sep 2018 17:20:33 -0700
From: Jaegeuk Kim <jaegeuk@...nel.org>
To: Chao Yu <chao@...nel.org>
Cc: Chao Yu <yuchao0@...wei.com>,
linux-f2fs-devel@...ts.sourceforge.net,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] f2fs: submit cached bio to avoid endless PageWriteback
On 09/21, Chao Yu wrote:
> 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?
I'm waiting for the previous reported issue. Do we have this in products?
>
> >
> > -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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