Re: [PATCH v3] f2fs: submit cached bio to avoid endless PageWriteback

From: Chao Yu
Date: Mon Sep 17 2018 - 21:47:02 EST

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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@xxxxxxxxxx>
>>>>
>>>> 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@xxxxxxxxxx>
>>>> ---
>>>> 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);

>
>>
>> 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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