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

From: Jaegeuk Kim
Date: Mon Sep 17 2018 - 21:04:49 EST

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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.

> {
> 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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