On 11/06, Yunlong Song wrote:
> f2fs_balance_fs only actives once in the commit_inmem_pages, but there
> are more than one page to commit, so all the other pages will miss the
> check. This will lead to out-of-free problem when commit a very large
> file. However, we cannot do f2fs_balance_fs for each inmem page, since
> this will break atomicity. As a result, we should collect prefree
> segments if needed.
> 
> Signed-off-by: Yunlong Song <yunlong.s...@huawei.com>
> ---
>  fs/f2fs/f2fs.h    |  1 +
>  fs/f2fs/segment.c | 24 +++++++++++++++++++++++-
>  2 files changed, 24 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 13a96b8..04ce48f 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -610,6 +610,7 @@ struct f2fs_inode_info {
>       struct list_head inmem_pages;   /* inmemory pages managed by f2fs */
>       struct task_struct *inmem_task; /* store inmemory task */
>       struct mutex inmem_lock;        /* lock for inmemory pages */
> +     unsigned long inmem_blocks;     /* inmemory blocks */
>       struct extent_tree *extent_tree;        /* cached extent_tree entry */
>       struct rw_semaphore dio_rwsem[2];/* avoid racing between dio and gc */
>       struct rw_semaphore i_mmap_sem;
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 46dfbca..b87ede4 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -210,6 +210,7 @@ void register_inmem_page(struct inode *inode, struct page 
> *page)
>               list_add_tail(&fi->inmem_ilist, &sbi->inode_list[ATOMIC_FILE]);
>       spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
>       inc_page_count(F2FS_I_SB(inode), F2FS_INMEM_PAGES);
> +     fi->inmem_blocks++;
>       mutex_unlock(&fi->inmem_lock);
>  
>       trace_f2fs_register_inmem_page(page, INMEM);
> @@ -221,6 +222,7 @@ static int __revoke_inmem_pages(struct inode *inode,
>       struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>       struct inmem_pages *cur, *tmp;
>       int err = 0;
> +     struct f2fs_inode_info *fi = F2FS_I(inode);
>  
>       list_for_each_entry_safe(cur, tmp, head, list) {
>               struct page *page = cur->page;
> @@ -263,6 +265,7 @@ static int __revoke_inmem_pages(struct inode *inode,
>               list_del(&cur->list);
>               kmem_cache_free(inmem_entry_slab, cur);
>               dec_page_count(F2FS_I_SB(inode), F2FS_INMEM_PAGES);
> +             fi->inmem_blocks--;
>       }
>       return err;
>  }
> @@ -302,6 +305,10 @@ void drop_inmem_pages(struct inode *inode)
>       if (!list_empty(&fi->inmem_ilist))
>               list_del_init(&fi->inmem_ilist);
>       spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
> +     if (fi->inmem_blocks) {
> +             f2fs_bug_on(sbi, 1);
> +             fi->inmem_blocks = 0;
> +     }
>       mutex_unlock(&fi->inmem_lock);
>  
>       clear_inode_flag(inode, FI_ATOMIC_FILE);
> @@ -326,6 +333,7 @@ void drop_inmem_page(struct inode *inode, struct page 
> *page)
>  
>       f2fs_bug_on(sbi, !cur || cur->page != page);
>       list_del(&cur->list);
> +     fi->inmem_blocks--;
>       mutex_unlock(&fi->inmem_lock);
>  
>       dec_page_count(sbi, F2FS_INMEM_PAGES);
> @@ -410,6 +418,16 @@ int commit_inmem_pages(struct inode *inode)
>  
>       INIT_LIST_HEAD(&revoke_list);
>       f2fs_balance_fs(sbi, true);
> +     if (prefree_segments(sbi)
> +             && has_not_enough_free_secs(sbi, 0,
> +             fi->inmem_blocks / BLKS_PER_SEC(sbi))) {
> +             struct cp_control cpc;
> +
> +             cpc.reason = __get_cp_reason(sbi);
> +             err = write_checkpoint(sbi, &cpc);
> +             if (err)
> +                     goto drop;

What do you want to guarantee with this? How about passing target # of segments
into f2fs_balance_fs() so that f2fs_gc() could secure wanted free space in a
loop?

Thanks,

> +     }
>       f2fs_lock_op(sbi);
>  
>       set_inode_flag(inode, FI_ATOMIC_COMMIT);
> @@ -429,7 +447,7 @@ int commit_inmem_pages(struct inode *inode)
>               ret = __revoke_inmem_pages(inode, &revoke_list, false, true);
>               if (ret)
>                       err = ret;
> -
> +drop:
>               /* drop all uncommitted pages */
>               __revoke_inmem_pages(inode, &fi->inmem_pages, true, false);
>       }
> @@ -437,6 +455,10 @@ int commit_inmem_pages(struct inode *inode)
>       if (!list_empty(&fi->inmem_ilist))
>               list_del_init(&fi->inmem_ilist);
>       spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
> +     if (fi->inmem_blocks) {
> +             f2fs_bug_on(sbi, 1);
> +             fi->inmem_blocks = 0;
> +     }
>       mutex_unlock(&fi->inmem_lock);
>  
>       clear_inode_flag(inode, FI_ATOMIC_COMMIT);
> -- 
> 1.8.5.2

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