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SubjectRe: [PATCH] f2fs: fix to relocate f2fs_balance_fs() in mkwrite()
Hi Chao,

I was testing this.

https://github.com/jaegeuk/f2fs/commit/76be33b9f1fce70dd2d3f04f66d0f78b418fe3f5

On 12/06, Chao Yu wrote:
> As Dinosaur Huang reported, there is a potential deadlock in between
> GC and mkwrite():
>
> Thread A Thread B
> - do_page_mkwrite
> - f2fs_vm_page_mkwrite
> - lock_page
> - f2fs_balance_fs
> - mutex_lock(gc_mutex)
> - f2fs_gc
> - do_garbage_collect
> - ra_data_block
> - grab_cache_page
> - f2fs_balance_fs
> - mutex_lock(gc_mutex)
>
> In order to fix this, we just move f2fs_balance_fs() out of page lock's
> coverage in f2fs_vm_page_mkwrite().
>
> Reported-by: Dinosaur Huang <dinosaur.huang@unisoc.com>
> Signed-off-by: Chao Yu <yuchao0@huawei.com>
> ---
> fs/f2fs/file.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index c0560d62dbee..ed3290225506 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -67,6 +67,8 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
>
> f2fs_bug_on(sbi, f2fs_has_inline_data(inode));
>
> + f2fs_balance_fs(sbi, true);
> +
> file_update_time(vmf->vma->vm_file);
> down_read(&F2FS_I(inode)->i_mmap_sem);
> lock_page(page);
> @@ -120,8 +122,6 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
> out_sem:
> up_read(&F2FS_I(inode)->i_mmap_sem);
>
> - f2fs_balance_fs(sbi, dn.node_changed);
> -
> sb_end_pagefault(inode->i_sb);
> err:
> return block_page_mkwrite_return(err);
> --
> 2.18.0.rc1

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