Re: [PATCH] fat: hold truncate_lock in fat_write_failed()

[OGAWA Hirofumi]

Matheus Alves de Almeida <matheus.aalmeida@xxxxxxxxxxxx> writes:

> The current fat_write_failed() implementation calls into
> fat_truncate_blocks() without holding truncate_lock. Make it so it is
> held exclusive while truncating.
>
> Fixes: 459f6ed3b8c7 ("fat: convert to use the new truncate convention.")
> Signed-off-by: Matheus Alves de Almeida <matheus.aalmeida@xxxxxxxxxxxx>
> ---
>  fs/fat/inode.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/fs/fat/inode.c b/fs/fat/inode.c
> index 141276fcf8db..2a16ed415631 100644
> --- a/fs/fat/inode.c
> +++ b/fs/fat/inode.c
> @@ -216,7 +216,9 @@ static void fat_write_failed(struct address_space *mapping, loff_t to)
>  
>  	if (to > inode->i_size) {
>  		truncate_pagecache(inode, inode->i_size);
> +		down_write(&MSDOS_I(inode)->truncate_lock);
>  		fat_truncate_blocks(inode, inode->i_size);
> +		up_write(&MSDOS_I(inode)->truncate_lock);

Which race this prevent?

Thanks.

>  	}
>  }

-- 
OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>