Re: [f2fs-dev] [PATCH] f2fs: remove race condition in releasing cblocks

[Jaegeuk Kim <jaegeuk@kernel.org>]

Hi Daeho,

Please let me integrate this patch into the original patch since it is still in
the dev branch.

Thanks,

On 05/08, Daeho Jeong wrote:
> From: Daeho Jeong <daehojeong@google.com>
> 
> Now, if writing pages and releasing compress blocks occur
> simultaneously, and releasing cblocks is executed more than one time
> to a file, then total block count of filesystem and block count of the
> file could be incorrect and damaged.
> 
> We have to execute releasing compress blocks only one time for a file
> without being interfered by writepages path.
> 
> Signed-off-by: Daeho Jeong <daehojeong@google.com>
> ---
>  fs/f2fs/file.c | 34 ++++++++++++++++++++++++----------
>  1 file changed, 24 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 4aab4b42d8ba..f7de2a1da528 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -3488,6 +3488,7 @@ static int f2fs_release_compress_blocks(struct file *filp, unsigned long arg)
>  	pgoff_t page_idx = 0, last_idx;
>  	unsigned int released_blocks = 0;
>  	int ret;
> +	int writecount;
>  
>  	if (!f2fs_sb_has_compression(F2FS_I_SB(inode)))
>  		return -EOPNOTSUPP;
> @@ -3502,20 +3503,33 @@ static int f2fs_release_compress_blocks(struct file *filp, unsigned long arg)
>  	if (ret)
>  		return ret;
>  
> -	if (!F2FS_I(inode)->i_compr_blocks)
> -		goto out;
> -
>  	f2fs_balance_fs(F2FS_I_SB(inode), true);
>  
>  	inode_lock(inode);
>  
> -	if (!IS_IMMUTABLE(inode)) {
> -		F2FS_I(inode)->i_flags |= F2FS_IMMUTABLE_FL;
> -		f2fs_set_inode_flags(inode);
> -		inode->i_ctime = current_time(inode);
> -		f2fs_mark_inode_dirty_sync(inode, true);
> +	writecount = atomic_read(&inode->i_writecount);
> +	if ((filp->f_mode & FMODE_WRITE && writecount != 1) || writecount) {
> +		ret = -EBUSY;
> +		goto out;
>  	}
>  
> +	if (IS_IMMUTABLE(inode)) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	ret = filemap_write_and_wait_range(inode->i_mapping, 0, LLONG_MAX);
> +	if (ret)
> +		goto out;
> +
> +	if (!F2FS_I(inode)->i_compr_blocks)
> +		goto out;
> +
> +	F2FS_I(inode)->i_flags |= F2FS_IMMUTABLE_FL;
> +	f2fs_set_inode_flags(inode);
> +	inode->i_ctime = current_time(inode);
> +	f2fs_mark_inode_dirty_sync(inode, true);
> +
>  	down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
>  	down_write(&F2FS_I(inode)->i_mmap_sem);
>  
> @@ -3554,9 +3568,9 @@ static int f2fs_release_compress_blocks(struct file *filp, unsigned long arg)
>  
>  	up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
>  	up_write(&F2FS_I(inode)->i_mmap_sem);
> -
> -	inode_unlock(inode);
>  out:
> +	inode_unlock(inode);
> +
>  	mnt_drop_write_file(filp);
>  
>  	if (ret >= 0) {
> -- 
> 2.26.2.645.ge9eca65c58-goog


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