Re: [PATCH 1/3] fs: Return EAGAIN when O_NONBLOCK write should block on frozen fs

[Jan Kara <jack@suse.cz>]

On Mon 12-11-12 12:17:50, Jan Kara wrote:
> When user asks for O_NONBLOCK behavior for a file descriptor, return
> EAGAIN instead of blocking on a frozen filesystem.
  Ups, forgot to add version into the subject. This is v3 of the series.

								Honza

> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
>  fs/btrfs/file.c    |    3 ++-
>  fs/cifs/file.c     |    3 ++-
>  fs/fuse/file.c     |    3 ++-
>  fs/ntfs/file.c     |    3 ++-
>  fs/ocfs2/file.c    |    3 ++-
>  fs/splice.c        |    3 ++-
>  fs/xfs/xfs_file.c  |    3 ++-
>  include/linux/fs.h |   10 ++++++++++
>  mm/filemap.c       |    3 ++-
>  9 files changed, 26 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> index 9ab1bed..6eb2e30 100644
> --- a/fs/btrfs/file.c
> +++ b/fs/btrfs/file.c
> @@ -1411,7 +1411,8 @@ static ssize_t btrfs_file_aio_write(struct kiocb *iocb,
>  	ssize_t err = 0;
>  	size_t count, ocount;
>  
> -	sb_start_write(inode->i_sb);
> +	if (!sb_start_file_write(file))
> +		return -EAGAIN;
>  
>  	mutex_lock(&inode->i_mutex);
>  
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index edb25b4..1629e47 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -2448,7 +2448,8 @@ cifs_writev(struct kiocb *iocb, const struct iovec *iov,
>  
>  	BUG_ON(iocb->ki_pos != pos);
>  
> -	sb_start_write(inode->i_sb);
> +	if (!sb_start_file_write(file))
> +		return -EAGAIN;
>  
>  	/*
>  	 * We need to hold the sem to be sure nobody modifies lock list
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 78d2837..641df9e 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -947,7 +947,8 @@ static ssize_t fuse_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
>  		return err;
>  
>  	count = ocount;
> -	sb_start_write(inode->i_sb);
> +	if (!sb_start_file_write(file))
> +		return -EAGAIN;
>  	mutex_lock(&inode->i_mutex);
>  
>  	/* We can write back this queue in page reclaim */
> diff --git a/fs/ntfs/file.c b/fs/ntfs/file.c
> index 1ecf464..028b349 100644
> --- a/fs/ntfs/file.c
> +++ b/fs/ntfs/file.c
> @@ -2118,7 +2118,8 @@ static ssize_t ntfs_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
>  
>  	BUG_ON(iocb->ki_pos != pos);
>  
> -	sb_start_write(inode->i_sb);
> +	if (!sb_start_file_write(file))
> +		return -EAGAIN;
>  	mutex_lock(&inode->i_mutex);
>  	ret = ntfs_file_aio_write_nolock(iocb, iov, nr_segs, &iocb->ki_pos);
>  	mutex_unlock(&inode->i_mutex);
> diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
> index 5a4ee77..93ef34d 100644
> --- a/fs/ocfs2/file.c
> +++ b/fs/ocfs2/file.c
> @@ -2265,7 +2265,8 @@ static ssize_t ocfs2_file_aio_write(struct kiocb *iocb,
>  	if (iocb->ki_left == 0)
>  		return 0;
>  
> -	sb_start_write(inode->i_sb);
> +	if (!sb_start_file_write(file))
> +		return -EAGAIN;
>  
>  	appending = file->f_flags & O_APPEND ? 1 : 0;
>  	direct_io = file->f_flags & O_DIRECT ? 1 : 0;
> diff --git a/fs/splice.c b/fs/splice.c
> index 13e5b47..a5ae831 100644
> --- a/fs/splice.c
> +++ b/fs/splice.c
> @@ -996,7 +996,8 @@ generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
>  	};
>  	ssize_t ret;
>  
> -	sb_start_write(inode->i_sb);
> +	if (!sb_start_file_write(out))
> +		return -EAGAIN;
>  
>  	pipe_lock(pipe);
>  
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index aa473fa..7d8af61 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -771,7 +771,8 @@ xfs_file_aio_write(
>  	if (ocount == 0)
>  		return 0;
>  
> -	sb_start_write(inode->i_sb);
> +	if (!sb_start_file_write(file))
> +		return -EAGAIN;
>  
>  	if (XFS_FORCED_SHUTDOWN(ip->i_mount)) {
>  		ret = -EIO;
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index b33cfc9..2325e95 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1401,6 +1401,16 @@ static inline int sb_start_write_trylock(struct super_block *sb)
>  	return __sb_start_write(sb, SB_FREEZE_WRITE, false);
>  }
>  
> +/*
> + * sb_start_write() for writing into a file. When file has O_NONBLOCK set,
> + * we use trylock semantics, otherwise we block on frozen filesystem.
> + */
> +static inline int sb_start_file_write(struct file *file)
> +{
> +	return __sb_start_write(file->f_mapping->host->i_sb, SB_FREEZE_WRITE,
> +				!(file->f_flags & O_NONBLOCK));
> +}
> +
>  /**
>   * sb_start_pagefault - get write access to a superblock from a page fault
>   * @sb: the super we write to
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 83efee7..3b2812b 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -2527,7 +2527,8 @@ ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
>  
>  	BUG_ON(iocb->ki_pos != pos);
>  
> -	sb_start_write(inode->i_sb);
> +	if (!sb_start_file_write(file))
> +		return -EAGAIN;
>  	mutex_lock(&inode->i_mutex);
>  	ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
>  	mutex_unlock(&inode->i_mutex);
> -- 
> 1.7.1
> 
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-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR