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.
Al, what do you think about these patches? They fix deadlock with BSD
process accounting and fs freezing...
Honza
> Signed-off-by: Jan Kara <jack@xxxxxxx>
> ---
> 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
>
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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