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    Subject[PATCH v19 02/15] splice: Make do_splice_to() generic and export it
    Date
    Rename do_splice_to() to vfs_splice_read() and export it so that it can be
    used as a helper when calling down to a lower layer filesystem as it
    performs all the necessary checks[1].

    Signed-off-by: David Howells <dhowells@redhat.com>
    Reviewed-by: Christoph Hellwig <hch@lst.de>
    cc: Miklos Szeredi <miklos@szeredi.hu>
    cc: Jens Axboe <axboe@kernel.dk>
    cc: Al Viro <viro@zeniv.linux.org.uk>
    cc: John Hubbard <jhubbard@nvidia.com>
    cc: David Hildenbrand <david@redhat.com>
    cc: Matthew Wilcox <willy@infradead.org>
    cc: linux-unionfs@vger.kernel.org
    cc: linux-block@vger.kernel.org
    cc: linux-fsdevel@vger.kernel.org
    cc: linux-mm@kvack.org
    Link: https://lore.kernel.org/r/CAJfpeguGksS3sCigmRi9hJdUec8qtM9f+_9jC1rJhsXT+dV01w@mail.gmail.com/ [1]
    ---
    fs/splice.c | 27 ++++++++++++++++++++-------
    include/linux/splice.h | 3 +++
    2 files changed, 23 insertions(+), 7 deletions(-)

    diff --git a/fs/splice.c b/fs/splice.c
    index abd21a455a2b..90ccd3666dca 100644
    --- a/fs/splice.c
    +++ b/fs/splice.c
    @@ -851,12 +851,24 @@ static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
    return out->f_op->splice_write(pipe, out, ppos, len, flags);
    }

    -/*
    - * Attempt to initiate a splice from a file to a pipe.
    +/**
    + * vfs_splice_read - Read data from a file and splice it into a pipe
    + * @in: File to splice from
    + * @ppos: Input file offset
    + * @pipe: Pipe to splice to
    + * @len: Number of bytes to splice
    + * @flags: Splice modifier flags (SPLICE_F_*)
    + *
    + * Splice the requested amount of data from the input file to the pipe. This
    + * is synchronous as the caller must hold the pipe lock across the entire
    + * operation.
    + *
    + * If successful, it returns the amount of data spliced, 0 if it hit the EOF or
    + * a hole and a negative error code otherwise.
    */
    -static long do_splice_to(struct file *in, loff_t *ppos,
    - struct pipe_inode_info *pipe, size_t len,
    - unsigned int flags)
    +long vfs_splice_read(struct file *in, loff_t *ppos,
    + struct pipe_inode_info *pipe, size_t len,
    + unsigned int flags)
    {
    unsigned int p_space;
    int ret;
    @@ -879,6 +891,7 @@ static long do_splice_to(struct file *in, loff_t *ppos,
    return warn_unsupported(in, "read");
    return in->f_op->splice_read(in, ppos, pipe, len, flags);
    }
    +EXPORT_SYMBOL_GPL(vfs_splice_read);

    /**
    * splice_direct_to_actor - splices data directly between two non-pipes
    @@ -949,7 +962,7 @@ ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
    size_t read_len;
    loff_t pos = sd->pos, prev_pos = pos;

    - ret = do_splice_to(in, &pos, pipe, len, flags);
    + ret = vfs_splice_read(in, &pos, pipe, len, flags);
    if (unlikely(ret <= 0))
    goto out_release;

    @@ -1097,7 +1110,7 @@ long splice_file_to_pipe(struct file *in,
    pipe_lock(opipe);
    ret = wait_for_space(opipe, flags);
    if (!ret)
    - ret = do_splice_to(in, offset, opipe, len, flags);
    + ret = vfs_splice_read(in, offset, opipe, len, flags);
    pipe_unlock(opipe);
    if (ret > 0)
    wakeup_pipe_readers(opipe);
    diff --git a/include/linux/splice.h b/include/linux/splice.h
    index a55179fd60fc..8f052c3dae95 100644
    --- a/include/linux/splice.h
    +++ b/include/linux/splice.h
    @@ -76,6 +76,9 @@ extern ssize_t splice_to_pipe(struct pipe_inode_info *,
    struct splice_pipe_desc *);
    extern ssize_t add_to_pipe(struct pipe_inode_info *,
    struct pipe_buffer *);
    +long vfs_splice_read(struct file *in, loff_t *ppos,
    + struct pipe_inode_info *pipe, size_t len,
    + unsigned int flags);
    extern ssize_t splice_direct_to_actor(struct file *, struct splice_desc *,
    splice_direct_actor *);
    extern long do_splice(struct file *in, loff_t *off_in,
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