diff options
| -rw-r--r-- | Documentation/DocBook/kernel-api.tmpl | 11 | ||||
| -rw-r--r-- | fs/splice.c | 109 |
2 files changed, 96 insertions, 24 deletions
diff --git a/Documentation/DocBook/kernel-api.tmpl b/Documentation/DocBook/kernel-api.tmpl index 38f88b6ae40..8c5698a8c2e 100644 --- a/Documentation/DocBook/kernel-api.tmpl +++ b/Documentation/DocBook/kernel-api.tmpl @@ -643,4 +643,15 @@ X!Idrivers/video/console/fonts.c !Edrivers/spi/spi.c </chapter> + <chapter id="splice"> + <title>splice API</title> + <para>) + splice is a method for moving blocks of data around inside the + kernel, without continually transferring it between the kernel + and user space. + </para> +!Iinclude/linux/splice.h +!Ffs/splice.c + </chapter> + </book> diff --git a/fs/splice.c b/fs/splice.c index 00850e56280..d257d666358 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -153,9 +153,16 @@ static const struct pipe_buf_operations user_page_pipe_buf_ops = { .get = generic_pipe_buf_get, }; -/* - * Pipe output worker. This fills a pipe with the information contained - * from splice_pipe_desc(). +/** + * splice_to_pipe - fill passed data into a pipe + * @pipe: pipe to fill + * @spd: data to fill + * + * Description: + * @spd contains a map of pages and len/offset tupples, a long with + * the struct pipe_buf_operations associated with these pages. This + * function will link that data to the pipe. + * */ ssize_t splice_to_pipe(struct pipe_inode_info *pipe, struct splice_pipe_desc *spd) @@ -281,19 +288,15 @@ __generic_file_splice_read(struct file *in, loff_t *ppos, page_cache_readahead(mapping, &in->f_ra, in, index, nr_pages); /* - * Now fill in the holes: - */ - error = 0; - - /* * Lookup the (hopefully) full range of pages we need. */ spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages); /* * If find_get_pages_contig() returned fewer pages than we needed, - * allocate the rest. + * allocate the rest and fill in the holes. */ + error = 0; index += spd.nr_pages; while (spd.nr_pages < nr_pages) { /* @@ -455,11 +458,16 @@ fill_it: /** * generic_file_splice_read - splice data from file to a pipe * @in: file to splice from + * @ppos: position in @in * @pipe: pipe to splice to * @len: number of bytes to splice * @flags: splice modifier flags * - * Will read pages from given file and fill them into a pipe. + * Description: + * Will read pages from given file and fill them into a pipe. Can be + * used as long as the address_space operations for the source implements + * a readpage() hook. + * */ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos, struct pipe_inode_info *pipe, size_t len, @@ -648,10 +656,18 @@ out_ret: return ret; } -/* - * Pipe input worker. Most of this logic works like a regular pipe, the - * key here is the 'actor' worker passed in that actually moves the data - * to the wanted destination. See pipe_to_file/pipe_to_sendpage above. +/** + * __splice_from_pipe - splice data from a pipe to given actor + * @pipe: pipe to splice from + * @sd: information to @actor + * @actor: handler that splices the data + * + * Description: + * This function does little more than loop over the pipe and call + * @actor to do the actual moving of a single struct pipe_buffer to + * the desired destination. See pipe_to_file, pipe_to_sendpage, or + * pipe_to_user. + * */ ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd, splice_actor *actor) @@ -744,6 +760,20 @@ ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd, } EXPORT_SYMBOL(__splice_from_pipe); +/** + * splice_from_pipe - splice data from a pipe to a file + * @pipe: pipe to splice from + * @out: file to splice to + * @ppos: position in @out + * @len: how many bytes to splice + * @flags: splice modifier flags + * @actor: handler that splices the data + * + * Description: + * See __splice_from_pipe. This function locks the input and output inodes, + * otherwise it's identical to __splice_from_pipe(). + * + */ ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out, loff_t *ppos, size_t len, unsigned int flags, splice_actor *actor) @@ -774,12 +804,14 @@ ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out, * generic_file_splice_write_nolock - generic_file_splice_write without mutexes * @pipe: pipe info * @out: file to write to + * @ppos: position in @out * @len: number of bytes to splice * @flags: splice modifier flags * - * Will either move or copy pages (determined by @flags options) from - * the given pipe inode to the given file. The caller is responsible - * for acquiring i_mutex on both inodes. + * Description: + * Will either move or copy pages (determined by @flags options) from + * the given pipe inode to the given file. The caller is responsible + * for acquiring i_mutex on both inodes. * */ ssize_t @@ -831,11 +863,13 @@ EXPORT_SYMBOL(generic_file_splice_write_nolock); * generic_file_splice_write - splice data from a pipe to a file * @pipe: pipe info * @out: file to write to + * @ppos: position in @out * @len: number of bytes to splice * @flags: splice modifier flags * - * Will either move or copy pages (determined by @flags options) from - * the given pipe inode to the given file. + * Description: + * Will either move or copy pages (determined by @flags options) from + * the given pipe inode to the given file. * */ ssize_t @@ -886,13 +920,15 @@ EXPORT_SYMBOL(generic_file_splice_write); /** * generic_splice_sendpage - splice data from a pipe to a socket - * @inode: pipe inode + * @pipe: pipe to splice from * @out: socket to write to + * @ppos: position in @out * @len: number of bytes to splice * @flags: splice modifier flags * - * Will send @len bytes from the pipe to a network socket. No data copying - * is involved. + * Description: + * Will send @len bytes from the pipe to a network socket. No data copying + * is involved. * */ ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out, @@ -946,8 +982,18 @@ static long do_splice_to(struct file *in, loff_t *ppos, return in->f_op->splice_read(in, ppos, pipe, len, flags); } -/* - * Splices from an input file to an actor, using a 'direct' pipe. +/** + * splice_direct_to_actor - splices data directly between two non-pipes + * @in: file to splice from + * @sd: actor information on where to splice to + * @actor: handles the data splicing + * + * Description: + * This is a special case helper to splice directly between two + * points, without requiring an explicit pipe. Internally an allocated + * pipe is cached in the process, and reused during the life time of + * that process. + * */ ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd, splice_direct_actor *actor) @@ -1077,6 +1123,21 @@ static int direct_splice_actor(struct pipe_inode_info *pipe, return do_splice_from(pipe, file, &sd->pos, sd->total_len, sd->flags); } +/** + * do_splice_direct - splices data directly between two files + * @in: file to splice from + * @ppos: input file offset + * @out: file to splice to + * @len: number of bytes to splice + * @flags: splice modifier flags + * + * Description: + * For use by do_sendfile(). splice can easily emulate sendfile, but + * doing it in the application would incur an extra system call + * (splice in + splice out, as compared to just sendfile()). So this helper + * can splice directly through a process-private pipe. + * + */ long do_splice_direct(struct file *in, loff_t *ppos, struct file *out, size_t len, unsigned int flags) { |