// SPDX-License-Identifier: GPL-2.0-only /* * "splice": joining two ropes together by interweaving their strands. * * This is the "extended pipe" functionality, where a pipe is used as * an arbitrary in-memory buffer. Think of a pipe as a small kernel * buffer that you can use to transfer data from one end to the other. * * The traditional unix read/write is extended with a "splice()" operation * that transfers data buffers to or from a pipe buffer. * * Named by Larry McVoy, original implementation from Linus, extended by * Jens to support splicing to files, network, direct splicing, etc and * fixing lots of bugs. * * Copyright (C) 2005-2006 Jens Axboe <[email protected]> * Copyright (C) 2005-2006 Linus Torvalds <[email protected]> * Copyright (C) 2006 Ingo Molnar <[email protected]> * */ #include <linux/bvec.h> #include <linux/fs.h> #include <linux/file.h> #include <linux/pagemap.h> #include <linux/splice.h> #include <linux/memcontrol.h> #include <linux/mm_inline.h> #include <linux/swap.h> #include <linux/writeback.h> #include <linux/export.h> #include <linux/syscalls.h> #include <linux/uio.h> #include <linux/fsnotify.h> #include <linux/security.h> #include <linux/gfp.h> #include <linux/net.h> #include <linux/socket.h> #include <linux/sched/signal.h> #include "internal.h" /* * Splice doesn't support FMODE_NOWAIT. Since pipes may set this flag to * indicate they support non-blocking reads or writes, we must clear it * here if set to avoid blocking other users of this pipe if splice is * being done on it. */ static noinline void noinline pipe_clear_nowait(struct file *file) { … } /* * Attempt to steal a page from a pipe buffer. This should perhaps go into * a vm helper function, it's already simplified quite a bit by the * addition of remove_mapping(). If success is returned, the caller may * attempt to reuse this page for another destination. */ static bool page_cache_pipe_buf_try_steal(struct pipe_inode_info *pipe, struct pipe_buffer *buf) { … } static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe, struct pipe_buffer *buf) { … } /* * Check whether the contents of buf is OK to access. Since the content * is a page cache page, IO may be in flight. */ static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe, struct pipe_buffer *buf) { … } const struct pipe_buf_operations page_cache_pipe_buf_ops = …; static bool user_page_pipe_buf_try_steal(struct pipe_inode_info *pipe, struct pipe_buffer *buf) { … } static const struct pipe_buf_operations user_page_pipe_buf_ops = …; static void wakeup_pipe_readers(struct pipe_inode_info *pipe) { … } /** * 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 tuples, along 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) { … } EXPORT_SYMBOL_GPL(…); ssize_t add_to_pipe(struct pipe_inode_info *pipe, struct pipe_buffer *buf) { … } EXPORT_SYMBOL(…); /* * Check if we need to grow the arrays holding pages and partial page * descriptions. */ int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd) { … } void splice_shrink_spd(struct splice_pipe_desc *spd) { … } /** * copy_splice_read - Copy data from a file and splice the copy into a pipe * @in: The file to read from * @ppos: Pointer to the file position to read from * @pipe: The pipe to splice into * @len: The amount to splice * @flags: The SPLICE_F_* flags * * This function allocates a bunch of pages sufficient to hold the requested * amount of data (but limited by the remaining pipe capacity), passes it to * the file's ->read_iter() to read into and then splices the used pages into * the pipe. * * Return: On success, the number of bytes read will be returned and *@ppos * will be updated if appropriate; 0 will be returned if there is no more data * to be read; -EAGAIN will be returned if the pipe had no space, and some * other negative error code will be returned on error. A short read may occur * if the pipe has insufficient space, we reach the end of the data or we hit a * hole. */ ssize_t copy_splice_read(struct file *in, loff_t *ppos, struct pipe_inode_info *pipe, size_t len, unsigned int flags) { … } EXPORT_SYMBOL(…); const struct pipe_buf_operations default_pipe_buf_ops = …; /* Pipe buffer operations for a socket and similar. */ const struct pipe_buf_operations nosteal_pipe_buf_ops = …; EXPORT_SYMBOL(…); static void wakeup_pipe_writers(struct pipe_inode_info *pipe) { … } /** * splice_from_pipe_feed - feed available data from a pipe to a file * @pipe: pipe to splice from * @sd: information to @actor * @actor: handler that splices the data * * Description: * This function loops over the pipe and calls @actor to do the * actual moving of a single struct pipe_buffer to the desired * destination. It returns when there's no more buffers left in * the pipe or if the requested number of bytes (@sd->total_len) * have been copied. It returns a positive number (one) if the * pipe needs to be filled with more data, zero if the required * number of bytes have been copied and -errno on error. * * This, together with splice_from_pipe_{begin,end,next}, may be * used to implement the functionality of __splice_from_pipe() when * locking is required around copying the pipe buffers to the * destination. */ static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd, splice_actor *actor) { … } /* We know we have a pipe buffer, but maybe it's empty? */ static inline bool eat_empty_buffer(struct pipe_inode_info *pipe) { … } /** * splice_from_pipe_next - wait for some data to splice from * @pipe: pipe to splice from * @sd: information about the splice operation * * Description: * This function will wait for some data and return a positive * value (one) if pipe buffers are available. It will return zero * or -errno if no more data needs to be spliced. */ static int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd) { … } /** * splice_from_pipe_begin - start splicing from pipe * @sd: information about the splice operation * * Description: * This function should be called before a loop containing * splice_from_pipe_next() and splice_from_pipe_feed() to * initialize the necessary fields of @sd. */ static void splice_from_pipe_begin(struct splice_desc *sd) { … } /** * splice_from_pipe_end - finish splicing from pipe * @pipe: pipe to splice from * @sd: information about the splice operation * * Description: * This function will wake up pipe writers if necessary. It should * be called after a loop containing splice_from_pipe_next() and * splice_from_pipe_feed(). */ static void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd) { … } /** * __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_sendmsg, or * pipe_to_user. * */ ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd, splice_actor *actor) { … } EXPORT_SYMBOL(…); /** * 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 pipe inode, * 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) { … } /** * iter_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 * * Description: * Will either move or copy pages (determined by @flags options) from * the given pipe inode to the given file. * This one is ->write_iter-based. * */ ssize_t iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out, loff_t *ppos, size_t len, unsigned int flags) { … } EXPORT_SYMBOL(…); #ifdef CONFIG_NET /** * splice_to_socket - splice data from a pipe to a socket * @pipe: pipe to splice from * @out: socket to write to * @ppos: position in @out * @len: number of bytes to splice * @flags: splice modifier flags * * Description: * Will send @len bytes from the pipe to a network socket. No data copying * is involved. * */ ssize_t splice_to_socket(struct pipe_inode_info *pipe, struct file *out, loff_t *ppos, size_t len, unsigned int flags) { … } #endif static int warn_unsupported(struct file *file, const char *op) { … } /* * Attempt to initiate a splice from pipe to file. */ static ssize_t do_splice_from(struct pipe_inode_info *pipe, struct file *out, loff_t *ppos, size_t len, unsigned int flags) { … } /* * Indicate to the caller that there was a premature EOF when reading from the * source and the caller didn't indicate they would be sending more data after * this. */ static void do_splice_eof(struct splice_desc *sd) { … } /* * Callers already called rw_verify_area() on the entire range. * No need to call it for sub ranges. */ static ssize_t do_splice_read(struct file *in, loff_t *ppos, struct pipe_inode_info *pipe, size_t len, unsigned int flags) { … } /** * 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. */ ssize_t vfs_splice_read(struct file *in, loff_t *ppos, struct pipe_inode_info *pipe, size_t len, unsigned int flags) { … } EXPORT_SYMBOL_GPL(…); /** * 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 lifetime of * that process. * */ ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd, splice_direct_actor *actor) { … } EXPORT_SYMBOL(…); static int direct_splice_actor(struct pipe_inode_info *pipe, struct splice_desc *sd) { … } static int splice_file_range_actor(struct pipe_inode_info *pipe, struct splice_desc *sd) { … } static void direct_file_splice_eof(struct splice_desc *sd) { … } static ssize_t do_splice_direct_actor(struct file *in, loff_t *ppos, struct file *out, loff_t *opos, size_t len, unsigned int flags, splice_direct_actor *actor) { … } /** * do_splice_direct - splices data directly between two files * @in: file to splice from * @ppos: input file offset * @out: file to splice to * @opos: output file offset * @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. * * Callers already called rw_verify_area() on the entire range. */ ssize_t do_splice_direct(struct file *in, loff_t *ppos, struct file *out, loff_t *opos, size_t len, unsigned int flags) { … } EXPORT_SYMBOL(…); /** * splice_file_range - splices data between two files for copy_file_range() * @in: file to splice from * @ppos: input file offset * @out: file to splice to * @opos: output file offset * @len: number of bytes to splice * * Description: * For use by ->copy_file_range() methods. * Like do_splice_direct(), but vfs_copy_file_range() already holds * start_file_write() on @out file. * * Callers already called rw_verify_area() on the entire range. */ ssize_t splice_file_range(struct file *in, loff_t *ppos, struct file *out, loff_t *opos, size_t len) { … } EXPORT_SYMBOL(…); static int wait_for_space(struct pipe_inode_info *pipe, unsigned flags) { … } static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe, struct pipe_inode_info *opipe, size_t len, unsigned int flags); ssize_t splice_file_to_pipe(struct file *in, struct pipe_inode_info *opipe, loff_t *offset, size_t len, unsigned int flags) { … } /* * Determine where to splice to/from. */ ssize_t do_splice(struct file *in, loff_t *off_in, struct file *out, loff_t *off_out, size_t len, unsigned int flags) { … } static ssize_t __do_splice(struct file *in, loff_t __user *off_in, struct file *out, loff_t __user *off_out, size_t len, unsigned int flags) { … } static ssize_t iter_to_pipe(struct iov_iter *from, struct pipe_inode_info *pipe, unsigned int flags) { … } static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf, struct splice_desc *sd) { … } /* * For lack of a better implementation, implement vmsplice() to userspace * as a simple copy of the pipes pages to the user iov. */ static ssize_t vmsplice_to_user(struct file *file, struct iov_iter *iter, unsigned int flags) { … } /* * vmsplice splices a user address range into a pipe. It can be thought of * as splice-from-memory, where the regular splice is splice-from-file (or * to file). In both cases the output is a pipe, naturally. */ static ssize_t vmsplice_to_pipe(struct file *file, struct iov_iter *iter, unsigned int flags) { … } static int vmsplice_type(struct fd f, int *type) { … } /* * Note that vmsplice only really supports true splicing _from_ user memory * to a pipe, not the other way around. Splicing from user memory is a simple * operation that can be supported without any funky alignment restrictions * or nasty vm tricks. We simply map in the user memory and fill them into * a pipe. The reverse isn't quite as easy, though. There are two possible * solutions for that: * * - memcpy() the data internally, at which point we might as well just * do a regular read() on the buffer anyway. * - Lots of nasty vm tricks, that are neither fast nor flexible (it * has restriction limitations on both ends of the pipe). * * Currently we punt and implement it as a normal copy, see pipe_to_user(). * */ SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, uiov, unsigned long, nr_segs, unsigned int, flags) { … } SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in, int, fd_out, loff_t __user *, off_out, size_t, len, unsigned int, flags) { … } /* * Make sure there's data to read. Wait for input if we can, otherwise * return an appropriate error. */ static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags) { … } /* * Make sure there's writeable room. Wait for room if we can, otherwise * return an appropriate error. */ static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags) { … } /* * Splice contents of ipipe to opipe. */ static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe, struct pipe_inode_info *opipe, size_t len, unsigned int flags) { … } /* * Link contents of ipipe to opipe. */ static ssize_t link_pipe(struct pipe_inode_info *ipipe, struct pipe_inode_info *opipe, size_t len, unsigned int flags) { … } /* * This is a tee(1) implementation that works on pipes. It doesn't copy * any data, it simply references the 'in' pages on the 'out' pipe. * The 'flags' used are the SPLICE_F_* variants, currently the only * applicable one is SPLICE_F_NONBLOCK. */ ssize_t do_tee(struct file *in, struct file *out, size_t len, unsigned int flags) { … } SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags) { … }
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