diff options
Diffstat (limited to 'fs/splice.c')
-rw-r--r-- | fs/splice.c | 127 |
1 files changed, 58 insertions, 69 deletions
diff --git a/fs/splice.c b/fs/splice.c index 3e06611d19ae..2420ead610a7 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -299,20 +299,36 @@ void splice_shrink_spd(struct splice_pipe_desc *spd) kfree(spd->partial); } -/* - * Splice data from an O_DIRECT file into pages and then add them to the output - * pipe. +/** + * 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 direct_splice_read(struct file *in, loff_t *ppos, - struct pipe_inode_info *pipe, - size_t len, unsigned int flags) +ssize_t copy_splice_read(struct file *in, loff_t *ppos, + struct pipe_inode_info *pipe, + size_t len, unsigned int flags) { struct iov_iter to; struct bio_vec *bv; struct kiocb kiocb; struct page **pages; ssize_t ret; - size_t used, npages, chunk, remain, reclaim; + size_t used, npages, chunk, remain, keep = 0; int i; /* Work out how much data we can actually add into the pipe */ @@ -326,7 +342,7 @@ ssize_t direct_splice_read(struct file *in, loff_t *ppos, if (!bv) return -ENOMEM; - pages = (void *)(bv + npages); + pages = (struct page **)(bv + npages); npages = alloc_pages_bulk_array(GFP_USER, npages, pages); if (!npages) { kfree(bv); @@ -349,11 +365,8 @@ ssize_t direct_splice_read(struct file *in, loff_t *ppos, kiocb.ki_pos = *ppos; ret = call_read_iter(in, &kiocb, &to); - reclaim = npages * PAGE_SIZE; - remain = 0; if (ret > 0) { - reclaim -= ret; - remain = ret; + keep = DIV_ROUND_UP(ret, PAGE_SIZE); *ppos = kiocb.ki_pos; file_accessed(in); } else if (ret < 0) { @@ -366,14 +379,12 @@ ssize_t direct_splice_read(struct file *in, loff_t *ppos, } /* Free any pages that didn't get touched at all. */ - reclaim /= PAGE_SIZE; - if (reclaim) { - npages -= reclaim; - release_pages(pages + npages, reclaim); - } + if (keep < npages) + release_pages(pages + keep, npages - keep); /* Push the remaining pages into the pipe. */ - for (i = 0; i < npages; i++) { + remain = ret; + for (i = 0; i < keep; i++) { struct pipe_buffer *buf = pipe_head_buf(pipe); chunk = min_t(size_t, remain, PAGE_SIZE); @@ -390,50 +401,7 @@ ssize_t direct_splice_read(struct file *in, loff_t *ppos, kfree(bv); return ret; } -EXPORT_SYMBOL(direct_splice_read); - -/** - * 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 - * - * Description: - * Will read pages from given file and fill them into a pipe. Can be - * used as long as it has more or less sane ->read_iter(). - * - */ -ssize_t generic_file_splice_read(struct file *in, loff_t *ppos, - struct pipe_inode_info *pipe, size_t len, - unsigned int flags) -{ - struct iov_iter to; - struct kiocb kiocb; - int ret; - - iov_iter_pipe(&to, ITER_DEST, pipe, len); - init_sync_kiocb(&kiocb, in); - kiocb.ki_pos = *ppos; - ret = call_read_iter(in, &kiocb, &to); - if (ret > 0) { - *ppos = kiocb.ki_pos; - file_accessed(in); - } else if (ret < 0) { - /* free what was emitted */ - pipe_discard_from(pipe, to.start_head); - /* - * callers of ->splice_read() expect -EAGAIN on - * "can't put anything in there", rather than -EFAULT. - */ - if (ret == -EFAULT) - ret = -EAGAIN; - } - - return ret; -} -EXPORT_SYMBOL(generic_file_splice_read); +EXPORT_SYMBOL(copy_splice_read); const struct pipe_buf_operations default_pipe_buf_ops = { .release = generic_pipe_buf_release, @@ -873,18 +841,32 @@ 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; if (unlikely(!(in->f_mode & FMODE_READ))) return -EBADF; + if (!len) + return 0; /* Don't try to read more the pipe has space for. */ p_space = pipe->max_usage - pipe_occupancy(pipe->head, pipe->tail); @@ -899,8 +881,15 @@ static long do_splice_to(struct file *in, loff_t *ppos, if (unlikely(!in->f_op->splice_read)) return warn_unsupported(in, "read"); + /* + * O_DIRECT and DAX don't deal with the pagecache, so we allocate a + * buffer, copy into it and splice that into the pipe. + */ + if ((in->f_flags & O_DIRECT) || IS_DAX(in->f_mapping->host)) + return copy_splice_read(in, ppos, pipe, len, flags); 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 @@ -970,7 +959,7 @@ 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; @@ -1118,7 +1107,7 @@ 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); |