From 70524490ee2ea1bbf6cee6c106597b3ac25a3fc2 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Tue, 11 Apr 2006 15:51:17 +0200 Subject: [PATCH] [PATCH] splice: add support for sys_tee() Basically an in-kernel implementation of tee, which uses splice and the pipe buffers as an intelligent way to pass data around by reference. Where the user space tee consumes the input and produces a stdout and file output, this syscall merely duplicates the data inside a pipe to another pipe. No data is copied, the output just grabs a reference to the input pipe data. Signed-off-by: Jens Axboe --- arch/i386/kernel/syscall_table.S | 1 + arch/ia64/kernel/entry.S | 1 + arch/powerpc/kernel/systbl.S | 1 + fs/pipe.c | 7 ++ fs/splice.c | 186 +++++++++++++++++++++++++++++++ include/asm-i386/unistd.h | 3 +- include/asm-ia64/unistd.h | 3 +- include/asm-powerpc/unistd.h | 3 +- include/asm-x86_64/unistd.h | 4 +- include/linux/pipe_fs_i.h | 1 + include/linux/syscalls.h | 2 + 11 files changed, 208 insertions(+), 4 deletions(-) diff --git a/arch/i386/kernel/syscall_table.S b/arch/i386/kernel/syscall_table.S index 4f58b9c0efe..f48bef15b4f 100644 --- a/arch/i386/kernel/syscall_table.S +++ b/arch/i386/kernel/syscall_table.S @@ -314,3 +314,4 @@ ENTRY(sys_call_table) .long sys_get_robust_list .long sys_splice .long sys_sync_file_range + .long sys_tee /* 315 */ diff --git a/arch/ia64/kernel/entry.S b/arch/ia64/kernel/entry.S index 6e16f6b35bd..e3079881121 100644 --- a/arch/ia64/kernel/entry.S +++ b/arch/ia64/kernel/entry.S @@ -1609,5 +1609,6 @@ sys_call_table: data8 sys_set_robust_list data8 sys_get_robust_list data8 sys_sync_file_range // 1300 + data8 sys_tee .org sys_call_table + 8*NR_syscalls // guard against failures to increase NR_syscalls diff --git a/arch/powerpc/kernel/systbl.S b/arch/powerpc/kernel/systbl.S index 1424eab450e..a14c9640384 100644 --- a/arch/powerpc/kernel/systbl.S +++ b/arch/powerpc/kernel/systbl.S @@ -323,3 +323,4 @@ COMPAT_SYS(pselect6) COMPAT_SYS(ppoll) SYSCALL(unshare) SYSCALL(splice) +SYSCALL(tee) diff --git a/fs/pipe.c b/fs/pipe.c index e984beb93a0..7fefb10db8d 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -131,12 +131,19 @@ static int anon_pipe_buf_steal(struct pipe_inode_info *pipe, return 0; } +static void anon_pipe_buf_get(struct pipe_inode_info *info, + struct pipe_buffer *buf) +{ + page_cache_get(buf->page); +} + static struct pipe_buf_operations anon_pipe_buf_ops = { .can_merge = 1, .map = anon_pipe_buf_map, .unmap = anon_pipe_buf_unmap, .release = anon_pipe_buf_release, .steal = anon_pipe_buf_steal, + .get = anon_pipe_buf_get, }; static ssize_t diff --git a/fs/splice.c b/fs/splice.c index 5d3eda64703..8d57e89924a 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -125,12 +125,19 @@ static void page_cache_pipe_buf_unmap(struct pipe_inode_info *info, kunmap(buf->page); } +static void page_cache_pipe_buf_get(struct pipe_inode_info *info, + struct pipe_buffer *buf) +{ + page_cache_get(buf->page); +} + static struct pipe_buf_operations page_cache_pipe_buf_ops = { .can_merge = 0, .map = page_cache_pipe_buf_map, .unmap = page_cache_pipe_buf_unmap, .release = page_cache_pipe_buf_release, .steal = page_cache_pipe_buf_steal, + .get = page_cache_pipe_buf_get, }; /* @@ -963,3 +970,182 @@ asmlinkage long sys_splice(int fd_in, loff_t __user *off_in, return error; } + +/* + * Link contents of ipipe to opipe. + */ +static int link_pipe(struct pipe_inode_info *ipipe, + struct pipe_inode_info *opipe, + size_t len, unsigned int flags) +{ + struct pipe_buffer *ibuf, *obuf; + int ret = 0, do_wakeup = 0, i; + + /* + * Potential ABBA deadlock, work around it by ordering lock + * grabbing by inode address. Otherwise two different processes + * could deadlock (one doing tee from A -> B, the other from B -> A). + */ + if (ipipe->inode < opipe->inode) { + mutex_lock(&ipipe->inode->i_mutex); + mutex_lock(&opipe->inode->i_mutex); + } else { + mutex_lock(&opipe->inode->i_mutex); + mutex_lock(&ipipe->inode->i_mutex); + } + + for (i = 0;; i++) { + if (!opipe->readers) { + send_sig(SIGPIPE, current, 0); + if (!ret) + ret = -EPIPE; + break; + } + if (ipipe->nrbufs - i) { + ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1)); + + /* + * If we have room, fill this buffer + */ + if (opipe->nrbufs < PIPE_BUFFERS) { + int nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1); + + /* + * Get a reference to this pipe buffer, + * so we can copy the contents over. + */ + ibuf->ops->get(ipipe, ibuf); + + obuf = opipe->bufs + nbuf; + *obuf = *ibuf; + + if (obuf->len > len) + obuf->len = len; + + opipe->nrbufs++; + do_wakeup = 1; + ret += obuf->len; + len -= obuf->len; + + if (!len) + break; + if (opipe->nrbufs < PIPE_BUFFERS) + continue; + } + + /* + * We have input available, but no output room. + * If we already copied data, return that. + */ + if (flags & SPLICE_F_NONBLOCK) { + if (!ret) + ret = -EAGAIN; + break; + } + if (signal_pending(current)) { + if (!ret) + ret = -ERESTARTSYS; + break; + } + if (do_wakeup) { + smp_mb(); + if (waitqueue_active(&opipe->wait)) + wake_up_interruptible(&opipe->wait); + kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN); + do_wakeup = 0; + } + + opipe->waiting_writers++; + pipe_wait(opipe); + opipe->waiting_writers--; + continue; + } + + /* + * No input buffers, do the usual checks for available + * writers and blocking and wait if necessary + */ + if (!ipipe->writers) + break; + if (!ipipe->waiting_writers) { + if (ret) + break; + } + if (flags & SPLICE_F_NONBLOCK) { + if (!ret) + ret = -EAGAIN; + break; + } + if (signal_pending(current)) { + if (!ret) + ret = -ERESTARTSYS; + break; + } + + if (waitqueue_active(&ipipe->wait)) + wake_up_interruptible_sync(&ipipe->wait); + kill_fasync(&ipipe->fasync_writers, SIGIO, POLL_OUT); + + pipe_wait(ipipe); + } + + mutex_unlock(&ipipe->inode->i_mutex); + mutex_unlock(&opipe->inode->i_mutex); + + if (do_wakeup) { + smp_mb(); + if (waitqueue_active(&opipe->wait)) + wake_up_interruptible(&opipe->wait); + kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN); + } + + return ret; +} + +/* + * 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. + */ +static long do_tee(struct file *in, struct file *out, size_t len, + unsigned int flags) +{ + struct pipe_inode_info *ipipe = in->f_dentry->d_inode->i_pipe; + struct pipe_inode_info *opipe = out->f_dentry->d_inode->i_pipe; + + /* + * Link ipipe to the two output pipes, consuming as we go along. + */ + if (ipipe && opipe) + return link_pipe(ipipe, opipe, len, flags); + + return -EINVAL; +} + +asmlinkage long sys_tee(int fdin, int fdout, size_t len, unsigned int flags) +{ + struct file *in; + int error, fput_in; + + if (unlikely(!len)) + return 0; + + error = -EBADF; + in = fget_light(fdin, &fput_in); + if (in) { + if (in->f_mode & FMODE_READ) { + int fput_out; + struct file *out = fget_light(fdout, &fput_out); + + if (out) { + if (out->f_mode & FMODE_WRITE) + error = do_tee(in, out, len, flags); + fput_light(out, fput_out); + } + } + fput_light(in, fput_in); + } + + return error; +} diff --git a/include/asm-i386/unistd.h b/include/asm-i386/unistd.h index 6a8dd83c350..d81d6cfc1bb 100644 --- a/include/asm-i386/unistd.h +++ b/include/asm-i386/unistd.h @@ -320,8 +320,9 @@ #define __NR_get_robust_list 312 #define __NR_splice 313 #define __NR_sync_file_range 314 +#define __NR_tee 315 -#define NR_syscalls 315 +#define NR_syscalls 316 /* * user-visible error numbers are in the range -1 - -128: see diff --git a/include/asm-ia64/unistd.h b/include/asm-ia64/unistd.h index 1c749acca02..a40ebec6aee 100644 --- a/include/asm-ia64/unistd.h +++ b/include/asm-ia64/unistd.h @@ -289,12 +289,13 @@ #define __NR_set_robust_list 1298 #define __NR_get_robust_list 1299 #define __NR_sync_file_range 1300 +#define __NR_tee 1301 #ifdef __KERNEL__ #include -#define NR_syscalls 277 /* length of syscall table */ +#define NR_syscalls 278 /* length of syscall table */ #define __ARCH_WANT_SYS_RT_SIGACTION diff --git a/include/asm-powerpc/unistd.h b/include/asm-powerpc/unistd.h index 536ba087305..c612f1a6277 100644 --- a/include/asm-powerpc/unistd.h +++ b/include/asm-powerpc/unistd.h @@ -302,8 +302,9 @@ #define __NR_ppoll 281 #define __NR_unshare 282 #define __NR_splice 283 +#define __NR_tee 284 -#define __NR_syscalls 284 +#define __NR_syscalls 285 #ifdef __KERNEL__ #define __NR__exit __NR_exit diff --git a/include/asm-x86_64/unistd.h b/include/asm-x86_64/unistd.h index f21ff2c1e96..d86494e23b6 100644 --- a/include/asm-x86_64/unistd.h +++ b/include/asm-x86_64/unistd.h @@ -611,8 +611,10 @@ __SYSCALL(__NR_set_robust_list, sys_set_robust_list) __SYSCALL(__NR_get_robust_list, sys_get_robust_list) #define __NR_splice 275 __SYSCALL(__NR_splice, sys_splice) +#define __NR_tee 276 +__SYSCALL(__NR_tee, sys_tee) -#define __NR_syscall_max __NR_splice +#define __NR_syscall_max __NR_tee #ifndef __NO_STUBS diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h index 123a7c24bc7..ef7f33c0be1 100644 --- a/include/linux/pipe_fs_i.h +++ b/include/linux/pipe_fs_i.h @@ -21,6 +21,7 @@ struct pipe_buf_operations { void (*unmap)(struct pipe_inode_info *, struct pipe_buffer *); void (*release)(struct pipe_inode_info *, struct pipe_buffer *); int (*steal)(struct pipe_inode_info *, struct pipe_buffer *); + void (*get)(struct pipe_inode_info *, struct pipe_buffer *); }; struct pipe_inode_info { diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index f001bad28d9..d3ebc0e68b2 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -574,6 +574,8 @@ asmlinkage long sys_splice(int fd_in, loff_t __user *off_in, int fd_out, loff_t __user *off_out, size_t len, unsigned int flags); +asmlinkage long sys_tee(int fdin, int fdout, size_t len, unsigned int flags); + asmlinkage long sys_sync_file_range(int fd, loff_t offset, loff_t nbytes, unsigned int flags); -- 2.20.1