REPO: https://github.com/smipi1/linux-tinification.git
BRANCH: tiny/config-syscall-splice
BACKGROUND: This patch-set forms part of the Linux Kernel Tinification effort (
https://tiny.wiki.kernel.org/).
GOAL: Support compiling out the splice family of syscalls (splice, vmsplice,
tee and sendfile) along with all supporting infrastructure if not needed.
Many embedded systems will not need the splice-family syscalls. Omitting them
saves space.
STRATEGY:
a. With the goal of eventually compiling out fs/splice.c, several functions
that are only used in support of the the splice family of syscalls are moved
into fs/splice.c from fs/read_write.c. The kernel_write function that is not
used to support the splice syscalls is moved to fs/read_write.c:
0001-fs-move-sendfile-syscall-into-fs-splice.patch
0002-fs-moved-kernel_write-to-fs-read_write.patch
b. Introduce an EXPERT kernel configuration option; CONFIG_SYSCALL_SPLICE; to
compile out the splice family of syscalls. This removes all userspace uses
of the splice infrastructure.
0003-fs-splice-support-compiling-out-splice-family-syscal.patch
c. Splice exports an operations struct, nosteal_pipe_buf_ops. Eliminate the
use of this struct when CONFIG_SYSCALL_SPLICE is undefined, so that splice
can later be compiled out:
0004-fs-fuse-support-compiling-out-splice.patch
0005-net-core-support-compiling-out-splice.patch
e. Compile out fs/splice.c. Functions exported by fs/splice are mocked out with
failing static inlines. This is done so as to all but eliminate the
maintenance burden on file-system drivers.
0006-fs-splice-full-support-for-compiling-out-splice.patch
RESULTS: A tinyconfig bloat-o-meter score for the entire patch-set:
add/remove: 0/41 grow/shrink: 5/7 up/down: 23/-8422 (-8399)
function old new delta
sys_pwritev 115 122 +7
sys_preadv 115 122 +7
fdput_pos 29 36 +7
sys_pwrite64 115 116 +1
sys_pread64 115 116 +1
pipe_to_null 4 - -4
generic_pipe_buf_nosteal 6 - -6
spd_release_page 10 - -10
fdput 11 - -11
PageUptodate 22 11 -11
lock_page 36 24 -12
signal_pending 39 26 -13
fdget 56 42 -14
page_cache_pipe_buf_release 16 - -16
user_page_pipe_buf_ops 20 - -20
splice_write_null 24 4 -20
page_cache_pipe_buf_ops 20 - -20
nosteal_pipe_buf_ops 20 - -20
default_pipe_buf_ops 20 - -20
generic_splice_sendpage 24 - -24
user_page_pipe_buf_steal 25 - -25
splice_shrink_spd 27 - -27
pipe_to_user 43 - -43
direct_splice_actor 47 - -47
default_file_splice_write 49 - -49
wakeup_pipe_writers 54 - -54
wakeup_pipe_readers 54 - -54
write_pipe_buf 71 - -71
page_cache_pipe_buf_confirm 80 - -80
splice_grow_spd 87 - -87
do_splice_to 87 - -87
ipipe_prep.part 92 - -92
splice_from_pipe 93 - -93
splice_from_pipe_next 107 - -107
pipe_to_sendpage 109 - -109
page_cache_pipe_buf_steal 114 - -114
opipe_prep.part 119 - -119
sys_sendfile 122 - -122
generic_file_splice_read 131 8 -123
sys_sendfile64 126 - -126
sys_vmsplice 137 - -137
do_splice_direct 148 - -148
vmsplice_to_user 205 - -205
__splice_from_pipe 246 - -246
splice_direct_to_actor 348 - -348
splice_to_pipe 371 - -371
do_sendfile 492 - -492
sys_tee 497 - -497
vmsplice_to_pipe 558 - -558
default_file_splice_read 688 - -688
iter_file_splice_write 702 4 -698
sys_splice 1075 - -1075
__generic_file_splice_read 1109 - -1109
Pieter Smith (6):
fs: move sendfile syscall into fs/splice
fs: moved kernel_write to fs/read_write
fs/splice: support compiling out splice-family syscalls
fs/fuse: support compiling out splice
net/core: support compiling out splice
fs/splice: full support for compiling out splice
fs/Makefile | 3 +-
fs/fuse/dev.c | 4 +-
fs/read_write.c | 181 +++------------------------------------------
fs/splice.c | 194 +++++++++++++++++++++++++++++++++++++++++++++----
include/linux/fs.h | 32 ++++++++
include/linux/skbuff.h | 9 +++
include/linux/splice.h | 42 +++++++++++
init/Kconfig | 10 +++
kernel/sys_ni.c | 8 ++
net/core/skbuff.c | 9 ++-
10 files changed, 300 insertions(+), 192 deletions(-)
--
2.1.0
sendfile functionally forms part of the splice group of syscalls (splice,
vmsplice and tee). Grouping sendfile with splice paves the way to compiling out
the splice group of syscalls for embedded systems that do not need these.
add/remove: 0/0 grow/shrink: 7/2 up/down: 86/-61 (25)
function old new delta
file_start_write 34 68 +34
file_end_write 29 58 +29
sys_pwritev 115 122 +7
sys_preadv 115 122 +7
fdput_pos 29 36 +7
sys_pwrite64 115 116 +1
sys_pread64 115 116 +1
sys_tee 497 491 -6
sys_splice 1075 1020 -55
Signed-off-by: Pieter Smith <[email protected]>
---
fs/read_write.c | 175 -------------------------------------------------------
fs/splice.c | 178 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 178 insertions(+), 175 deletions(-)
diff --git a/fs/read_write.c b/fs/read_write.c
index 7d9318c..d9451ba 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1191,178 +1191,3 @@ COMPAT_SYSCALL_DEFINE5(pwritev, compat_ulong_t, fd,
}
#endif
-static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
- size_t count, loff_t max)
-{
- struct fd in, out;
- struct inode *in_inode, *out_inode;
- loff_t pos;
- loff_t out_pos;
- ssize_t retval;
- int fl;
-
- /*
- * Get input file, and verify that it is ok..
- */
- retval = -EBADF;
- in = fdget(in_fd);
- if (!in.file)
- goto out;
- if (!(in.file->f_mode & FMODE_READ))
- goto fput_in;
- retval = -ESPIPE;
- if (!ppos) {
- pos = in.file->f_pos;
- } else {
- pos = *ppos;
- if (!(in.file->f_mode & FMODE_PREAD))
- goto fput_in;
- }
- retval = rw_verify_area(READ, in.file, &pos, count);
- if (retval < 0)
- goto fput_in;
- count = retval;
-
- /*
- * Get output file, and verify that it is ok..
- */
- retval = -EBADF;
- out = fdget(out_fd);
- if (!out.file)
- goto fput_in;
- if (!(out.file->f_mode & FMODE_WRITE))
- goto fput_out;
- retval = -EINVAL;
- in_inode = file_inode(in.file);
- out_inode = file_inode(out.file);
- out_pos = out.file->f_pos;
- retval = rw_verify_area(WRITE, out.file, &out_pos, count);
- if (retval < 0)
- goto fput_out;
- count = retval;
-
- if (!max)
- max = min(in_inode->i_sb->s_maxbytes, out_inode->i_sb->s_maxbytes);
-
- if (unlikely(pos + count > max)) {
- retval = -EOVERFLOW;
- if (pos >= max)
- goto fput_out;
- count = max - pos;
- }
-
- fl = 0;
-#if 0
- /*
- * We need to debate whether we can enable this or not. The
- * man page documents EAGAIN return for the output at least,
- * and the application is arguably buggy if it doesn't expect
- * EAGAIN on a non-blocking file descriptor.
- */
- if (in.file->f_flags & O_NONBLOCK)
- fl = SPLICE_F_NONBLOCK;
-#endif
- file_start_write(out.file);
- retval = do_splice_direct(in.file, &pos, out.file, &out_pos, count, fl);
- file_end_write(out.file);
-
- if (retval > 0) {
- add_rchar(current, retval);
- add_wchar(current, retval);
- fsnotify_access(in.file);
- fsnotify_modify(out.file);
- out.file->f_pos = out_pos;
- if (ppos)
- *ppos = pos;
- else
- in.file->f_pos = pos;
- }
-
- inc_syscr(current);
- inc_syscw(current);
- if (pos > max)
- retval = -EOVERFLOW;
-
-fput_out:
- fdput(out);
-fput_in:
- fdput(in);
-out:
- return retval;
-}
-
-SYSCALL_DEFINE4(sendfile, int, out_fd, int, in_fd, off_t __user *, offset, size_t, count)
-{
- loff_t pos;
- off_t off;
- ssize_t ret;
-
- if (offset) {
- if (unlikely(get_user(off, offset)))
- return -EFAULT;
- pos = off;
- ret = do_sendfile(out_fd, in_fd, &pos, count, MAX_NON_LFS);
- if (unlikely(put_user(pos, offset)))
- return -EFAULT;
- return ret;
- }
-
- return do_sendfile(out_fd, in_fd, NULL, count, 0);
-}
-
-SYSCALL_DEFINE4(sendfile64, int, out_fd, int, in_fd, loff_t __user *, offset, size_t, count)
-{
- loff_t pos;
- ssize_t ret;
-
- if (offset) {
- if (unlikely(copy_from_user(&pos, offset, sizeof(loff_t))))
- return -EFAULT;
- ret = do_sendfile(out_fd, in_fd, &pos, count, 0);
- if (unlikely(put_user(pos, offset)))
- return -EFAULT;
- return ret;
- }
-
- return do_sendfile(out_fd, in_fd, NULL, count, 0);
-}
-
-#ifdef CONFIG_COMPAT
-COMPAT_SYSCALL_DEFINE4(sendfile, int, out_fd, int, in_fd,
- compat_off_t __user *, offset, compat_size_t, count)
-{
- loff_t pos;
- off_t off;
- ssize_t ret;
-
- if (offset) {
- if (unlikely(get_user(off, offset)))
- return -EFAULT;
- pos = off;
- ret = do_sendfile(out_fd, in_fd, &pos, count, MAX_NON_LFS);
- if (unlikely(put_user(pos, offset)))
- return -EFAULT;
- return ret;
- }
-
- return do_sendfile(out_fd, in_fd, NULL, count, 0);
-}
-
-COMPAT_SYSCALL_DEFINE4(sendfile64, int, out_fd, int, in_fd,
- compat_loff_t __user *, offset, compat_size_t, count)
-{
- loff_t pos;
- ssize_t ret;
-
- if (offset) {
- if (unlikely(copy_from_user(&pos, offset, sizeof(loff_t))))
- return -EFAULT;
- ret = do_sendfile(out_fd, in_fd, &pos, count, 0);
- if (unlikely(put_user(pos, offset)))
- return -EFAULT;
- return ret;
- }
-
- return do_sendfile(out_fd, in_fd, NULL, count, 0);
-}
-#endif
diff --git a/fs/splice.c b/fs/splice.c
index f5cb9ba..c1a2861 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -28,6 +28,7 @@
#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/socket.h>
@@ -2039,3 +2040,180 @@ SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
return error;
}
+
+static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
+ size_t count, loff_t max)
+{
+ struct fd in, out;
+ struct inode *in_inode, *out_inode;
+ loff_t pos;
+ loff_t out_pos;
+ ssize_t retval;
+ int fl;
+
+ /*
+ * Get input file, and verify that it is ok..
+ */
+ retval = -EBADF;
+ in = fdget(in_fd);
+ if (!in.file)
+ goto out;
+ if (!(in.file->f_mode & FMODE_READ))
+ goto fput_in;
+ retval = -ESPIPE;
+ if (!ppos) {
+ pos = in.file->f_pos;
+ } else {
+ pos = *ppos;
+ if (!(in.file->f_mode & FMODE_PREAD))
+ goto fput_in;
+ }
+ retval = rw_verify_area(READ, in.file, &pos, count);
+ if (retval < 0)
+ goto fput_in;
+ count = retval;
+
+ /*
+ * Get output file, and verify that it is ok..
+ */
+ retval = -EBADF;
+ out = fdget(out_fd);
+ if (!out.file)
+ goto fput_in;
+ if (!(out.file->f_mode & FMODE_WRITE))
+ goto fput_out;
+ retval = -EINVAL;
+ in_inode = file_inode(in.file);
+ out_inode = file_inode(out.file);
+ out_pos = out.file->f_pos;
+ retval = rw_verify_area(WRITE, out.file, &out_pos, count);
+ if (retval < 0)
+ goto fput_out;
+ count = retval;
+
+ if (!max)
+ max = min(in_inode->i_sb->s_maxbytes, out_inode->i_sb->s_maxbytes);
+
+ if (unlikely(pos + count > max)) {
+ retval = -EOVERFLOW;
+ if (pos >= max)
+ goto fput_out;
+ count = max - pos;
+ }
+
+ fl = 0;
+#if 0
+ /*
+ * We need to debate whether we can enable this or not. The
+ * man page documents EAGAIN return for the output at least,
+ * and the application is arguably buggy if it doesn't expect
+ * EAGAIN on a non-blocking file descriptor.
+ */
+ if (in.file->f_flags & O_NONBLOCK)
+ fl = SPLICE_F_NONBLOCK;
+#endif
+ file_start_write(out.file);
+ retval = do_splice_direct(in.file, &pos, out.file, &out_pos, count, fl);
+ file_end_write(out.file);
+
+ if (retval > 0) {
+ add_rchar(current, retval);
+ add_wchar(current, retval);
+ fsnotify_access(in.file);
+ fsnotify_modify(out.file);
+ out.file->f_pos = out_pos;
+ if (ppos)
+ *ppos = pos;
+ else
+ in.file->f_pos = pos;
+ }
+
+ inc_syscr(current);
+ inc_syscw(current);
+ if (pos > max)
+ retval = -EOVERFLOW;
+
+fput_out:
+ fdput(out);
+fput_in:
+ fdput(in);
+out:
+ return retval;
+}
+
+SYSCALL_DEFINE4(sendfile, int, out_fd, int, in_fd, off_t __user *, offset, size_t, count)
+{
+ loff_t pos;
+ off_t off;
+ ssize_t ret;
+
+ if (offset) {
+ if (unlikely(get_user(off, offset)))
+ return -EFAULT;
+ pos = off;
+ ret = do_sendfile(out_fd, in_fd, &pos, count, MAX_NON_LFS);
+ if (unlikely(put_user(pos, offset)))
+ return -EFAULT;
+ return ret;
+ }
+
+ return do_sendfile(out_fd, in_fd, NULL, count, 0);
+}
+
+SYSCALL_DEFINE4(sendfile64, int, out_fd, int, in_fd, loff_t __user *, offset, size_t, count)
+{
+ loff_t pos;
+ ssize_t ret;
+
+ if (offset) {
+ if (unlikely(copy_from_user(&pos, offset, sizeof(loff_t))))
+ return -EFAULT;
+ ret = do_sendfile(out_fd, in_fd, &pos, count, 0);
+ if (unlikely(put_user(pos, offset)))
+ return -EFAULT;
+ return ret;
+ }
+
+ return do_sendfile(out_fd, in_fd, NULL, count, 0);
+}
+
+#ifdef CONFIG_COMPAT
+COMPAT_SYSCALL_DEFINE4(sendfile, int, out_fd, int, in_fd,
+ compat_off_t __user *, offset, compat_size_t, count)
+{
+ loff_t pos;
+ off_t off;
+ ssize_t ret;
+
+ if (offset) {
+ if (unlikely(get_user(off, offset)))
+ return -EFAULT;
+ pos = off;
+ ret = do_sendfile(out_fd, in_fd, &pos, count, MAX_NON_LFS);
+ if (unlikely(put_user(pos, offset)))
+ return -EFAULT;
+ return ret;
+ }
+
+ return do_sendfile(out_fd, in_fd, NULL, count, 0);
+}
+
+COMPAT_SYSCALL_DEFINE4(sendfile64, int, out_fd, int, in_fd,
+ compat_loff_t __user *, offset, compat_size_t, count)
+{
+ loff_t pos;
+ ssize_t ret;
+
+ if (offset) {
+ if (unlikely(copy_from_user(&pos, offset, sizeof(loff_t))))
+ return -EFAULT;
+ ret = do_sendfile(out_fd, in_fd, &pos, count, 0);
+ if (unlikely(put_user(pos, offset)))
+ return -EFAULT;
+ return ret;
+ }
+
+ return do_sendfile(out_fd, in_fd, NULL, count, 0);
+}
+#endif
+
--
2.1.0
kernel_write shares infrastructure with the read_write translation unit but not
with the splice translation unit. Grouping kernel_write with the read_write
translation unit is more logical. It also paves the way to compiling out the
splice group of syscalls for embedded systems that do not need them.
Signed-off-by: Pieter Smith <[email protected]>
---
fs/read_write.c | 16 ++++++++++++++++
fs/splice.c | 16 ----------------
2 files changed, 16 insertions(+), 16 deletions(-)
diff --git a/fs/read_write.c b/fs/read_write.c
index d9451ba..f4c8d8b 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1191,3 +1191,19 @@ COMPAT_SYSCALL_DEFINE5(pwritev, compat_ulong_t, fd,
}
#endif
+ssize_t kernel_write(struct file *file, const char *buf, size_t count,
+ loff_t pos)
+{
+ mm_segment_t old_fs;
+ ssize_t res;
+
+ old_fs = get_fs();
+ set_fs(get_ds());
+ /* The cast to a user pointer is valid due to the set_fs() */
+ res = vfs_write(file, (__force const char __user *)buf, count, &pos);
+ set_fs(old_fs);
+
+ return res;
+}
+EXPORT_SYMBOL(kernel_write);
+
diff --git a/fs/splice.c b/fs/splice.c
index c1a2861..44b201b 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -583,22 +583,6 @@ static ssize_t kernel_readv(struct file *file, const struct iovec *vec,
return res;
}
-ssize_t kernel_write(struct file *file, const char *buf, size_t count,
- loff_t pos)
-{
- mm_segment_t old_fs;
- ssize_t res;
-
- old_fs = get_fs();
- set_fs(get_ds());
- /* The cast to a user pointer is valid due to the set_fs() */
- res = vfs_write(file, (__force const char __user *)buf, count, &pos);
- set_fs(old_fs);
-
- return res;
-}
-EXPORT_SYMBOL(kernel_write);
-
ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)
--
2.1.0
Many embedded systems will not need the splice-family syscalls (splice,
vmsplice, tee and sendfile). Omitting them saves space. This adds a new EXPERT
config option CONFIG_SYSCALL_SPLICE (default y) to support compiling them out.
The goal is to completely compile out fs/splice. To achieve this, the remaining
patch-set will deal with fs/splice exports. As far as possible, the impact on
other device drivers will be minimized so as to reduce the maintenance burden
of CONFIG_SYSCALL_SPLICE.
The use of exported functions will be solved by transparently mocking them out
with static inlines. Use of the exported pipe_buf_operations struct however
require direct modification in fs/fuse and net/core. The next two patches will
deal with this.
Once all exports are solved, fs/splice can be compiled out.
The bloat benefit of this patch given a tinyconfig is:
add/remove: 0/16 grow/shrink: 2/5 up/down: 114/-3693 (-3579)
function old new delta
splice_direct_to_actor 348 416 +68
splice_to_pipe 371 417 +46
splice_from_pipe_next 107 106 -1
fdput 11 - -11
signal_pending 39 26 -13
fdget 56 42 -14
user_page_pipe_buf_ops 20 - -20
user_page_pipe_buf_steal 25 - -25
file_end_write 58 29 -29
file_start_write 68 34 -34
pipe_to_user 43 - -43
wakeup_pipe_readers 54 - -54
do_splice_to 87 - -87
ipipe_prep.part 92 - -92
opipe_prep.part 119 - -119
sys_sendfile 122 - -122
sys_sendfile64 126 - -126
sys_vmsplice 137 - -137
vmsplice_to_user 205 - -205
sys_tee 491 - -491
do_sendfile 492 - -492
vmsplice_to_pipe 558 - -558
sys_splice 1020 - -1020
Signed-off-by: Pieter Smith <[email protected]>
---
fs/splice.c | 2 ++
init/Kconfig | 10 ++++++++++
kernel/sys_ni.c | 8 ++++++++
3 files changed, 20 insertions(+)
diff --git a/fs/splice.c b/fs/splice.c
index 44b201b..7c4c695 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1316,6 +1316,7 @@ long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
return ret;
}
+#ifdef CONFIG_SYSCALL_SPLICE
static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
struct pipe_inode_info *opipe,
size_t len, unsigned int flags);
@@ -2200,4 +2201,5 @@ COMPAT_SYSCALL_DEFINE4(sendfile64, int, out_fd, int, in_fd,
return do_sendfile(out_fd, in_fd, NULL, count, 0);
}
#endif
+#endif
diff --git a/init/Kconfig b/init/Kconfig
index d811d5f..dec9819 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1571,6 +1571,16 @@ config NTP
system clock to an NTP server, you can disable this option to save
space.
+config SYSCALL_SPLICE
+ bool "Enable splice/vmsplice/tee/sendfile syscalls" if EXPERT
+ default y
+ help
+ This option enables the splice, vmsplice, tee and sendfile syscalls. These
+ are used by applications to: move data between buffers and arbitrary file
+ descriptors; "copy" data between buffers; or copy data from userspace into
+ buffers. If building an embedded system where no applications use these
+ syscalls, you can disable this option to save space.
+
config PCI_QUIRKS
default y
bool "Enable PCI quirk workarounds" if EXPERT
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index d2f5b00..25d5551 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -170,6 +170,14 @@ cond_syscall(sys_fstat);
cond_syscall(sys_stat);
cond_syscall(sys_uname);
cond_syscall(sys_olduname);
+cond_syscall(sys_vmsplice);
+cond_syscall(sys_splice);
+cond_syscall(sys_tee);
+cond_syscall(sys_sendfile);
+cond_syscall(sys_sendfile64);
+cond_syscall(compat_sys_vmsplice);
+cond_syscall(compat_sys_sendfile);
+cond_syscall(compat_sys_sendfile64);
/* arch-specific weak syscall entries */
cond_syscall(sys_pciconfig_read);
--
2.1.0
To implement splice support, fs/fuse makes use of nosteal_pipe_buf_ops. This
struct is exported by fs/splice. The goal of the larger patch set is to
completely compile out fs/splice, so uses of the exported struct need to be
compiled out along with fs/splice.
This patch therefore compiles out splice support in fs/fuse when
CONFIG_SYSCALL_SPLICE is undefined.
Signed-off-by: Pieter Smith <[email protected]>
---
fs/fuse/dev.c | 4 ++--
include/linux/fs.h | 6 ++++++
2 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index ca88731..f8f92a4 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1291,7 +1291,7 @@ static ssize_t fuse_dev_read(struct kiocb *iocb, const struct iovec *iov,
return fuse_dev_do_read(fc, file, &cs, iov_length(iov, nr_segs));
}
-static ssize_t fuse_dev_splice_read(struct file *in, loff_t *ppos,
+static ssize_t __maybe_unused fuse_dev_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe,
size_t len, unsigned int flags)
{
@@ -2144,7 +2144,7 @@ const struct file_operations fuse_dev_operations = {
.llseek = no_llseek,
.read = do_sync_read,
.aio_read = fuse_dev_read,
- .splice_read = fuse_dev_splice_read,
+ .splice_read = __splice_p(fuse_dev_splice_read),
.write = do_sync_write,
.aio_write = fuse_dev_write,
.splice_write = fuse_dev_splice_write,
diff --git a/include/linux/fs.h b/include/linux/fs.h
index a957d43..04c0975 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2443,6 +2443,12 @@ extern int blkdev_fsync(struct file *filp, loff_t start, loff_t end,
int datasync);
extern void block_sync_page(struct page *page);
+#ifdef CONFIG_SYSCALL_SPLICE
+#define __splice_p(x) x
+#else
+#define __splice_p(x) NULL
+#endif
+
/* fs/splice.c */
extern ssize_t generic_file_splice_read(struct file *, loff_t *,
struct pipe_inode_info *, size_t, unsigned int);
--
2.1.0
To implement splice support, net/core makes use of nosteal_pipe_buf_ops. This
struct is exported by fs/splice. The goal of the larger patch set is to
completely compile out fs/splice, so uses of the exported struct need to be
compiled out along with fs/splice.
This patch therefore compiles out splice support in net/core when
CONFIG_SYSCALL_SPLICE is undefined. The compiled out function skb_splice_bits
is transparently mocked out with a static inline. The greater patch set removes
userspace splice support so it cannot be called anyway.
Signed-off-by: Pieter Smith <[email protected]>
---
include/linux/skbuff.h | 9 +++++++++
net/core/skbuff.c | 9 ++++++---
2 files changed, 15 insertions(+), 3 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index a59d934..54a50c1 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2640,9 +2640,18 @@ int skb_copy_bits(const struct sk_buff *skb, int offset, void *to, int len);
int skb_store_bits(struct sk_buff *skb, int offset, const void *from, int len);
__wsum skb_copy_and_csum_bits(const struct sk_buff *skb, int offset, u8 *to,
int len, __wsum csum);
+#ifdef CONFIG_SYSCALL_SPLICE
int skb_splice_bits(struct sk_buff *skb, unsigned int offset,
struct pipe_inode_info *pipe, unsigned int len,
unsigned int flags);
+#else
+static inline int skb_splice_bits(struct sk_buff *skb, unsigned int offset,
+ struct pipe_inode_info *pipe, unsigned int len,
+ unsigned int flags)
+{
+ return -EPERM;
+}
+#endif
void skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to);
unsigned int skb_zerocopy_headlen(const struct sk_buff *from);
int skb_zerocopy(struct sk_buff *to, struct sk_buff *from,
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 61059a0..74fad8a 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1781,9 +1781,9 @@ static bool __splice_segment(struct page *page, unsigned int poff,
* Map linear and fragment data from the skb to spd. It reports true if the
* pipe is full or if we already spliced the requested length.
*/
-static bool __skb_splice_bits(struct sk_buff *skb, struct pipe_inode_info *pipe,
- unsigned int *offset, unsigned int *len,
- struct splice_pipe_desc *spd, struct sock *sk)
+static bool __maybe_unused __skb_splice_bits(struct sk_buff *skb, struct pipe_inode_info *pipe,
+ unsigned int *offset, unsigned int *len,
+ struct splice_pipe_desc *spd, struct sock *sk)
{
int seg;
@@ -1821,6 +1821,7 @@ static bool __skb_splice_bits(struct sk_buff *skb, struct pipe_inode_info *pipe,
* the frag list, if such a thing exists. We'd probably need to recurse to
* handle that cleanly.
*/
+#ifdef CONFIG_SYSCALL_SPLICE
int skb_splice_bits(struct sk_buff *skb, unsigned int offset,
struct pipe_inode_info *pipe, unsigned int tlen,
unsigned int flags)
@@ -1876,6 +1877,8 @@ done:
return ret;
}
+#endif /* #ifdef CONFIG_SYSCALL_SPLICE */
+
/**
* skb_store_bits - store bits from kernel buffer to skb
--
2.1.0
Entirely compile out splice translation unit when the system is configured
without splice family of syscalls (i.e. CONFIG_SYSCALL_SPLICE is undefined).
Exported fs/splice functions are transparently mocked out with static inlines.
Because userspace support for splice has already been removed by this
patch-set, the exported functions cannot be called anyway. Mocking them out
prevents a maintenance burden on file system drivers.
The bloat score resulting from this patch given a tinyconfig is:
add/remove: 0/25 grow/shrink: 0/5 up/down: 0/-4845 (-4845)
function old new delta
pipe_to_null 4 - -4
generic_pipe_buf_nosteal 6 - -6
spd_release_page 10 - -10
PageUptodate 22 11 -11
lock_page 36 24 -12
page_cache_pipe_buf_release 16 - -16
splice_write_null 24 4 -20
page_cache_pipe_buf_ops 20 - -20
nosteal_pipe_buf_ops 20 - -20
default_pipe_buf_ops 20 - -20
generic_splice_sendpage 24 - -24
splice_shrink_spd 27 - -27
direct_splice_actor 47 - -47
default_file_splice_write 49 - -49
wakeup_pipe_writers 54 - -54
write_pipe_buf 71 - -71
page_cache_pipe_buf_confirm 80 - -80
splice_grow_spd 87 - -87
splice_from_pipe 93 - -93
splice_from_pipe_next 106 - -106
pipe_to_sendpage 109 - -109
page_cache_pipe_buf_steal 114 - -114
generic_file_splice_read 131 8 -123
do_splice_direct 148 - -148
__splice_from_pipe 246 - -246
splice_direct_to_actor 416 - -416
splice_to_pipe 417 - -417
default_file_splice_read 688 - -688
iter_file_splice_write 702 4 -698
__generic_file_splice_read 1109 - -1109
The bloat score for the entire CONFIG_SYSCALL_SPLICE patch-set is:
add/remove: 0/41 grow/shrink: 5/7 up/down: 23/-8422 (-8399)
function old new delta
sys_pwritev 115 122 +7
sys_preadv 115 122 +7
fdput_pos 29 36 +7
sys_pwrite64 115 116 +1
sys_pread64 115 116 +1
pipe_to_null 4 - -4
generic_pipe_buf_nosteal 6 - -6
spd_release_page 10 - -10
fdput 11 - -11
PageUptodate 22 11 -11
lock_page 36 24 -12
signal_pending 39 26 -13
fdget 56 42 -14
page_cache_pipe_buf_release 16 - -16
user_page_pipe_buf_ops 20 - -20
splice_write_null 24 4 -20
page_cache_pipe_buf_ops 20 - -20
nosteal_pipe_buf_ops 20 - -20
default_pipe_buf_ops 20 - -20
generic_splice_sendpage 24 - -24
user_page_pipe_buf_steal 25 - -25
splice_shrink_spd 27 - -27
pipe_to_user 43 - -43
direct_splice_actor 47 - -47
default_file_splice_write 49 - -49
wakeup_pipe_writers 54 - -54
wakeup_pipe_readers 54 - -54
write_pipe_buf 71 - -71
page_cache_pipe_buf_confirm 80 - -80
splice_grow_spd 87 - -87
do_splice_to 87 - -87
ipipe_prep.part 92 - -92
splice_from_pipe 93 - -93
splice_from_pipe_next 107 - -107
pipe_to_sendpage 109 - -109
page_cache_pipe_buf_steal 114 - -114
opipe_prep.part 119 - -119
sys_sendfile 122 - -122
generic_file_splice_read 131 8 -123
sys_sendfile64 126 - -126
sys_vmsplice 137 - -137
do_splice_direct 148 - -148
vmsplice_to_user 205 - -205
__splice_from_pipe 246 - -246
splice_direct_to_actor 348 - -348
splice_to_pipe 371 - -371
do_sendfile 492 - -492
sys_tee 497 - -497
vmsplice_to_pipe 558 - -558
default_file_splice_read 688 - -688
iter_file_splice_write 702 4 -698
sys_splice 1075 - -1075
__generic_file_splice_read 1109 - -1109
Signed-off-by: Pieter Smith <[email protected]>
---
fs/Makefile | 3 ++-
fs/splice.c | 2 --
include/linux/fs.h | 26 ++++++++++++++++++++++++++
include/linux/splice.h | 42 ++++++++++++++++++++++++++++++++++++++++++
4 files changed, 70 insertions(+), 3 deletions(-)
diff --git a/fs/Makefile b/fs/Makefile
index fb7646e..9395622 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -10,7 +10,7 @@ obj-y := open.o read_write.o file_table.o super.o \
ioctl.o readdir.o select.o dcache.o inode.o \
attr.o bad_inode.o file.o filesystems.o namespace.o \
seq_file.o xattr.o libfs.o fs-writeback.o \
- pnode.o splice.o sync.o utimes.o \
+ pnode.o sync.o utimes.o \
stack.o fs_struct.o statfs.o fs_pin.o
ifeq ($(CONFIG_BLOCK),y)
@@ -22,6 +22,7 @@ endif
obj-$(CONFIG_PROC_FS) += proc_namespace.o
obj-$(CONFIG_FSNOTIFY) += notify/
+obj-$(CONFIG_SYSCALL_SPLICE) += splice.o
obj-$(CONFIG_EPOLL) += eventpoll.o
obj-$(CONFIG_ANON_INODES) += anon_inodes.o
obj-$(CONFIG_SIGNALFD) += signalfd.o
diff --git a/fs/splice.c b/fs/splice.c
index 7c4c695..44b201b 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1316,7 +1316,6 @@ long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
return ret;
}
-#ifdef CONFIG_SYSCALL_SPLICE
static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
struct pipe_inode_info *opipe,
size_t len, unsigned int flags);
@@ -2201,5 +2200,4 @@ COMPAT_SYSCALL_DEFINE4(sendfile64, int, out_fd, int, in_fd,
return do_sendfile(out_fd, in_fd, NULL, count, 0);
}
#endif
-#endif
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 04c0975..9b3054e 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2449,6 +2449,7 @@ extern void block_sync_page(struct page *page);
#define __splice_p(x) NULL
#endif
+#ifdef CONFIG_SYSCALL_SPLICE
/* fs/splice.c */
extern ssize_t generic_file_splice_read(struct file *, loff_t *,
struct pipe_inode_info *, size_t, unsigned int);
@@ -2458,6 +2459,31 @@ extern ssize_t iter_file_splice_write(struct pipe_inode_info *,
struct file *, loff_t *, size_t, unsigned int);
extern ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe,
struct file *out, loff_t *, size_t len, unsigned int flags);
+#else
+static inline ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
+ struct pipe_inode_info *pipe, size_t len, unsigned int flags)
+{
+ return -EPERM;
+}
+
+static inline ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
+ struct pipe_inode_info *pipe, size_t len, unsigned int flags)
+{
+ return -EPERM;
+}
+
+static inline ssize_t iter_file_splice_write(struct pipe_inode_info *pipe,
+ struct file *out, loff_t *ppos, size_t len, unsigned int flags)
+{
+ return -EPERM;
+}
+
+static inline ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe,
+ struct file *out, loff_t *ppos, size_t len, unsigned int flags)
+{
+ return -EPERM;
+}
+#endif
extern void
file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping);
diff --git a/include/linux/splice.h b/include/linux/splice.h
index da2751d..5097a79 100644
--- a/include/linux/splice.h
+++ b/include/linux/splice.h
@@ -65,6 +65,7 @@ typedef int (splice_actor)(struct pipe_inode_info *, struct pipe_buffer *,
typedef int (splice_direct_actor)(struct pipe_inode_info *,
struct splice_desc *);
+#ifdef CONFIG_SYSCALL_SPLICE
extern ssize_t splice_from_pipe(struct pipe_inode_info *, struct file *,
loff_t *, size_t, unsigned int,
splice_actor *);
@@ -74,13 +75,54 @@ extern ssize_t splice_to_pipe(struct pipe_inode_info *,
struct splice_pipe_desc *);
extern ssize_t splice_direct_to_actor(struct file *, struct splice_desc *,
splice_direct_actor *);
+#else /* #ifdef CONFIG_SYSCALL_SPLICE */
+static inline 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)
+{
+ return -EPERM;
+}
+
+static inline ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
+ splice_actor *actor)
+{
+ return -EPERM;
+}
+
+static inline ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
+ struct splice_pipe_desc *spd)
+{
+ return -EPERM;
+}
+
+static inline ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
+ splice_direct_actor *actor)
+{
+ return -EPERM;
+}
+#endif /* #ifdef CONFIG_SYSCALL_SPLICE */
/*
* for dynamic pipe sizing
*/
+#ifdef CONFIG_SYSCALL_SPLICE
extern int splice_grow_spd(const struct pipe_inode_info *, struct splice_pipe_desc *);
extern void splice_shrink_spd(struct splice_pipe_desc *);
extern void spd_release_page(struct splice_pipe_desc *, unsigned int);
+#else /* #ifdef CONFIG_SYSCALL_SPLICE */
+static inline int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
+{
+ return -EPERM;
+}
+
+static inline void splice_shrink_spd(struct splice_pipe_desc *spd)
+{
+}
+
+static inline void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
+{
+}
+#endif /* #ifdef CONFIG_SYSCALL_SPLICE */
extern const struct pipe_buf_operations page_cache_pipe_buf_ops;
#endif
--
2.1.0
Truly removing sendfile/sendpage means that you can't even compile NFS
into the tree.
I cannot take this patch series seriously, sorry.
On Sun, Nov 23, 2014 at 01:46:23PM -0500, David Miller wrote:
> Truly removing sendfile/sendpage means that you can't even compile NFS
> into the tree.
If you mean the in-kernel nfsd (CONFIG_NFSD), that already has a large
stack of "select" and "depends on", both directly and indirectly; adding
a "select SPLICE_SYSCALL" to it seems fine. (That select does need
adding, though. Pieter, you need to test-compile more than just
tinyconfig and defconfig. Try an allyesconfig with *just* splice turned
off, and make sure that compiles.)
Given the requirements of running a file server in the kernel, I'd
expect CONFIG_NFSD to end up with several more selects of optional
functionality in the future. It seems rather likely that the average
embedded system will be compiling out NFS. :)
Also, this patch series compiles out splice and sendfile, including
several *users* of sendpage; it doesn't compile out the sendpage
support/infrastructure itself.
- Josh Triplett
On Sun, Nov 23, 2014 at 11:43:26AM -0800, Josh Triplett wrote:
> On Sun, Nov 23, 2014 at 01:46:23PM -0500, David Miller wrote:
> > Truly removing sendfile/sendpage means that you can't even compile NFS
> > into the tree.
>
> If you mean the in-kernel nfsd (CONFIG_NFSD), that already has a large
> stack of "select" and "depends on", both directly and indirectly; adding
> a "select SPLICE_SYSCALL" to it seems fine. (That select does need
> adding, though. Pieter, you need to test-compile more than just
> tinyconfig and defconfig. Try an allyesconfig with *just* splice turned
> off, and make sure that compiles.)
Did exacly that. Took forever on my hardware, but no problems.
> Given the requirements of running a file server in the kernel, I'd
> expect CONFIG_NFSD to end up with several more selects of optional
> functionality in the future. It seems rather likely that the average
> embedded system will be compiling out NFS. :)
>
> Also, this patch series compiles out splice and sendfile, including
> several *users* of sendpage; it doesn't compile out the sendpage
> support/infrastructure itself.
>
> - Josh Triplett
On Sun, Nov 23, 2014 at 3:20 PM, Pieter Smith <[email protected]> wrote:
> To implement splice support, fs/fuse makes use of nosteal_pipe_buf_ops. This
> struct is exported by fs/splice. The goal of the larger patch set is to
> completely compile out fs/splice, so uses of the exported struct need to be
> compiled out along with fs/splice.
>
> This patch therefore compiles out splice support in fs/fuse when
> CONFIG_SYSCALL_SPLICE is undefined.
>
> Signed-off-by: Pieter Smith <[email protected]>
> ---
> fs/fuse/dev.c | 4 ++--
> include/linux/fs.h | 6 ++++++
> 2 files changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index ca88731..f8f92a4 100644
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -1291,7 +1291,7 @@ static ssize_t fuse_dev_read(struct kiocb *iocb, const struct iovec *iov,
> return fuse_dev_do_read(fc, file, &cs, iov_length(iov, nr_segs));
> }
>
> -static ssize_t fuse_dev_splice_read(struct file *in, loff_t *ppos,
> +static ssize_t __maybe_unused fuse_dev_splice_read(struct file *in, loff_t *ppos,
> struct pipe_inode_info *pipe,
> size_t len, unsigned int flags)
> {
> @@ -2144,7 +2144,7 @@ const struct file_operations fuse_dev_operations = {
> .llseek = no_llseek,
> .read = do_sync_read,
> .aio_read = fuse_dev_read,
> - .splice_read = fuse_dev_splice_read,
> + .splice_read = __splice_p(fuse_dev_splice_read),
> .write = do_sync_write,
> .aio_write = fuse_dev_write,
> .splice_write = fuse_dev_splice_write,
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index a957d43..04c0975 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2443,6 +2443,12 @@ extern int blkdev_fsync(struct file *filp, loff_t start, loff_t end,
> int datasync);
> extern void block_sync_page(struct page *page);
>
> +#ifdef CONFIG_SYSCALL_SPLICE
> +#define __splice_p(x) x
> +#else
> +#define __splice_p(x) NULL
> +#endif
> +
This needs to go into a different patch.
One logical change per patch please. :-)
--
Thanks,
//richard
On Sun, Nov 23, 2014 at 11:29:08PM +0100, Richard Weinberger wrote:
> On Sun, Nov 23, 2014 at 3:20 PM, Pieter Smith <[email protected]> wrote:
> > To implement splice support, fs/fuse makes use of nosteal_pipe_buf_ops. This
> > struct is exported by fs/splice. The goal of the larger patch set is to
> > completely compile out fs/splice, so uses of the exported struct need to be
> > compiled out along with fs/splice.
> >
> > This patch therefore compiles out splice support in fs/fuse when
> > CONFIG_SYSCALL_SPLICE is undefined.
> >
> > Signed-off-by: Pieter Smith <[email protected]>
> > ---
> > fs/fuse/dev.c | 4 ++--
> > include/linux/fs.h | 6 ++++++
> > 2 files changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> > index ca88731..f8f92a4 100644
> > --- a/fs/fuse/dev.c
> > +++ b/fs/fuse/dev.c
> > @@ -1291,7 +1291,7 @@ static ssize_t fuse_dev_read(struct kiocb *iocb, const struct iovec *iov,
> > return fuse_dev_do_read(fc, file, &cs, iov_length(iov, nr_segs));
> > }
> >
> > -static ssize_t fuse_dev_splice_read(struct file *in, loff_t *ppos,
> > +static ssize_t __maybe_unused fuse_dev_splice_read(struct file *in, loff_t *ppos,
> > struct pipe_inode_info *pipe,
> > size_t len, unsigned int flags)
> > {
> > @@ -2144,7 +2144,7 @@ const struct file_operations fuse_dev_operations = {
> > .llseek = no_llseek,
> > .read = do_sync_read,
> > .aio_read = fuse_dev_read,
> > - .splice_read = fuse_dev_splice_read,
> > + .splice_read = __splice_p(fuse_dev_splice_read),
> > .write = do_sync_write,
> > .aio_write = fuse_dev_write,
> > .splice_write = fuse_dev_splice_write,
> > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > index a957d43..04c0975 100644
> > --- a/include/linux/fs.h
> > +++ b/include/linux/fs.h
> > @@ -2443,6 +2443,12 @@ extern int blkdev_fsync(struct file *filp, loff_t start, loff_t end,
> > int datasync);
> > extern void block_sync_page(struct page *page);
> >
> > +#ifdef CONFIG_SYSCALL_SPLICE
> > +#define __splice_p(x) x
> > +#else
> > +#define __splice_p(x) NULL
> > +#endif
> > +
>
> This needs to go into a different patch.
> One logical change per patch please. :-)
Easy enough to merge this one into the patch introducing
CONFIG_SYSCALL_SPLICE, then.
- Josh Triplett
On Sun, Nov 23, 2014 at 09:30:40PM +0100, Pieter Smith wrote:
> On Sun, Nov 23, 2014 at 11:43:26AM -0800, Josh Triplett wrote:
> > On Sun, Nov 23, 2014 at 01:46:23PM -0500, David Miller wrote:
> > > Truly removing sendfile/sendpage means that you can't even compile NFS
> > > into the tree.
> >
> > If you mean the in-kernel nfsd (CONFIG_NFSD), that already has a large
> > stack of "select" and "depends on", both directly and indirectly; adding
> > a "select SPLICE_SYSCALL" to it seems fine. (That select does need
> > adding, though. Pieter, you need to test-compile more than just
> > tinyconfig and defconfig. Try an allyesconfig with *just* splice turned
> > off, and make sure that compiles.)
>
> Did exacly that. Took forever on my hardware, but no problems.
Ah, I see. Looking more closely at nfsd, it looks like it already has a
code path for filesystems that don't do splice. I think, rather than
making nfsd select SPLICE_SYSCALL, that it would suffice to change the
"rqstp->rq_splice_ok = true;" in svc_process_common (net/sunrpc/svc.c)
to:
rqstp->rq_splice_ok = IS_ENABLED(CONFIG_SPLICE_SYSCALL);
Then nfsd should simply *always* fall back to its non-splice support.
That said, given that it seems exceedingly unlikely that anyone would
use the in-kernel nfsd on a system trying to minimize kernel size, it
still seems cleaner to just "select SPLICE_SYSCALL" from NFSD in
Kconfig. That avoids making any changes at all to the nfsd source in
this patch series.
- Josh Triplett
On Sun, 23 Nov 2014 15:36:37 -0800
Josh Triplett <[email protected]> wrote:
> On Sun, Nov 23, 2014 at 09:30:40PM +0100, Pieter Smith wrote:
> > On Sun, Nov 23, 2014 at 11:43:26AM -0800, Josh Triplett wrote:
> > > On Sun, Nov 23, 2014 at 01:46:23PM -0500, David Miller wrote:
> > > > Truly removing sendfile/sendpage means that you can't even compile NFS
> > > > into the tree.
> > >
> > > If you mean the in-kernel nfsd (CONFIG_NFSD), that already has a large
> > > stack of "select" and "depends on", both directly and indirectly; adding
> > > a "select SPLICE_SYSCALL" to it seems fine. (That select does need
> > > adding, though. Pieter, you need to test-compile more than just
> > > tinyconfig and defconfig. Try an allyesconfig with *just* splice turned
> > > off, and make sure that compiles.)
> >
> > Did exacly that. Took forever on my hardware, but no problems.
>
> Ah, I see. Looking more closely at nfsd, it looks like it already has a
> code path for filesystems that don't do splice. I think, rather than
> making nfsd select SPLICE_SYSCALL, that it would suffice to change the
> "rqstp->rq_splice_ok = true;" in svc_process_common (net/sunrpc/svc.c)
> to:
>
> rqstp->rq_splice_ok = IS_ENABLED(CONFIG_SPLICE_SYSCALL);
>
> Then nfsd should simply *always* fall back to its non-splice support.
>
I'd probably prefer the above, actually. We have to keep supporting
non-splice enabled fs' for the forseeable future, so we may as well
allow people to run nfsd in such configurations. It could even be
useful for testing the non-splice-enabled codepaths.
> That said, given that it seems exceedingly unlikely that anyone would
> use the in-kernel nfsd on a system trying to minimize kernel size, it
> still seems cleaner to just "select SPLICE_SYSCALL" from NFSD in
> Kconfig. That avoids making any changes at all to the nfsd source in
> this patch series.
>
--
Jeff Layton <[email protected]>
On Sun, Nov 23, 2014 at 07:28:10PM -0500, Jeff Layton wrote:
> On Sun, 23 Nov 2014 15:36:37 -0800
> Josh Triplett <[email protected]> wrote:
>
> > On Sun, Nov 23, 2014 at 09:30:40PM +0100, Pieter Smith wrote:
> > > On Sun, Nov 23, 2014 at 11:43:26AM -0800, Josh Triplett wrote:
> > > > On Sun, Nov 23, 2014 at 01:46:23PM -0500, David Miller wrote:
> > > > > Truly removing sendfile/sendpage means that you can't even compile NFS
> > > > > into the tree.
> > > >
> > > > If you mean the in-kernel nfsd (CONFIG_NFSD), that already has a large
> > > > stack of "select" and "depends on", both directly and indirectly; adding
> > > > a "select SPLICE_SYSCALL" to it seems fine. (That select does need
> > > > adding, though. Pieter, you need to test-compile more than just
> > > > tinyconfig and defconfig. Try an allyesconfig with *just* splice turned
> > > > off, and make sure that compiles.)
> > >
> > > Did exacly that. Took forever on my hardware, but no problems.
> >
> > Ah, I see. Looking more closely at nfsd, it looks like it already has a
> > code path for filesystems that don't do splice. I think, rather than
> > making nfsd select SPLICE_SYSCALL, that it would suffice to change the
> > "rqstp->rq_splice_ok = true;" in svc_process_common (net/sunrpc/svc.c)
> > to:
> >
> > rqstp->rq_splice_ok = IS_ENABLED(CONFIG_SPLICE_SYSCALL);
> >
> > Then nfsd should simply *always* fall back to its non-splice support.
> >
>
> I'd probably prefer the above, actually. We have to keep supporting
> non-splice enabled fs' for the forseeable future, so we may as well
> allow people to run nfsd in such configurations. It could even be
> useful for testing the non-splice-enabled codepaths.
Good point!
- Josh Triplett
On Mon, Nov 24, 2014 at 12:36 AM, Josh Triplett <[email protected]> wrote:
> On Sun, Nov 23, 2014 at 09:30:40PM +0100, Pieter Smith wrote:
>> On Sun, Nov 23, 2014 at 11:43:26AM -0800, Josh Triplett wrote:
>> > On Sun, Nov 23, 2014 at 01:46:23PM -0500, David Miller wrote:
>> > > Truly removing sendfile/sendpage means that you can't even compile NFS
>> > > into the tree.
>> >
>> > If you mean the in-kernel nfsd (CONFIG_NFSD), that already has a large
>> > stack of "select" and "depends on", both directly and indirectly; adding
>> > a "select SPLICE_SYSCALL" to it seems fine. (That select does need
>> > adding, though. Pieter, you need to test-compile more than just
>> > tinyconfig and defconfig. Try an allyesconfig with *just* splice turned
>> > off, and make sure that compiles.)
>>
>> Did exacly that. Took forever on my hardware, but no problems.
>
> Ah, I see. Looking more closely at nfsd, it looks like it already has a
> code path for filesystems that don't do splice. I think, rather than
> making nfsd select SPLICE_SYSCALL, that it would suffice to change the
> "rqstp->rq_splice_ok = true;" in svc_process_common (net/sunrpc/svc.c)
> to:
>
> rqstp->rq_splice_ok = IS_ENABLED(CONFIG_SPLICE_SYSCALL);
>
> Then nfsd should simply *always* fall back to its non-splice support.
Hence I suggest adding to the nfsd help text:
While nfsd works without SPLICE_SYSCALL, you may want to enable
SPLICE_SYSCALL for <...> (performance?) reasons.
(Hmm, does Kconfig need a "suggests", cfr. Debian package dependencies?)
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
On Mon, Nov 24, 2014 at 09:38:20AM +0100, Geert Uytterhoeven wrote:
> On Mon, Nov 24, 2014 at 12:36 AM, Josh Triplett <[email protected]> wrote:
> > On Sun, Nov 23, 2014 at 09:30:40PM +0100, Pieter Smith wrote:
> >> On Sun, Nov 23, 2014 at 11:43:26AM -0800, Josh Triplett wrote:
> >> > On Sun, Nov 23, 2014 at 01:46:23PM -0500, David Miller wrote:
> >> > > Truly removing sendfile/sendpage means that you can't even compile NFS
> >> > > into the tree.
> >> >
> >> > If you mean the in-kernel nfsd (CONFIG_NFSD), that already has a large
> >> > stack of "select" and "depends on", both directly and indirectly; adding
> >> > a "select SPLICE_SYSCALL" to it seems fine. (That select does need
> >> > adding, though. Pieter, you need to test-compile more than just
> >> > tinyconfig and defconfig. Try an allyesconfig with *just* splice turned
> >> > off, and make sure that compiles.)
> >>
> >> Did exacly that. Took forever on my hardware, but no problems.
> >
> > Ah, I see. Looking more closely at nfsd, it looks like it already has a
> > code path for filesystems that don't do splice. I think, rather than
> > making nfsd select SPLICE_SYSCALL, that it would suffice to change the
> > "rqstp->rq_splice_ok = true;" in svc_process_common (net/sunrpc/svc.c)
> > to:
> >
> > rqstp->rq_splice_ok = IS_ENABLED(CONFIG_SPLICE_SYSCALL);
> >
> > Then nfsd should simply *always* fall back to its non-splice support.
>
> Hence I suggest adding to the nfsd help text:
>
> While nfsd works without SPLICE_SYSCALL, you may want to enable
> SPLICE_SYSCALL for <...> (performance?) reasons.
It already seems sufficiently unlikely to enable NFSD while disabling
SPLICE_SYSCALL (in the latter case, turning on EXPERT to do so). It
doesn't seem worth adding such a note to NFSD. At most, I'd say that
NFSD might want a note somewhere in its documentation saying that it
takes advantage of filesystems with splice support if serving files from
one, and if running on a kernel that has splice.
> (Hmm, does Kconfig need a "suggests", cfr. Debian package dependencies?)
Perhaps, though that seems much lower priority than, for instance,
transitive "select".
- Josh Triplett
On Sun, Nov 23, 2014 at 03:23:02PM -0800, Josh Triplett wrote:
> On Sun, Nov 23, 2014 at 11:29:08PM +0100, Richard Weinberger wrote:
> > On Sun, Nov 23, 2014 at 3:20 PM, Pieter Smith <[email protected]> wrote:
> > > To implement splice support, fs/fuse makes use of nosteal_pipe_buf_ops. This
> > > struct is exported by fs/splice. The goal of the larger patch set is to
> > > completely compile out fs/splice, so uses of the exported struct need to be
> > > compiled out along with fs/splice.
> > >
> > > This patch therefore compiles out splice support in fs/fuse when
> > > CONFIG_SYSCALL_SPLICE is undefined.
> > >
> > > Signed-off-by: Pieter Smith <[email protected]>
> > > ---
> > > fs/fuse/dev.c | 4 ++--
> > > include/linux/fs.h | 6 ++++++
> > > 2 files changed, 8 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> > > index ca88731..f8f92a4 100644
> > > --- a/fs/fuse/dev.c
> > > +++ b/fs/fuse/dev.c
> > > @@ -1291,7 +1291,7 @@ static ssize_t fuse_dev_read(struct kiocb *iocb, const struct iovec *iov,
> > > return fuse_dev_do_read(fc, file, &cs, iov_length(iov, nr_segs));
> > > }
> > >
> > > -static ssize_t fuse_dev_splice_read(struct file *in, loff_t *ppos,
> > > +static ssize_t __maybe_unused fuse_dev_splice_read(struct file *in, loff_t *ppos,
> > > struct pipe_inode_info *pipe,
> > > size_t len, unsigned int flags)
> > > {
> > > @@ -2144,7 +2144,7 @@ const struct file_operations fuse_dev_operations = {
> > > .llseek = no_llseek,
> > > .read = do_sync_read,
> > > .aio_read = fuse_dev_read,
> > > - .splice_read = fuse_dev_splice_read,
> > > + .splice_read = __splice_p(fuse_dev_splice_read),
> > > .write = do_sync_write,
> > > .aio_write = fuse_dev_write,
> > > .splice_write = fuse_dev_splice_write,
> > > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > > index a957d43..04c0975 100644
> > > --- a/include/linux/fs.h
> > > +++ b/include/linux/fs.h
> > > @@ -2443,6 +2443,12 @@ extern int blkdev_fsync(struct file *filp, loff_t start, loff_t end,
> > > int datasync);
> > > extern void block_sync_page(struct page *page);
> > >
> > > +#ifdef CONFIG_SYSCALL_SPLICE
> > > +#define __splice_p(x) x
> > > +#else
> > > +#define __splice_p(x) NULL
> > > +#endif
> > > +
> >
> > This needs to go into a different patch.
> > One logical change per patch please. :-)
>
> Easy enough to merge this one into the patch introducing
> CONFIG_SYSCALL_SPLICE, then.
>
> - Josh Triplett
The patch introducing CONFIG_SYSCALL_SPLICE (PATCH 3) only compiles out the
syscalls. PATCH 6 on the other hand, compiles out fs/splice.c. This patch
allows fs/fuse to be compiled when fs/splice.c is compiled out. If I am to
squash it, it would be logical to include it in PATCH 6, not 3.
Is this agreeable?
PATCH 5 does the same as this one for net/core. Should I still keep PATCH 5
separate from a maintainership perspective?
- Pieter Smith
On Sun, Nov 23, 2014 at 04:32:51PM -0800, Josh Triplett wrote:
> On Sun, Nov 23, 2014 at 07:28:10PM -0500, Jeff Layton wrote:
> > On Sun, 23 Nov 2014 15:36:37 -0800
> > Josh Triplett <[email protected]> wrote:
> >
> > > On Sun, Nov 23, 2014 at 09:30:40PM +0100, Pieter Smith wrote:
> > > > On Sun, Nov 23, 2014 at 11:43:26AM -0800, Josh Triplett wrote:
> > > > > On Sun, Nov 23, 2014 at 01:46:23PM -0500, David Miller wrote:
> > > > > > Truly removing sendfile/sendpage means that you can't even compile NFS
> > > > > > into the tree.
> > > > >
> > > > > If you mean the in-kernel nfsd (CONFIG_NFSD), that already has a large
> > > > > stack of "select" and "depends on", both directly and indirectly; adding
> > > > > a "select SPLICE_SYSCALL" to it seems fine. (That select does need
> > > > > adding, though. Pieter, you need to test-compile more than just
> > > > > tinyconfig and defconfig. Try an allyesconfig with *just* splice turned
> > > > > off, and make sure that compiles.)
> > > >
> > > > Did exacly that. Took forever on my hardware, but no problems.
> > >
> > > Ah, I see. Looking more closely at nfsd, it looks like it already has a
> > > code path for filesystems that don't do splice. I think, rather than
> > > making nfsd select SPLICE_SYSCALL, that it would suffice to change the
> > > "rqstp->rq_splice_ok = true;" in svc_process_common (net/sunrpc/svc.c)
> > > to:
> > >
> > > rqstp->rq_splice_ok = IS_ENABLED(CONFIG_SPLICE_SYSCALL);
> > >
> > > Then nfsd should simply *always* fall back to its non-splice support.
> > >
> >
> > I'd probably prefer the above, actually. We have to keep supporting
> > non-splice enabled fs' for the forseeable future, so we may as well
> > allow people to run nfsd in such configurations. It could even be
> > useful for testing the non-splice-enabled codepaths.
>
> Good point!
>
> - Josh Triplett
I'll add this to svc_process_common. I can squash this into PATCH 3, which is
where the syscalls can be compiled out. The log entry may however get a little
crowded and multi-functional.
Should I keep this as a separate patch?
On Mon, Nov 24, 2014 at 11:01:38AM +0100, Pieter Smith wrote:
> On Sun, Nov 23, 2014 at 04:32:51PM -0800, Josh Triplett wrote:
> > On Sun, Nov 23, 2014 at 07:28:10PM -0500, Jeff Layton wrote:
> > > On Sun, 23 Nov 2014 15:36:37 -0800
> > > Josh Triplett <[email protected]> wrote:
> > >
> > > > On Sun, Nov 23, 2014 at 09:30:40PM +0100, Pieter Smith wrote:
> > > > > On Sun, Nov 23, 2014 at 11:43:26AM -0800, Josh Triplett wrote:
> > > > > > On Sun, Nov 23, 2014 at 01:46:23PM -0500, David Miller wrote:
> > > > > > > Truly removing sendfile/sendpage means that you can't even compile NFS
> > > > > > > into the tree.
> > > > > >
> > > > > > If you mean the in-kernel nfsd (CONFIG_NFSD), that already has a large
> > > > > > stack of "select" and "depends on", both directly and indirectly; adding
> > > > > > a "select SPLICE_SYSCALL" to it seems fine. (That select does need
> > > > > > adding, though. Pieter, you need to test-compile more than just
> > > > > > tinyconfig and defconfig. Try an allyesconfig with *just* splice turned
> > > > > > off, and make sure that compiles.)
> > > > >
> > > > > Did exacly that. Took forever on my hardware, but no problems.
> > > >
> > > > Ah, I see. Looking more closely at nfsd, it looks like it already has a
> > > > code path for filesystems that don't do splice. I think, rather than
> > > > making nfsd select SPLICE_SYSCALL, that it would suffice to change the
> > > > "rqstp->rq_splice_ok = true;" in svc_process_common (net/sunrpc/svc.c)
> > > > to:
> > > >
> > > > rqstp->rq_splice_ok = IS_ENABLED(CONFIG_SPLICE_SYSCALL);
> > > >
> > > > Then nfsd should simply *always* fall back to its non-splice support.
> > > >
> > >
> > > I'd probably prefer the above, actually. We have to keep supporting
> > > non-splice enabled fs' for the forseeable future, so we may as well
> > > allow people to run nfsd in such configurations. It could even be
> > > useful for testing the non-splice-enabled codepaths.
> >
> > Good point!
> >
> > - Josh Triplett
>
> I'll add this to svc_process_common. I can squash this into PATCH 3, which is
> where the syscalls can be compiled out. The log entry may however get a little
> crowded and multi-functional.
>
> Should I keep this as a separate patch?
I'd keep it as a separate patch, yes. It doesn't become necessary until
patch 6, so you can add it as a new patch between patches 3 and 6.
- Josh Triplett
On Mon, Nov 24, 2014 at 10:49:31AM +0100, Pieter Smith wrote:
> On Sun, Nov 23, 2014 at 03:23:02PM -0800, Josh Triplett wrote:
> > On Sun, Nov 23, 2014 at 11:29:08PM +0100, Richard Weinberger wrote:
> > > On Sun, Nov 23, 2014 at 3:20 PM, Pieter Smith <[email protected]> wrote:
> > > > To implement splice support, fs/fuse makes use of nosteal_pipe_buf_ops. This
> > > > struct is exported by fs/splice. The goal of the larger patch set is to
> > > > completely compile out fs/splice, so uses of the exported struct need to be
> > > > compiled out along with fs/splice.
> > > >
> > > > This patch therefore compiles out splice support in fs/fuse when
> > > > CONFIG_SYSCALL_SPLICE is undefined.
> > > >
> > > > Signed-off-by: Pieter Smith <[email protected]>
> > > > ---
> > > > fs/fuse/dev.c | 4 ++--
> > > > include/linux/fs.h | 6 ++++++
> > > > 2 files changed, 8 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> > > > index ca88731..f8f92a4 100644
> > > > --- a/fs/fuse/dev.c
> > > > +++ b/fs/fuse/dev.c
> > > > @@ -1291,7 +1291,7 @@ static ssize_t fuse_dev_read(struct kiocb *iocb, const struct iovec *iov,
> > > > return fuse_dev_do_read(fc, file, &cs, iov_length(iov, nr_segs));
> > > > }
> > > >
> > > > -static ssize_t fuse_dev_splice_read(struct file *in, loff_t *ppos,
> > > > +static ssize_t __maybe_unused fuse_dev_splice_read(struct file *in, loff_t *ppos,
> > > > struct pipe_inode_info *pipe,
> > > > size_t len, unsigned int flags)
> > > > {
> > > > @@ -2144,7 +2144,7 @@ const struct file_operations fuse_dev_operations = {
> > > > .llseek = no_llseek,
> > > > .read = do_sync_read,
> > > > .aio_read = fuse_dev_read,
> > > > - .splice_read = fuse_dev_splice_read,
> > > > + .splice_read = __splice_p(fuse_dev_splice_read),
> > > > .write = do_sync_write,
> > > > .aio_write = fuse_dev_write,
> > > > .splice_write = fuse_dev_splice_write,
> > > > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > > > index a957d43..04c0975 100644
> > > > --- a/include/linux/fs.h
> > > > +++ b/include/linux/fs.h
> > > > @@ -2443,6 +2443,12 @@ extern int blkdev_fsync(struct file *filp, loff_t start, loff_t end,
> > > > int datasync);
> > > > extern void block_sync_page(struct page *page);
> > > >
> > > > +#ifdef CONFIG_SYSCALL_SPLICE
> > > > +#define __splice_p(x) x
> > > > +#else
> > > > +#define __splice_p(x) NULL
> > > > +#endif
> > > > +
> > >
> > > This needs to go into a different patch.
> > > One logical change per patch please. :-)
> >
> > Easy enough to merge this one into the patch introducing
> > CONFIG_SYSCALL_SPLICE, then.
> >
> > - Josh Triplett
>
> The patch introducing CONFIG_SYSCALL_SPLICE (PATCH 3) only compiles out the
> syscalls. PATCH 6 on the other hand, compiles out fs/splice.c. This patch
> allows fs/fuse to be compiled when fs/splice.c is compiled out. If I am to
> squash it, it would be logical to include it in PATCH 6, not 3.
The suggestion wasn't to move the fs/fuse/dev.c bits; those should
definitely stay in this patch. The suggestion was just to move the bit
of the patch defining __splice_p from this patch to patch 3. (Note that
you need to define it before you use it, so it can't go in patch 6.)
- Josh Triplett
On Mon, Nov 24, 2014 at 08:05:10AM -0800, Josh Triplett wrote:
> On Mon, Nov 24, 2014 at 10:49:31AM +0100, Pieter Smith wrote:
> > On Sun, Nov 23, 2014 at 03:23:02PM -0800, Josh Triplett wrote:
> > > On Sun, Nov 23, 2014 at 11:29:08PM +0100, Richard Weinberger wrote:
> > > > On Sun, Nov 23, 2014 at 3:20 PM, Pieter Smith <[email protected]> wrote:
> > > > > To implement splice support, fs/fuse makes use of nosteal_pipe_buf_ops. This
> > > > > struct is exported by fs/splice. The goal of the larger patch set is to
> > > > > completely compile out fs/splice, so uses of the exported struct need to be
> > > > > compiled out along with fs/splice.
> > > > >
> > > > > This patch therefore compiles out splice support in fs/fuse when
> > > > > CONFIG_SYSCALL_SPLICE is undefined.
> > > > >
> > > > > Signed-off-by: Pieter Smith <[email protected]>
> > > > > ---
> > > > > fs/fuse/dev.c | 4 ++--
> > > > > include/linux/fs.h | 6 ++++++
> > > > > 2 files changed, 8 insertions(+), 2 deletions(-)
> > > > >
> > > > > diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> > > > > index ca88731..f8f92a4 100644
> > > > > --- a/fs/fuse/dev.c
> > > > > +++ b/fs/fuse/dev.c
> > > > > @@ -1291,7 +1291,7 @@ static ssize_t fuse_dev_read(struct kiocb *iocb, const struct iovec *iov,
> > > > > return fuse_dev_do_read(fc, file, &cs, iov_length(iov, nr_segs));
> > > > > }
> > > > >
> > > > > -static ssize_t fuse_dev_splice_read(struct file *in, loff_t *ppos,
> > > > > +static ssize_t __maybe_unused fuse_dev_splice_read(struct file *in, loff_t *ppos,
> > > > > struct pipe_inode_info *pipe,
> > > > > size_t len, unsigned int flags)
> > > > > {
> > > > > @@ -2144,7 +2144,7 @@ const struct file_operations fuse_dev_operations = {
> > > > > .llseek = no_llseek,
> > > > > .read = do_sync_read,
> > > > > .aio_read = fuse_dev_read,
> > > > > - .splice_read = fuse_dev_splice_read,
> > > > > + .splice_read = __splice_p(fuse_dev_splice_read),
> > > > > .write = do_sync_write,
> > > > > .aio_write = fuse_dev_write,
> > > > > .splice_write = fuse_dev_splice_write,
> > > > > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > > > > index a957d43..04c0975 100644
> > > > > --- a/include/linux/fs.h
> > > > > +++ b/include/linux/fs.h
> > > > > @@ -2443,6 +2443,12 @@ extern int blkdev_fsync(struct file *filp, loff_t start, loff_t end,
> > > > > int datasync);
> > > > > extern void block_sync_page(struct page *page);
> > > > >
> > > > > +#ifdef CONFIG_SYSCALL_SPLICE
> > > > > +#define __splice_p(x) x
> > > > > +#else
> > > > > +#define __splice_p(x) NULL
> > > > > +#endif
> > > > > +
> > > >
> > > > This needs to go into a different patch.
> > > > One logical change per patch please. :-)
> > >
> > > Easy enough to merge this one into the patch introducing
> > > CONFIG_SYSCALL_SPLICE, then.
> > >
> > > - Josh Triplett
> >
> > The patch introducing CONFIG_SYSCALL_SPLICE (PATCH 3) only compiles out the
> > syscalls. PATCH 6 on the other hand, compiles out fs/splice.c. This patch
> > allows fs/fuse to be compiled when fs/splice.c is compiled out. If I am to
> > squash it, it would be logical to include it in PATCH 6, not 3.
>
> The suggestion wasn't to move the fs/fuse/dev.c bits; those should
> definitely stay in this patch. The suggestion was just to move the bit
> of the patch defining __splice_p from this patch to patch 3. (Note that
> you need to define it before you use it, so it can't go in patch 6.)
I would, again, argue that stuff like __splice_p() not be implemented at
all please. It will only cause a huge proliferation of stuff like this
that will not make any sense, and only cause a trivial, if any, amount
of code savings.
I thought you were going to not do this type of thing until you got the
gcc optimizer working for function callbacks.
Again, don't do this please.
thanks,
greg k-h
On Mon, Nov 24, 2014 at 11:34:12AM -0800, Greg KH wrote:
> On Mon, Nov 24, 2014 at 08:05:10AM -0800, Josh Triplett wrote:
> > On Mon, Nov 24, 2014 at 10:49:31AM +0100, Pieter Smith wrote:
> > > On Sun, Nov 23, 2014 at 03:23:02PM -0800, Josh Triplett wrote:
> > > > On Sun, Nov 23, 2014 at 11:29:08PM +0100, Richard Weinberger wrote:
> > > > > On Sun, Nov 23, 2014 at 3:20 PM, Pieter Smith <[email protected]> wrote:
> > > > > > To implement splice support, fs/fuse makes use of nosteal_pipe_buf_ops. This
> > > > > > struct is exported by fs/splice. The goal of the larger patch set is to
> > > > > > completely compile out fs/splice, so uses of the exported struct need to be
> > > > > > compiled out along with fs/splice.
> > > > > >
> > > > > > This patch therefore compiles out splice support in fs/fuse when
> > > > > > CONFIG_SYSCALL_SPLICE is undefined.
> > > > > >
> > > > > > Signed-off-by: Pieter Smith <[email protected]>
> > > > > > ---
> > > > > > fs/fuse/dev.c | 4 ++--
> > > > > > include/linux/fs.h | 6 ++++++
> > > > > > 2 files changed, 8 insertions(+), 2 deletions(-)
> > > > > >
> > > > > > diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> > > > > > index ca88731..f8f92a4 100644
> > > > > > --- a/fs/fuse/dev.c
> > > > > > +++ b/fs/fuse/dev.c
> > > > > > @@ -1291,7 +1291,7 @@ static ssize_t fuse_dev_read(struct kiocb *iocb, const struct iovec *iov,
> > > > > > return fuse_dev_do_read(fc, file, &cs, iov_length(iov, nr_segs));
> > > > > > }
> > > > > >
> > > > > > -static ssize_t fuse_dev_splice_read(struct file *in, loff_t *ppos,
> > > > > > +static ssize_t __maybe_unused fuse_dev_splice_read(struct file *in, loff_t *ppos,
> > > > > > struct pipe_inode_info *pipe,
> > > > > > size_t len, unsigned int flags)
> > > > > > {
> > > > > > @@ -2144,7 +2144,7 @@ const struct file_operations fuse_dev_operations = {
> > > > > > .llseek = no_llseek,
> > > > > > .read = do_sync_read,
> > > > > > .aio_read = fuse_dev_read,
> > > > > > - .splice_read = fuse_dev_splice_read,
> > > > > > + .splice_read = __splice_p(fuse_dev_splice_read),
> > > > > > .write = do_sync_write,
> > > > > > .aio_write = fuse_dev_write,
> > > > > > .splice_write = fuse_dev_splice_write,
> > > > > > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > > > > > index a957d43..04c0975 100644
> > > > > > --- a/include/linux/fs.h
> > > > > > +++ b/include/linux/fs.h
> > > > > > @@ -2443,6 +2443,12 @@ extern int blkdev_fsync(struct file *filp, loff_t start, loff_t end,
> > > > > > int datasync);
> > > > > > extern void block_sync_page(struct page *page);
> > > > > >
> > > > > > +#ifdef CONFIG_SYSCALL_SPLICE
> > > > > > +#define __splice_p(x) x
> > > > > > +#else
> > > > > > +#define __splice_p(x) NULL
> > > > > > +#endif
> > > > > > +
> > > > >
> > > > > This needs to go into a different patch.
> > > > > One logical change per patch please. :-)
> > > >
> > > > Easy enough to merge this one into the patch introducing
> > > > CONFIG_SYSCALL_SPLICE, then.
> > > >
> > > > - Josh Triplett
> > >
> > > The patch introducing CONFIG_SYSCALL_SPLICE (PATCH 3) only compiles out the
> > > syscalls. PATCH 6 on the other hand, compiles out fs/splice.c. This patch
> > > allows fs/fuse to be compiled when fs/splice.c is compiled out. If I am to
> > > squash it, it would be logical to include it in PATCH 6, not 3.
> >
> > The suggestion wasn't to move the fs/fuse/dev.c bits; those should
> > definitely stay in this patch. The suggestion was just to move the bit
> > of the patch defining __splice_p from this patch to patch 3. (Note that
> > you need to define it before you use it, so it can't go in patch 6.)
>
> I would, again, argue that stuff like __splice_p() not be implemented at
> all please. It will only cause a huge proliferation of stuff like this
> that will not make any sense, and only cause a trivial, if any, amount
> of code savings.
>
> I thought you were going to not do this type of thing until you got the
> gcc optimizer working for function callbacks.
Compared to the previous patchset, there are now only two instances of
ifdefs outside of the splice code for this, and this is one of them. In
this case, the issue is no longer about making the code for this
splice_read function disappear, but rather to eliminate a reference to a
bit of splice functionality (used *inside* the FUSE splice code) that
will not work without SPLICE_SYSCALL.
Would you prefer to see this specific case handled via an #ifdef in
fs/fuse/dev.c rather than introducing a __splice_p that people might be
inclined to propagate? That'd be fine; the code could simply wrap
fuse_dev_splice_read in an #ifdef and have the #else define a NULL
fuse_dev_splice_read.
- Josh Triplett
On Mon, Nov 24, 2014 at 12:14:50PM -0800, [email protected] wrote:
> > I would, again, argue that stuff like __splice_p() not be implemented at
> > all please. It will only cause a huge proliferation of stuff like this
> > that will not make any sense, and only cause a trivial, if any, amount
> > of code savings.
> >
> > I thought you were going to not do this type of thing until you got the
> > gcc optimizer working for function callbacks.
>
> Compared to the previous patchset, there are now only two instances of
> ifdefs outside of the splice code for this, and this is one of them. In
> this case, the issue is no longer about making the code for this
> splice_read function disappear, but rather to eliminate a reference to a
> bit of splice functionality (used *inside* the FUSE splice code) that
> will not work without SPLICE_SYSCALL.
>
> Would you prefer to see this specific case handled via an #ifdef in
> fs/fuse/dev.c rather than introducing a __splice_p that people might be
> inclined to propagate? That'd be fine; the code could simply wrap
> fuse_dev_splice_read in an #ifdef and have the #else define a NULL
> fuse_dev_splice_read.
Yes, I would prefer that, but I'm not the fuse maintainer.
thanks,
greg k-h
On Mon, Nov 24, 2014 at 12:22:14PM -0800, Greg KH wrote:
> On Mon, Nov 24, 2014 at 12:14:50PM -0800, [email protected] wrote:
> > > I would, again, argue that stuff like __splice_p() not be implemented at
> > > all please. It will only cause a huge proliferation of stuff like this
> > > that will not make any sense, and only cause a trivial, if any, amount
> > > of code savings.
> > >
> > > I thought you were going to not do this type of thing until you got the
> > > gcc optimizer working for function callbacks.
> >
> > Compared to the previous patchset, there are now only two instances of
> > ifdefs outside of the splice code for this, and this is one of them. In
> > this case, the issue is no longer about making the code for this
> > splice_read function disappear, but rather to eliminate a reference to a
> > bit of splice functionality (used *inside* the FUSE splice code) that
> > will not work without SPLICE_SYSCALL.
> >
> > Would you prefer to see this specific case handled via an #ifdef in
> > fs/fuse/dev.c rather than introducing a __splice_p that people might be
> > inclined to propagate? That'd be fine; the code could simply wrap
> > fuse_dev_splice_read in an #ifdef and have the #else define a NULL
> > fuse_dev_splice_read.
>
> Yes, I would prefer that, but I'm not the fuse maintainer.
>
> thanks,
>
> greg k-h
Okay. I'll do my part to prevent the type of proliferation guaranteed to rate
high on the respected K-H icky-scale. __splice_p() goes the way of the dodo
in favor of the solution presented by Josh.
I pray that the Gods of fuse maintenance will look favorable upon the result.