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basic/copy: use copy_file_range() 

For btrfs, c_f_r() is like BTRFS_IOC_CLONE which we already used, but also
works when max_bytes is set. We do call copy_bytes in coredump code with
max_bytes set, and for large files, so we might see some benefit from using
c_f_r() on btrfs.

For other filesystems, c_f_r() falls back to do_splice_direct(), the same as
sendfile, which we already call, so there shouldn't be much difference.

Tested with test-copy and systemd-coredump on Linux 4.3 (w/o c_f_r)
and 4.5 (w/ c_f_r).
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2016-03-15 19:26:34 -04:00
parent 1d4b557d1b
commit a44202e98b
2 changed files with 38 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
TODO
View File

@ -49,8 +49,6 @@ Features:
* cache sd_event_now() result from before the first iteration...
* support for the new copy_file_range() syscall
* add systemctl stop --job-mode=triggering that follows TRIGGERED_BY deps and adds them to the same transaction
* Maybe add a way how users can "pin" units into memory, so that they are not subject to automatic GC?

40
src/basic/copy.c
View File

@ -40,6 +40,7 @@
#include "fs-util.h"
#include "io-util.h"
#include "macro.h"
#include "missing.h"
#include "string-util.h"
#include "strv.h"
#include "time-util.h"
@ -48,10 +49,29 @@
#define COPY_BUFFER_SIZE (16*1024u)
static ssize_t try_copy_file_range(int fd_in, loff_t *off_in,
int fd_out, loff_t *off_out,
size_t len,
unsigned int flags) {
static int have = -1;
ssize_t r;
if (have == false)
return -ENOSYS;
r = copy_file_range(fd_in, off_in, fd_out, off_out, len, flags);
if (_unlikely_(have < 0))
have = r >= 0 || errno != ENOSYS;
if (r >= 0)
return r;
else
return -errno;
}
int copy_bytes(int fdf, int fdt, uint64_t max_bytes, bool try_reflink) {
bool try_sendfile = true, try_splice = true;
bool try_cfr = true, try_sendfile = true, try_splice = true;
int r;
size_t m = SSIZE_MAX; /* that the maximum that sendfile accepts */
size_t m = SSIZE_MAX; /* that the maximum that sendfile and c_f_r accept */
assert(fdf >= 0);
assert(fdt >= 0);
@ -78,6 +98,22 @@ int copy_bytes(int fdf, int fdt, uint64_t max_bytes, bool try_reflink) {
m = (size_t) max_bytes;
}
/* First try copy_file_range(), unless we already tried */
if (try_cfr) {
n = try_copy_file_range(fdf, NULL, fdt, NULL, m, 0u);
if (n < 0) {
if (!IN_SET(n, -EINVAL, -ENOSYS, -EXDEV))
return n;
try_cfr = false;
/* use fallback below */
} else if (n == 0) /* EOF */
break;
else
/* Success! */
goto next;
}
/* First try sendfile(), unless we already tried */
if (try_sendfile) {
n = sendfile(fdt, fdf, NULL, m);