>From v4.4, linux kernel starts to support direct I/O and
AIO to backing file for loop driver, so allow losetup to
enable the feature by using LOOP_SET_DIRECT_IO ioctl cmd.
Signed-off-by: Ming Lei <tom.leiming@xxxxxxxxx>
---
include/loopdev.h | 2 ++
lib/loopdev.c | 18 ++++++++++++++++++
sys-utils/losetup.c | 27 +++++++++++++++++++++++++--
3 files changed, 45 insertions(+), 2 deletions(-)
diff --git a/include/loopdev.h b/include/loopdev.h
index 573a569..9a7f6ba 100644
--- a/include/loopdev.h
+++ b/include/loopdev.h
@@ -23,6 +23,7 @@
#define LOOP_GET_STATUS64 0x4C05
/* #define LOOP_CHANGE_FD 0x4C06 */
#define LOOP_SET_CAPACITY 0x4C07
+#define LOOP_SET_DIRECT_IO 0x4C08
/* /dev/loop-control interface */
#ifndef LOOP_CTL_ADD
@@ -164,6 +165,7 @@ extern int loopcxt_next(struct loopdev_cxt *lc);
extern int loopcxt_setup_device(struct loopdev_cxt *lc);
extern int loopcxt_delete_device(struct loopdev_cxt *lc);
extern int loopcxt_set_capacity(struct loopdev_cxt *lc);
+extern int loopcxt_set_dio(struct loopdev_cxt *lc, unsigned long use_dio);
int loopcxt_set_offset(struct loopdev_cxt *lc, uint64_t offset);
int loopcxt_set_sizelimit(struct loopdev_cxt *lc, uint64_t sizelimit);
diff --git a/lib/loopdev.c b/lib/loopdev.c
index fe047cd..ff99dd4 100644
--- a/lib/loopdev.c
+++ b/lib/loopdev.c
@@ -1315,6 +1315,24 @@ int loopcxt_set_capacity(struct loopdev_cxt *lc)
return 0;
}
+int loopcxt_set_dio(struct loopdev_cxt *lc, unsigned long use_dio)
+{
+ int fd = loopcxt_get_fd(lc);
+
+ if (fd < 0)
+ return -EINVAL;
+
+ /* Kernels prior to v4.4 don't support this ioctl */
+ if (ioctl(fd, LOOP_SET_DIRECT_IO, use_dio) < 0) {
+ int rc = -errno;
+ DBG(CXT, ul_debugobj(lc, "LOOP_SET_DIRECT_IO failed: %m"));
+ return rc;
+ }
+
+ DBG(CXT, ul_debugobj(lc, "direct io set"));
+ return 0;
+}
+
int loopcxt_delete_device(struct loopdev_cxt *lc)
{
int fd = loopcxt_get_fd(lc);
diff --git a/sys-utils/losetup.c b/sys-utils/losetup.c
index a68b222..68f7777 100644
--- a/sys-utils/losetup.c
+++ b/sys-utils/losetup.c
@@ -35,6 +35,7 @@ enum {
A_SHOW_ONE, /* print info about one device */
A_FIND_FREE, /* find first unused */
A_SET_CAPACITY, /* set device capacity */
+ A_SET_DIRECT_IO, /* set accessing backing file by direct io */
};
enum {
@@ -393,6 +394,7 @@ static void usage(FILE *out)
fputs(_(" --sizelimit <num> device is limited to <num> bytes of the file\n"), out);
fputs(_(" -P, --partscan create a partitioned loop device\n"), out);
fputs(_(" -r, --read-only set up a read-only loop device\n"), out);
+ fputs(_(" --direct-io open backing file with O_DIRECT\n"), out);
fputs(_(" --show print device name after setup (with -f)\n"), out);
fputs(_(" -v, --verbose verbose mode\n"), out);
@@ -446,11 +448,13 @@ int main(int argc, char **argv)
int res = 0, showdev = 0, lo_flags = 0;
char *outarg = NULL;
int list = 0;
+ unsigned long use_dio = 0, set_dio = 0;
enum {
OPT_SIZELIMIT = CHAR_MAX + 1,
OPT_SHOW,
- OPT_RAW
+ OPT_RAW,
+ OPT_DIO
};
static const struct option longopts[] = {
{ "all", 0, 0, 'a' },
@@ -468,6 +472,7 @@ int main(int argc, char **argv)
{ "sizelimit", 1, 0, OPT_SIZELIMIT },
{ "partscan", 0, 0, 'P' },
{ "read-only", 0, 0, 'r' },
+ { "direct-io", 1, 0, OPT_DIO },
{ "raw", 0, 0, OPT_RAW },
{ "show", 0, 0, OPT_SHOW },
{ "verbose", 0, 0, 'v' },
@@ -557,6 +562,10 @@ int main(int argc, char **argv)
case OPT_SHOW:
showdev = 1;
break;
+ case OPT_DIO:
+ set_dio = 1;
+ use_dio = strtoul_or_err(optarg, _("failed to parse dio"));
+ break;
case 'v':
break;
case 'V':
@@ -609,8 +618,13 @@ int main(int argc, char **argv)
if (!act && optind + 1 == argc) {
/*
* losetup [--list] <device>
+ * OR
+ * losetup --direct-io DIO <device>
*/
- act = A_SHOW_ONE;
+ if (!set_dio)
+ act = A_SHOW_ONE;
+ else
+ act = A_SET_DIRECT_IO;
if (!is_loopdev(argv[optind]) ||
loopcxt_set_device(&lc, argv[optind]))
err(EXIT_FAILURE, _("%s: failed to use device"),
@@ -695,6 +709,8 @@ int main(int argc, char **argv)
if (showdev)
printf("%s\n", loopcxt_get_device(&lc));
warn_size(file, sizelimit);
+ if (set_dio)
+ goto lo_set_dio;
}
break;
}
@@ -747,6 +763,13 @@ int main(int argc, char **argv)
warn(_("%s: set capacity failed"),
loopcxt_get_device(&lc));
break;
+ case A_SET_DIRECT_IO:
+ lo_set_dio:
+ res = loopcxt_set_dio(&lc, use_dio);
+ if (res)
+ warn(_("%s: set direct io failed"),
+ loopcxt_get_device(&lc));
+ break;
default:
usage(stderr);
break;
--
1.9.1
--
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