On Thu, Aug 7, 2008 at 1:26 PM, Archie Cobbs <archie@xxxxxxxxxxxx> wrote:
> I have an application involving the loopback device where it would be
> valuable for the underlying file to be opened with the O_DIRECT flag.
>
> Any thoughts one way or the other about adding support to losetup(8)
> and mount(8) for a 'direct' option that would enable this?
>
> I will propose a patch if people think this would be a reasonable thing to do.
Add support for opening loopback files with O_DIRECT.
Signed-off-by: Archie L. Cobbs <archie@xxxxxxxxxxxx>
---
mount/lomount.c | 18 ++++++++++++------
mount/lomount.h | 1 +
mount/losetup.8 | 10 +++++++++-
mount/mount.8 | 4 ++--
mount/mount.c | 6 +++++-
5 files changed, 29 insertions(+), 10 deletions(-)
---
--- a/mount/lomount.c
+++ b/mount/lomount.c
@@ -660,6 +660,8 @@ set_loop(const char *device, const char *file,
unsigned long long offset,
}
mode = (*options & SETLOOP_RDONLY) ? O_RDONLY : O_RDWR;
+ if (*options & SETLOOP_DIRECT)
+ mode |= O_DIRECT;
if ((ffd = open(file, mode)) < 0) {
if (!(*options & SETLOOP_RDONLY) && errno == EROFS)
ffd = open(file, mode = O_RDONLY);
@@ -879,12 +881,13 @@ main(int argc, char **argv) {
int delete, find, c, all;
int res = 0;
int showdev = 0;
- int ro = 0;
+ int setoptions = 0;
int pfd = -1;
unsigned long long off, slimit;
struct option longopts[] = {
{ "all", 0, 0, 'a' },
{ "detach", 0, 0, 'd' },
+ { "direct", 0, 0, 'n' },
{ "encryption", 1, 0, 'e' },
{ "find", 0, 0, 'f' },
{ "help", 0, 0, 'h' },
@@ -911,14 +914,14 @@ main(int argc, char **argv) {
if ((p = strrchr(progname, '/')) != NULL)
progname = p+1;
- while ((c = getopt_long(argc, argv, "ade:E:fhj:o:p:rsv",
+ while ((c = getopt_long(argc, argv, "ade:E:fhj:no:p:rsv",
longopts, NULL)) != -1) {
switch (c) {
case 'a':
all = 1;
break;
case 'r':
- ro = 1;
+ setoptions |= SETLOOP_RDONLY;
break;
case 'd':
delete = 1;
@@ -933,6 +936,9 @@ main(int argc, char **argv) {
case 'j':
assoc = optarg;
break;
+ case 'n':
+ setoptions |= SETLOOP_DIRECT;
+ break;
case 'o':
offset = optarg;
break;
@@ -959,7 +965,7 @@ main(int argc, char **argv) {
usage();
} else if (delete) {
if (argc != optind+1 || encryption || offset || sizelimit ||
- find || all || showdev || assoc || ro)
+ find || all || showdev || assoc || setoptions)
usage();
} else if (find) {
if (all || assoc || argc < optind || argc > optind+1)
@@ -968,7 +974,7 @@ main(int argc, char **argv) {
if (argc > 2)
usage();
} else if (assoc) {
- if (encryption || showdev || passfd || ro)
+ if (encryption || showdev || passfd || setoptions)
usage();
} else {
if (argc < optind+1 || argc > optind+2)
@@ -1012,7 +1018,7 @@ main(int argc, char **argv) {
if (passfd && sscanf(passfd, "%d", &pfd) != 1)
usage();
do {
- res = set_loop(device, file, off, slimit,
encryption, pfd, &ro);
+ res = set_loop(device, file, off, slimit,
encryption, pfd, &setoptions);
if (res == 2 && find) {
if (verbose)
printf("stolen
loop=%s...trying again\n",
diff --git a/mount/lomount.h b/mount/lomount.h
index 59108d4..5fae55a 100644
--- a/mount/lomount.h
+++ b/mount/lomount.h
@@ -10,3 +10,4 @@ extern char *loopfile_used (const char *filename,
unsigned long long offset);
#define SETLOOP_RDONLY (1<<0) /* Open loop read-only */
#define SETLOOP_AUTOCLEAR (1<<1) /* Automatically detach loop on
close (2.6.25?) */
+#define SETLOOP_DIRECT (1<<2) /* Open underlying file with O_DIRECT */
diff --git a/mount/losetup.8 b/mount/losetup.8
index 84f82e7..8aa7955 100644
--- a/mount/losetup.8
+++ b/mount/losetup.8
@@ -37,10 +37,11 @@ Setup loop device:
.IR offset ]
.RB [ \-\-sizelimit
.IR limit ]
+.in +8
.RB [ \-p
.IR pfd ]
.RB [ \-r ]
-.in +8
+.RB [ \-n ]
.RB { \-f [ \-\-show ] | \fIloop_device\fP }
.I file
.in -13
@@ -83,6 +84,13 @@ print help
.IP "\fB\-j, \-\-associated \fIfile\fP"
show status of all loop devices associated with given
.I file
+.IP "\fB\-n, \-\-direct\fP"
+Pass the
+.BR O_DIRECT
+flag to
+.BR open (2)
+when opening
+.I file
.IP "\fB\-o, \-\-offset \fIoffset\fP"
the data start is moved \fIoffset\fP bytes into the specified file or
device
diff --git a/mount/mount.8 b/mount/mount.8
index 7487923..dd6d75a 100644
--- a/mount/mount.8
+++ b/mount/mount.8
@@ -2061,8 +2061,8 @@ to correspond to the file
and then mount this device on
.IR /mnt .
-This type of mount knows about four options, namely
-.BR loop ", " offset ", " sizelimit " and " encryption ,
+This type of mount knows about five options, namely
+.BR loop ", " offset ", " sizelimit ", " encryption " and " direct
that are really options to
.BR \%losetup (8).
(These options can be used in addition to those specific
diff --git a/mount/mount.c b/mount/mount.c
index be05135..58866e6 100644
--- a/mount/mount.c
+++ b/mount/mount.c
@@ -102,10 +102,11 @@ struct opt_map {
#define MS_OWNER 0x10000000
#define MS_GROUP 0x08000000
#define MS_COMMENT 0x02000000
+#define MS_DIRECT 0x00020000
#define MS_LOOP 0x00010000
/* Options that we keep the mount system call from seeing. */
-#define MS_NOSYS (MS_NOAUTO|MS_USERS|MS_USER|MS_COMMENT|MS_LOOP)
+#define MS_NOSYS
(MS_NOAUTO|MS_USERS|MS_USER|MS_COMMENT|MS_LOOP|MS_DIRECT)
/* Options that we keep from appearing in the options field in the mtab. */
#define MS_NOMTAB (MS_REMOUNT|MS_NOAUTO|MS_USERS|MS_USER)
@@ -161,6 +162,7 @@ static const struct opt_map opt_map[] = {
{ "nomand", 0, 1, MS_MANDLOCK }, /* Forbid mandatory locks on this FS */
#endif
{ "loop", 1, 0, MS_LOOP }, /* use a loop device */
+ { "direct", 0, 0, MS_DIRECT }, /* open loopback file with O_DIRECT */
#ifdef MS_NOATIME
{ "atime", 0, 1, MS_NOATIME }, /* Update access time */
{ "noatime", 0, 0, MS_NOATIME }, /* Do not update access time */
@@ -911,6 +913,8 @@ loop_check(const char **spec, const char **type, int *flags,
if (*flags & MS_RDONLY)
loop_opts |= SETLOOP_RDONLY;
+ if (*flags & MS_DIRECT)
+ loop_opts |= SETLOOP_DIRECT;
offset = opt_offset ? strtoull(opt_offset, NULL, 0) : 0;
sizelimit = opt_sizelimit ? strtoull(opt_sizelimit, NULL, 0) : 0;
Thanks,
-Archie
--
Archie L. Cobbs
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