mount: create loop devices with LO_FLAGS_AUTOCLEAR flag
The "autolooped" mount (mount [-oloop] IMAGE /DIR/DIR)
always creates AUTOCLEARed loopdevs, so that umounting
drops them (and this does not require any code in the
umount userspace).
This happens since circa linux-2.6.25:
commit 96c5865559cee0f9cbc5173f3c949f6ce3525581
Date: Wed Feb 6 01:36:27 2008 -0800
Subject: Allow auto-destruction of loop devices
IOW: in this case, umount does not have to use -d
to drop the loopdev.
The explicit loop mount (mount /dev/loopN /DIR/DIR)
does not do this. In this case, umount without -d
should not drop loopdev.
Unfortunately, bbox umount currently always implies -d,
this probably needs fixing.
function old new delta
set_loop 537 597 +60
singlemount 1101 1138 +37
losetup_main 419 432 +13
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/0 up/down: 110/0) Total: 110 bytes
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/libbb/loop.c b/libbb/loop.c
index d30b378..f0d4296 100644
--- a/libbb/loop.c
+++ b/libbb/loop.c
@@ -78,22 +78,24 @@
return rc;
}
-/* Returns 0 if mounted RW, 1 if mounted read-only, <0 for error.
- *device is loop device to use, or if *device==NULL finds a loop device to
- mount it on and sets *device to a strdup of that loop device name. This
- search will re-use an existing loop device already bound to that
- file/offset if it finds one.
+/* Returns opened fd to the loop device, <0 on error.
+ * *device is loop device to use, or if *device==NULL finds a loop device to
+ * mount it on and sets *device to a strdup of that loop device name. This
+ * search will re-use an existing loop device already bound to that
+ * file/offset if it finds one.
*/
-int FAST_FUNC set_loop(char **device, const char *file, unsigned long long offset, int ro)
+int FAST_FUNC set_loop(char **device, const char *file, unsigned long long offset, unsigned flags)
{
char dev[LOOP_NAMESIZE];
char *try;
bb_loop_info loopinfo;
struct stat statbuf;
- int i, dfd, ffd, mode, rc = -1;
+ int i, dfd, ffd, mode, rc;
+
+ rc = dfd = -1;
/* Open the file. Barf if this doesn't work. */
- mode = ro ? O_RDONLY : O_RDWR;
+ mode = (flags & BB_LO_FLAGS_READ_ONLY) ? O_RDONLY : O_RDWR;
open_ffd:
ffd = open(file, mode);
if (ffd < 0) {
@@ -144,20 +146,35 @@
/* If device is free, claim it. */
if (rc && errno == ENXIO) {
- memset(&loopinfo, 0, sizeof(loopinfo));
- safe_strncpy((char *)loopinfo.lo_file_name, file, LO_NAME_SIZE);
- loopinfo.lo_offset = offset;
/* Associate free loop device with file. */
if (ioctl(dfd, LOOP_SET_FD, ffd) == 0) {
- if (ioctl(dfd, BB_LOOP_SET_STATUS, &loopinfo) == 0)
- rc = 0;
- else
+ memset(&loopinfo, 0, sizeof(loopinfo));
+ safe_strncpy((char *)loopinfo.lo_file_name, file, LO_NAME_SIZE);
+ loopinfo.lo_offset = offset;
+ /*
+ * Used by mount to set LO_FLAGS_AUTOCLEAR.
+ * LO_FLAGS_READ_ONLY is not set because RO is controlled by open type of the file.
+ * Note that closing LO_FLAGS_AUTOCLEARed dfd before mount
+ * is wrong (would free the loop device!)
+ */
+ loopinfo.lo_flags = (flags & ~BB_LO_FLAGS_READ_ONLY);
+ rc = ioctl(dfd, BB_LOOP_SET_STATUS, &loopinfo);
+ if (rc != 0 && (loopinfo.lo_flags & BB_LO_FLAGS_AUTOCLEAR)) {
+ /* Old kernel, does not support LO_FLAGS_AUTOCLEAR? */
+ /* (this code path is not tested) */
+ loopinfo.lo_flags -= BB_LO_FLAGS_AUTOCLEAR;
+ rc = ioctl(dfd, BB_LOOP_SET_STATUS, &loopinfo);
+ }
+ if (rc != 0) {
ioctl(dfd, LOOP_CLR_FD, 0);
+ }
}
} else {
rc = -1;
}
- close(dfd);
+ if (rc != 0) {
+ close(dfd);
+ }
try_again:
if (*device) break;
}
@@ -165,7 +182,7 @@
if (rc == 0) {
if (!*device)
*device = xstrdup(dev);
- return (mode == O_RDONLY); /* 1:ro, 0:rw */
+ return dfd;
}
return rc;
}