emo/busybox
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

mount: create loop devices with LO_FLAGS_AUTOCLEAR flag

Browse Source 
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>
This commit is contained in:
Denys Vlasenko
2017-03-16 16:49:37 +01:00
parent 018804204f
commit ab518eea9c
4 changed files with 87 additions and 21 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
include/libbb.h
View File

@ -1329,10 +1329,15 @@ extern int get_linux_version_code(void) FAST_FUNC;
extern char *query_loop(const char *device) FAST_FUNC;
extern int del_loop(const char *device) FAST_FUNC;
/* If *devname is not NULL, use that name, otherwise try to find free one,
/*
* If *devname is not NULL, use that name, otherwise try to find free one,
* malloc and return it in *devname.
* return value: 1: read-only loopdev was setup, 0: rw, < 0: error */
extern int set_loop(char **devname, const char *file, unsigned long long offset, int ro) FAST_FUNC;
* return value is the opened fd to the loop device, or < on error
*/
extern int set_loop(char **devname, const char *file, unsigned long long offset, unsigned flags) FAST_FUNC;
/* These constants match linux/loop.h (without BB_ prefix): */
#define BB_LO_FLAGS_READ_ONLY 1
#define BB_LO_FLAGS_AUTOCLEAR 4
/* Like bb_ask below, but asks on stdin with no timeout. */
char *bb_ask_stdin(const char * prompt) FAST_FUNC;