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| author | Denys Vlasenko | 2017-03-16 16:49:37 +0100 |
|---|---|---|
| committer | Denys Vlasenko | 2017-03-16 16:55:47 +0100 |
| commit | ab518eea9c41235a3fcde80f3ea99669eaade621 (patch) | |
| tree | 4bd1783e343316fa11c2ade135dbe0b0561689a9 /util-linux/mount.c | |
| parent | 018804204f41e6e60cec536843275f8fdd4d3620 (diff) | |
| download | busybox-ab518eea9c41235a3fcde80f3ea99669eaade621.zip busybox-ab518eea9c41235a3fcde80f3ea99669eaade621.tar.gz | |
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>
Diffstat (limited to 'util-linux/mount.c')
| -rw-r--r-- | util-linux/mount.c | 21 |
1 files changed, 20 insertions, 1 deletions
diff --git a/util-linux/mount.c b/util-linux/mount.c index f0245f7..6bb1852 100644 --- a/util-linux/mount.c +++ b/util-linux/mount.c @@ -1887,6 +1887,7 @@ static int nfsmount(struct mntent *mp, unsigned long vfsflags, char *filteropts) // NB: mp->xxx fields may be trashed on exit static int singlemount(struct mntent *mp, int ignore_busy) { + int loopfd = -1; int rc = -1; unsigned long vfsflags; char *loopFile = NULL, *filteropts = NULL; @@ -2026,7 +2027,20 @@ static int singlemount(struct mntent *mp, int ignore_busy) if (ENABLE_FEATURE_MOUNT_LOOP && S_ISREG(st.st_mode)) { loopFile = bb_simplify_path(mp->mnt_fsname); mp->mnt_fsname = NULL; // will receive malloced loop dev name - if (set_loop(&mp->mnt_fsname, loopFile, 0, /*ro:*/ (vfsflags & MS_RDONLY)) < 0) { + + // mount always creates AUTOCLEARed loopdevs, so that umounting + // drops them without any code in the 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 + loopfd = set_loop(&mp->mnt_fsname, + loopFile, + 0, + ((vfsflags & MS_RDONLY) ? BB_LO_FLAGS_READ_ONLY : 0) + | BB_LO_FLAGS_AUTOCLEAR + ); + if (loopfd < 0) { if (errno == EPERM || errno == EACCES) bb_error_msg(bb_msg_perm_denied_are_you_root); else @@ -2074,6 +2088,8 @@ static int singlemount(struct mntent *mp, int ignore_busy) } // If mount failed, clean up loop file (if any). + // (Newer kernels which support LO_FLAGS_AUTOCLEAR should not need this, + // merely "close(loopfd)" should do it?) if (ENABLE_FEATURE_MOUNT_LOOP && rc && loopFile) { del_loop(mp->mnt_fsname); if (ENABLE_FEATURE_CLEAN_UP) { @@ -2086,6 +2102,9 @@ static int singlemount(struct mntent *mp, int ignore_busy) if (ENABLE_FEATURE_CLEAN_UP) free(filteropts); + if (loopfd >= 0) + close(loopfd); + if (errno == EBUSY && ignore_busy) return 0; if (errno == ENOENT && (vfsflags & MOUNT_NOFAIL)) |