From a19643e643c5b9bc151aaecf9f36989234b8ca4e Mon Sep 17 00:00:00 2001 From: Andrey Vagin Date: Thu, 10 Apr 2014 14:52:32 +0400 Subject: [PATCH] mount: cut a common part of sources for bind-mounts The source of the root mount may be not equal to "/" and we need to take this fact into account, when we bind-mount it to somewhere. For example: 11877 ? Ss 0:00 ./bind-mount --pidfile=bind-mount.pid --outfile=bind-mount.out --dirname=bind-mount.test 11880 ? Ss 0:00 \_ ./bind-mount --pidfile=bind-mount.pid --outfile=bind-mount.out --dirname=bind-mount.test [root@avagin-fc19-cr crtools]# cat /proc/11880/mountinfo 68 42 8:3 /root/git/crtools/test / rw,relatime - ext4 /dev/sda3 rw,data=ordered 43 68 0:33 / /proc rw,relatime - proc proc rw 44 68 0:34 / /dev/pts rw,relatime - devpts pts rw,mode=666,ptmxmode=666 45 68 8:3 /root/git/crtools/test/zdtm/live/static/bind-mount.test/test /zdtm/live/static/bind-mount.test/bind rw,relatime - ext4 /dev/sda3 rw,data=ordered The 45 mount is bind-mount of the 68 mount. mi(45)->root = /root/git/crtools/test/zdtm/live/static/bind-mount.test/test mi(68)->root = /root/git/crtools/test so the comman part is "/root/git/crtools/test" and the command is mount --bind /zdtm/live/static/bind-mount.test/test /zdtm/live/static/bind-mount.test/bind Signed-off-by: Andrey Vagin Signed-off-by: Pavel Emelyanov --- mount.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/mount.c b/mount.c index cd2fe04ae..a87a4302d 100644 --- a/mount.c +++ b/mount.c @@ -1137,11 +1137,26 @@ static int restore_ext_mount(struct mount_info *mi) static int do_bind_mount(struct mount_info *mi) { - char rpath[PATH_MAX]; bool shared = mi->shared_id && mi->shared_id == mi->bind->shared_id; if (!mi->need_plugin) { - snprintf(rpath, sizeof(rpath), "%s%s", mi->bind->mountpoint, mi->root); + char rpath[PATH_MAX]; + int tok = 0; + + /* + * Cut common part of root. + * For non-root binds the source is always "/" (checked) + * so this will result in this slash removal only. + */ + while (mi->root[tok] == mi->bind->root[tok]) { + tok++; + if (mi->bind->root[tok] == '\0') + break; + BUG_ON(mi->root[tok] == '\0'); + } + + snprintf(rpath, sizeof(rpath), "%s/%s", + mi->bind->mountpoint, mi->root + tok); pr_info("\tBind %s to %s\n", rpath, mi->mountpoint); if (mount(rpath, mi->mountpoint, NULL,