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mounts: if a mount can't be mounted, it is queued in postpone list (v4)

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Try to restore mounts while a postpone list isn't empty and check
that each iteration has some progress, otherwice it will fails for
preventing infinite loops

v2: rework logic about postpone list
    add more comments

v3: one more attempt to make it more readable
v4: Here is a master class from Pavel how to write self-documented code.

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
This commit is contained in:
Andrey Vagin
2013-08-29 18:52:43 +04:00
committed by Pavel Emelyanov
parent 2b4a8d29d6
commit e01072c05a
2 changed files with 58 additions and 5 deletions
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2
include/proc_parse.h
View File

@@ -121,6 +121,8 @@ struct mount_info {
struct list_head mnt_slave_list;/* list of slave mounts */
struct list_head mnt_slave; /* slave list entry */
struct mount_info *mnt_master; /* slave is on master->mnt_slave_list */
struct list_head postpone;
};
struct proc_posix_timer {

61
mount.c
View File

@@ -570,12 +570,30 @@ int dump_mnt_ns(int ns_pid, struct cr_fdset *fdset)
return 0;
}
#define MNT_TREE_WALK(_r, _el, _fn_f, _fn_r) do { \
/*
* _fn_f - pre-order traversal function
* _fn_f - post-order traversal function
* _plist - a postpone list. _el is added to this list, if _fn_f returns
* a positive value, and all lower elements are not enumirated.
*/
#define MNT_TREE_WALK(_r, _el, _fn_f, _fn_r, _plist, _prgs) do { \
struct mount_info *_mi = _r; \
\
while (1) { \
if (_fn_f(_mi)) \
int ret; \
\
list_del_init(&_mi->postpone); \
\
ret = _fn_f(_mi); \
if (ret < 0) \
return -1; \
else if (ret > 0) { \
list_add_tail(&_mi->postpone, _plist); \
goto up; \
} \
\
_prgs++; \
\
if (!list_empty(&_mi->children)) { \
_mi = list_entry(_mi->children._el, \
struct mount_info, siblings); \
@@ -598,18 +616,50 @@ int dump_mnt_ns(int ns_pid, struct cr_fdset *fdset)
#define MNT_WALK_NONE 0 &&
static int mnt_tree_for_each(struct mount_info *m,
static int mnt_tree_for_each(struct mount_info *start,
int (*fn)(struct mount_info *))
{
MNT_TREE_WALK(m, next, fn, MNT_WALK_NONE);
struct mount_info *tmp;
LIST_HEAD(postpone);
LIST_HEAD(postpone2);
int progress;
pr_debug("Start with %d:%s\n", start->mnt_id, start->mountpoint);
list_add(&start->postpone, &postpone);
again:
progress = 0;
list_for_each_entry_safe(start, tmp, &postpone, postpone)
MNT_TREE_WALK(start, next, fn, MNT_WALK_NONE, &postpone2, progress);
if (!progress) {
struct mount_info *m;
pr_err("A few mount points can't be mounted");
list_for_each_entry(m, &postpone2, postpone) {
pr_err("%d:%d %s %s %s\n", m->mnt_id,
m->parent_mnt_id, m->root,
m->mountpoint, m->source);
}
return -1;
}
list_splice_init(&postpone2, &postpone);
if (!list_empty(&postpone))
goto again;
return 0;
}
static int mnt_tree_for_each_reverse(struct mount_info *m,
int (*fn)(struct mount_info *))
{
MNT_TREE_WALK(m, prev, MNT_WALK_NONE, fn);
int progress;
MNT_TREE_WALK(m, prev, MNT_WALK_NONE, fn, (struct list_head *) NULL, progress);
return 0;
}
@@ -765,6 +815,7 @@ struct mount_info *mnt_entry_alloc()
INIT_LIST_HEAD(&new->siblings);
INIT_LIST_HEAD(&new->mnt_slave_list);
INIT_LIST_HEAD(&new->mnt_share);
INIT_LIST_HEAD(&new->postpone);
new->mnt_master = NULL;
}
return new;