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d_invalidate(): unhash immediately

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Once that is done, we can just hunt mountpoints down one by one;
no new mountpoints can be added from now on, so we don't need
anything tricky in finish() callback, etc.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2018-04-15 18:21:47 -04:00
parent 60cc43fc88
commit ff17fa561a
1 changed files with 16 additions and 46 deletions
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62
fs/dcache.c
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@ -1542,78 +1542,48 @@ void shrink_dcache_for_umount(struct super_block *sb)
}
}
struct detach_data {
struct select_data select;
struct dentry *mountpoint;
};
static enum d_walk_ret detach_and_collect(void *_data, struct dentry *dentry)
static enum d_walk_ret find_submount(void *_data, struct dentry *dentry)
{
struct detach_data *data = _data;
struct dentry **victim = _data;
if (d_mountpoint(dentry)) {
__dget_dlock(dentry);
data->mountpoint = dentry;
*victim = dentry;
return D_WALK_QUIT;
}
return select_collect(&data->select, dentry);
}
static void check_and_drop(void *_data)
{
struct detach_data *data = _data;
if (!data->mountpoint && list_empty(&data->select.dispose))
__d_drop(data->select.start);
return D_WALK_CONTINUE;
}
/**
* d_invalidate - detach submounts, prune dcache, and drop
* @dentry: dentry to invalidate (aka detach, prune and drop)
*
* no dcache lock.
*
* The final d_drop is done as an atomic operation relative to
* rename_lock ensuring there are no races with d_set_mounted. This
* ensures there are no unhashed dentries on the path to a mountpoint.
*/
void d_invalidate(struct dentry *dentry)
{
/*
* If it's already been dropped, return OK.
*/
bool had_submounts = false;
spin_lock(&dentry->d_lock);
if (d_unhashed(dentry)) {
spin_unlock(&dentry->d_lock);
return;
}
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
/* Negative dentries can be dropped without further checks */
if (!dentry->d_inode) {
d_drop(dentry);
if (!dentry->d_inode)
return;
}
shrink_dcache_parent(dentry);
for (;;) {
struct detach_data data;
data.mountpoint = NULL;
INIT_LIST_HEAD(&data.select.dispose);
data.select.start = dentry;
data.select.found = 0;
d_walk(dentry, &data, detach_and_collect, check_and_drop);
if (!list_empty(&data.select.dispose))
shrink_dentry_list(&data.select.dispose);
else if (!data.mountpoint)
struct dentry *victim = NULL;
d_walk(dentry, &victim, find_submount, NULL);
if (!victim) {
if (had_submounts)
shrink_dcache_parent(dentry);
return;
if (data.mountpoint) {
detach_mounts(data.mountpoint);
dput(data.mountpoint);
}
had_submounts = true;
detach_mounts(victim);
dput(victim);
}
}
EXPORT_SYMBOL(d_invalidate);